TY - JOUR A1 - Kaluza, Benjamin F. A1 - Wallace, Helen A1 - Heard, Tim A. A1 - Klein, Aelxandra-Maria A1 - Leonhardt, Sara D. T1 - Urban gardens promote bee foraging over natural habitats and plantations JF - Ecology and Evolution N2 - Increasing human land use for agriculture and housing leads to the loss of natural habitat and to widespread declines in wild bees. Bee foraging dynamics and fitness depend on the availability of resources in the surrounding landscape, but how precisely landscape related resource differences affect bee foraging patterns remains unclear. To investigate how landscape and its interaction with season and weather drive foraging and resource intake in social bees, we experimentally compared foraging activity, the allocation of foragers to different resources (pollen, nectar, and resin) and overall resource intake in the Australian stingless bee Tetragonula carbonaria (Apidae, Meliponini). Bee colonies were monitored in different seasons over two years. We compared foraging patterns and resource intake between the bees' natural habitat (forests) and two landscapes differently altered by humans (suburban gardens and agricultural macadamia plantations). We found foraging activity as well as pollen and nectar forager numbers to be highest in suburban gardens, intermediate in forests and low in plantations. Foraging patterns further differed between seasons, but seasonal variations strongly differed between landscapes. Sugar and pollen intake was low in plantations, but contrary with our predictions, it was even higher in gardens than in forests. In contrast, resin intake was similar across landscapes. Consequently, differences in resource availability between natural and altered landscapes strongly affect foraging patterns and thus resource intake in social bees. While agricultural monocultures largely reduce foraging success, suburban gardens can increase resource intake well above rates found in natural habitats of bees, indicating that human activities can both decrease and increase the availability of resources in a landscape and thus reduce or enhance bee fitness. KW - urbanization KW - anthropogenic activities KW - climate factors KW - meliponines KW - resource availability Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-162713 VL - 6 IS - 5 ER - TY - JOUR A1 - Becker, Nils A1 - Kucharski, Robert A1 - Rössler, Wolfgang A1 - Maleszka, Ryszard T1 - Age‐dependent transcriptional and epigenomic responses to light exposure in the honey bee brain JF - FEBS Open Bio N2 - Light is a powerful environmental stimulus of special importance in social honey bees that undergo a behavioral transition from in-hive to outdoor foraging duties. Our previous work has shown that light exposure induces structural neuronal plasticity in the mushroom bodies (MBs), a brain center implicated in processing inputs from sensory modalities. Here, we extended these analyses to the molecular level to unravel light-induced transcriptomic and epigenomic changes in the honey bee brain. We have compared gene expression in brain compartments of 1- and 7-day-old light-exposed honey bees with age-matched dark-kept individuals. We have found a number of differentially expressed genes (DEGs), both novel and conserved, including several genes with reported roles in neuronal plasticity. Most of the DEGs show age-related changes in the amplitude of light-induced expression and are likely to be both developmentally and environmentally regulated. Some of the DEGs are either known to be methylated or are implicated in epigenetic processes suggesting that responses to light exposure are at least partly regulated at the epigenome level. Consistent with this idea light alters the DNA methylation pattern of bgm, one of the DEGs affected by light exposure, and the expression of microRNA miR-932. This confirms the usefulness of our approach to identify candidate genes for neuronal plasticity and provides evidence for the role of epigenetic processes in driving the molecular responses to visual stimulation. KW - DNA methylation KW - insect brain KW - light-induced gene expression KW - microRNA KW - neuronal plasticity Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-147080 VL - 6 IS - 7 ER - TY - JOUR A1 - Joschinski, Jens A1 - Beer, Katharina A1 - Helfrich-Förster, Charlotte A1 - Krauss, Jochen T1 - Pea Aphids (Hemiptera: Aphididae) Have Diurnal Rhythms When Raised Independently of a Host Plant JF - Journal of Insect Science N2 - Seasonal timing is assumed to involve the circadian clock, an endogenous mechanism to track time and measure day length. Some debate persists, however, and aphids were among the first organisms for which circadian clock involvement was questioned. Inferences about links to phenology are problematic, as the clock itself is little investigated in aphids. For instance, it is unknown whether aphids possess diurnal rhythms at all. Possibly, the close interaction with host plants prevents independent measurements of rhythmicity. We reared the pea aphid Acyrthosiphon pisum (Harris) on an artificial diet, and recorded survival, moulting, and honeydew excretion. Despite their plant-dependent life style, aphids were independently rhythmic under light–dark conditions. This first demonstration of diurnal aphid rhythms shows that aphids do not simply track the host plant’s rhythmicity. KW - artificial diet KW - circadian clock KW - hourglass clock KW - Acyrthosiphon pisum KW - photoperiodism Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-168783 VL - 16 IS - 1 ER - TY - JOUR A1 - Sommerlandt, Frank M. J. A1 - Spaethe, Johannes A1 - Rössler, Wolfgang A1 - Dyer, Adrian G. T1 - Does Fine Color Discrimination Learning in Free-Flying Honeybees Change Mushroom-Body Calyx Neuroarchitecture? JF - PLoS One N2 - Honeybees learn color information of rewarding flowers and recall these memories in future decisions. For fine color discrimination, bees require differential conditioning with a concurrent presentation of target and distractor stimuli to form a long-term memory. Here we investigated whether the long-term storage of color information shapes the neural network of microglomeruli in the mushroom body calyces and if this depends on the type of conditioning. Free-flying honeybees were individually trained to a pair of perceptually similar colors in either absolute conditioning towards one of the colors or in differential conditioning with both colors. Subsequently, bees of either conditioning groups were tested in non-rewarded discrimination tests with the two colors. Only bees trained with differential conditioning preferred the previously learned color, whereas bees of the absolute conditioning group, and a stimuli-naïve group, chose randomly among color stimuli. All bees were then kept individually for three days in the dark to allow for complete long-term memory formation. Whole-mount immunostaining was subsequently used to quantify variation of microglomeruli number and density in the mushroom-body lip and collar. We found no significant differences among groups in neuropil volumes and total microglomeruli numbers, but learning performance was negatively correlated with microglomeruli density in the absolute conditioning group. Based on these findings we aim to promote future research approaches combining behaviorally relevant color learning tests in honeybees under free-flight conditions with neuroimaging analysis; we also discuss possible limitations of this approach.q KW - bees KW - behavioral conditioning KW - learning KW - color vision KW - vision KW - calyx KW - cognition KW - honey bees Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-147932 VL - 11 IS - 10 ER - TY - JOUR A1 - Mildner, Stephanie A1 - Roces, Flavio T1 - Plasticity of Daily Behavioral Rhythms in Foragers and Nurses of the Ant Camponotus rufipes: Influence of Social Context and Feeding Times JF - PLoS One N2 - Daily activities within an ant colony need precise temporal organization, and an endogenous clock appears to be essential for such timing processes. A clock drives locomotor rhythms in isolated workers in a number of ant species, but its involvement in activities displayed in the social context is unknown. We compared locomotor rhythms in isolated individuals and behavioral rhythms in the social context of workers of the ant Camponotus rufipes. Both forager and nurse workers exhibited circadian rhythms in locomotor activity under constant conditions, indicating the involvement of an endogenous clock. Activity was mostly nocturnal and synchronized with the 12:12h light-dark-cycle. To evaluate whether rhythmicity was maintained in the social context and could be synchronized with non-photic zeitgebers such as feeding times, daily behavioral activities of single workers inside and outside the nest were quantified continuously over 24 hours in 1656 hours of video recordings. Food availability was limited to a short time window either at day or at night, thus mimicking natural conditions of temporally restricted food access. Most foragers showed circadian foraging behavior synchronized with food availability, either at day or nighttime. When isolated thereafter in single locomotor activity monitors, foragers mainly displayed arrhythmicity. Here, high mortality suggested potential stressful effects of the former restriction of food availability. In contrast, nurse workers showed high overall activity levels in the social context and performed their tasks all around the clock with no circadian pattern, likely to meet the needs of the brood. In isolation, the same individuals exhibited in turn strong rhythmic activity and nocturnality. Thus, endogenous activity rhythms were inhibited in the social context, and timing of daily behaviors was flexibly adapted to cope with task demands. As a similar socially-mediated plasticity in circadian rhythms was already shown in honey bees, the temporal organization in C. rufipes and honey bees appear to share similar basic features. KW - honey bees KW - biological locomotion KW - foraging KW - circadian rhythms KW - chronobiology KW - insects KW - nurses KW - ants Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-148010 VL - 12 IS - 1 ER - TY - JOUR A1 - Menzel, Florian A1 - Blüthgen, Nico A1 - Tolasch, Till A1 - Conrad, Jürgen A1 - Beifuss, Uwe A1 - Beuerle, Till A1 - Schmitt, Thomas T1 - Crematoenones - a novel substance class exhibited by ants functions as appeasement signal JF - Frontiers in Zoology N2 - Background: Parasitic, commensalistic, and mutualistic guests in social insect colonies often circumvent their hosts' nestmate recognition system to be accepted. These tolerance strategies include chemical mimicry and chemical insignificance. While tolerance strategies have been studied intensively in social parasites, little is known about these mechanisms in non-parasitic interactions. Here, we describe a strategy used in a parabiotic association, i.e. two mutualistic ant species that regularly share a common nest although they have overlapping food niches. One of them, Crematogaster modiglianii, produces an array of cuticular compounds which represent a substance class undescribed in nature so far. They occur in high abundances, which suggests an important function in the ant's association with its partner Camponotus rufifemur. Results: We elucidated the structure of one of the main compounds from cuticular extracts using gas chromatography, mass spectrometry, chemical derivatizations and nuclear magnetic resonance spectroscopy (NMR). The compound consists of two fused six-membered rings with two alkyl groups, one of which carries a keto functionality. To our knowledge, this is the first report on the identification of this substance class in nature. We suggest naming the compound crematoenone. In behavioural assays, crematoenones reduced interspecific aggression. Camponotus showed less aggression to allospecific cuticular hydrocarbons when combined with crematoenones. Thus, they function as appeasement substances. However, although the crematoenone composition was highly colony-specific, interspecific recognition was mediated by cuticular hydrocarbons, and not by crematoenones. Conclusions: Crematenones enable Crematogaster to evade Camponotus aggression, and thus reduce potential costs from competition with Camponotus. Hence, they seem to be a key factor in the parabiosis, and help Crematogaster to gain a net benefit from the association and thus maintain a mutualistic association over evolutionary time. To our knowledge, putative appeasement substances have been reported only once so far, and never between non-parasitic species. Since most organisms associated with social insects need to overcome their nestmate recognition system, we hypothesize that appeasement substances might play an important role in the evolution and maintenance of other mutualistic associations as well, by allowing organisms to reduce costs from antagonistic behaviour of other species. KW - cuticular hydrocarbons KW - appeasement substance KW - bees KW - ecology KW - parasitism KW - alkyloctahydronaphthalene KW - usurpation KW - venom KW - pheromone KW - crematogaster KW - parabiotic ants KW - Dufours gland KW - polyergus rufescens KW - formicidae KW - interspecific aggression KW - nestmate recognition cues KW - parabiotic association Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-122595 SN - 1742-9994 VL - 10 IS - 32 ER - TY - THES A1 - Herter, Eva Kristine T1 - Characterization of direct Myc target genes in Drosophila melanogaster and Investigating the interaction of Chinmo and Myc T1 - Charakterisierung direkter Myc Zielgene in Drosophila melanogaster und Interaktionsanalyse der Proteine Chinmo und Myc N2 - The correct regulation of cell growth and proliferation is essential during normal animal development. Myc proteins function as transcription factors, being involved in the con-trol of many growth- and proliferation-associated genes and deregulation of Myc is one of the main driving factors of human malignancies. The first part of this thesis focuses on the identification of directly regulated Myc target genes in Drosophila melanogaster, by combining ChIPseq and RNAseq approaches. The analysis results in a core set of Myc target genes of less than 300 genes which are mainly involved in ribosome biogenesis. Among these genes we identify a novel class of Myc targets, the non-coding small nucleolar RNAs (snoRNAs). In vivo studies show that loss of snoRNAs not only impairs growth during normal development, but that overexpression of several snoRNAs can also enhance tumor development in a neu-ronal tumor model. Together the data show that Myc acts as a master regulator of ribo-some biogenesis and that Myc’s transforming effects in tumor development are at least partially mediated by the snoRNAs. In the second part of the thesis, the interaction of Myc and the Zf-protein Chinmo is described. Co-immunoprecipitations of the two proteins performed under endogenous and exogenous conditions show that they interact physically and that neither the two Zf-domains nor the BTB/POZ-domain of Chinmo are important for this interaction. Fur-thermore ChIP experiments and Myc dependent luciferase assays show that Chinmo and Myc share common target genes, and that Chinmo is presumably also involved in their regulation. While the exact way of how Myc and Chinmo genetically interact with each other still has to be investigated, we show that their interaction is important in a tumor model. Overexpression of the tumor-suppressors Ras and Chinmo leads to tu-mor formation in Drosophila larvae, which is drastically impaired upon loss of Myc. N2 - Die korrekte Regulation von Zellwachstum und Proliferation ist von entscheidender Bedeutung für die Entwicklung von Tieren. Myc-Proteine fungieren als Transkriptions-faktoren, die in die Funktionskontrolle vieler Gene eingebunden sind die eine Rolle bei Zellwachstum und Proliferation spielen. Fehlregulierung von Myc ist ein Hauptfaktor menschlicher Tumorbildung. Der erste Teil dieser Dissertation beschäftigt sich mit der Identifizierung direkt regulierter Myc Zielgene in Drosophila melanogaster durch Kombination von ChIPseq und RNAseq Analysen. Insgesamt wurde eine Hauptgruppe von weniger als 300 Myc Ziel-genen identifiziert, von denen der Großteil eine Funktion in der Ribosomen Biogenese hat. Unter diesen Genen haben wir eine neue Klasse an Myc Zielgenen identifiziert, die nicht-codierenden „small nucleolar RNAs“ (snoRNAs). In vivo Experimente zeigen, dass der Verlust der snoRNAs nicht nur das Wachstum während der natürlichen Ent-wicklung beeinträchtigt, sondern auch, dass Überexpression verschiedener snoRNAs die Tumorbildung in einem neuronalen Tumormodel begünstigt. Zusammenfassend zeigen die Daten, dass Myc maßgeblich Ribosomen Biogenese steuert und dass der transformierende Effekt, den Myc in der Tumorentwicklung inne hat, zumindest teilwei-se durch die snoRNAs gesteuert wird. Im zweiten Teil der Arbeit wird die Interaktion von Myc und dem Zink-Finger Protein Chinmo beschrieben. Co-Immunoprezipitationen der zwei Proteine die unter endogenen und exogenen Bedingungen durchgeführt wurden zeigen, dass sie physisch miteinander interagieren und dass weder Chinmos Zf-Domänen noch seine BTB/POZ-Domäne für diese Interaktion verantwortlich sind. ChIP-Versuche und Myc abhängige Luciferase-Assays zeigen weiterhin, dass Chinmo und Myc gemeinsame Zielgene besitzen und dass Chinmo darüber hinaus wahrscheinlich auch an ihrer Regulation beteiligt ist. Während der genaue Zusammenhang der genetischen Interaktionen von Myc und Chinmo noch ungewiss ist und weiterer Untersuchungen bedarf, kann gezeigt werden, dass die Interaktion der beiden Proteine in einem Tumormodel eine Rolle spielt. Die Tumorbildung die durch Überexpression des Tumorsuppressors Ras zusammen mit Chinmo hervorgerufen wird, wird durch den Verlust von Myc stark reduziert. KW - Myc KW - Drosophila melanogaster KW - Transcription KW - snoRNA KW - Ribosome KW - Growth KW - Taufliege KW - Transkription Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-122272 ER - TY - JOUR A1 - Holzschuh, Andrea A1 - Dormann, Carsten F. A1 - Tscharntke, Teja A1 - Steffan-Dewenter, Ingolf T1 - Mass-flowering crops enhance wild bee abundance JF - Oecologia N2 - Although agricultural habitats can provide enormous amounts of food resources for pollinator species, links between agricultural and (semi-)natural habitats through dispersal and foraging movements have hardly