TY - JOUR A1 - Streinzer, Martin A1 - Brockmann, Axel A1 - Nagaraja, Narayanappa A1 - Spaethe, Johannes T1 - Sex and Caste-Specific Variation in Compound Eye Morphology of Five Honeybee Species JF - PLoS ONE N2 - Ranging from dwarfs to giants, the species of honeybees show remarkable differences in body size that have placed evolutionary constrains on the size of sensory organs and the brain. Colonies comprise three adult phenotypes, drones and two female castes, the reproductive queen and sterile workers. The phenotypes differ with respect to tasks and thus selection pressures which additionally constrain the shape of sensory systems. In a first step to explore the variability and interaction between species size-limitations and sex and caste-specific selection pressures in sensory and neural structures in honeybees, we compared eye size, ommatidia number and distribution of facet lens diameters in drones, queens and workers of five species (Apis andreniformis, A. florea, A. dorsata, A. mellifera, A. cerana). In these species, male and female eyes show a consistent sex-specific organization with respect to eye size and regional specialization of facet diameters. Drones possess distinctly enlarged eyes with large dorsal facets. Aside from these general patterns, we found signs of unique adaptations in eyes of A. florea and A. dorsata drones. In both species, drone eyes are disproportionately enlarged. In A. dorsata the increased eye size results from enlarged facets, a likely adaptation to crepuscular mating flights. In contrast, the relative enlargement of A. florea drone eyes results from an increase in ommatidia number, suggesting strong selection for high spatial resolution. Comparison of eye morphology and published mating flight times indicates a correlation between overall light sensitivity and species-specific mating flight times. The correlation suggests an important role of ambient light intensities in the regulation of species-specific mating flight times and the evolution of the visual system. Our study further deepens insights into visual adaptations within the genus Apis and opens up future perspectives for research to better understand the timing mechanisms and sensory physiology of mating related signals. KW - eyes KW - foraging KW - honey bees KW - insect flight KW - physiological parameters KW - sensory systems KW - vision KW - visual system Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-96412 ER - TY - JOUR A1 - Sponsler, Douglas A1 - Kallnik, Katharina A1 - Requier, Fabrice A1 - Classen, Alice A1 - Maihoff, A. Fabienne A1 - Sieger, Johanna A1 - Steffan-Dewenter, Ingolf T1 - Floral preferences of mountain bumble bees are constrained by functional traits but flexible through elevation and season JF - Oikos N2 - Patterns of resource use by animals can clarify how ecological communities have assembled in the past, how they currently function and how they are likely to respond to future perturbations. Bumble bees (Hymentoptera: Bombus spp.) and their floral hosts provide a diverse yet tractable system in which to explore resource selection in the context of plant–pollinator networks. Under conditions of resource limitation, the ability of bumble bees species to coexist should depend on dietary niche overlap. In this study, we report patterns and dynamics of floral morphotype preferences in a mountain bumble bee community based on ~13 000 observations of bumble bee floral visits recorded along a 1400 m elevation gradient. We found that bumble bees are highly selective generalists, rarely visiting floral morphotypes at the rates predicted by their relative abundances. Preferences also differed markedly across bumble bee species, and these differences were well-explained by variation in bumble bee tongue length, generating patterns of preference similarity that should be expected to predict competition under conditions of resource limitation. Within species, though, morphotype preferences varied by elevation and season, possibly representing adaptive flexibility in response to the high elevational and seasonal turnover of mountain floral communities. Patterns of resource partitioning among bumble bee communities may determine which species can coexist under the altered distributions of bumble bees and their floral hosts caused by climate and land use change. KW - resource selection KW - coexistence KW - competition KW - foraging KW - niche KW - pollinator Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-259653 VL - 2022 IS - 3 ER - TY - JOUR A1 - Schilcher, Felix A1 - Hilsmann, Lioba A1 - Rauscher, Lisa A1 - Değirmenci, Laura A1 - Krischke, Markus A1 - Krischke, Beate A1 - Ankenbrand, Markus A1 - Rutschmann, Benjamin A1 - Mueller, Martin J. A1 - Steffan-Dewenter, Ingolf A1 - Scheiner, Ricarda T1 - In vitro rearing changes social task performance and physiology in honeybees JF - Insects N2 - In vitro rearing of honeybee larvae is an established method that enables exact control and monitoring of developmental factors and allows controlled application of pesticides or pathogens. However, only a few studies have investigated how the rearing method itself affects the behavior of the resulting adult honeybees. We raised honeybees in vitro according to a standardized protocol: marking the emerging honeybees individually and inserting them into established colonies. Subsequently, we investigated the behavioral performance of nurse bees and foragers and quantified the physiological factors underlying the social organization. Adult honeybees raised in vitro differed from naturally reared honeybees in their probability of performing social tasks. Further, in vitro-reared bees foraged for a shorter duration in their life and performed fewer foraging trips. Nursing behavior appeared to be unaffected by rearing condition. Weight was also unaffected by rearing condition. Interestingly, juvenile hormone titers, which normally increase strongly around the time when a honeybee becomes a forager, were significantly lower in three- and four-week-old in vitro bees. The effects of the rearing environment on individual sucrose responsiveness and lipid levels were rather minor. These data suggest that larval rearing conditions can affect the task performance and physiology of adult bees despite equal weight, pointing to an important role of the colony environment for these factors. Our observations of behavior and metabolic pathways offer important novel insight into how the rearing environment affects adult honeybees. KW - honeybee KW - artificial rearing KW - behavior KW - in vitro KW - juvenile hormone KW - triglycerides KW - PER KW - foraging KW - nursing Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-252305 SN - 2075-4450 VL - 13 IS - 1 ER - TY - THES A1 - Röschard, Jacqueline T1 - Cutter, carriers and bucket brigades ... T1 - Fouragierentscheidungen der grasschneidenden Ameise Atta vollenweideri N2 - This study investigates the foraging behaviour of grass-cutting ants, Atta vollenweideri, with specific consideration of the following issues: (a) cutting behaviour and the determination of fragment size, (b) the effect of load size on transport economics, (c) division of labour and task-partitioning. Grass-cutting ants, Atta vollenweideri, harvest grass fragments that serve as substrate for the cultivation of a symbiotic fungus. Foragers were observed to cut grass fragments across the blade, thus resulting in longish, rectangular-shaped fragments in contrast to the semicircular fragments of leaf-cutting ants. Cutting was very time-consuming: In tough grasses like the typical grassland species Paspallum intermedium and Cyperus entrerrianus, cutting times lasted up to more than 20 minutes per fragment and roughly half of all initiated cutting attempts were given up by the ants. Foragers harvesting the softer grass Leersia hexandra were smaller than those foraging on the hard grasses. Fragment size determination and the extent of size-matching between ant body size and fragment size was investigated regarding possible effects of tissue toughness on decision-making and as a function of the distance from the nest. Tissue toughness affected decision-making such that fragment width correlated with ant body mass for the hard grass but not for the soft one, suggesting that when cutting is difficult, larger ants tend to select wider grasses to initiate cutting. The length of the fragments cut out of the two grass species differed statistically, but showed a large overlap in their distribution. Distance from the nest affected load size as well as the extent of size-matching: Fragments collected directly after cutting were significantly larger than those carried on