@article{SchilcherHilsmannAnkenbrandetal.2022, author = {Schilcher, Felix and Hilsmann, Lioba and Ankenbrand, Markus J. and Krischke, Markus and Mueller, Martin J. and Steffan-Dewenter, Ingolf and Scheiner, Ricarda}, title = {Honeybees are buffered against undernourishment during larval stages}, series = {Frontiers in Insect Science}, volume = {2}, journal = {Frontiers in Insect Science}, issn = {2673-8600}, doi = {10.3389/finsc.2022.951317}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-304646}, year = {2022}, abstract = {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.}, language = {en} } @article{SchilcherHilsmannRauscheretal.2021, author = {Schilcher, Felix and Hilsmann, Lioba and Rauscher, Lisa and Değirmenci, Laura and Krischke, Markus and Krischke, Beate and Ankenbrand, Markus and Rutschmann, Benjamin and Mueller, Martin J. and Steffan-Dewenter, Ingolf and Scheiner, Ricarda}, title = {In vitro rearing changes social task performance and physiology in honeybees}, series = {Insects}, volume = {13}, journal = {Insects}, number = {1}, issn = {2075-4450}, doi = {10.3390/insects13010004}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-252305}, year = {2021}, abstract = {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.}, language = {en} } @article{HesselbachSeegerSchilcheretal.2020, author = {Hesselbach, Hannah and Seeger, Johannes and Schilcher, Felix and Ankenbrand, Markus and Scheiner, Ricarda}, title = {Chronic exposure to the pesticide flupyradifurone can lead to premature onset of foraging in honeybees Apis mellifera}, series = {Journal of Applied Ecology}, volume = {57}, journal = {Journal of Applied Ecology}, number = {3}, doi = {10.1111/1365-2664.13555}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-212769}, pages = {609-618}, year = {2020}, abstract = {1.Honeybees Apis mellifera and other pollinating insects suffer from pesticides in agricultural landscapes. Flupyradifurone is the active ingredient of a novel pesticide by the name of 'Sivanto', introduced by Bayer AG (Crop Science Division, Monheim am Rhein, Germany). It is recommended against sucking insects and marketed as 'harmless' to honeybees. Flupyradifurone binds to nicotinergic acetylcholine receptors like neonicotinoids, but it has a different mode of action. So far, little is known on how sublethal flupyradifurone doses affect honeybees. 2. We chronically applied a sublethal and field-realistic concentration of flupyradifurone to test for long-term effects on flight behaviour using radio-frequency identification. We examined haematoxylin/eosin-stained brains of flupyradifurone-treated bees to investigate possible changes in brain morphology and brain damage. 3. A field-realistic flupyradifurone dose of approximately 1.0 μg/bee/day significantly increased mortality. Pesticide-treated bees initiated foraging earlier than control bees. No morphological damage in the brain was observed. 4. Synthesis and applications. The early onset of foraging induced by a chronical application of flupyradifurone could be disadvantageous for honeybee colonies, reducing the period of in-hive tasks and life expectancy of individuals. Radio-frequency identification technology is a valuable tool for studying pesticide effects on lifetime foraging behaviour of insects.}, language = {en} } @article{SchilcherThammStrubeBlossetal.2021, author = {Schilcher, Felix and Thamm, Markus and Strube-Bloss, Martin and Scheiner, Ricarda}, title = {Opposing actions of octopamine and tyramine on honeybee vision}, series = {Biomolecules}, volume = {11}, journal = {Biomolecules}, number = {9}, issn = {2218-273X}, doi = {10.3390/biom11091374}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-246214}, year = {2021}, abstract = {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.}, language = {en} } @phdthesis{Schilcher2023, author = {Schilcher, Felix}, title = {Regulation of the nurse-forager transition in honeybees (\(Apis\) \(mellifera\))}, doi = {10.25972/OPUS-28935}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-289352}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2023}, abstract = {Honeybees are among the few animals that rely on eusociality to survive. While the task of queen and drones is only reproduction, all other tasks are accomplished by sterile female worker bees. Different tasks are mostly divided by worker bees of different ages (temporal polyethism). Young honeybees perform tasks inside the hive like cleaning and nursing. Older honeybees