been studied. In 67 study sites, we assessed the interactions between mass-flowering oilseed rape fields and semi-natural grasslands at different spatial scales, and their effects on the number of brood cells of a solitary cavity-nesting bee. The probability that the bee Osmia bicornis colonized trap nests in oilseed rape fields increased from 12 to 59 % when grassland was nearby, compared to fields isolated from grassland. In grasslands, the number of brood cells of O. bicornis in trap nests was 55 % higher when adjacent to oilseed rape compared to isolated grasslands. The percentage of oilseed rape pollen in the larval food was higher in oilseed rape fields and grasslands adjacent to oilseed rape than in isolated grasslands. In both oilseed rape fields and grasslands, the number of brood cells was positively correlated with the percentage of oilseed rape pollen in the larval food. We show that mass-flowering agricultural habitats—even when they are intensively managed—can strongly enhance the abundance of a solitary bee species nesting in nearby semi-natural habitats. Our results suggest that positive effects of agricultural habitats have been underestimated and might be very common (at least) for generalist species in landscapes consisting of a mixture of agricultural and semi-natural habitats. These effects might also have—so far overlooked—implications for interspecific competition and mutualistic interactions in semi-natural habitats. KW - spillover KW - trap nests KW - pollen KW - oilseed rape KW - canola Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-126852 VL - 172 IS - 2 ER - TY - JOUR A1 - Azzami, Klara A1 - Ritter, Wolfgang A1 - Tautz, Jürgen A1 - Beier, Hildburg T1 - Infection of honey bees with acute bee paralysis virus does not trigger humoral or cellular immune responses JF - Archives of Virology N2 - We have studied the responses of honey bees at different life stages (Apis mellifera) to controlled infection with acute bee paralysis virus and have identified the haemolymph of infected larvae and adult worker bees as the compartment where massive propagation of ABPV occurs. Insects respond with a broad spectrum of induced innate immune reactions to bacterial infections, whereas defence mechanisms based on RNA interference play a major role in antiviral immunity. In this study, we have determined that honey bee larvae and adult workers do not produce a humoral immune reaction upon artificial infection with ABPV, in contrast to control individuals challenged with Escherichia coli. ABPV-infected bees produced neither elevated levels of specific antimicrobial peptides (AMPs), such as hymenoptaecin and defensin, nor any general antimicrobial activity, as revealed by inhibition-zone assays. Additionally, adult bees did not generate melanised nodules upon ABPV infection, an important cellular immune function activated by bacteria and viruses in some insects. Challenge of bees with both ABPV and E. coli showed that innate humoral and cellular immune reactions are induced in mixed infections, albeit at a reduced level. KW - chemosensory protein KW - bee larva KW - adult bee KW - honey bee KW - larva KW - work bee KW - infected bee KW - immune response KW - young work bee KW - capsid protein KW - abdominal KW - tergite KW - haemolymph KW - sample KW - Imd pathway KW - worker bee larva KW - antimicrobial KW - peptide Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-126863 VL - 157 IS - 4 ER - TY - JOUR A1 - Dusik, Verena A1 - Senthilan, Pingkalai R. A1 - Mentzel, Benjamin A1 - Hartlieb, Heiko A1 - Wülbeck, Corina A1 - Yoshii, Taishi A1 - Raabe, Thomas A1 - Helfrich-Förster, Charlotte T1 - The MAP Kinase p38 Is Part of Drosophila melanogaster's Circadian Clock JF - PLoS Genetics N2 - All organisms have to adapt to acute as well as to regularly occurring changes in the environment. To deal with these major challenges organisms evolved two fundamental mechanisms: the p38 mitogen-activated protein kinase (MAPK) pathway, a major stress pathway for signaling stressful events, and circadian clocks to prepare for the daily environmental changes. Both systems respond sensitively to light. Recent studies in vertebrates and fungi indicate that p38 is involved in light-signaling to the circadian clock providing an interesting link between stress-induced and regularly rhythmic adaptations of animals to the environment, but the molecular and cellular mechanisms remained largely unknown. Here, we demonstrate by immunocytochemical means that p38 is expressed in Drosophila melanogaster's clock neurons and that it is activated in a clock-dependent manner. Surprisingly, we found that p38 is most active under darkness and, besides its circadian activation, additionally gets inactivated by light. Moreover, locomotor activity recordings revealed that p38 is essential for a wild-type timing of evening activity and for maintaining ∼ 24 h behavioral rhythms under constant darkness: flies with reduced p38 activity in clock neurons, delayed evening activity and lengthened the period of their free-running rhythms. Furthermore, nuclear translocation of the clock protein Period was significantly delayed on the expression of a dominant-negative form of p38b in Drosophila's most important clock neurons. Western Blots revealed that p38 affects the phosphorylation degree of Period, what is likely the reason for its effects on nuclear entry of Period. In vitro kinase assays confirmed our Western Blot results and point to p38 as a potential "clock kinase" phosphorylating Period. Taken together, our findings indicate that the p38 MAP Kinase is an integral component of the core circadian clock of Drosophila in addition to playing a role in stress-input pathways. KW - in vitro kinase assay KW - biological locomotion KW - circadian oscillators KW - MAPK signaling cascades KW - circadian rhythms KW - drosophila melanogaster KW - neurons KW - phosphorylation Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-119433 SN - 1553-7404 VL - 10 IS - 8 ER - TY - JOUR A1 - Zhang, Shaowu A1 - Si, Aung A1 - Pahl, Mario T1 - Visually guided decision making in foraging honeybees JF - Frontiers in Neuroscience N2 - Honeybees can easily be trained to perform different types of discrimination tasks under controlled laboratory conditions. This review describes a range of experiments carried out with free-flying forager honeybees under such conditions. The research done over the past 30 or so years suggests that cognitive abilities (learning and perception) in insects are more intricate and flexible than was originally imagined. It has become apparent that honeybees are capable of a variety of visually guided tasks, involving decision making under challenging situations: this includes simultaneously making use of different sensory modalities, such as vision and olfaction, and learning to use abstract concepts such as “sameness” and “difference.” Many studies have shown that decision making in foraging honeybees is highly flexible. The trained animals learn how to solve a task, and do so with a high accuracy, but when they are presented with a new variation of the task, they apply the learnt rules from the earlier setup to the new situation, and solve the new task as well. Honeybees therefore not only feature a rich behavioral repertoire to choose from, but also make decisions most apt to the current situation. The experiments in this review give an insight into the environmental cues and cognitive resources that are probably highly significant for a forager bee that must continually make decisions regarding patches of resources to be exploited. Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-124228 VL - 6 IS - 88 ER - TY - JOUR A1 - Herter, Eva K. A1 - Stauch, Maria A1 - Gallant, Maria A1 - Wolf, Elmar A1 - Raabe, Thomas A1 - Gallant, Peter T1 - snoRNAs are a novel class of biologically relevant Myc targets JF - BMC Biology N2 - Background Myc proteins are essential regulators of animal growth during normal development, and their deregulation is one of the main driving factors of human malignancies. They function as transcription factors that (in vertebrates) control many growth- and proliferation-associated genes, and in some contexts contribute to global gene regulation. Results We combine chromatin immunoprecipitation-sequencing (ChIPseq) and RNAseq approaches in Drosophila tissue culture cells to identify a core set of less than 500 Myc target genes, whose salient function resides in the control of ribosome biogenesis. Among these genes we find the non-coding snoRNA genes as a large novel class of Myc targets. All assayed snoRNAs are affected by Myc, and many of them are subject to direct transcriptional activation by Myc, both in Drosophila and in vertebrates. The loss of snoRNAs impairs growth during normal development, whereas their overexpression increases tumor mass in a model for neuronal tumors. Conclusions This work shows that Myc acts as a master regulator of snoRNP biogenesis. In addition, in combination with recent observations of snoRNA involvement in human cancer, it raises the possibility that Myc’s transforming effects are partially mediated by this class of non-coding transcripts. KW - Drosophila KW - ribosome KW - snoRNA KW - Myc Transcription KW - growth Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-124956 VL - 13 IS - 25 ER - TY - JOUR A1 - Lichtenstein, Leonie A1 - Sommerlandt, Frank M. J. A1 - Spaethe, Johannes T1 - Dumb and Lazy? A Comparison of Color Learning and Memory Retrieval in Drones and Workers of the Buff-Tailed Bumblebee, Bombus terrestris, by Means of PER Conditioning JF - PLoS One N2 - More than 100 years ago, Karl von Frisch showed that honeybee workers learn and discriminate colors. Since then, many studies confirmed the color learning capabilities of females from various hymenopteran species. Yet, little is known about visual learning and memory in males despite the fact that in most bee species males must take care of their own needs and must find rewarding flowers to obtain food. Here we used the proboscis extension response (PER) paradigm to study the color learning capacities of workers and drones of the bumblebee, Bombus terrestris. Light stimuli were paired with sucrose reward delivered to the insects’ antennae and inducing a reflexive extension of the proboscis. We evaluated color learning (i.e. conditioned PER to color stimuli) in absolute and differential conditioning protocols and mid-term memory retention was measured two hours after conditioning. Different monochromatic light stimuli in combination with neutral density filters were used to ensure that the bumblebees could only use chromatic and not achromatic (e.g. brightness) information. Furthermore, we tested if bees were able to transfer the learned information from the PER conditioning to a novel discrimination task in a Y-maze. Both workers and drones were capable of learning and discriminating between monochromatic light stimuli and retrieved the learned stimulus after two hours. Drones performed as well as workers during conditioning and in the memory test, but failed in the transfer test in contrast to workers. Our data clearly show that bumblebees can learn to associate a color stimulus with a sugar reward in PER conditioning and that both workers and drones reach similar acquisition and mid-term retention performances. Additionally, we provide evidence that only workers transfer the learned information from a Pavlovian to an operant situation. KW - memory KW - bumblebees KW - behavioral conditioning KW - honey bees KW - flowers KW - sucrose KW - bees KW - learning Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-125832 VL - 10 IS - 7 ER - TY - JOUR A1 - Strube-Bloss, Martin F. A1 - Brown, Austin A1 - Spaethe, Johannes A1 - Schmitt, Thomas A1 - Rössler, Wolfgang T1 - Extracting the Behaviorally Relevant Stimulus: Unique Neural Representation of Farnesol, a Component of the Recruitment Pheromone of Bombus terrestris JF - PLoS One N2 - To trigger innate behavior, sensory neural networks are pre-tuned to extract biologically relevant stimuli. Many male-female or insect-plant interactions depend on this phenomenon. Especially communication among individuals within social groups depends on innate behaviors. One example is the efficient recruitment of nest mates by successful bumblebee foragers. Returning foragers release a recruitment pheromone in the nest while they perform a ‘dance’ behavior to activate unemployed nest mates. A major component of this pheromone is the sesquiterpenoid farnesol. How farnesol is processed and perceived by the olfactory system, has not yet been identified. It is much likely that processing farnesol involves an innate mechanism for the extraction of relevant information to trigger a fast and reliable behavioral response. To test this hypothesis, we used population response analyses of 100 antennal lobe (AL) neurons recorded in alive bumblebee workers under repeated stimulation with four behaviorally different, but chemically related odorants (geraniol, citronellol, citronellal and farnesol). The analysis identified a unique neural representation of the recruitment pheromone component compared to the other odorants that are predominantly emitted by flowers. The farnesol induced population activity in the AL allowed a reliable separation of farnesol from all other chemically related odor stimuli we tested. We conclude that the farnesol induced population activity may reflect a predetermined representation within the AL-neural network allowing efficient and fast extraction of a behaviorally relevant stimulus. Furthermore, the results show that population response analyses of multiple single AL-units may provide a powerful tool to identify distinct representations of behaviorally relevant odors. KW - instinct KW - plant-insect interactions KW - pheromones KW - bumblebees KW - odorants KW - principal component analysis KW - neurons KW - action potentials Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-125875 VL - 10 IS - 9 ER - TY - JOUR A1 - Leonhardt, Sara D. A1 - Kaltenpoth, Martin T1 - Microbial Communities of Three Sympatric Australian Stingless Bee Species JF - PLoS ONE N2 - Bacterial symbionts of insects have received increasing attention due to their prominent role in nutrient acquisition and defense. In social bees, symbiotic bacteria can maintain colony homeostasis and fitness, and the loss or alteration of the bacterial community may be associated with the ongoing bee decline observed worldwide. However, analyses of microbiota associated with bees have been largely confined to the social honeybees (Apis mellifera) and bumblebees (Bombus spec.), revealing – among other taxa – host-specific lactic acid bacteria (LAB, genus Lactobacillus) that are not found in solitary bees. Here, we characterized the microbiota of three Australian stingless bee species (Apidae: Meliponini) of two phylogenetically distant genera (Tetragonula and Austroplebeia). Besides common plant bacteria, we find LAB in all three species, showing that LAB are shared by honeybees, bumblebees and stingless bees across geographical regions. However, while LAB of the honeybee-associated Firm4–5 clusters were present in Tetragonula, they were lacking in Austroplebeia. Instead, we found a novel clade of likely host-specific LAB in all three Australian stingless bee species which forms a sister clade to a large cluster of Halictidae-associated lactobacilli. Our findings indicate both a phylogenetic and geographical signal of host-specific LAB in stingless bees and highlight stingless bees as an interesting group to investigate the evolutionary history of the bee-LAB association. KW - bacteria KW - lactic acid bacteria KW - sequence alignment KW - insects KW - lactobacillus KW - sequence databases KW - honey bees Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-119341 VL - 9 IS - 8 ER - TY - JOUR A1 - Yilmaz, Ayse A1 - Aksoy, Volkan A1 - Camlitepe, Yilmaz A1 - Giurfa, Martin T1 - Eye structure, activity rhythms, and visually-driven behavior are tuned to visual niche in ants JF - Frontiers in Behavioral Neuroscience N2 - Insects have evolved physiological adaptations and behavioral strategies that allow them to cope with a broad spectrum of environmental challenges and contribute to their evolutionary success. Visual performance plays a key role in this success. Correlates between life style and eye organization have been reported in various insect species. Yet, if and how visual ecology translates effectively into different visual discrimination and learning capabilities has been less explored. Here we report results from optical and behavioral analyses performed in two sympatric ant species, Formica cunicularia and Camponotus aethiops. We show that the former are diurnal while the latter are cathemeral. Accordingly, F. cunicularia workers present compound eyes with higher resolution, while C. aethiops workers exhibit eyes with lower resolution but higher sensitivity. The discrimination and learning of visual stimuli differs significantly between these species in controlled dual-choice experiments: discrimination learning of small-field visual stimuli is achieved by F. cunicularia but not by C. aethiops, while both species master the discrimination of large-field visual stimuli. Our work thus provides a paradigmatic example about how timing of foraging activities and visual environment match the organization of compound eyes and visually-driven behavior. This correspondence underlines the relevance of an ecological/evolutionary framework for analyses in behavioral neuroscience. KW - visual learning KW - ant KW - activity rhythm KW - camponotus aethiops KW - formica cunicularia KW - compound eye Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-119595 VL - 8 ER - TY - JOUR A1 - Stejskal, Kerstin A1 - Streinzer, Martin A1 - Dyer, Adrian A1 - Paulus, Hannes F. A1 - Spaethe, Johannes T1 - Functional Significance of Labellum Pattern Variation in a Sexually Deceptive Orchid (Ophrys heldreichii): Evidence of Individual Signature Learning Effects JF - PLoS One N2 - Mimicking female insects to attract male pollinators is an important strategy in sexually deceptive orchids of the genus Ophrys, and some species possess flowers with conspicuous labellum patterns. The function of the variation of the patterns remains unresolved, with suggestions that these enhance pollinator communication. We investigated the possible function of the labellum