the trail. This indicates that fragments were cut once again on their way to the nest. Size-matching depended on the trail sector considered, and was stronger in ants sampled closer to the nest, suggesting that carriers either cut fragments in sizes corresponding to their body mass prior transport, or transferred them to nestmates of different size after a short carrying distance. During transport, a worker takes a fragment with its mandibles at one end and carries it in a more or less vertical position. Thus, load length might particularly affect maneuverability, because of the marked displacement of the gravitational center. Conversely, based on the energetic of cutting, workers might maximise their individual harvesting rate by cutting long grass fragments, since the longer a grass fragment, the larger is the amount of material harvested per unit cutting effort. I therefore investigated the economics of load transport by focusing on the effects of load size (mass and length) on gross material transport rate to the nest. When controlling for fragment mass, both running speed of foragers and gross material transport rate was observed to be higher for short fragments. In contrast, if fragment mass was doubled and length maintained, running speed differed according to the mass of the loads, with the heavier fragments being transported at the lower pace. For the sizes tested, heavy fragments yielded a higher transport rate in spite of the lower speed of transport, as they did not slow down foragers so much that it counterbalanced the positive effects of fragment mass on material transport rate. The sizes of the fragments cut by grass-cutting ants under natural conditions therefore may represent the outcome of an evolutionary trade-off between maximising harvesting rate at the cutting site and minimising the effects of fragment size on material transport rates. I investigated division of labour and task partitioning during foraging by recording the behaviour of marked ants while cutting, and by monitoring the transport of fragments from the cutting until they reached the nest. A. vollenweideri foragers showed division of labour between cutting and carrying, with larger workers cutting the fragments, and smaller ones transporting them. This division was absent for food sources very close to the nest, when no physical trail was present. Along the trail, the transport of fragment was a partitioned task, i.e., workers formed bucket brigades composed of 2 to 5 carriers. This sequential load transport occurred more often on long than on short trails. The first carriers of a bucket brigade covered only short distances before dropping their fragments, turned back and continued foraging at the same food source. The last carriers covered the longest distance. There was no particular location on the trail for load dropping , i.e., fragments were not cached. I tested the predictions of two hypotheses about the causes of bucket brigades: First, bucket brigades might occur because of load-carriage effects: A load that is too big for an ant to be carried is dropped and carried further by nestmates. Second, fragments carried by bucket brigades might reach the nest quicker than if they are transported by a single carrier. Third, bucket brigades might enhance information flow among foragers: By transferring the load a worker may return earlier back to the foraging site and be able to reinforce the chemical trail, thus recruitment. In addition, the dropped fragment itself may contain information for unladen foragers about currently harvested sources and may enable them to choose between sources of different quality. I investigated load-carriage effects and possible time-saving by presenting ants with fragments of different but defined sizes. Load size did not affect frequency of load dropping nor the distance the first carrier covered before dropping, and transport time by bucket brigades was significantly longer than by single carriers. In order to study the information transfer hypothesis, I presented ants with fragments of different attractivity but constant size. Ants carrying high-quality fragments would be expected to drop them more often than workers transporting low-quality fragments, thus increasing the frequency of bucket brigades. My results show that increasing load quality increased the