In Vitro Rearing Changes Social Task Performance and Physiology in Honeybees.

Felix Schilcher,Beate Krischke,Ricarda Scheiner,Ingolf Steffan-Dewenter,Markus Krischke,Markus Ankenbrand,Martin J Mueller,Laura Değirmenci,Lioba Hilsmann,Lisa Rauscher,Benjamin Rutschmann

doi:10.3390/insects13010004

Abstract

Simple SummaryThe rearing of honeybee larvae in the laboratory is an important tool for studying the effects of plant protection products or pathogens on developing and adult bees, yet how rearing under artificial conditions affects the later social behavior and physiology of the honeybees is mostly unknown. We, here, show that honeybees reared in the laboratory generally had a lower probability for performing nursing or foraging tasks compared to bees reared under natural conditions in bee colonies. Nursing behavior itself appeared normal in in vitro honeybees. In contrast, bees reared in the laboratory foraged for a shorter period in life and performed fewer trips compared to bees reared in colonies. In addition, in vitro honeybees did not display the typical increase in juvenile hormone titer, which goes hand-in-hand with the initiation of foraging in colony-reared bees.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.

Highlights

Eusociality and division of labour are key factors in a functioning honeybee colony
The individuals performing nursing tasks did not differ in their task performance between rearing conditions, i.e., onset of nursing behavior (Figure 1B and Table 2), teTrambliena2t)i,otneromf innuartsioinngobfenhuarvsiionrg(Fbieghuarveio1rC(aFnigduTreab1lCe 2a)nadnTdanbulers2in) gansdpannu(rFsiinggursep1aDn.and Table 2)
The likelihood for performing these tasks was significantly reduced in bees reared in vitro compared to naturally reared honeybees

Summary

Introduction

Eusociality and division of labour are key factors in a functioning honeybee colony. The colony strongly depends on the proper execution and appropriate timing of various tasks by its members [1,2]. At about 20 days of age, honeybees leave the colony to collect resources for the colony, e.g., nectar and pollen [1,2]. This age-dependent behavioral shift is very plastic. Another study showed that nurse bees infested with the varroa mite are less attracted to brood pheromone compared to uninfested honeybees [7]. How these environmental stressors can influence the colony on a developmental level is poorly understood

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Conclusion