pattern in Ophrys heldreichii, an orchid species in which the conspicuous and complex labellum pattern contrasts with a dark background. The orchid is pollinated exclusively by males of the solitary bee, Eucera berlandi. Comparisons of labellum patterns revealed that patterns within inflorescences are more similar than those of other conspecific plants. Field observations showed that the males approach at a great speed and directly land on flowers, but after an unsuccessful copulation attempt, bees hover close and visually scan the labellum pattern for up to a minute. Learning experiments conducted with honeybees as an accessible model of bee vision demonstrated that labellum patterns of different plants can be reliably learnt; in contrast, patterns of flowers from the same inflorescence could not be discriminated. These results support the hypothesis that variable labellum patterns in O. heldreichii are involved in flower-pollinator communication which would likely help these plants to avoid geitonogamy. KW - nectar KW - color discrimination KW - bees KW - vision KW - evolution KW - pollination KW - guides KW - honeybee KW - apis mellifera KW - insects KW - signals KW - recognize images Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-137582 VL - 10 IS - 11 ER - TY - JOUR A1 - Partho, Halder A1 - Chen, Yi-chun A1 - Brauckhoff, Janine A1 - Hofbauer, Alois A1 - Dabauvalle, Marie-Christine A1 - Lewandrowski, Urs A1 - Winkler, Christiane A1 - Sickmann, Albert A1 - Buchner, Erich T1 - Identification of Eps15 as Antigen Recognized by the Monoclonal Antibodies aa2 and ab52 of the Wuerzburg Hybridoma Library against Drosophila Brain JF - PLoS One N2 - The Wuerzburg Hybridoma Library against the Drosophila brain represents a collection of around 200 monoclonal antibodies that bind to specific structures in the Drosophila brain. Here we describe the immunohistochemical staining patterns, the Western blot signals of one- and two-dimensional electrophoretic separation, and the mass spectrometric characterization of the target protein candidates recognized by the monoclonal antibodies aa2 and ab52 from the library. Analysis of a mutant of a candidate gene identified the Drosophila homolog of the Epidermal growth factor receptor Pathway Substrate clone 15 (Eps15) as the antigen for these two antibodies. KW - neuropil KW - immunohistochemistry techniques KW - gel electrophoresis KW - immunoprecipitation KW - silver staining KW - drosophila melanogaster KW - antigen processing and recognition KW - hybridomas Y1 - 2011 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-137957 VL - 6 IS - 12 ER - TY - JOUR A1 - Rössler, Wolfgang A1 - Brill, Martin F. T1 - Parallel processing in the honeybee olfactory pathway: structure, function, and evolution JF - Journal of Comparative Physiology A N2 - Animals face highly complex and dynamic olfactory stimuli in their natural environments, which require fast and reliable olfactory processing. Parallel processing is a common principle of sensory systems supporting this task, for example in visual and auditory systems, but its role in olfaction remained unclear. Studies in the honeybee focused on a dual olfactory pathway. Two sets of projection neurons connect glomeruli in two antennal-lobe hemilobes via lateral and medial tracts in opposite sequence with the mushroom bodies and lateral horn. Comparative studies suggest that this dual-tract circuit represents a unique adaptation in Hymenoptera. Imaging studies indicate that glomeruli in both hemilobes receive redundant sensory input. Recent simultaneous multi-unit recordings from projection neurons of both tracts revealed widely overlapping response profiles strongly indicating parallel olfactory processing. Whereas lateral-tract neurons respond fast with broad (generalistic) profiles, medial-tract neurons are odorant specific and respond slower. In analogy to “what-” and “where” subsystems in visual pathways, this suggests two parallel olfactory subsystems providing “what-” (quality) and “when” (temporal) information. Temporal response properties may support across-tract coincidence coding in higher centers. Parallel olfactory processing likely enhances perception of complex odorant mixtures to decode the diverse and dynamic olfactory world of a social insect. KW - multi-unit recording KW - antennal lobe KW - glomeruli KW - projection neurons KW - mushroom bodies Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-132548 VL - 199 ER - TY - JOUR A1 - Holzschuh, Andrea A1 - Dormann, Carsten F. A1 - Tscharntke, Teja A1 - Steffan-Dewenter, Ingolf T1 - Mass-flowering crops enhance wild bee abundance JF - Oecologia N2 - Although agricultural habitats can provide enormous amounts of food resources for pollinator species, links between agricultural and (semi-)natural habitats through dispersal and foraging movements have hardly been studied. In 67 study sites, we assessed the interactions between mass-flowering oilseed rape fields and semi-natural grasslands at different spatial scales, and their effects on the number of brood cells of a solitary cavity-nesting bee. The probability that the bee Osmia bicornis colonized trap nests in oilseed rape fields increased from 12 to 59 % when grassland was nearby, compared to fields isolated from grassland. In grasslands, the number of brood cells of O. bicornis in trap nests was 55 % higher when adjacent to oilseed rape compared to isolated grasslands. The percentage of oilseed rape pollen in the larval food was higher in oilseed rape fields and grasslands adjacent to oilseed rape than in isolated grasslands. In both oilseed rape fields and grasslands, the number of brood cells was positively correlated with the percentage of oilseed rape pollen in the larval food. We show that mass-flowering agricultural habitats—even when they are intensively managed—can strongly enhance the abundance of a solitary bee species nesting in nearby semi-natural habitats. Our results suggest that positive effects of agricultural habitats have been underestimated and might be very common (at least) for generalist species in landscapes consisting of a mixture of agricultural and semi-natural habitats. These effects might also have—so far overlooked—implications for interspecific competition and mutualistic interactions in semi-natural habitats. KW - spillover KW - pollen KW - oilseed rape KW - canola KW - trap nests Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-132149 VL - 172 IS - 2 ER - TY - JOUR A1 - Hendriksma, Harmen P. A1 - Küting, Meike A1 - Härtel, Stephan A1 - Näther, Astrid A1 - Dohrmann, Anja B. A1 - Steffan-Dewenter, Ingolf A1 - Tebbe, Christoph C. T1 - Effect of Stacked Insecticidal Cry Proteins from Maize Pollen on Nurse Bees (Apis mellifera carnica) and Their Gut Bacteria JF - PLoS ONE N2 - Honey bee pollination is a key ecosystem service to nature and agriculture. However, biosafety research on genetically modified crops rarely considers effects on nurse bees from intact colonies, even though they receive and primarily process the largest amount of pollen. The objective of this study was to analyze the response of nurse bees and their gut bacteria to pollen from Bt maize expressing three different insecticidal Cry proteins (Cry1A.105, Cry2Ab2, and Cry3Bb1). Naturally Cry proteins are produced by bacteria (Bacillus thuringiensis). Colonies of Apis mellifera carnica were kept during anthesis in flight cages on field plots with the Bt maize, two different conventionally bred maize varieties, and without cages, 1-km outside of the experimental maize field to allow ad libitum foraging to mixed pollen sources. During their 10-days life span, the consumption of Bt maize pollen had no effect on their survival rate, body weight and rates of pollen digestion compared to the conventional maize varieties. As indicated by ELISA-quantification of Cry1A.105 and Cry3Bb1, more than 98% of the recombinant proteins were degraded. Bacterial population sizes in the gut were not affected by the genetic modification. Bt-maize, conventional varieties and mixed pollen sources selected for significantly different bacterial communities which were, however, composed of the same dominant members, including Proteobacteria in the midgut and Lactobacillus sp. and Bifidobacterium sp. in the hindgut. Surprisingly, Cry proteins from natural sources, most likely B. thuringiensis, were detected in bees with no exposure to Bt maize. The natural occurrence of Cry proteins and the lack of detectable effects on nurse bees and their gut bacteria give no indication for harmful effects of this Bt maize on nurse honey bees. KW - communities KW - 16S ribosomal-RNA KW - T-RFLP analysis KW - honey bees KW - bacillus thuringiensis KW - risk assessment KW - multivariate analyses KW - worker honeybees KW - corn pollen KW - larvae Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-131025 VL - 8 IS - 3 ER - TY - JOUR A1 - Scharmann, Mathias A1 - Thornham, Daniel G. A1 - Grafe, T. Ulmar A1 - Federle, Walter T1 - A Novel Type of Nutritional Ant-Plant Interaction: Ant Partners of Carnivorous Pitcher Plants Prevent Nutrient Export by Dipteran Pitcher Infauna JF - PLoS ONE N2 - Many plants combat herbivore and pathogen attack indirectly by attracting predators of their herbivores. Here we describe a novel type of insect-plant interaction where a carnivorous plant uses such an indirect defence to prevent nutrient loss to kleptoparasites. The ant Camponotus schmitzi is an obligate inhabitant of the carnivorous pitcher plant Nepenthes bicalcarata in Borneo. It has recently been suggested that this ant-plant interaction is a nutritional mutualism, but the detailed mechanisms and the origin of the ant-derived nutrient supply have remained unexplained. We confirm that N. bicalcarata host plant leaves naturally have an elevated \(^{15}N/^{14}N\) stable isotope abundance ratio (\(\delta ^{15}N\)) when colonised by C. schmitzi. This indicates that a higher proportion of the plants' nitrogen is insect-derived when C. schmitzi ants are present (ca. 100%, vs. 77% in uncolonised plants) and that more nitrogen is available to them. We demonstrated direct flux of nutrients from the ants to the host plant in a \(^{15}N\) pulse-chase experiment. As C. schmitzi ants only feed on nectar and pitcher contents of their host, the elevated foliar \(\delta ^{15}N\) cannot be explained by classic ant-feeding (myrmecotrophy) but must originate from a higher efficiency of the pitcher traps. We discovered that C. schmitzi ants not only increase the pitchers' capture efficiency by keeping the pitchers' trapping surfaces clean, but they also reduce nutrient loss from the pitchers by predating dipteran pitcher inhabitants (infauna). Consequently, nutrients the pitchers would have otherwise lost via emerging flies become available as ant colony waste. The plants' prey is therefore conserved by the ants. The interaction between C. schmitzi, N. bicalcarata and dipteran pitcher infauna represents a new type of mutualism where animals mitigate the damage by nutrient thieves to a plant. KW - community KW - alternative trapping strategies KW - leaf-litter utilization KW - nepenthes bicalcarata KW - camponotus schmitzi KW - food web KW - epiphytic fern KW - nitrogen KW - prey KW - rafflesiana Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-130952 VL - 8 IS - 5 ER - TY - JOUR A1 - Moll, Karin A1 - Roces, Flavio A1 - Federle, Walter T1 - How Load-Carrying Ants Avoid Falling Over: Mechanical Stability during Foraging in Atta vollenweideri Grass-Cutting Ants JF - PLoS ONE N2 - Background: Foraging workers of grass-cutting ants (Atta vollenweideri) regularly carry grass fragments larger than their Fragment length has been shown to influence the ants' running speed and thereby the colony's food intake rate. We investigated whether and how grass-cutting ants maintain stability when carrying fragments of two different lengths but identical mass. Principal Findings: Ants carried all fragments in an upright, backwards-tilted position, but held long fragments more vertically than short ones. All carrying ants used an alternating tripod gait, where mechanical stability was increased by overlapping stance phases of consecutive steps. The overlap was greatest for ants carrying long fragments, resulting in more legs contacting the ground simultaneously. For all ants, the projection of the total centre of mass (ant and fragment) was often outside the supporting tripod, i.e. the three feet that would be in stance for a non-overlapping tripod gait. Stability was only achieved through additional legs in ground contact. Tripod stability (quantified as the minimum distance of the centre of mass to the edge of the supporting tripod) was significantly smaller for ants with long fragments. Here, tripod stability was lowest at the beginning of each step, when the center of mass was near the posterior margin of the supporting tripod. By contrast, tripod stability was lowest at the end of each step for ants carrying short fragments. Consistently, ants with long fragments mainly fell backwards, whereas ants carrying short fragments mainly fell forwards or to the side. Assuming that transporting ants adjust neither the fragment angle nor the gait, they would be less stable and more likely to fall over. Conclusions: In grass-cutting ants, the need to maintain static stability when carrying long grass fragments has led to multiple kinematic adjustments at the expense of a reduced material transport rate. KW - selection KW - tissue transport KW - stepping patterns KW - size determination KW - leaf-cutter ants KW - locomotion KW - distance KW - formicidae KW - strategies KW - cephalotes Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-131211 VL - 8 IS - 1 ER - TY - JOUR A1 - Sommerlandt, F. M. J. A1 - Huber, W. A1 - Spaethe, J. T1 - Social Information in the Stingless Bee, Trigona corvina Cockerell (Hymenoptera: Apidae): The Use of Visual and Olfactory Cues at the Food Site JF - Sociobiology N2 - For social insects, colony performance is largely dependent on the quantity and quality of food intake and thus on the efficiency of its foragers. In addition to innate preferences and previous experience, foragers can use social information to decide when and where to forage. In some stingless bee (Meliponini) species, individual foraging decisions are shown to be influenced by the presence of social information at resource sites. In dual choice tests, we studied whether visual and/or olfactory cues affect individual decision-making in rigona corvina Cockerell and if this information is species-specific. We found that T. corvina foragers possess local enhancement: they are attracted by olfactory and visual cues released by conspecifics but avoid feeders associated with heterospecific individuals of the species Tetragona ziegleri (Friese). Overall, olfactory cues seem to be more important than visual cues, but information by visual cues alone is sufficient for discrimination. KW - visual cues KW - recruitment KW - local enhancement KW - odor marks KW - communication Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-118120 VL - 61 IS - 4 ER - TY - THES A1 - Brill, Martin Fritz T1 - Processing and plasticity within the dual olfactory pathway in the honeybee brain T1 - Verarbeitung und Plastizität in der dualen olfaktorischen Bahn im Gehirn der Honigbiene N2 - In their natural environment animals face complex and highly dynamic olfactory input. This requires fast and reliable processing of olfactory information, in vertebrates as well as invertebrates. Parallel processing has been shown to improve processing speed and power in other sensory systems like auditory or visual. In the olfactory system less is known about olfactory coding in general and parallel processing in particular. With its elaborated olfactory system and due to their specialized neuroanatomy, honeybees are well-suited model organism to study parallel olfactory processing. The honeybee possesses a unique neuronal architecture - a dual olfactory pathway. Two mirror-imaged output projection neuron (PN) pathways connect the first olfactory processing stage, the antennal lobe (analog to the vertebrates olfactory bulb, OB), with the second, the mushroom body (MB) known to be involved in orientation and learning and memory, and the lateral horn (LH). The medial antennal lobe-protocerebral tract (m-APT) first innervates the MB and thereafter the LH, while the other, the lateral-APT (l-APT) projects in opposite direction. The neuroanatomy and evolution of these pathways has been analyzed, yet little is known about its physiology. To analyze the function of the dual olfactory pathway a new established recording method was designed and is described in the first chapter of this thesis (multi-unit-recordings). This is now the first time where odor response from several PNs of both tracts is recorded simultaneously and with high temporal precision. In the second chapter the PN odor responses are analyzed. The major findings are: both tracts responded to all tested odors but with differing characteristics. Since recent studies describe the input to the two tracts being rather similar, the results now indicate differential odor processing along the tracts, therefore this is a good indicator for parallel processing. PNs of the m-APT process odors in a sparse manner with delayed response latencies, but with high odor-specificity. PNs of the l-APT in contrast respond to several odor stimuli and respond in general faster. In some PN originating from both tracts, characteristics of odor-identity coding via response latencies were found. Analyzing the over-all dynamic range of the PNs both l- and m-APT PNs were tested over a large odor concentration range (10-6 to 10-2) (3. chapter). The PNs responded with linear and non-linear correlation of the response strength to the odor concentration. In most cases the l-APT is comparatively more sensitive to low odor concentrations. Response latency decreases with increasing odor concentration in both tracts. Alternative coding principles and elaboration on the hypothesis whether the dual olfactory pathway may contribute coincidental innervation to the next higher-order neurons, the Kenyon cells (KC), is subject of the 4. chapter. Cross-correlations and synchronous responses of both tracts show that in principle odors may be coded via temporal coding. Results suggest that odor processing is enhanced if both tracts contribute to olfactory