frequency of bucket brigades as well as it decreased the carrying distance of the first carrier. In other words, more attractive loads were dropped more frequently and after a shorter distance than less attractive ones with the first carriers returning to the foraging site to continue foraging. Summing up, neither load-carriage effects nor time-saving caused the occurrence of bucket brigades. Rather, the benefit might be found at colony level in an enhanced information flow. N2 - Die vorliegende Dissertation untersucht das Sammelverhalten der grasschneidenden Ameise Atta vollenweideri, unter besonderer Berücksichtigung der folgenden Themen: (a) das Schneideverhalten und die Wahl der Fragmentgröße, (b) der Effekt der Fragmentgröße auf den Transport und (c) die Arbeitsteilung während des Sammelns. Die Grasschneiderameise Atta vollenweideri sammelt Grasfragmente, die im Nest zerkleinert werden, um darauf einen symbiotischen Pilz zu züchten. Die Sammlerinnen schnitten ihre Fragmente quer über die Halmbreite, so dass längliche, rechteckige Fragmente entstehen, im Gegensatz zu den halbkreisförmigen Fragmenten der Blattschneiderameisen. Das Schneiden war ein sehr zeitaufwendiger Prozess: Bei harten Gräsern wie die für die Savanne typischen Paspallum intermedium und Cyperus entrerrianus betrug die Schneidezeit pro Fragment bis zu 20 Minuten oder länger. Etwa die Hälfte aller begonnenen Schnitte wurde von den Ameisen aufgegeben. Sammlerinnen, die das weichere Gras Leersia hexandra ernteten, waren kleiner als diejenigen, die die harten Gräser schnitten. Ich untersuchte, inwiefern die Härte des geschnittenen Materials und die Entfernung vom Nest einen Einfluss auf die Wahl der Fragmentgröße und auf die Stärke der Korrelation zwischen Ameisen- und Fragmentgröße hat. Die Länge „harter“ und „weicher“ Fragmente unterschied sich zwar statistisch, zeigte aber eine starke Überlappung. Die Korrelation zwischen Ameisen- und Fragmentgröße existierte bei dem harten Gras, nicht jedoch bei dem weichen Gras. Das heißt, dann wenn das Schneiden schwierig wird, suchen sich größere Tiere breitere Halme zum Schneiden (bzw. kleinere Tiere schmalere Halme). Sowohl Fragmentgröße als auch die Stärke der Korrelation zwischen Fragment- und Ameisengewicht hing von der Entfernung zum Nest ab: Fragmente, die ich direkt nach dem Schneiden sammelte, waren signifikant größer als solche, die ich auf dem Trail sammelte. Dies bedeutet, dass die Fragmente auf ihrem Weg zum Nest ein zweites Mal geschnitten wurden. Die Korrelation zwischen Fragment- und Ameisengewicht war um so stärker, je näher am Nest die Tiere gesammelt wurden, was bedeutet, dass die Trägerinnen entweder die Fragmente vor dem Transport entsprechend ihrer eigenen Körpergröße geschnitten hatten, oder aber dass die Fragmente nach einer kurzen Strecke an Nestgenossinnen anderer Körpergröße übergeben wurden. Um ein Fragment zu transportieren, packen A. vollenweideri-Arbeiterinnen das Fragment mit den Mandibeln an einem Ende und halten es mehr oder weniger senkrecht. Daher ist zu vermuten, dass lange Fragmente schwieriger zu manövrieren sind, da sich der Schwerpunkt mit zunehmender Länge nach oben verschiebt. Lange Fragmente haben jedoch den Vorteil, dass die Menge an geerntetem Material pro Schneideversuch größer ist als bei kurzen; Arbeiterinnen könnten also ihre Sammelrate jedoch dadurch maximieren, dass sie möglichst lange Fragmente schneiden. Im Hinblick auf die Schneidekosten wären dann also lange Fragmente vorteilhaft, im Hinblick auf den Transport hingegen kurze. Ich untersuchte daher den Effekt der Fragmentgröße (Länge und Gewicht) auf den Transport. Waren die Fragmente gleich schwer aber unterschiedlich lang, war die Laufgeschwindigkeit der Arbeiterinnen und damit auch die Eintragsrate bei den kurzen Fragmenten höher. Wenn hingegen das Fragmentgewicht verdoppelt und die Länge konstant gehalten wurde, unterschied sich die Laufgeschwindigkeit entsprechend dem Gewicht der Fragmente: Schwere Fragmente wurden langsamer getragen als leichte. Die Transportrate hingegen war für die schwereren Fragmente höher, da der höhere Eintrag aufgrund des zusätzlichen Gewichts die langsamere Laufgeschwindigkeit aufwog. Die Fragmentgrößen, die Grasschneiderameisen unter natürlichen Bedingungen schneiden, könnten daher im Laufe der Evolution aufgrund des Kompromisses entstanden