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Caste differences in the mushroom bodies of swarm-founding paper wasps: implications for brain plasticity and brain evolution (Vespidae, Epiponini)
Journal article   Peer reviewed

Caste differences in the mushroom bodies of swarm-founding paper wasps: implications for brain plasticity and brain evolution (Vespidae, Epiponini)

Sean O'Donnell, Susan J. Bulova, Sara DeLeon, Meghan Barrett and Katherine Fiocca
Behavioral ecology and sociobiology, v 71(8)
01 Aug 2017

Abstract

Behavioral Sciences Ecology Environmental Sciences & Ecology Life Sciences & Biomedicine Science & Technology Zoology
Eusocial insect reproductive castes (in Hymenoptera, female reproductive queens and sterile workers) differ dramatically in behavior. Castes may differ in the cognitive demands that affect patterns of brain tissue investment. Queens and workers diverge most strongly in the advanced eusocial, or swarm-founding species, where queens do not forage and rarely leave their nests. We asked whether reproductive castes of swarm-founding paper wasps in the tribe Epiponini differed in the relative sizes of their mushroom bodies (MB), a key brain region involved in sensory integration, and in learning and memory. We measured brain-size corrected volumes of the MB dendritic-field neuropils (calyces) and the MB axonal bundles (peducles and lobes) for queens and workers from 16 species of 10 genera of the tribe Epiponini. The subject species spanned much of the epiponine phylogeny, differing in colony size and degree of caste differentiation. Queens had significantly higher relative MB investment than workers, both for the MB in toto and for the MB calyces. The magnitude of queen-worker MB size differences did not covary significantly with body size, but species with larger colonies had stronger caste differences in MB size. A review of caste differences in MB volume across a wide range of social Hymenoptera taxa suggested a positive association of MB investment with social dominance is widespread. Significance statement Social insect castes (reproducing queens and sterile workers) differ strongly in behavior, particularly in swarm-founding species where queens are largely nest-bound. Caste comparisons are a powerful model for understanding brain/behavior relationships. We measured the relative size of a key insect brain region, the mushroom bodies (MB), in 16 swarm-founding wasp species. MBare involved in sensory integration, and in learning and memory. Queens had relatively larger MB than workers, and the magnitude of the queen-worker differences increased with species average colony size. We suggest the reproductive dominance and social contact of nest-bound queens promotes greater mushroom body investment.

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Web of Science research areas
Behavioral Sciences
Ecology
Zoology
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