coding together. In another project the distribution of the inhibitory neurotransmitter GABA (gamma-aminobutyric acid) was measured in the bee’s MB during adult maturation (5. chapter). GABAergic inhibition is of high importance in odor coding. An almost threefold decrease in the total amount of GABAergic innervation was found during adult maturation in the l- and m-APT target region, in particular at the change in division of labor during the transition from a young nurse bee to an older forager bee. The results fit well into the current understanding of brain development in the honeybee and other social insects during adult maturation, which was described as presynaptic pruning and KC dendritic outgrowth. Combining anatomical and functional properties of the bee’s dual olfactory pathway suggests that both rate and temporal coding are implemented along two parallel streams. Comparison with recent work on analog output pathways of the vertebrate’s OB indicates that parallel processing of olfactory information may be a common principle across distant taxa. N2 - In ihrem natürlichen Lebensraum sind Lebewesen mit komplexen und hoch dynamischen olfaktorischen Reizen konfrontiert, was eine schnelle und zuverlässige Duft-Verarbeitung sowohl bei Insekten als auch bei Wirbeltieren erfordert. Im visuellen oder auditorischen System wird sensorischer Eingang durch Parallel-Verarbeitung schneller und effektiver an höhere Gehirnzentren übertragen und verarbeitet. Im olfaktorischen System ist generell und im speziellen über Parallel-Verarbeitung noch wenig bekannt. Die Honigbiene stellt jedoch mit ihrer hoch spezialisierten Duftwahrnehmung und ihrem Duft und Pheromon gesteuerten Verhalten aufgrund ihrer Neuroanatomie einen besonderen Modelorganismus für die Erforschung der Duftverarbeitung und insbesondere der olfaktorischen Parallel-Verarbeitung dar. Honigbienen besitzen „duale olfaktorische Bahnen“, die ausschließlich in Hymenopteren (Bienen, Ameisen, Wespen) als Merkmal ausgeprägt sind. Gebildet werden sie aus zwei spiegelbildlichen Projektions-Neuronen (PN) Ausgangs-Trakten, die das erste olfaktorische Verarbeitungs-Zentrum, den Antennal-Lobus (vergleichbar mit dem Olfaktorischen Bulbus der Wirbeltiere, OB) mit sekundären Verarbeitungszentren, dem Pilzkörper (MB) und dem lateralen Horn (LH) verbinden. Der mediale Antennal-Lobusprotocerebrale Trakt (m-APT) innerviert erst den MB und dann das LH, der laterale Trakt (l-APT) projiziert in umgekehrter Reihenfolge. Der MB ist bei Orientierung, Lernen und Gedächtnis involviert, über die Funktion des LH ist in der Biene noch wenig bekannt. Über die Neuroanatomie und Evolution dieser dualen Bahnen wurde viel geforscht, die Funktion und damit ihre Physiologie sind allerdings noch unzureichend aufgeklärt. Die vorliegende Dissertation beschäftigt sich deshalb mit der Duftverarbeitung im Bienengehirn und im Speziellen mit Parallelverarbeitung in der Olfaktorik. Für die Aufklärung wurde eine neu entwickelte und in dieser Dissertation beschriebene Messmethode etabliert (1. Kapitel). Mit Hilfe dieser Messapparatur (Multi-Unit Recordings) ist es jetzt das erste Mal möglich, hoch-zeitaufgelöst simultan aus beiden Trakten mehrere PNs auf unterschiedliche Düfte hin zu untersuchen. Das 2. Kapitel beschäftigt sich eingehender mit der Analyse von Duftanworten der PN. Die Hauptergebnisse sind, dass beide Trakte auf alle getesteten Düfte regieren, dies aber mit unterschiedlichen Charakteristiken tun. Da gezeigt wurde, dass beide Trakte ähnlichen olfaktorischen Eingang erhalten, die Trakte aber Düfte unterschiedlich verarbeiten, stellen diese Ergebnisse ein erstes Indiz für Parallelverarbeitung im olfaktorischen System der Biene dar. M-APT PN reagieren mit Zeitverzögerung und duftspezifisch, d.h. selektiver auf Düfte. Dagegen reagieren l-APT PN vergleichsweise schneller und duft-unspezifischer auf die in dieser Arbeit verwendeten Düfte. In einigen PN beider Trakte wurde gefunden, dass die PN Duft-Identitäten über duftspezifische Antwort-Latenzen abgebildet werden können. Um Aufschluss über die Gesamtdynamik der PN zu gewinnen, wurden l- und m-APT PN Antworten über weite Duftkonzentrationen (10-6 bis 10-2) hin untersucht (3. Kapitel). Die PN reagierten mit linearen und nicht-linearen Korrelationen. Zudem sind in den meisten Fällen l-APT PN bei schwachen Duftkonzentrationen sensitiver. Die Antwort-Latenz ist zur Duftkonzentration in beiden Trakten negativ-proportional. Alternative Kodierungsmöglichkeiten und die Ausarbeitung der Hypothese, dass die dualen Bahnen eine Koinzidenzverschaltung auf die nächst höheren Neurone, die Kenyon Zellen (KC), bilden könnten, wird im 4. Kapitel behandelt. Dazu zeigen Kreuz-Korrelationsanalysen und synchrone Antwortmuster aus beiden Trakten, dass prinzipiell Düfte auch über Zeit-Kodierung verarbeitet werden können. Generell zeigt sich, dass die dualen olfaktorischen Bahnen eine verbesserte Duftkodierung gegenüber einem Trakt gewährleisten. In einem weiteren Ansatz wurde die alterskorrelierte Plastizität der inhibitorischen GABAergen (gamma-Aminobuttersäure) Innervation im Pilzkörper der Biene während der Adult-Reifung bestimmt (5. Kapitel). Inhibition ist für olfaktorische Kodierung sehr wichtig. Eine fast dreifache Reduktion in der Gesamtmenge von GABA wurde während der Adult-Reifung in beiden Zielregionen der dualen olfaktorischen Bahn gleichermaßen gefunden. Dieser Effekt wurde mit einer insgesamt halbierten GABA Innervierung ebenfalls im visuellen Innervationsgebiet des MB gefunden. Die Ergebnisse passen gut in das derzeitige Verständnis von Adultplastizität der Pilzkörper in der Honigbiene, in denen eine Ausdünnung (Pruning) präsynaptischer Endigungen von PN und ein Auswachsen von KC-Dendriten beschrieben wurde. Aus den neuroanatomischen und physiologischen Eigenschaften der dualen olfaktorischen Bahnen lässt sich schlussfolgern, dass Düfte sowohl über Raten- als auch Zeit-Kodierung bis hin zu Koinzidenz-Verschaltungen verarbeitet werden können. Zudem zeigen derzeitige Arbeiten über analoge Ausgangs-Trakte im OB von Wirbeltieren, dass Parallelverarbeitung im olfaktorischen System ein allgemeines Kodierungsprinzip über weit entfernte Taxa zu sein scheint. KW - Tierphysiologie KW - Geruchssinn KW - Nervennetz KW - Nervenzelle KW - Biene KW - Antennallobus KW - antennal lobe KW - olfaction KW - multi-unit recording KW - Insekten KW - Geruch KW - Physiologie Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-85600 ER - TY - JOUR A1 - Keller, Alexander A1 - Brandel, Annette A1 - Becker, Mira C. A1 - Balles, Rebecca A1 - Abdelmohsen, Usama Ramadan A1 - Ankenbrand, Markus J. A1 - Sickel, Wiebke T1 - Wild bees and their nests host Paenibacillus bacteria with functional potential of avail JF - Microbiome N2 - Background: In previous studies, the gram-positive firmicute genus Paenibacillus was found with significant abundances in nests of wild solitary bees. Paenibacillus larvae is well-known for beekeepers as a severe pathogen causing the fatal honey bee disease American foulbrood, and other members of the genus are either secondary invaders of European foulbrood or considered a threat to honey bees. We thus investigated whether Paenibacillus is a common bacterium associated with various wild bees and hence poses a latent threat to honey bees visiting the same flowers. Results: We collected 202 samples from 82 individuals or nests of 13 bee species at the same location and screened each for Paenibacillus using high-throughput sequencing-based 16S metabarcoding. We then isolated the identified strain Paenibacillus MBD-MB06 from a solitary bee nest and sequenced its genome. We did find conserved toxin genes and such encoding for chitin-binding proteins, yet none specifically related to foulbrood virulence or chitinases. Phylogenomic analysis revealed a closer relationship to strains of root-associated Paenibacillus rather than strains causing foulbrood or other accompanying diseases. We found anti-microbial evidence within the genome, confirmed by experimental bioassays with strong growth inhibition of selected fungi as well as gram-positive and gram-negative bacteria. Conclusions: The isolated wild bee associate Paenibacillus MBD-MB06 is a common, but irregularly occurring part of wild bee microbiomes, present on adult body surfaces and guts and within nests especially in megachilids. It was phylogenetically and functionally distinct from harmful members causing honey bee colony diseases, although it shared few conserved proteins putatively toxic to insects that might indicate ancestral predisposition for the evolution of insect pathogens within the group. By contrast, our strain showed anti-microbial capabilities and the genome further indicates abilities for chitin-binding and biofilm-forming, suggesting it is likely a useful associate to avoid fungal penetration of the bee cuticula and a beneficial inhabitant of nests to repress fungal threats in humid and nutrient-rich environments of wild bee nests. KW - 16S metabarcoding KW - American foulbrood KW - anti-microbial activit KW - bacterial genomics KW - bioassays KW - European foulbrood KW - Paenibacterin KW - phylogenomics KW - bee disease KW - pathogen vector Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-177554 VL - 6 IS - 229 ER - TY - JOUR A1 - Schilcher, Felix A1 - Hilsmann, Lioba A1 - Ankenbrand, Markus J. A1 - Krischke, Markus A1 - Mueller, Martin J. A1 - Steffan-Dewenter, Ingolf A1 - Scheiner, Ricarda T1 - Honeybees are buffered against undernourishment during larval stages JF - Frontiers in Insect Science N2 - The negative impact of juvenile undernourishment on adult behavior has been well reported for vertebrates, but relatively little is known about invertebrates. In honeybees, nutrition has long been known to affect task performance and timing of behavioral transitions. Whether and how a dietary restriction during larval development affects the task performance of adult honeybees is largely unknown. We raised honeybees in-vitro, varying the amount of a standardized diet (150 µl, 160 µl, 180 µl in total). Emerging adults were marked and inserted into established colonies. Behavioral performance of nurse bees and foragers was investigated and physiological factors known to be involved in the regulation of social organization were quantified. Surprisingly, adult honeybees raised under different feeding regimes did not differ in any of the behaviors observed. No differences were observed in physiological parameters apart from weight. Honeybees were lighter when undernourished (150 µl), while they were heavier under the overfed treatment (180 µl) compared to the control group raised under a normal diet (160 µl). These data suggest that dietary restrictions during larval development do not affect task performance or physiology in this social insect despite producing clear effects on adult weight. We speculate that possible effects of larval undernourishment might be compensated during the early period of adult life. KW - nutrition KW - juvenile hormone KW - nurse bees KW - foragers KW - triglycerides KW - undernourishment KW - task allocation Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-304646 SN - 2673-8600 VL - 2 ER - TY - JOUR A1 - Voulgari‐Kokota, Anna A1 - Ankenbrand, Markus J. A1 - Grimmer, Gudrun A1 - Steffan‐Dewenter, Ingolf A1 - Keller, Alexander T1 - Linking pollen foraging of megachilid bees to their nest bacterial microbiota JF - Ecology and Evolution N2 - Solitary bees build their nests by modifying the interior of natural cavities, and they provision them with food by importing collected pollen. As a result, the microbiota of the solitary bee nests may be highly dependent on introduced materials. In order to investigate how the collected pollen is associated with the nest microbiota, we used metabarcoding of the ITS2 rDNA and the 16S rDNA to simultaneously characterize the pollen composition and the bacterial communities of 100 solitary bee nest chambers belonging to seven megachilid species. We found a weak correlation between bacterial and pollen alpha diversity and significant associations between the composition of pollen and that of the nest microbiota, contributing to the understanding of the link between foraging and bacteria acquisition for solitary bees. Since solitary bees cannot establish bacterial transmission routes through eusociality, this link could be essential for obtaining bacterial symbionts for this group of valuable pollinators. KW - foraging patterns KW - nest microbiota KW - plant–microbe–pollinator triangle KW - pollination network KW - solitary bees KW - wild bees Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-201749 SN - 00 VL - 2019 IS - 9 ER - TY - JOUR A1 - Stoevesandt, Johanna A1 - Hosp, Christine A1 - Kerstan, Andreas A1 - Trautmann, Axel T1 - Safety of 100 µg venom immunotherapy rush protocols in children compared to adults JF - Allergy, Asthma & Clinical Immunology N2 - Background: There is a paucity of studies examining the safety of venom immunotherapy (VIT) in children. We aimed to assess the incidence of anaphylactic side effects during rush VIT in a cohort of pediatric patients and adult controls. Methods: 72 consecutive cycles of VIT-buildup in 71 children/adolescents aged 7–17 years were retrospectively evaluated and compared to an adult control group (n = 981) with regard to baseline parameters (sex, causative venom, severity of index sting reaction, results of allergy testing, comorbidities) and the incidence of anaphylactic adverse reactions. Results: Compared to adults, severe index sting-induced anaphylaxis was significantly less common in children (P = .001). Children were more likely to suffer from bee venom allergy (P < .001) and showed higher levels of bee venom-specific IgE (P = .013), but lower serum tryptase concentrations (P = .014). The overall rate of VIT-induced anaphylactic reactions was higher in children than in adults (6.9% vs 2.5%, P = .046 by univariate analysis). In the final binary logistic regression model, however, only bee VIT (P = .039; odds ratio 2.25; confidence interval 1.04–4.87) and 5-day compared to 3-day buildup protocols (P = .011; odds ratio 2.64; confidence interval 1.25–5.57) were associated with an increased risk of treatment-induced anaphylaxis. All pediatric patients finally reached and tolerated the target maintenance dose of 100 µg. Conclusions: The higher anaphylactic reaction rate observed in pediatric patients may be attributed to a greater prevalence of bee venom allergy. VIT-induced anaphylaxis in children is usually mild and does not affect further updosing and maintenance of VIT. KW - anaphylaxis KW - bee KW - buildup phase KW - hymenoptera KW - pediatric KW - risk factor KW - vespula Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-157830 VL - 13 IS - 32 ER - TY - JOUR A1 - Beer, Katharina A1 - Härtel, Stephan A1 - Helfrich-Förster, Charlotte T1 - The pigment-dispersing factor neuronal network systematically grows in developing honey bees JF - The Journal of Comparative Neurology N2 - The neuropeptide pigment-dispersing factor (PDF) plays a prominent role in the circadian clock of many insects including honey bees. In the honey bee brain, PDF is expressed in about 15 clock neurons per hemisphere that lie between the central brain and the optic lobes. As in other insects, the bee PDF neurons form wide arborizations in the brain, but certain differences are evident. For example, they arborize only sparsely in the accessory medulla (AME), which serves as important communication center of the circadian clock in cockroaches and flies. Furthermore, all bee PDF neurons cluster together, which makes it impossible to distinguish individual projections. Here, we investigated the developing bee PDF network and found that the first three PDF neurons arise in the third larval instar and form a dense network of varicose fibers at the base of the developing medulla that strongly resembles the AME of hemimetabolous insects. In addition, they send faint fibers toward the lateral superior protocerebrum. In last larval instar, PDF cells with larger somata appear and send fibers toward the distal medulla and the medial protocerebrum. In the dorsal part of the medulla serpentine layer, a small PDF knot evolves from which PDF fibers extend ventrally. This knot disappears during metamorphosis and the varicose arborizations in the putative AME become fainter. Instead, a new strongly stained PDF fiber hub appears in front of the lobula. Simultaneously, the number of PDF neurons increases and the PDF neuronal network in the brain gets continuously more complex. KW - apis mellifera KW - circadian clock KW - immunohistochemistry KW - larval and pupal development KW - neuroanatomy Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-257300 VL - 530 IS - 9 ER - TY - JOUR A1 - Arenas, Andrés A1 - Roces, Flavio T1 - Avoidance of plants unsuitable for the symbiotic fungus in leaf-cutting ants: Learning can take place entirely at the colony dump JF - PLoS ONE N2 - Plants initially accepted by foraging leaf-cutting ants are later avoided if they prove unsuitable for their symbiotic fungus. Plant avoidance is mediated by the waste produced in the fungus garden soon after the incorporation of the unsuitable leaves, as foragers can learn plant odors and cues from the damaged fungus that are both present in the recently produced waste particles. We asked whether avoidance learning of plants unsuitable for the symbiotic fungus can take place entirely at the colony dump. In order to investigate whether cues available in the waste chamber induce plant avoidance in naïve subcolonies, we exchanged the waste produced by subcolonies fed either fungicide-treated privet leaves or untreated leaves and measured the acceptance of untreated privet leaves before and after the exchange of waste. Second, we evaluated whether foragers could perceive the avoidance cues directly at the dump by quantifying the visits of labeled foragers to the waste chamber. Finally, we asked whether foragers learn to specifically avoid untreated leaves of a plant after a confinement over 3 hours in the dump of subcolonies that were previously fed fungicide-treated leaves of that species. After the exchange of the waste chambers, workers from subcolonies that had access to waste from fungicide-treated privet leaves learned to avoid that plant. One-third of the labeled foragers visited the dump. Furthermore, naïve foragers learned to avoid a specific, previously