sein, einerseits die Ernterate am Schneideort zu maximieren und andrerseits die negativen Effekten der Fragmentgröße auf den Transport möglichst gering zu halten. Ich untersuchte die Arbeitsteilung während des Sammelns, indem ich das Verhalten schneidender Tiere beobachtete und indem ich den Fragmenttransport vom Schneideplatz bis zum Nest verfolgte. Schneiden und Tragen von Fragmenten wurde von unterschiedlichen Arbeiterinnengruppen durchgeführt, wobei größere Sammlerinnen die Fragmente schnitten und kleinere sie transportierten. Diese Arbeitsteilung existierte nicht, wenn die Futterquelle sehr nah war, wenn also kein sichtbarer Trail vorhanden war. Der Transport selbst war ebenfalls unterteilt: Die Trägerinnen bildeten Arbeitsketten, die aus zwei bis fünf Trägerinnen bestanden. Diese Arbeitsketten kamen häufiger auf langen als auf kurzen Trails vor. Die ersten Trägerinnen einer solchen Arbeitskette legten nur eine kurze Strecke zurück, bevor sie das Fragment ablegten oder an eine Nestgenossin abgaben. Sie kehrten dann zur gleichen Futterquelle zurück und sammelten weiter. Die letzten Trägerinnen einer Arbeitskette transportierten die Fragmente über die größte Strecke. Es gab keine speziellen Orte auf dem Trail, an denen die Fragmente abgelegt wurden. Ich testete die Voraussagen zweier Hypothesen über den Entstehungsgrund von Arbeitsketten: Nach der ersten Hypothese könnten Arbeitsketten aufgrund von Transporteffekten entstehen, wenn z. B. ein Fragment für eine Ameise zu groß ist, daher abgelegt und von Nestgenossinnen weitergetragen wird. Fragmente könnten auch durch Arbeitsketten schneller transportiert werden, als wenn ein Tier die ganze Strecke bis zum Nest läuft. Nach der zweiten Hypothese könnten Arbeitsketten den Informationsfluss unter den Sammlerinnen erhöhen: Indem sie ein Fragment abgibt, kann eine Sammlerin früher zum Ernteort zurückkehren, sie kann so die Trailmarkierung verstärken und Nestgenossinnen rekrutieren. Zudem könnten unbeladene Arbeiterinnen durch das abgelegte Fragment selbst darüber informiert werden, was gerade geerntet wird. Dies könnte den Sammlerinnen die Möglichkeit geben, zwischen Futterquellen unterschiedlicher Attraktivität zu wählen. Ich untersuchte die Transporteffekte und die mögliche Zeitersparnis, indem ich Ameisen Fragmente unterschiedlicher, jedoch definierter Größe sammeln ließ. Die Fragmentgröße hatte weder einen Einfluss auf die Wahrscheinlichkeit, dass ein Fragment abgegeben wurde, noch auf die Strecke, die es vor der Abgabe getragen wurde. Die Transportzeiten waren höher für Fragmente, die durch Arbeitsketten transportiert wurden, als für solche, die ein Tier die ganze Strecke trug. Um die Informationsfluss-Hypothese zu untersuchen, ließ ich die Ameisen Fragmente sammeln, die gleich groß jedoch unterschiedlicher Attraktivität waren. Nach dieser Hypothese würde man erwarten, dass Ameisen ihre Fragmente eher ablegen, wenn sie attraktiv sind, um dann an den Ernteort zurückzukehren, so dass Arbeitsketten häufiger bei attraktiven Fragmenten auftreten sollten als bei weniger attraktiven. Meine Ergebnisse zeigen, dass ein Anstieg in der Attraktivität der Fragmente die Häufigkeit der Arbeitsketten erhöhte und dass die Strecke, die die erste Trägerin zurücklegte, kürzer war als bei weniger attraktiven Fragmenten. Anders ausgedrückt, attraktivere Fragmente wurden häufiger und nach kürzeren Strecken abgelegt als weniger attraktive. Das bedeutet also, dass die Ursache für das Vorkommen von Arbeitsketten weder in Transporteffekten noch in einer Zeitersparnis beim Transport zu suchen ist. Es scheint vielmehr, dass der Vorteil auf Kolonieebene liegt, indem der Informationsfluss unter den Sammlerinnen erhöht wird. KW - Atta KW - Nahrungserwerb KW - Verhalten KW - Grasschneiderameise KW - Atta vollenweideri KW - Sammeln KW - Fouragieren KW - Entscheidungen KW - Arbeitsketten KW - Information KW - Fragmentgröße KW - gras-cutting ants KW - Atta vollenweideri KW - foraging KW - decision-making KW - bucket brigades KW - task-partitioning KW - load size KW - size-matching KW - information Y1 - 2002 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-2240 ER - TY - JOUR A1 - Römer, Daniela A1 - Roces, Flavio T1 - Nest Enlargement in Leaf-Cutting Ants: Relocated Brood and Fungus Trigger the Excavation of New Chambers N2 - During colony growth, leaf-cutting ants