Monday, December 11, 2006 - 8:35 AM

Social aggression, reproductive dominance and mushroom body organization in the paper wasp Polistes instabilis

Yamile Molina, and Sean O'Donnell, University of Washington, Animal Behaviour Program, Box 351525, Psychology Dept, Seattle, WA

The mushroom bodies in insect brains have been implicated in sensory integration, as well as learning and memory. Eusocial insects are excellent models for testing functional neural plasticity in the mushroom bodies because of the nest mates are geneticallly related, but show task-related differences in environmental experience and social interactions. Previous research on eusocial insects shows experience-dependent changes in neural structure (i.e. enlarged mushroom body calyces) to be positively correlated with task performance and social interactions. In this study, we quantified relationships of task performance and social dominance with mushroom body development following nest mate removals in Polistes instabilis, a primitively eusocial paper wasp. We recorded rates of abdominal vibrations, biting interactions, and foraging before and after experimental removals of socially dominant workers. We found that reproductive and social dominance were both positively associated with increases in calycal neuropil relative to the Kenyon cell body region. Furthermore, post-removal rates of foraging were negatively associated with calyx: Kenyon cell body layer ratios. These findings suggest that neural organization may actually reflect social mechanisms (i.e. dominance) behind task performance in some cases, rather than the cognitive challenges of the tasks themselves.

Species 1: Hymenoptera Vespidae Polistes instabilis (paper wasp)

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