unsuitable plant if exposed solely to cues of the dump during confinement. We suggest that cues at the dump enable foragers to predict the unsuitable effects of plants even if they had never been experienced in the fungus garden. KW - leaves KW - ants KW - fungi KW - foraging KW - animal sociality KW - social systems KW - learning KW - symbiosis Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-157559 VL - 12 IS - 3 ER - TY - JOUR A1 - Kohl, Patrick Laurenz A1 - Rutschmann, Benjamin T1 - The neglected bee trees: European beech forests as a home for feral honey bee colonies JF - PeerJ N2 - It is a common belief that feral honey bee colonies (Apis mellifera L.) were eradicated in Europe through the loss of habitats, domestication by man and spread of pathogens and parasites. Interestingly, no scientific data are available, neither about the past nor the present status of naturally nesting honeybee colonies. We expected near-natural beech (Fagus sylvatica L.) forests to provide enough suitable nest sites to be a home for feral honey bee colonies in Europe. Here, we made a first assessment of their occurrence and density in two German woodland areas based on two methods, the tracing of nest sites based on forager flight routes (beelining technique), and the direct inspection of potential cavity trees. Further, we established experimental swarms at forest edges and decoded dances for nest sites performed by scout bees in order to study how far swarms from beekeeper-managed hives would potentially move into a forest. We found that feral honey bee colonies regularly inhabit tree cavities in near-natural beech forests at densities of at least 0.11-0.14 colonies/km\(^{2}\). Colonies were not confined to the forest edges; they were also living deep inside the forests. We estimated a median distance of 2,600 m from the bee trees to the next apiaries, while scout bees in experimental swarms communicated nest sites in close distances (median: 470 m). We extrapolate that there are several thousand feral honey bee colonies in German woodlands. These have to be taken in account when assessing the role of forest areas in providing pollination services to the surrounding land, and their occurrence has implications for the species' perception among researchers, beekeepers and conservationists. This study provides a starting point for investigating the life-histories and the ecological interactions of honey bees in temperate European forest environments. KW - Apis mellifera KW - beech forests KW - black woodpecker KW - dispersal KW - Fagus sylvatica KW - feral honey bees KW - hollow tree KW - swarming KW - tree cavity KW - wild honey bees Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-176512 VL - 6 IS - e4602 ER - TY - THES A1 - Lindenberg [verh. Schubert], Annekathrin T1 - Timing of sensory preferences in \(Camponotus\) Ants T1 - Zeitliche Anpassung sensorischer Präferenzen in \(Camponotus\) Ameisen N2 - Ants belong to the most successful insects living on our planet earth. One criterion of their tremendous success is the division of labor among workers that can be related to age (age¬– or temporal polyethism) and/ or body size (size–related polymorphism). Young ants care for the queen and brood in the nest interior and switch to foraging tasks in the outside environment with ongoing age. This highly flexible interior–exterior transition probably allows the ant workers to properly match the colony needs and is one of the most impressive behaviors a single worker undergoes during its life. As environmental stimuli are changing with this transition, workers are required to perform a new behavioral repertoire. This requires significant adaptions in sensory and higher¬–order integration centers in the brain, like the mushroom bodies. Furthermore, foragers need proper time measuring mechanisms to cope with daily environmental changes and to adapt their own mode of life. Therefore, they possess a functional endogenous clock that generates rhythms with a period length of approximately 24 hours. The species–rich genus of Camponotus ants constitute a rewarding model to study how behavioral duties of division of labor were performed and modulated within the colony and how synaptic plasticity in the brain is processed, as they can divide their labor to both, age and body size, simultaneously. In my PhD thesis, I started to investigate the behavioral repertoire (like foraging and locomotor activity) of two sympatric Camponotus species, C. mus and C. rufipes workers under natural and under controlled conditions. Furthermore, I focused on the division of labor in C. rufipes workers and started to examine structural and ultrastructural changes of neuronal architectures in the brain that are accompanied by the interior–exterior transition of C. rufipes ants. In the first part of my thesis, I started to analyze the temporal organization of task allocation throughout the life of single C. rufipes workers. Constant video–tracking of individually labeled workers for up to 11 weeks, revealed an age–related division of labor of interior and exterior workers. After emergence, young individuals are tended to by older ones within the first 48 hours of their lives before they themselves start nurturing larvae and pupae. Around 52% switch to foraging duties at an age of 14–20 days. The workers that switched to foraging tasks are mainly media–sized workers and seem to be more specialized than nurses. Variations in proportion and the age of switching workers between and within different subcolonies indicate how highly flexible and plastic the age–related division of labor occurs in this ant species. Most of the observed workers were engaged in foraging tasks exclusively during nighttime. As the experiments were conducted in the laboratory, they are completely lacking environmental stimuli of the ants´ natural habitat. I therefore asked in a second study, how workers of the two closely related Camponotus species, C. rufipes and C. mus, adapt their daily activity patterns (foraging and locomotor activity) under natural (in Uruguay, South America) and controlled (in the laboratory) conditions to changing thermal conditions. Monitoring the foraging activity of both Camponotus species in a field experiment revealed, that C. mus workers are exclusively diurnal, whereas C. rufipes foragers are predominantly nocturnal. However, some nests showed an elevated daytime activity, which could be an adaption to seasonally cold night temperatures. To further investigate the impact of temperature and light on the differing foraging activity patterns in the field, workers of both Camponotus species were artificially exposed to different thermal regimes in the laboratory, simulating local winter and summer conditions. Here again, C. mus workers display solely diurnal locomotor activity, whereas workers of C. rufipes shifted their locomotor activity from diurnal under thermal winter conditions to nocturnal under thermal summer conditions. Hence, the combination of both, field work and laboratory studies, shows that daily activity is mostly shaped by thermal conditions and that temperature cycles are not just limiting foraging activity but can be used as zeitgeber to schedule the outside activities of the nests. Once an individual worker switches from indoor duties to exterior foraging tasks, it is confronted with an entirely new set of sensory information. To cope with changes of the environmental conditions and to facilitate the behavioral switch, workers need a highly flexible and plastic neuronal system. Hence, my thesis further focuses on the underlying neuronal adaptations of the visual system, including the optic lobes as the primary visual neuropil and the mushroom bodies as secondary visual brain neuropil, that are accompanied with the behavioral switch from nursing to foraging. The optic lobes as well as the mushroom bodies of light–deprived workers show an `experience–independent´ volume increase during the first two weeks of adulthood. An additional light exposure for 4 days induces an `experience–dependent´ decrease of synaptic complexes in the mushroom body collar, followed by an increase after extended light exposure for 14 days. I therefore conclude, that the plasticity of the central visual system represents important components for the optimal timing of the interior–exterior transitions and flexibility of the age–related division of labor. These remarkable structural changes of synaptic complexes suggest an active involvement of the mushroom body neuropil in the lifetime plasticity that promotes the interior–exterior transition of Camponotus rufipes ants. Beside these investigations of neuronal plasticity of synaptic complexes in the mushroom bodies on a structural level, I further started to examine mushroom body synaptic structures at the ultrastructural level. Until recently, the detection of synaptic components in projection neuron axonal boutons were below resolution using classical Transmission Electron Microscopy. Therefore, I started to implement Electron Tomography to increase the synaptic resolution to understand architectural changes in neuronal plasticity process. By acquiring double tilt series and consecutive computation of the acquired tilt information, I am now able to resolve individual clear–core and dense–core vesicles within the projection neuron cytoplasm of C. rufipes ants. I additionally was able to reveal single postsynaptic Kenyon cell dendritic spines (~62) that surround one individual projection neuron bouton. With this, I could reveal first insights into the complex neuronal architecture of single projection neuron boutons in the olfactory mushroom body lip region. The high resolution images of synaptic architectures at the ultrastructural level, received with Electron Tomography would promote the understanding of architectural changes in neuronal plasticity. In my PhD thesis, I demonstrate that the temporal organization within Camponotus colonies involves the perfect timing of different tasks. Temperature seems to be the most scheduling abiotic factors of foraging and locomotor activity. The ants do not only need to adapt their behavioral repertoire in accordance to the interior–exterior switch, also the parts in the peripheral and central that process visual information need to adapt to the new sensory environment. N2 - Ameisen gehören zu den erfolgreichsten Insekten unserer Erde. Hauptverantwortlich für ihren enormen Erfolg ist die Arbeitsteilung der Arbeiterinnenkaste. Ameisenarbeiterinnen können sich ihre Aufgaben abhängig ihrer Körpergröße teilen (Größenpolymorphismus), indem unterschiedlich große Tiere verschiedenen Aufgaben in der Kolonie nachgehen. Zusätzlich kann die Arbeitsteilung aber auch altersbedingt sein (auch genannt Alters– oder zeitlicher Polyethismus): Junge Ameisen kümmern sich um die Königin und Brut innerhalb des Nestes, bevor sie mit zunehmendem Alter das Nest verlassen und zu Futtersammlerinnen (Furageuren) werden. Der extrem anpassungsfähige Wechsel von Innen¬– zu Außendiensttieren ist einer der erstaunlichsten Verhaltensweisen, die Arbeiterinnen an den Tag legen und ermöglicht es ihnen, den unterschiedlichen Bedürfnissen ihrer Kolonie nachzugehen. Der Übergang der Ammentätigkeit zum Furagieren ist mit beträchtlichen Veränderungen der sensorischen Umgebung der einzelnen Arbeiterinnen verbunden und erfordert eine Verhaltensanpassung an diese neuen Gegebenheiten. Wenn sich die Verhaltensweisen der Arbeiterinnen ändert, führt das zu Anpassungen der sensorischen und höheren Verschaltungszentren in bestimmten Gehirnarealen. Eines dieser sensorischen Verarbeitungszentren sind die Pilzkörper. Außerdem müssen Furageure in der Lage sein, tägliche Veränderungen ihrer Umwelt wahrzunehmen, um ihre Verhaltensweisen stets optimal an die sich ändernde Umwelt anzupassen. Dafür brauchen sie eine funktionierende innere Uhr, die rhythmisch mit einer Periodenlänge von ca. 24 Stunden läuft. Die artenreiche Gattung der Camponotus Ameisen ist ein geeigneter Organismus, um die Verhaltensweisen die mit der Arbeitsteilung der Arbeiterinnenkaste einhergehen, zu untersuchen, da sowohl der Größenpolymorphismus als auch der Alterspolyethismus zeitgleich in dieser Gattung auftauchen können. Dadurch eignen sich Camponotus Ameisen auch hervorragend, um strukturelle Veränderungen synaptischer Komplexe im Gehirn, die sich durch die Arbeitsteilung ändern können, zu untersuchen. In meiner Doktorarbeit habe ich damit angefangen, die Verteilung von bestimmten Aufgaben (Ammen und Furageure) von C. rufipes Arbeiterinnen zu untersuchen. Mithilfe von Videoaufnahmen über elf Wochen, konnte ich sowohl eine altersabhängige, als auch eine größenabhängige Arbeitsteilung zwischen Ammen und Furageuren für diese Art zeigen. Frisch geschlüpfte Tiere wurden innerhalb der ersten 48 Stunden von anderen Ammen umsorgt, bevor sie selbst zu Ammen wurden und Aufgaben wie Brutpflege übernommen haben. Nach rund 14–20 Tagen sind 53% der Ammen zu Furageuren gewechselt. Zusätzlich zu der altersabhängigen Arbeitsteilung konnte ich zeigen, dass die Körpergröße der Ammen deutlich breiter gestreut ist als die der Furageure, was in einer höheren Spezialisierung der Furageure resultiert. Proportionale Unterschiede des Alters und der Größe der Tiere, die diesen Wechsel vollzogen haben zeigen, wie hoch flexibel und anpassungsfähig die Arbeitsteilung innerhalb der Arbeiterinnenkaste sein kann. Die meisten der beobachteten Furageure waren außerdem fast ausschließlich nachtaktiv. Da ich diese Experimente im Labor durchgeführt habe, fehlt es komplett an der natürlichen sensorischen Umgebung der Tiere. In dem zweiten Teil meiner Doktorarbeit habe ich mich damit beschäftigt, ob sich tägliche Aktivitätsmuster (Furagier– und Bewegungsaktivität) von Arbeiterinnen zweier nah verwandter Camponotus Arten (C. rufipes und C. mus) unter natürlichen Bedingungen (in Uruguay, Südamerika) und unter kontrollierten Bedingungen (im Labor), in Abhängigkeit von den abiotischen Faktoren Licht und Temperatur, verändern können. Meine Ergebnisse zeigen, dass C. mus Arbeiterinnen unter natürlichen Bedingungen strikt tagaktiv sind, wohingegen C. rufipes Arbeiterinnen vornehmlich nachts furagierten. Ein paar C. rufipes Nester zeigten allerdings eine erhöhte Furagieraktivität tagsüber, was auf die saisonal kalten Nächte zurückzuführen sein könnte. Um den Einfluss von Licht und Temperatur, der sich auf die Furagieraktivität im Feld gezeigt hat, genauer untersuchen zu können, wurden Arbeiterinnen beider Camponotus Arten verschiedenen Licht– und Temperaturbedingungen im Labor ausgesetzt. Auch hier zeigten Arbeiterinnen der Gattung C. mus eine strikt tagaktive Bewegungsaktivität, wohingegen C. rufipes Arbeiterinnen von tagaktiv unter Winter Temperaturbedingungen zu nachaktiv unter Sommer Temperaturbedingungen wechselten. Die Kombination aus den Ergebnissen der Feld– und Laborstudien zeigen deutlich, dass die generelle Aktivität der beiden Arten hauptsächlich durch Licht und Temperatur beeinflusst wird und dass Temperaturzyklen nicht nur ein limitierender Faktor der Furagieraktivität sind, sondern auch als Zeitgeber dienen können um Aktivität generell zu regulieren. Wenn der Übergang von Innen– zu Außendiensttieren stattgefunden hat, ändert sich die komplette sensorische Umgebung der Furageure. Um diese Veränderungen verarbeiten zu können, brauchen Arbeiterinnen ein hoch anpassungsfähiges und flexibles neuronales System. Daher beschäftigte ich mich in meiner Doktorarbeit außerdem mit den zugrundeliegenden neuronalen Anpassungen der visuellen Verarbeitungsregionen im Gehirn, wie die optischen Loben und die Pilzkörper, die mit dem Wechsel von Ammen zu Furageuren einhergehen. Ich konnte zeigen, dass die optischen Loben und die Pilzkörper von im Dunkeln gehaltenen Arbeiterinnen eine `Erfahrungs–unabhängige´ Volumenszunahme innerhalb der ersten zwei Wochen nach dem Schlupf zeigen. Eine folgende Lichtexposition von vier Tagen führte zu einer `Erfahrungs–abhängigen´ Abnahme der synaptischen Strukturen im Pilzkörper, die allerdings durch eine länger anhaltende Lichtexposition von 14 Tagen wieder anstieg. Diese Plastizität des zentralen visuellen Nervensystems repräsentiert eine wichtige Komponente für die optimale zeitliche Anpassung des Wechsels von Ammen zu Furageuren und die enorme Flexibilität der altersabhängigen Arbeitsteilung. Außerdem scheinen die Pilzkörper durch diese beeindruckenden strukturellen Veränderungen der synaptischen Komplexe aktiv an dieser neuronalen Plastizität beteiligt zu sein und daher den Übergang von Innen– zu Außendiensttieren in C. rufipes Ameisen zu unterstützen. Neben meinen Untersuchungen zur neuronalen Plastizität synaptischer Komplexe im Pilzkörper auf der strukturellen Ebene, habe ich damit begonnen, diese Plastizität der neuronalen Komplexe auch auf Ultrastruktur Ebene zu untersuchen. Durch die zu geringe Auflösungsmöglichkeit der klassischen Transmissions Elektronenmikroskopie, konnten bisher einzelne synaptischer Komponenten in den axonalen Endigungen der Projektionsneurone nicht detektiert werden. Deswegen habe ich damit angefangen, die Methode der Elektronen Tomographie zu etablieren um die Auflösung synaptischer Komplexe zu verbessern. Mit dieser höheren Auflösung ist es möglich, bauliche Veränderungen der synaptischen Komplexe in Plastizitätsprozessen besser zu verstehen. Mit der Durchführung von `double tilt´ Serien und der anschließenden Verarbeitung der erhaltenen Bildinformation, war es mir möglich, einzelne `clear–core´ und `dense–core´ Vesikel innerhalb des Zytoplasmas der Projektionsneurone von C. rufipes Ameisen detektieren. Außerdem konnte ich mit dieser Methode einzelne postsynaptische dendritische Dornen der Kenyon Zellen (~62) identifizieren, die ein einzelnes Endknöpfchen eines Projektionsneurons umgeben. In diesem Teil meiner Arbeit konnte ich erste Einblicke in die komplexe neuronale Bauweise einzelner Endigungen der Projektionsneurone in der olfaktorischen Region der Pilzkörper zeigen. Die hochauflösenden Bilder synaptischer Komplexe auf dem Ultrastruktur Level, die man mit der Elektronen Tomographie erzielen kann, bringen das Verständnis baulicher Veränderungen innerhalb der neuronales Plastizität voran. In meiner Doktorarbeit konnte ich zeigen, dass die zeitliche Organisation verschiedener Aufgaben innerhalb der Kolonien von Camponotus Ameisen einer perfekten Zeitplanung bedarf. Hier scheinen die abiotischen Faktoren Temperatur und Licht den größten Einfluss