Caste- and Sex-Specific Differential Investment in Brain Regions of Australian Ants

Abstract

Even within a single species, closely related individuals exhibit distinct lifestyles that demand different information processing requirements. Worker ants are ambulatory and handle tasks like colony maintenance and foraging, while winged reproductive castes focus on mating and colony founding. Here, we compare the volumes of functionally distinct brain regions across alate males, alate females, and workers in two species of ants native to Australia, Myrmecia midas and Rhytidoponera metallica, to assess adaptations to behavioural, ecological, and locomotor demands. Female castes in both species had larger brains with pronounced mushroom bodies, supporting their broader behavioural repertoire and navigational tasks. In comparison, males exhibited smaller brains but enlarged optic lobes and central complexes, highlighting the significance of vision and orientation in mate searching. Species-specific patterns were also noted: R. metallica individuals consistently had larger antennal lobes and smaller optic lobes across castes, indicating a reliance on olfactory cues. However, the mushroom bodies remained comparatively similar. These findings demonstrate how caste- and species-specific sensory demands shape neural architecture and serve as a basis for understanding the interplay between brain structure and function.