enlarge their nests by excavating tunnels and chambers housing their fungus gardens and brood. Workers are expected to excavate new nest chambers at locations across the soil profile that offer suitable environmental conditions for brood and fungus rearing. It is an open question whether new chambers are excavated in advance, or will emerge around brood or fungus initially relocated to a suitable site in a previously-excavated tunnel. In the laboratory, we investigated the mechanisms underlying the excavation of new nest chambers in the leaf-cutting ant Acromyrmex lundi. Specifically, we asked whether workers relocate brood and fungus to suitable nest locations, and to what extent the relocated items trigger the excavation of a nest chamber and influence its shape. When brood and fungus were exposed to unfavorable environmental conditions, either low temperatures or low humidity, both were relocated, but ants clearly preferred to relocate the brood first. Workers relocated fungus to places containing brood, demonstrating that subsequent fungus relocation spatially follows the brood deposition. In addition, more ants aggregated at sites containing brood. When presented with a choice between two otherwise identical digging sites, but one containing brood, ants' excavation activity was higher at this site, and the shape of the excavated cavity was more rounded and chamber-like. The presence of fungus also led to the excavation of rounder shapes, with higher excavation activity at the site that also contained brood. We argue that during colony growth, workers preferentially relocate brood to suitable locations along a tunnel, and that relocated brood spatially guides fungus relocation and leads to increased digging activity around them. We suggest that nest chambers are not excavated in advance, but emerge through a self-organized process resulting from the aggregation of workers and their density-dependent digging behavior around the relocated brood and fungus. KW - fungi KW - ants KW - fungal structure KW - fungal pathogens KW - foraging KW - humidity KW - pupae KW - fungal diseases Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-112860 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 - Ruedenauer, Fabian A. A1 - Raubenheimer, David A1 - Kessner-Beierlein, Daniela A1 - Grund-Mueller, Nils A1 - Noack, Lisa A1 - Spaethe, Johannes A1 - Leonhardt, Sara D. T1 - Best be(e) on low fat: linking nutrient perception, regulation and fitness JF - Ecology Letters N2 - Preventing malnutrition through consuming nutritionally appropriate resources represents a challenge for foraging animals. This is due to often high variation in the nutritional quality of available resources. Foragers consequently need to evaluate different food sources. However, even the same food source can provide a plethora of nutritional and non‐nutritional cues, which could serve for quality assessment. We show that bumblebees, Bombus terrestris , overcome this challenge by relying on lipids as nutritional cue when selecting pollen. The bees ‘prioritised’ lipid perception in learning experiments and avoided lipid consumption in feeding experiments, which supported survival and reproduction. In contrast, survival and reproduction were severely reduced by increased lipid contents. Our study highlights the importance of fat regulation for pollen foraging bumblebees. It also reveals that nutrient perception, nutrient regulation and reproductive fitness can be linked, which represents an effective strategy enabling quick foraging decisions that prevent malnutrition and maximise fitness. KW - bee decline KW - foraging KW - nutrition KW - plant-insect interactions KW - pollen quality KW - PER KW - resource use Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-208709 VL - 23 IS - 3 ER - TY - JOUR A1 - Pielström, Steffen A1 - Roces, Flavio T1 - Sequential Soil Transport and Its Influence on the Spatial Organisation of Collective Digging in Leaf-Cutting Ants JF - PLoS ONE N2 - The Chaco leaf-cutting ant Atta vollenweideri (Forel) inhabits large and deep subterranean nests composed of a large number of fungus and refuse chambers. The ants dispose of the excavated soil by forming small pellets that are carried to the surface. For ants in general, the organisation of underground soil transport during nest building remains