auf die Furagieraktivität und die generelle Aktivität zu haben. Die Ameisenarbeiterinnen müssen nicht nur ihre Verhaltensweise nach dem Übergang von Ammen zu Furageuren anpassen, es müssen sich auch die Teile des Gehirns, die für die Verarbeitung visueller Reize zuständig sind, dieser neuen sensorischen Umgebung anpassen. KW - Rossameise KW - Pilzkörper KW - Arbeitsteilung KW - Furagieraktivität KW - foraging activity KW - Neuronales visuelles System KW - neuronal visual system KW - Camponotus rufipes Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-160948 ER - TY - JOUR A1 - Stein, Katharina A1 - Coulibaly, Drissa A1 - Stenchly, Kathrin A1 - Goetze, Dethardt A1 - Porembski, Stefan A1 - Lindner, André A1 - Konaté, Souleymane A1 - Linsenmair, Eduard K. T1 - Bee pollination increases yield quantity and quality of cash crops in Burkina Faso, West Africa JF - Scientific Reports N2 - Mutualistic biotic interactions as among flowering plants and their animal pollinators are a key component of biodiversity. Pollination, especially by insects, is a key element in ecosystem functioning, and hence constitutes an ecosystem service of global importance. Not only sexual reproduction of plants is ensured, but also yields are stabilized and genetic variability of crops is maintained, counteracting inbreeding depression and facilitating system resilience. While experiencing rapid environmental change, there is an increased demand for food and income security, especially in sub-Saharan communities, which are highly dependent on small scale agriculture. By combining exclusion experiments, pollinator surveys and field manipulations, this study for the first time quantifies the contribution of bee pollinators to smallholders’ production of the major cash crops, cotton and sesame, in Burkina Faso. Pollination by honeybees and wild bees significantly increased yield quantity and quality on average up to 62%, while exclusion of pollinators caused an average yield gap of 37% in cotton and 59% in sesame. Self-pollination revealed inbreeding depression effects on fruit set and low germination rates in the F1-generation. Our results highlight potential negative consequences of any pollinator decline, provoking risks to agriculture and compromising crop yields in sub-Saharan West Africa. KW - bees KW - pollination KW - Burkina Faso KW - cash crops KW - cotton KW - sesame Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-169914 VL - 7 IS - 17691 ER - TY - JOUR A1 - Scheiner, Ricarda A1 - Entler, Brian V. A1 - Barron, Andrew B. A1 - Scholl, Christina A1 - Thamm, Markus T1 - The Effects of Fat Body Tyramine Level on Gustatory Responsiveness of Honeybees (Apis mellifera) Differ between Behavioral Castes JF - Frontiers in Systems Neuroscience N2 - Division of labor is a hallmark of social insects. In the honeybee (Apis mellifera) each sterile female worker performs a series of social tasks. The most drastic changes in behavior occur when a nurse bee, who takes care of the brood and the queen in the hive, transitions to foraging behavior. Foragers provision the colony with pollen, nectar or water. Nurse bees and foragers differ in numerous behaviors, including responsiveness to gustatory stimuli. Differences in gustatory responsiveness, in turn, might be involved in regulating division of labor through differential sensory response thresholds. Biogenic amines are important modulators of behavior. Tyramine and octopamine have been shown to increase gustatory responsiveness in honeybees when injected into the thorax, thereby possibly triggering social organization. So far, most of the experiments investigating the role of amines on gustatory responsiveness have focused on the brain. The potential role of the fat body in regulating sensory responsiveness and division of labor has large been neglected. We here investigated the role of the fat body in modulating gustatory responsiveness through tyramine signaling in different social roles of honeybees. We quantified levels of tyramine, tyramine receptor gene expression and the effect of elevating fat body tyramine titers on gustatory responsiveness in both nurse bees and foragers. Our data suggest that elevating the tyramine titer in the fat body pharmacologically increases gustatory responsiveness in foragers, but not in nurse bees. This differential effect of tyramine on gustatory responsiveness correlates with a higher natural gustatory responsiveness of foragers, with a higher tyramine receptor (Amtar1) mRNA expression in fat bodies of foragers and with lower baseline tyramine titers in fat bodies of foragers compared to those of nurse bees. We suggest that differential tyramine signaling in the fat body has an important role in the plasticity of division of labor through changing gustatory responsiveness. KW - behavior KW - biogenic amines KW - division of labor KW - nurse bee KW - forager KW - PER KW - octopamine KW - insect Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-157874 VL - 11 IS - 55 ER - TY - JOUR A1 - Drescher, Nora A1 - Klein, Alexandra-Maria A1 - Schmitt, Thomas A1 - Leonhardt, Sara Diana T1 - A clue on bee glue: New insight into the sources and factors driving resin intake in honeybees (Apis mellifera) JF - PLoS ONE N2 - Honeybees (Apis mellifera) are threatened by numerous pathogens and parasites. To prevent infections they apply cooperative behavioral defenses, such as allo-grooming and hygiene, or they use antimicrobial plant resin. Resin is a chemically complex and highly variable mixture of many bioactive compounds. Bees collect the sticky material from different plant species and use it for nest construction and protection. Despite its importance for colony health, comparatively little is known about the precise origins and variability in resin spectra collected by honeybees. To identify the botanical resin sources of A. mellifera in Western Europe we chemically compared resin loads of individual foragers and tree resins. We further examined the resin intake of 25 colonies from five different apiaries to assess the effect of location on variation in the spectra of collected resin. Across all colonies and apiaries, seven distinct resin types were categorized according to their color and chemical composition. Matches between bee-collected resin and tree resin indicated that bees used poplar (Populus balsamifera, P. x canadensis), birch (Betula alba), horse chestnut (Aesculus hippocastanum) and coniferous trees (either Picea abies or Pinus sylvestris) as resin sources. Our data reveal that honeybees collect a comparatively broad and variable spectrum of resin sources, thus assuring protection against a variety of antagonists sensitive to different resins and/or compounds. We further unravel distinct preferences for specific resins and resin chemotypes, indicating that honeybees selectively search for bioactive resin compounds. KW - Honey bees KW - Poplars KW - Trees KW - Forests KW - Chemical composition KW - Bees KW - Conifers KW - Phenols Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-200935 VL - 14 IS - 2 ER - TY - JOUR A1 - Kaluza, Benjamin F. A1 - Wallace, Helen M. A1 - Heard, Tim A. A1 - Minden, Vanessa A1 - Klein, Alexandra A1 - Leonhardt, Sara D. T1 - Social bees are fitter in more biodiverse environments JF - Scientific Reports N2 - Bee population declines are often linked to human impacts, especially habitat and biodiversity loss, but empirical evidence is lacking. To clarify the link between biodiversity loss and bee decline, we examined how floral diversity affects (reproductive) fitness and population growth of a social stingless bee. For the first time, we related available resource diversity and abundance to resource (quality and quantity) intake and colony reproduction, over more than two years. Our results reveal plant diversity as key driver of bee fitness. Social bee colonies were fitter and their populations grew faster in more florally diverse environments due to a continuous supply of food resources. Colonies responded to high plant diversity with increased resource intake and colony food stores. Our findings thus point to biodiversity loss as main reason for the observed bee decline. KW - biodiversity KW - ecosystem services KW - social bees KW - fitness Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-177231 VL - 8 IS - 12353 ER - TY - THES A1 - Franzke, Myriam T1 - Keep on track : The use of visual cues for orientation in monarch butterflies T1 - Auf Kurs bleiben : Die Nutzung visueller Hinweise zur Orientierung bei Monarchfaltern N2 - The monarch butterfly (Danaus plexippus) performs one of the most astonishing behaviors in the animal kingdom: every fall millions of these butterflies leave their breeding grounds in North Amerika and migrate more than 4.000 km southwards until they reach their overwintering habitat in Central Mexico. To maintain their migratory direction over this enormous distance, the butterflies use a time-compensated sun compass. Beside this, skylight polarization, the Earth’s magnetic field and specific mountain ranges seem to guide the butterflies as well the south. In contrast to this fascinating orientation ability, the behavior of the butterflies in their non-migratory state received less attention. Although they do not travel long distances, they still need to orient themselves to find food, mating partners or get away from competitors. The aim of the present doctoral thesis was to investigate use of visual cues for orientation in migrating as well as non-migrating monarch butterflies. For this, field experiments investigating the migration of the butterflies in Texas (USA) were combined with experiments testing the orientation performance of non-migratory butterflies in Germany. In the first project, I recorded the heading directions of tethered butterflies during their annual fall migration. In an outdoor flight simulator, the butterflies maintained a southwards direction as long as they had a view of the sun’s position. Relocating the position of the sun by 180° using a mirror, revealed that the sun is the animals’ main orientation reference. Furthermore, I demonstrated that when the sun is blocked and a green light stimulus (simulated sun) is introduced, the animals interpreted this stimulus as the ‘real’ sun. However, this cue was not sufficient to set the migratory direction when simulated as the only visual cue in indoor experiments. When I presented the butterflies a linear polarization pattern additionally to the simulated sun, the animals headed in the correct southerly direction showing that multiple skylight cues are required to guide the butterflies during their migration. In the second project, I, furthermore, demonstrated that non-migrating butterflies are able to maintain a constant direction with respect to a simulated sun. Interestingly, they ignored the spectral component of the stimulus and relied on the intensity instead. When a panoramic skyline was presented as the only orientation reference, the butterflies maintained their direction only for short time windows probably trying to stabilize their flight based on optic-flow information. Next, I investigated whether the butterflies combine celestial with local cues by simulating a sun stimulus together with a panoramic skyline. Under this conditions, the animals’ directedness was increased demonstrating that they combine multiple visual cues for spatial orientation. Following up on the observation that a sun stimulus resulted in a different behavior than the panoramic skyline, I investigated in my third project which orientation strategies the butterflies use by presenting different simulated cues to them. While a bright stripe on a dark background elicited a strong attraction of the butterflies steering in the direction of the stimulus, the inverted version of the stimulus was used for flight stabilization. In contrast to this, the butterflies maintained arbitrary directions with a high directedness with respect to a simulated sun. In an ambiguous scenery with two identical stimuli (two bright stripes, two dark stripes, or two sun stimuli) set 180° apart, a constant flight course was only achieved when two sun stimuli were displayed suggesting an involvement of the animals’ internal compass. In contrast, the butterflies used two dark stripes for flight stabilization and were alternatingly attracted by two bright stripes. This shows that monarch butterflies use stimulus-dependent orientation strategies and gives the first evidence for different neuronal pathways controlling the output behavior. N2 - Der Monarchfalter (Danaus plexippus) vollführt eine der atemberaubendsten Verhaltensweisen im Tierreich: Jeden Herbst verlassen Millionen dieser Schmetterlinge ihre Brutgebiete in Nordamerika und migrieren mehr als 4000 km südwärts bis sie ihr Überwinterungsgebiet in Zentralmexico erreichen. Um ihre Migrationsrichtung über diese enorme Distanz einzuhalten, benutzen die Schmetterlinge einen zeitkompensierten Sonnenkompass. Daneben scheinen polarisiertes Licht, das Erdmagnetfeld und bestimmte Gebirgsketten die Schmetterlinge nach Süden zu führen. Im Gegensatz zu dieser faszinierenden Orientierungsfähigkeit wurde dem Verhalten der Schmetterlinge in ihrem nicht-migrierendem Zustand wenig Beachtung geschenkt. Obwohl diese keine großen Distanzen zurücklegen, müssen sie sich dennoch orientieren, um Futter und Paarungspartner zu finden oder Konkurrenten zu entfliehen. Das Ziel der vorliegenden Doktorarbeit war es, die Nutzung visueller Hinweise für die Orientierung von sowohl migrierenden als auch nicht-migrierenden Monarchfaltern zu untersuchen. Dazu wurden Feldexperimente, in denen die Migration der Schmetterlinge in Texas (USA) untersucht wurden, mit Experimenten, in denen das Orientierungsvermögen von nicht-migrierenden Schmetterlingen in Deutschland getestet wurde, verknüpft. Im ersten Projekt habe ich die Flugrichtung von Schmetterlingen während der jährlichen Herbstmigration aufgezeichnet. In einem Flugsimulator im Freien hielten die Schmetterlinge eine südliche Richtung, solange sie eine freie Sicht auf die Sonne hatten. Eine Versetzung der Sonnenposition um 180° mit Hilfe eines Spiegels zeigte auf, dass die Sonne die wichtigste Orientierungsreferenz der Tiere ist. Des Weiteren konnte ich zeigen, dass die Tiere, wenn die Sonne blockiert und ein grüner Lichtstimulus (simulierte Sonne) eingeschaltet wurde, diese simulierte Sonne als "echte" Sonne interpretierten. Dieser Hinweis reichte jedoch nicht aus, um die Migrationsrichtung festzulegen, wenn er als einziger visueller Hinweis im Labor simuliert wurde. Als ich den Schmetterlingen zusätzlich zur simulierten Sonne ein lineares Polarisationsmuster präsentierte, flogen die Tiere in die richtige, südliche Richtung. Das zeigt, dass mehrere Himmelshinweise erforderlich sind, um die Schmetterlinge während ihrer Migration zu steuern. Im zweiten Projekt habe ich weiterhin gezeigt, dass nicht migrierende Schmetterlinge in der Lage sind eine konstante Richtung relativ zu einer simulierten Sonne beizubehalten. Interessanterweise ignorierten sie die spektrale Komponente des Stimulus und verließen sich stattdessen auf die Intensität. Als ein Panorama als einzige Orientierungsreferenz präsentiert wurde, hielten die Schmetterlinge ihre Richtung nur für kurze Zeitfenster und versuchten vermutlich, ihren Flug basierend auf Informationen des optischen Flusses zu stabilisieren. Als Nächstes untersuchte ich, ob die Schmetterlinge Himmelshinweise und lokale Hinweisen kombinieren, indem ich eine Sonne zusammen mit einem Panorama simulierte. Unter diesen Bedingungen war die Gerichtetheit der Flüge erhöht, was zeigt, dass die Tiere mehrere visuelle Hinweise zur räumlichen Orientierung kombinieren. Beruhend auf der Beobachtung, dass ein Sonnenstimulus zu einem anderen Verhaltensmuster führte als das Panorama, untersuchte ich in meinem dritten Projekt, welche Orientierungsstrategien die Schmetterlinge verwenden. Hierfür präsentierte ich den Tieren verschiedene simulierte Hinweise. Während ein heller Streifen auf dunklem Hintergrund eine starke Anziehungskraft auf die Schmetterlinge, die in die Richtung des Reizes flogen, ausübte, wurde die invertierte Version des Stimulus zur Flugstabilisierung verwendet. Im Gegensatz dazu hielten die Schmetterlinge beliebige Richtungen mit einer hohen Gerichtetheit relativ zu einer simulierten Sonne ein. In einer uneindeutigen Szenerie mit zwei identischen Reizen (zwei helle Streifen, zwei dunkle Streifen oder zwei Sonnenstimuli), die um 180° versetzt waren, wurde eine konstante Flugrichtung nur dann erreicht, wenn zwei Sonnenstimuli gezeigt wurden. Das deutet auf eine Beteiligung des inneren Kompasses der Tiere hin. Im Gegensatz dazu nutzten die Schmetterlinge zwei dunkle Streifen zur Flugstabilisierung und wurden abwechselnd von zwei hellen Streifen angezogen. Dies zeigt, dass Monarchfalter stimulus-abhängige Orientierungsstrategien verwenden, und liefert den ersten Nachweis für unterschiedliche neuronale Verschaltungswege, die das Verhalten steuern. KW - Monarchfalter KW - Orientierung KW - Visuelle Orientierung KW - Schmetterlinge KW - Insekten KW - visual cue Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-284709 ER - TY - JOUR A1 - Rössler, Wolfgang A1 - Spaethe, Johannes A1 - Groh, Claudia T1 - Pitfalls of using confocal-microscopy based automated quantification of synaptic complexes in honeybee mushroom bodies (response to Peng and Yang 2016) JF - Scientific Reports N2 - A recent study by Peng and Yang in Scientific Reports using confocal-microscopy based automated quantification of anti-synapsin labeled microglomeruli in the mushroom bodies of honeybee brains reports potentially incorrect numbers of microglomerular densities. Whereas several previous studies using visually supervised or automated counts from confocal images and analyses of serial 3D electron-microscopy data reported consistent numbers of synaptic complexes per volume, Peng and Yang revealed extremely low numbers differing by a factor of 18 or more from those obtained in visually supervised counts, and by a factor 22–180 from numbers in two other studies using automated counts. This extreme discrepancy is especially disturbing as close comparison of raw confocal images of anti-synapsin labeled whole-mount brain preparations are highly similar across these studies. We conclude that these discrepancies may reside in potential misapplication of confocal imaging followed by erroneous use of automated image