work at the periphery of the nest and fulfill tasks like guarding the hive entrance. The oldest honeybees eventually leave the hive to forage for resources until they die. However, uncontrollable circumstances might force the colony to adapt or perish. For example, the introduced Varroa destructor mite or the deformed wing virus might erase a lot of in-hive bees. On the other hand, environmental events might kill a lot of foragers, leaving the colony with no new food intake. Therefore, adaptability of task allocation must be a priority for a honeybee colony. In my dissertation, I employed a wide range of behavioral, molecular biological and analytical techniques to unravel the underlying molecular and physiological mechanisms of the honeybee division of labor, especially in conjunction with honeybee malnourishment. The genes AmOARα1, AmTAR1, Amfor and vitellogenin have long been implied to be important for the transition from in-hive tasks to foraging. I have studied in detail expression of all of these genes during the transition from nursing to foraging to understand how their expression patterns change during this important phase of life. My focus lay on gene expression in the honeybee brain and fat body. I found an increase in the AmOARα1 and the Amforα mRNA expression with the transition from in-hive tasks to foraging and a decrease in expression of the other genes in both tissues. Interestingly, I found the opposite pattern of the AmOARα1 and AmTAR1 mRNA expression in the honeybee fat body during orientation flights. Furthermore, I closely observed juvenile hormone titers and triglyceride levels during this crucial time. Juvenile hormone titers increased with the transition from in-hive tasks to foraging and triglyceride levels decreased. Furthermore, in-hive bees and foragers also differ on a behavioral and physiological level. For example, foragers are more responsive towards light and sucrose. I proposed that modulation via biogenic amines, especially via octopamine and tyramine, can increase or decrease the responsiveness of honeybees. For that purpose, in-hive bees and foragers were injected with both biogenic amines and the receptor response was quantified 1 using electroretinography. In addition, I studied the behavioral response of the bees to light using a phototaxis assay. Injecting octopamine increased the receptor response and tyramine decreased it. Also, both groups of honeybees showed an increased phototactic response when injected with octopamine and a decreased response when injected with tyramine, independent of locomotion. Additionally, nutrition has long been implied to be a driver for division of labor. Undernourished honeybees are known to speed up their transition to foragers, possibly to cope with the missing resources. Furthermore, larval undernourishment has also been implied to speed up the transition from in-hive bees to foragers, due to increasing levels of juvenile hormone titers in adult honeybees after larval starvation. Therefore, I reared honeybees in-vitro to compare the hatched adult bees of starved and overfed larvae to bees reared under the standard in-vitro rearing diet. However, first I had to investigate whether the in-vitro rearing method affects adult honeybees. I showed effects of in-vitro rearing on behavior, with in-vitro reared honeybees foraging earlier and for a shorter time than hive reared honeybees. Yet, nursing behavior was unaffected. Afterwards, I investigated the effects of different larval diets on adult honeybee workers. I found no effects of malnourishment on behavioral or physiological factors besides a difference in weight. Honeybee weight increased with increasing amounts of larval food, but the effect seemed to vanish after a week. These results show the complexity and adaptability of the honeybee division of labor. They show the importance of the biogenic amines octopamine and tyramine and of the corresponding receptors AmOARα1 and AmTAR1 in modulating the transition from inhive bees to foragers. Furthermore, they show that in-vitro rearing has no effects on nursing behavior, but that it speeds up the transition from nursing to foraging, showing strong similarities to effects of larval pollen undernourishment. However, larval malnourishment showed almost no effects on honeybee task allocation or physiology. It seems that larval malnourishment can be easily compensated during the early lifetime of adult honeybees.}, subject = {Biene}, language = {en} }