completely unknown. In the laboratory, we investigated how soil pellets are formed and transported, and whether their occurrence influences the spatial organisation of collective digging. Similar to leaf transport, we discovered size matching between soil pellet mass and carrier mass. Workers observed while digging excavated pellets at a rate of 26 per hour. Each excavator deposited its pellets in an individual cluster, independently of the preferred deposition sites of other excavators. Soil pellets were transported sequentially over 2 m, and the transport involved up to 12 workers belonging to three functionally distinct groups: excavators, several short-distance carriers that dropped the collected pellets after a few centimetres, and long-distance, last carriers that reached the final deposition site. When initiating a new excavation, the proportion of long-distance carriers increased from 18% to 45% within the first five hours, and remained unchanged over more than 20 hours. Accumulated, freshly-excavated pellets significantly influenced the workers' decision where to start digging in a choice experiment. Thus, pellets temporarily accumulated as a result of their sequential transport provide cues that spatially organise collective nest excavation. KW - animal behavior KW - ants KW - confidence interval KW - decision making KW - foraging KW - fungal structure KW - fungi KW - hormone transport Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-96275 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 - THES A1 - Paul, Jürgen T1 - The Mouthparts of Ants T1 - Die Mundwerkzeuge der Ameisen N2 - Ant mandible movements cover a wide range of forces, velocities and precision. The key to the versatility of mandible functions is the mandible closer muscle. In ants, this muscle is generally composed of distinct muscle fiber types that differ in morphology and contractile properties. Volume proportions of the fiber types are species-specific and correlate with feeding habits. Two biomechanical models explain how the attachment angles are optimized with respect to force and velocity output and how filament-attached fibers help to generate the largest force output from the available head capsule volume. In general, the entire mandible closer muscle is controlled by 10-12 motor neurons, some of which exclusively supply specific muscle fiber groups. Simultaneous recordings of muscle activity and mandible movement reveal that fast movements require rapid contractions of fast muscle fibers. Slow and accurate movements result from the activation of slow muscle fibers. Forceful movements are generated by simultaneous co-activation of all muscle fiber types. For fine control, distinct fiber bundles can be activated independently of each other. Retrograde tracing shows that most dendritic arborizations of the different sets of motor neurons share the same neuropil in the suboesophageal ganglion. In addition, some motor neurons invade specific parts of the neuropil. The labiomaxillary complex of ants is essential for food intake. I investigated the anatomical design of the labiomaxillary complex in various ant species focusing on movement mechanisms. The protraction of the glossa is a non muscular movement. Upon relaxation of the glossa retractor muscles, the glossa protracts elastically. I compared the design of the labiomaxillary complex of ants with that of the honey bee, and suggest an elastic mechanism for glossa protraction in honey bees as well. Ants employ two different techniques for liquid food intake, in which the glossa works either as a passive duct (sucking), or as an up- and downwards moving shovel (licking). For collecting fluids at ad libitum food sources, workers of a given species always use only one of both techniques. The species-specific feeding technique depends on the existence of a well developed crop and on the resulting mode of transporting the fluid food. In order to evaluate the performance of collecting liquids during foraging, I measured fluid intake rates of four ant species adapted to different ecological niches. Fluid intake rate depends on sugar concentration and the associated fluid viscosity, on the species-specific feeding technique, and on the extent of specialization on collecting liquid food. Furthermore, I compared the four ant species in terms of glossa surface