analysis software. Consequently, the reported microglomerular densities during maturation and after manipulation by insecticides require validation by application of appropriate confocal imaging methods and analyses tools that rely on skilled observers. We suggest several improvements towards more reliable or standardized automated or semi-automated synapse counts in whole mount preparations of insect brains. KW - confocal-microscopy based automated quantification KW - mushroom bodies KW - honeybees KW - brain Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-170451 VL - 7 IS - 9786 ER - TY - JOUR A1 - Peters, Birte A1 - Keller, Alexander A1 - Leonhardt, Sara Diana T1 - Diets maintained in a changing world: Does land-use intensification alter wild bee communities by selecting for flexible generalists? JF - Ecology and evolution N2 - Biodiversity loss, as often found in intensively managed agricultural landscapes, correlates with reduced ecosystem functioning, for example, pollination by insects, and with altered plant composition, diversity, and abundance. But how does this change in floral resource diversity and composition relate to occurrence and resource use patterns of trap-nesting solitary bees? To better understand the impact of land-use intensification on communities of trap-nesting solitary bees in managed grasslands, we investigated their pollen foraging, reproductive fitness, and the nutritional quality of larval food along a land-use intensity gradient in Germany. We found bee species diversity to decrease with increasing land-use intensity irrespective of region-specific community compositions and interaction networks. Land use also strongly affected the diversity and composition of pollen collected by bees. Lack of suitable pollen sources likely explains the absence of several bee species at sites of high land-use intensity. The only species present throughout, Osmia bicornis (red mason bee), foraged on largely different pollen sources across sites. In doing so, it maintained a relatively stable, albeit variable nutritional quality of larval diets (i.e., protein to lipid (P:L) ratio). The observed changes in bee–plant pollen interaction patterns indicate that only the flexible generalists, such as O. bicornis, may be able to compensate the strong alterations in floral resource landscapes and to obtain food of sufficient quality through readily shifting to alternative plant sources. In contrast, other, less flexible, bee species disappear. KW - bee decline KW - biodiversity exploratories KW - foraging KW - metabarcoding KW - pollen nutrients KW - solitary bees Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-312786 SN - 2045-7758 VL - 12 IS - 5 ER - TY - JOUR A1 - Danner, Nadja A1 - Keller, Alexander A1 - Härtel, Stephan A1 - Steffan-Dewenter, Ingolf T1 - Honey bee foraging ecology: Season but not landscape diversity shapes the amount and diversity of collected pollen JF - PLoS ONE N2 - The availability of pollen in agricultural landscapes is essential for the successful growth and reproduction of honey bee colonies (Apis mellifera L.). The quantity and diversity of collected pollen can influence the growth and health of honey bee colonies, but little is known about the influence of landscape structure on pollen diet. In a field experiment, we rotated 16 honey bee colonies across 16 agricultural landscapes, used traps to collect samples of collected pollen and observed intra-colonial dance communication to gain information about foraging distances. DNA metabarcoding was applied to analyze mixed pollen samples. Neither the amount of collected pollen nor pollen diversity was related to landscape diversity. However, we found a strong seasonal variation in the amount and diversity of collected pollen in all sites independent of landscape diversity. The observed increase in foraging distances with decreasing landscape diversity suggests that honey bees compensated for lower landscape diversity by increasing their pollen foraging range in order to maintain pollen amount and diversity. Our results underscore the importance of a diverse pollen diet for honey bee colonies. Agri-environmental schemes aiming to support pollinators should focus on possible spatial and temporal gaps in pollen availability and diversity in agricultural landscapes. KW - honey bees KW - pollen KW - season KW - foraging Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-170424 VL - 12 IS - 8 ER - TY - JOUR A1 - Drescher, Nora A1 - Klein, Alexandra-Maria A1 - Neumann, Peter A1 - Yañez, Orlando A1 - Leonhardt, Sara D. T1 - Inside Honeybee Hives: Impact of Natural Propolis on the Ectoparasitic Mite Varroa destructor and Viruses JF - Insects N2 - Social immunity is a key factor for honeybee health, including behavioral defense strategies such as the collective use of antimicrobial plant resins (propolis). While laboratory data repeatedly show significant propolis effects, field data are scarce, especially at the colony level. Here, we investigated whether propolis, as naturally deposited in the nests, can protect honeybees against ectoparasitic mites Varroa destructor and associated viruses, which are currently considered the most serious biological threat to European honeybee subspecies, Apis mellifera, globally. Propolis intake of 10 field colonies was manipulated by either reducing or adding freshly collected propolis. Mite infestations, titers of deformed wing virus (DWV) and sacbrood virus (SBV), resin intake, as well as colony strength were recorded monthly from July to September 2013. We additionally examined the effect of raw propolis volatiles on mite survival in laboratory assays. Our results showed no significant effects of adding or removing propolis on mite survival and infestation levels. However, in relation to V. destructor, DWV titers increased significantly less in colonies with added propolis than in propolis-removed colonies, whereas SBV titers were similar. Colonies with added propolis were also significantly stronger than propolis-removed colonies. These findings indicate that propolis may interfere with the dynamics of V. destructor-transmitted viruses, thereby further emphasizing the importance of propolis for honeybee health. KW - social immunity KW - Apis mellifera KW - deformed wing virus KW - plant-insect interactions KW - resin KW - sacbrood virus Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-171164 VL - 8 IS - 1 ER - TY - JOUR A1 - Grob, Robin A1 - Fleischmann, Pauline N. A1 - Grübel, Kornelia A1 - Wehner, Rüdiger A1 - Rössler, Wolfgang T1 - The role of celestial compass information in Cataglyphis ants during learning walks and for neuroplasticity in the central complex and mushroom bodies JF - Frontiers in Behavioral Neuroscience N2 - Central place foragers are faced with the challenge to learn the position of their nest entrance in its surroundings, in order to find their way back home every time they go out to search for food. To acquire navigational information at the beginning of their foraging career, Cataglyphis noda performs learning walks during the transition from interior worker to forager. These small loops around the nest entrance are repeatedly interrupted by strikingly accurate back turns during which the ants stop and precisely gaze back to the nest entrance—presumably to learn the landmark panorama of the nest surroundings. However, as at this point the complete navigational toolkit is not yet available, the ants are in need of a reference system for the compass component of the path integrator to align their nest entrance-directed gazes. In order to find this directional reference system, we systematically manipulated the skylight information received by ants during learning walks in their natural habitat, as it has been previously suggested that the celestial compass, as part of the path integrator, might provide such a reference system. High-speed video analyses of distinct learning walk elements revealed that even exclusion from the skylight polarization pattern, UV-light spectrum and the position of the sun did not alter the accuracy of the look back to the nest behavior. We therefore conclude that C. noda uses a different reference system to initially align their gaze directions. However, a comparison of neuroanatomical changes in the central complex and the mushroom bodies before and after learning walks revealed that exposure to UV light together with a naturally changing polarization pattern was essential to induce neuroplasticity in these high-order sensory integration centers of the ant brain. This suggests a crucial role of celestial information, in particular a changing polarization pattern, in initially calibrating the celestial compass system. KW - sky-compass pathway KW - visual orientation KW - look-back behavior KW - desert ants KW - vector navigation KW - memory KW - central complex KW - mushroom body Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-159235 VL - 11 IS - 226 ER - TY - JOUR A1 - Römer, Daniela A1 - Bollazzi, Martin A1 - Roces, Flavio T1 - Carbon dioxide sensing in an obligate insect-fungus symbiosis: CO\(_{2}\) preferences of leaf-cutting ants to rear their mutualistic fungus JF - PLoS ONE N2 - Defense against biotic or abiotic stresses is one of the benefits of living in symbiosis. Leaf-cutting ants, which live in an obligate mutualism with a fungus, attenuate thermal and desiccation stress of their partner through behavioral responses, by choosing suitable places for fungus-rearing across the soil profile. The underground environment also presents hypoxic (low oxygen) and hypercapnic (high carbon dioxide) conditions, which can negatively influence the symbiont. Here, we investigated whether workers of the leaf-cutting ant Acromyrmex lundii use the CO\(_{2}\) concentration as an orientation cue when selecting a place to locate their fungus garden, and whether they show preferences for specific CO\(_{2}\) concentrations. We also evaluated whether levels preferred by workers for fungus-rearing differ from those selected for themselves. In the laboratory, CO\(_{2}\) preferences were assessed in binary choices between chambers with different CO\(_{2}\) concentrations, by quantifying number of workers in each chamber and amount of relocated fungus. Leaf-cutting ants used the CO\(_{2}\) concentration as a spatial cue when selecting places for fungus-rearing. A. lundii preferred intermediate CO\(_{2}\) levels, between 1 and 3%, as they would encounter at soil depths where their nest chambers are located. In addition, workers avoided both atmospheric and high CO\(_{2}\) levels as they would occur outside the nest and at deeper soil layers, respectively. In order to prevent fungus desiccation, however, workers relocated fungus to high CO\(_{2}\) levels, which were otherwise avoided. Workers’ CO\(_{2}\) preferences for themselves showed no clear-cut pattern. We suggest that workers avoid both atmospheric and high CO\(_{2}\) concentrations not because they are detrimental for themselves, but because of their consequences for the symbiotic partner. Whether the preferred CO\(_{2}\) concentrations are beneficial for symbiont growth remains to be investigated, as well as whether the observed preferences for fungus-rearing influences the ants’ decisions where to excavate new chambers across the soil profile. KW - fungi KW - nesting habits KW - carbon dioxide KW - ants KW - social systems KW - humidity KW - symbiosis KW - fungal physiology Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-159561 VL - 12 IS - 4 ER - TY - JOUR A1 - Halboth, Florian A1 - Roces, Flavio T1 - The construction of ventilation turrets in Atta vollenweideri leaf-cutting ants: Carbon dioxide levels in the nest tunnels, but not airflow or air humidity, influence turret structure JF - PLoS ONE N2 - Nest ventilation in the leaf-cutting ant Atta vollenweideri is driven via a wind-induced mechanism. On their nests, workers construct small turrets that are expected to facilitate nest ventilation. We hypothesized that the construction and structural features of the turrets would depend on the colony’s current demands for ventilation and thus might be influenced by the prevailing environmental conditions inside the nest. Therefore, we tested whether climate-related parameters, namely airflow, air humidity and CO\(_{2}\) levels in the outflowing nest air influenced turret construction in Atta vollenweideri. In the laboratory, we simulated a semi-natural nest arrangement with fungus chambers, a central ventilation tunnel providing outflow of air and an aboveground building arena for turret construction. In independent series, different climatic conditions inside the ventilation tunnel were experimentally generated, and after 24 hours, several features of the built turret were quantified, i.e., mass, height, number and surface area (aperture) of turret openings. Turret mass and height were similar in all experiments even when no airflow was provided in the ventilation tunnel. However, elevated CO\(_{2}\) levels led to the construction of a turret with several minor openings and a larger total aperture. This effect was statistically significant at higher CO\(_{2}\) levels of 5% and 10% but not at 1% CO\(_{2}\). The construction of a turret with several minor openings did not depend on the strong differences in CO\(_{2}\) levels between the outflowing and the outside air, since workers also built permeated turrets even when the CO\(_{2}\) levels inside and outside were both similarly high. We propose that the construction of turrets with several openings and larger opening surface area might facilitate the removal of CO\(_{2}\) from the underground nest structure and could therefore be involved in the control of nest climate in leaf-cutting ants. KW - carbon dioxide KW - animal sociality KW - ants KW - fungi KW - humidity KW - social systems KW - nesting habits KW - fungal structure Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-159133 VL - 12 IS - 11 ER - TY - JOUR A1 - Nürnberger, Fabian A1 - Steffan-Dewenter, Ingolf A1 - Härtel, Stephan T1 - Combined effects of waggle dance communication and landscape heterogeneity on nectar and pollen uptake in honey bee colonies JF - PeerJ N2 - The instructive component of waggle dance communication has been shown to increase resource uptake of Apis mellifera colonies in highly heterogeneous resource environments, but an assessment of its relevance in temperate landscapes with different levels of resource heterogeneity is currently lacking. We hypothesized that the advertisement of resource locations via dance communication would be most relevant in highly heterogeneous landscapes with large spatial variation of floral resources. To test our hypothesis, we placed 24 Apis mellifera colonies with either disrupted or unimpaired instructive component of dance communication in eight Central European agricultural landscapes that differed in heterogeneity and resource availability. We monitored colony weight change and pollen harvest as measure of foraging success. Dance disruption did not significantly alter colony weight change, but decreased pollen harvest compared to the communicating colonies by 40%. There was no general effect of resource availability on nectar or pollen foraging success, but the effect of landscape heterogeneity on nectar uptake was stronger when resource availability was high. In contrast to our hypothesis, the effects of disrupted bee communication on nectar and pollen foraging success were not stronger in landscapes with heterogeneous compared to homogenous resource environments. Our results indicate that in temperate regions intra-colonial communication of resource locations benefits pollen foraging more than nectar foraging, irrespective of landscape heterogeneity. We conclude that the so far largely unexplored role of dance communication in pollen foraging requires further consideration as pollen is a crucial resource for colony development and health. KW - Apis mellifera KW - orientation KW - recruitment KW - landscape ecology KW - foraging behaviour KW - floral resource distribution Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-170813 VL - 5 IS - e3441 ER - TY - JOUR A1 - Lichtenstein, Leonie A1 - Grübel, Kornelia A1 - Spaethe, Johannes T1 - Opsin expression patterns coincide with photoreceptor development during pupal development in the honey bee, Apis mellifera JF - BMC Developmental Biology N2 - Background: The compound eyes of insects allow them to catch photons and convert the energy into electric signals. All compound eyes consist of numerous ommatidia, each comprising a fixed number of photoreceptors. Different ommatidial types are characterized by a specific set of photoreceptors differing in spectral sensitivity. In honey bees, males and females possess different ommatidial types forming distinct retinal mosaics. However, data are lacking on retinal ontogeny and the mechanisms by which the eyes are patterned. In this study, we investigated the intrinsic temporal and circadian expression patterns of the opsins that give rise to the ultraviolet, blue and green sensitive photoreceptors, as well as the morphological maturation of the retina during pupal development of honey bees. Results: qPCR and histological labeling revealed that temporal opsin mRNA expression differs between sexes and correlates with rhabdom elongation during photoreceptor development. In the first half of the pupal stage, when the rhabdoms of the photoreceptors are still short, worker and (dorsal) drone retinae exhibit similar expression patterns with relatively high levels of UV (UVop) and only marginal levels of blue (BLop) and green (Lop1) opsin mRNA. In the second half of pupation, when photoreceptors and rhabdoms elongate, opsin expression in workers becomes dominated by Lop1 mRNA. In contrast, the dorsal drone eye shows high expression levels of UVop and BLop mRNA, whereas Lop1 mRNA level decreases. Interestingly, opsin expression levels increase up to 22-fold during early adult life. We also found evidence that opsin expression in adult bees is under the control of the endogenous clock. Conclusions: Our data indicate that the formation of the sex-specific retinal composition of photoreceptors takes place during the second half of the pupal development, and that opsin mRNA expression levels continue to increase in young bees, which stands in contrast to Drosophila, where the highest expression levels are found during the late pupal stage