Meeting Abstract
Social animals face unique selection pressures, including selection on brain development. In some bees, the brains of social queens, social workers, and solitary individuals are morphologically distinct. The mushroom bodies are the brain regions in insects responsible for higher-order processing, and these tend to be relatively larger in older bees compared to newly-emerged bees and larger in social bees compared to their solitary counterparts. That mushroom bodies are plastic over time suggests that the brain differences between solitary and social bees develop over the adult lifetime of the bees, but whether these changes are due to age or experience is not known. We tested the hypothesis that adult experience alters brain morphology in the facultatively social sweat bee Megalopta genalis. We collected four groups of bees: newly-emerged bees with no experience, bees that had experience with their mothers and searching for nest sites, bees that lacked these experiences but were placed in observation nests that mimicked natural nests, and bees that were isolated for ten days, completely lacking any natural experience. Using confocal microscopy, we measured total brain volume and relative mushroom body volume on the brains of bees from these four groups. Our analyses suggest that there were not significant differences in total brain volume among the four groups, but that there were significant differences in relative mushroom body volume. However, no clear pattern emerged, as newly-emerged bees and bees from observation nests had higher relative mushroom body volumes than bees in the other groups. A follow-up study will determine if changes in the brain across development show the same pattern in solitary and social bees, given that differences between a solitary and social developmental trajectory might help explain our results.