characteristics and relative volumes of the muscles that control licking and sucking. Both probably reflect adaptations to the species-specific ecological niche and determine the physiological performance of liquid feeding. Despite species-specific differences, single components of the whole system are closely adjusted to each other according to a general rule. N2 - Ameisenmandibeln führen eine Vielzahl verschiedener Bewegungen bezüglich Kraft, Geschwindigkeit und Präzision aus. Der Schlüssel zu dieser Vielfalt ist der Mandibelschließmuskel. In Ameisen besteht dieser Muskel aus verschiedenen Muskelfasertypen, die sich sowohl morphologisch als auch anhand ihrer kontraktilen Eigenschaften unterscheiden. Die Anteile der Fasertypen am Gesamtvolumen des Mandibelschließers sind artspezifisch und korrelieren mit der für die Art typischen Lebensweise. Zwei biomechanische Modelle erklären, wie die Angriffswinkel der Muskelfasern am Apodem im Hinblick auf Kraft und Geschwindigkeit optimiert werden und wie Filamentfasern dazu beitragen, aus dem vorhandenen Kopfkapselvolumen die größtmögliche Kraft zu entwickeln. Der gesamte Mandibelschließmuskel wird von 10-12 Motoneuronen gesteuert, wovon manche ausschließlich bestimmte Muskelfasergruppen innervieren. Gleichzeitige Aufnahmen von Muskelaktivität und Mandibelbewegung ergeben, daß schnelle Bewegungen rasche Kontraktionen schneller Muskelfasern bedürfen. Langsame und präzise Bewegungen resultieren aus der Aktivierung langsamer Muskelfasern. Kraftvolle Bewegungen werden durch gleichzeitige Aktivierung aller Muskelfasertypen erzeugt. Für die Feinabstimmung können unterschiedliche Muskelfaserbündel unabhängig voneinander aktiviert werden. Retrograde Färbungsexperimente zeigen, daß die meisten dendritischen Verästelungen der verschiedenen Motoneuronen im gleichen Neuropil im Unterschlundganglion verlaufen. Darüberhinaus dringen einige Motoneuronen in jeweils spezifische Bereiche des Neuropils ein. Der Labiomaxillar-Komplex ist für die Nahrungsaufnahme der Ameisen essentiell. Ich untersuchte den Bauplan und die Bewegungsmechanismen des Labiomaxillar-Komplexes bei verschiedenen Ameisenarten. Das Herausklappen der Glossa beruht auf einer nicht durch Muskelkontraktion hervorgerufenen Bewegung. Bei Relaxation der Glossa-Rückziehmuskeln klappt die Glossa infolge elastischer Eigenschaften aus. Ein Vergleich des Bauplans des Labiomaxillar-Komplexes von Ameisen mit dem der Honigbiene legt nahe, daß die Glossa der Honigbiene ebenfalls mittels Elastizität in die exponierte Position gebracht wird. Um flüssige Nahrung aufzunehmen, nutzen Ameisen ihre Glossa entweder als passiven Kanal (Saugen) oder als eine sich auf- und abwärts bewegende Schaufel (Lecken). Während des Sammelns von Flüssigkeiten an ad libitum Futterquellen bedienen sich Arbeiterinnen einer Art stets nur einer von beiden Aufnahmetechniken. Die jeweils artspezifische Nahrungsaufnahmetechnik hängt von dem Vorhandensein eines gut ausgeprägten Kropfes sowie der daraus resultierenden Weise des Nahrungstransportes ab. Um die Leistung der Aufnahme flüssiger Nahrung zu beurteilen, bestimmte ich die Aufnahmeraten vier verschiedener Ameisenarten, die an unterschiedliche ökologische Nischen angepaßt sind. Die Aufnahmerate hängt von der Zuckerkonzentration und der damit verbundenen Viskosität ab, außerdem von der artspezifischen Aufnahmetechnik und dem Grad der Anpassung an das Sammeln flüssiger Nahrung. Darüberhinaus verglich ich die vier Ameisenarten bezüglich der Charakteristika der Glossaoberfläche sowie der relativen Volumina der am Lecken und Saugen beteiligten Muskeln. Beide spiegeln wahrscheinlich Anpassungen an die artspezifische ökologische Nische wieder und bestimmen die physiologischen Leistungen der Aufnahme flüssiger Nahrung. Trotz artspezifischer Unterschiede sind die einzelnen Komponenten des Systems entsprechend einer allgemeineren Regel fein aufeinander abgestimmt. KW - Ameisen KW - Mundgliedmassen KW - Ameisen KW - Insekten KW - Mundwerkzeuge KW - Verhaltensphysiologie KW - Biomechanik KW - Funktionsmorphologie KW - Neurobiologie KW - Muskelfasertypen KW - ants KW - insects KW - mouthparts KW - behavioral physiology KW - biomechanics KW - functional morphology KW - neurobiology KW - muscle fiber types KW - foraging Y1 - 2001 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-1179130 ER -