and remain constant in adults. From an evolutionary perspective, we hypothesize that the delayed retinal maturation during the early adult phase is linked to the delayed transition from indoor to outdoor activities in bees, when vision becomes important. KW - insect vision KW - photoreceptor KW - spectral sensitivity KW - visual pigments KW - behavioral transition Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-175665 VL - 18 IS - 1 ER - TY - JOUR A1 - Frank, Erik Thomas A1 - Schmitt, Thomas A1 - Hovestadt, Thomas A1 - Mitesser, Oliver A1 - Stiegler, Jonas A1 - Linsenmair, Karl Eduard T1 - Saving the injured: Rescue behavior in the termite-hunting ant Megaponera analis JF - Science Advances N2 - Predators of highly defensive prey likely develop cost-reducing adaptations. The ant Megaponera analis is a specialized termite predator, solely raiding termites of the subfamily Macrotermitinae (in this study, mostly colonies of Pseudocanthotermes sp.) at their foraging sites. The evolutionary arms race between termites and ants led to various defensive mechanisms in termites (for example, a caste specialized in fighting predators). Because M. analis incurs high injury/mortality risks when preying on termites, some risk-mitigating adaptations seem likely to have evolved. We show that a unique rescue behavior in M. analis, consisting of injured nestmates being carried back to the nest, reduces combat mortality. After a fight, injured ants are carried back by their nestmates; these ants have usually lost an extremity or have termites clinging to them and are able to recover within the nest. Injured ants that are forced experimentally to return without help, die in 32% of the cases. Behavioral experiments show that two compounds, dimethyl disulfide and dimethyl trisulfide, present in the mandibular gland reservoirs, trigger the rescue behavior. A model accounting for this rescue behavior identifies the drivers favoring its evolution and estimates that rescuing enables maintenance of a 28.7% larger colony size. Our results are the first to explore experimentally the adaptive value of this form of rescue behavior focused on injured nestmates in social insects and help us to identify evolutionary drivers responsible for this type of behavior to evolve in animals. KW - Megaponera analis KW - rescue behavior Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-157933 VL - 3 IS - 4 ER - TY - JOUR A1 - Heiby, Julia C. A1 - Rajab, Suhaila A1 - Rat, Charlotte A1 - Johnson, Christopher M. A1 - Neuweiler, Hannes T1 - Conservation of folding and association within a family of spidroin N-terminal domains JF - Scientific Reports N2 - Web spiders synthesize silk fibres, nature’s toughest biomaterial, through the controlled assembly of fibroin proteins, so-called spidroins. The highly conserved spidroin N-terminal domain (NTD) is a pH-driven self-assembly device that connects spidroins to super-molecules in fibres. The degree to which forces of self-assembly is conserved across spider glands and species is currently unknown because quantitative measures are missing. Here, we report the comparative investigation of spidroin NTDs originating from the major ampullate glands of the spider species Euprosthenops australis, Nephila clavipes, Latrodectus hesperus, and Latrodectus geometricus. We characterized equilibrium thermodynamics and kinetics of folding and self-association using dynamic light scattering, stopped-flow fluorescence and circular dichroism spectroscopy in combination with thermal and chemical denaturation experiments. We found cooperative two-state folding on a sub-millisecond time scale through a late transition state of all four domains. Stability was compromised by repulsive electrostatic forces originating from clustering of point charges on the NTD surface required for function. pH-driven dimerization proceeded with characteristic fast kinetics yielding high affinities. Results showed that energetics and kinetics of NTD self-assembly are highly conserved across spider species despite the different silk mechanical properties and web geometries they produce. KW - spider KW - N-terminal domain KW - spidroin Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-159272 VL - 7 ER - TY - JOUR A1 - Groh, Claudia A1 - Rössler, Wolfgang T1 - Analysis of Synaptic Microcircuits in the Mushroom Bodies of the Honeybee JF - Insects N2 - Mushroom bodies (MBs) are multisensory integration centers in the insect brain involved in learning and memory formation. In the honeybee, the main sensory input region (calyx) of MBs is comparatively large and receives input from mainly olfactory and visual senses, but also from gustatory/tactile modalities. Behavioral plasticity following differential brood care, changes in sensory exposure or the formation of associative long-term memory (LTM) was shown to be associated with structural plasticity in synaptic microcircuits (microglomeruli) within olfactory and visual compartments of the MB calyx. In the same line, physiological studies have demonstrated that MB-calyx microcircuits change response properties after associative learning. The aim of this review is to provide an update and synthesis of recent research on the plasticity of microcircuits in the MB calyx of the honeybee, specifically looking at the synaptic connectivity between sensory projection neurons (PNs) and MB intrinsic neurons (Kenyon cells). We focus on the honeybee as a favorable experimental insect for studying neuronal mechanisms underlying complex social behavior, but also compare it with other insect species for certain aspects. This review concludes by highlighting open questions and promising routes for future research aimed at understanding the causal relationships between neuronal and behavioral plasticity in this charismatic social insect. KW - mushroom body KW - microglomeruli KW - projection neurons KW - Kenyon cells KW - dendritic specializations KW - structural synaptic plasticity KW - behavioral plasticity KW - vision KW - olfaction Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-200774 SN - 2075-4450 VL - 11 IS - 1 ER - TY - JOUR A1 - Kaya-Zeeb, Sinan A1 - Delac, Saskia A1 - Wolf, Lena A1 - Marante, Ana Luiza A1 - Scherf-Clavel, Oliver A1 - Thamm, Markus T1 - Robustness of the honeybee neuro-muscular octopaminergic system in the face of cold stress JF - Frontiers in Physiology N2 - In recent decades, our planet has undergone dramatic environmental changes resulting in the loss of numerous species. This contrasts with species that can adapt quickly to rapidly changing ambient conditions, which require physiological plasticity and must occur rapidly. The Western honeybee (Apis mellifera) apparently meets this challenge with remarkable success, as this species is adapted to numerous climates, resulting in an almost worldwide distribution. Here, coordinated individual thermoregulatory activities ensure survival at the colony level and thus the transmission of genetic material. Recently, we showed that shivering thermogenesis, which is critical for honeybee thermoregulation, depends on octopamine signaling. In this study, we tested the hypothesis that the thoracic neuro-muscular octopaminergic system strives for a steady-state equilibrium under cold stress to maintain endogenous thermogenesis. We can show that this applies for both, octopamine provision by flight muscle innervating neurons and octopamine receptor expression in the flight muscles. Additionally, we discovered alternative splicing for AmOARβ2. At least the expression of one isoform is needed to survive cold stress conditions. We assume that the thoracic neuro-muscular octopaminergic system is finely tuned in order to contribute decisively to survival in a changing environment. KW - honeybees KW - thermogenesis KW - cold stress KW - octopamine KW - octopamine receptors KW - gene expression Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-288753 SN - 1664-042X VL - 13 ER - TY - JOUR A1 - Villagomez, Gemma N. A1 - Nürnberger, Fabian A1 - Requier, Fabrice A1 - Schiele, Susanne A1 - Steffan-Dewenter, Ingo T1 - Effects of temperature and photoperiod on the seasonal timing of Western honey bee colonies and an early spring flowering plant JF - Ecology and Evolution N2 - Temperature and photoperiod are important Zeitgebers for plants and pollinators to synchronize growth and reproduction with suitable environmental conditions and their mutualistic interaction partners. Global warming can disturb this temporal synchronization since interacting species may respond differently to new combinations of photoperiod and temperature under future climates, but experimental studies on the potential phenological responses of plants and pollinators are lacking. We simulated current and future combinations of temperature and photoperiod to assess effects on the overwintering and spring phenology of an early flowering plant species (Crocus sieberi) and the Western honey bee (Apis mellifera). We could show that increased mean temperatures in winter and early spring advanced the flowering phenology of C. sieberi and intensified brood rearing activity of A. mellifera but did not advance their brood rearing activity. Flowering phenology of C. sieberi also relied on photoperiod, while brood rearing activity of A. mellifera did not. The results confirm that increases in temperature can induce changes in phenological responses and suggest that photoperiod can also play a critical role in these responses, with currently unknown consequences for real-world ecosystems in a warming climate. KW - Apis mellifera KW - climate change KW - rocus sieberi KW - phenology KW - plant–pollinator interaction KW - temporal mismatch Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-258770 VL - 11 IS - 12 ER - TY - JOUR A1 - Ruedenauer, Fabian A. A1 - Wöhrle, Christine A1 - Spaethe, Johannes A1 - Leonhardt, Sara D. T1 - Do honeybees (Apis mellifera) differentiate between different pollen types? JF - PLoS ONE N2 - Bees receive nectar and pollen as reward for pollinating plants. Pollen of different plant species varies widely in nutritional composition. In order to select pollen of appropriate nutritional quality, bees would benefit if they could distinguish different pollen types. Whether they rely on visual, olfactory and/or chemotactile cues to distinguish between different pollen types, has however been little studied. In this study, we examined whether and how Apis mellifera workers differentiate between almond and apple pollen. We used differential proboscis extension response conditioning with olfactory and chemotactile stimulation, in light and darkness, and in summer and winter bees. We found that honeybees were only able to differentiate between different pollen types, when they could use both chemotactile and olfactory cues. Visual cues further improved learning performance. Summer bees learned faster than winter bees. Our results thus highlight the importance of multisensory information for pollen discrimination. KW - pollen KW - bees KW - honey bees KW - conditioned response KW - behavioral conditioning KW - foraging KW - nutrients KW - sensory cues Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-177537 VL - 13 IS - 11 ER - TY - JOUR A1 - Kropf, Jan A1 - Rössler, Wolfgang T1 - In-situ recording of ionic currents in projection neurons and Kenyon cells in the olfactory pathway of the honeybee JF - PLoS ONE N2 - The honeybee olfactory pathway comprises an intriguing pattern of convergence and divergence: ~60.000 olfactory sensory neurons (OSN) convey olfactory information on ~900 projection neurons (PN) in the antennal lobe (AL). To transmit this information reliably, PNs employ relatively high spiking frequencies with complex patterns. PNs project via a dual olfactory pathway to the mushroom bodies (MB). This pathway comprises the medial (m-ALT) and the lateral antennal lobe tract (l-ALT). PNs from both tracts transmit information from a wide range of similar odors, but with distinct differences in coding properties. In the MBs, PNs form synapses with many Kenyon cells (KC) that encode odors in a spatially and temporally sparse way. The transformation from complex information coding to sparse coding is a well-known phenomenon in insect olfactory coding. Intrinsic neuronal properties as well as GABAergic inhibition are thought to contribute to this change in odor representation. In the present study, we identified intrinsic neuronal properties promoting coding differences between PNs and KCs using in-situ patch-clamp recordings in the intact brain. We found very prominent K+ currents in KCs clearly differing from the PN currents. This suggests that odor coding differences between PNs and KCs may be caused by differences in their specific ion channel properties. Comparison of ionic currents of m- and l-ALT PNs did not reveal any differences at a qualitative level. KW - action potentials KW - olfaction KW - honeybee Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-175869 VL - 13 IS - 1 ER - TY - JOUR A1 - Schilcher, Felix A1 - Thamm, Markus A1 - Strube-Bloss, Martin A1 - Scheiner, Ricarda T1 - Opposing actions of octopamine and tyramine on honeybee vision JF - Biomolecules N2 - The biogenic amines octopamine and tyramine are important neurotransmitters in insects and other protostomes. They play a pivotal role in the sensory responses, learning and memory and social organisation of honeybees. Generally, octopamine and tyramine are believed to fulfil similar roles as their deuterostome counterparts epinephrine and norepinephrine. In some cases opposing functions of both amines have been observed. In this study, we examined the functions of tyramine and octopamine in honeybee responses to light. As a first step, electroretinography was used to analyse the effect of both amines on sensory sensitivity at the photoreceptor level. Here, the maximum receptor response was increased by octopamine and decreased by tyramine. As a second step, phototaxis experiments were performed to quantify the behavioural responses to light following treatment with either amine. Octopamine increased the walking speed towards different light sources while tyramine decreased it. This was independent of locomotor activity. Our results indicate that tyramine and octopamine act as functional opposites in processing responses to light. KW - biogenic amines KW - neurotransmitter KW - phototaxis KW - ERG KW - behaviour KW - modulation KW - visual system KW - octopamine KW - tyramine KW - Apis mellifera Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-246214 SN - 2218-273X VL - 11 IS - 9 ER - TY - JOUR A1 - Fleischmann, Pauline N. A1 - Grob, Robin A1 - Rössler, Wolfgang T1 - Kompass im Kopf : wie Wüstenameisen lernen heimzukehren JF - Biologie in unserer Zeit N2 - Erfolgreiche räumliche Orientierung ist für viele Tiere eine alltägliche Herausforderung. Cataglyphis‐Wüstenameisen sind bekannt für ihre Navigationsfähigkeiten, mit deren Hilfe sie nach langen Futtersuchläufen problemlos zum Nest zurückfinden. Wie aber nehmen naive Ameisen ihre Navigationssysteme in Betrieb? Nach mehrwöchigem Innendienst im dunklen Nest werden sie zu Sammlerinnen bei hellem Sonnenschein. Dieser Wechsel erfordert einen drastischen Wandel im Verhalten sowie neuronale Veränderungen im Gehirn. Erfahrene Ameisen orientieren sich vor allem visuell, sie nutzen einen Himmelskompass und Landmarkenpanoramen. Daher absolvieren naive Ameisen stereotype Lernläufe, um ihren Kompass zu kalibrieren und die Nestumgebung kennenzulernen. Während der Lernläufe blicken sie wiederholt zum Nesteingang zurück und prägen sich so ihren Heimweg ein. Zur Ausrichtung ihrer Blicke nutzen sie das Erdmagnetfeld als Kompassreferenz. Cataglyphis‐Ameisen besitzen hierfür einen Magnetkompass, der bislang unbekannt war. N2 - Successful spatial orientation is a daily challenge for many animals. Cataglyphis desert ants are famous for their navi­gational performances. They return to the nest after exten­sive foraging trips without any problems. How do ants take their navigational systems into operation? After conducting different tasks in the dark nest for several weeks, they be­come foragers under bright sun light. This transition re­quires both a drastic switch in behavior and neuronal changes in the brain. Experienced foragers mainly rely on visual cues. They use a celestial compass and landmark panoramas. For that reason, naïve ants perform stereotype learning walks to calibrate their compass systems and ac­quire information about the nest’s surroundings. During their learning walks, the ants frequently look back to the nest entrance to learn the homing direction. For aligning their gazes, they use the earth’s magnetic field as a com­pass reference. This magnetic compass in Cataglyphis ants was previously unknown. KW - Cataglyphis-Wüstenameisen KW - Magnetkompass KW - Insektennavigation KW - Himmelskompass Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-219260 SN - 1521-415X VL - 50 IS - 2 ER - TY - JOUR A1 - Hesselbach, Hannah A1 - Scheiner, Ricarda T1 - Effects of the novel pesticide flupyradifurone (Sivanto) on honeybee taste and cognition JF - Scientific Reports N2 - Due to intensive agriculture honeybees are threatened by various pesticides. The use of one group of them, the neonicotinoids, was recently restricted by the European Union. These chemicals bind to the nicotinic acetylcholine receptor (nAchR) in the honeybee brain. Recently, Bayer AG released a new pesticide by the name of “Sivanto” against sucking insects. It is assumed to be harmless for honeybees, although its active ingredient, flupyradifurone, binds nAchR similar to the neonicotinoids. We investigated if this pesticide affects the taste for sugar and cognitive performance in honeybee foragers. These bees are directly exposed to the pesticide while foraging for pollen or nectar. Our results demonstrate that flupyradifurone can reduce taste and appetitive learning performance in honeybees foraging for pollen and nectar, although only the highest concentration had significant effects. Most likely, honeybee foragers will not be exposed to these high concentrations. Therefore, the appropriate use of this pesticide is considered safe for honeybees, at least with respect to the behaviors studied here. KW - animal behaviour KW - chemical ecology KW - pesticide KW - honeybee KW - taste KW - cognition KW - flupyradifurone Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-175853 VL - 8 IS - 4954 ER -