Determining the Causal Link of Honey Bee Gut Microbial Composition on Behavioral Maturation

Emerging studies have supported the association between gut microbiome and host behaviors. However, it is unclear whether changes in the gut microbiome cause changes in host behaviors or vice versa. The European honey bee, Apis mellifera, is an excellent animal model for identifying the causal link between microbiome and behavioral changes over the lifetime of the host as the honey bee gut contains a simple microbiome composed of only nine bacterial taxa clusters. In honey bees, division of labor occurs through behavioral maturation where age determines what task a bee does. For example, older bees forage while younger bees perform brood care (nursing) and other in-hive tasks. Single cohort colonies (SCCs), or colonies composed of individuals of the same age, uncouple chronological age effects on honey bee behavioral maturation (nursing → foraging). SCCs results from our previous experiment reveal a highly significant difference in the gut microbiota between nurses and foragers, independent of age, specifically in the abundance of Lactobacillus mellis and Bifidobacterium asteroides

The gut microbiome defines social group membership in honey bee colonies

In the honey bee, genetically related colony members innately develop colony-specific cuticular hydrocarbon profiles, which serve as pheromonal nestmate recognition cues. Yet, despite high intracolony relatedness, the innate development of colony-specific chemical signatures by individual colony members is largely determined by the colony environment, rather than solely relying on genetic variants shared by nestmates. Therefore, it is puzzling how a nongenic factor could drive the innate development of a quantitative trait that is shared by members of the same colony. Here, we provide one solution to this conundrum by showing that nestmate recognition cues in honey bees are defined, at least in part, by shared characteristics of the gut microbiome across individual colony members. These results illustrate the importance of host-microbiome interactions as a source of variation in animal behavioral traits

A pleiotropic chemoreceptor facilitates the production and perception of mating pheromones

Summary: Optimal mating decisions depend on the robust coupling of signal production and perception because independent changes in either could carry a fitness cost. However, since the perception and production of mating signals are often mediated by different tissues and cell types, the mechanisms that drive and maintain their coupling remain unknown for most animal species. Here, we show that in Drosophila, behavioral responses to, and the production of, a putative inhibitory mating pheromone are co-regulated by Gr8a, a member of the Gustatory receptor gene family. Specifically, through behavioral and pheromonal data, we found that Gr8a independently regulates the behavioral responses of males and females to a putative inhibitory pheromone, as well as its production in the fat body and oenocytes of males. Overall, these findings provide a relatively simple molecular explanation for how pleiotropic receptors maintain robust mating signaling systems at the population and species levels