Comparative neuroanatomy of ant mushroom bodies

Ants exhibit complex social behaviors and diverse ecological adaptations which make them a great subject for neuroanatomical studies. One of the key parts of their brain, mushroom bodies, receive and process olfactory and visual inputs from the antennal and visual lobes and are responsible for learning and storing sensory information. Their calyces have been speculated to be a key to the ants‘ diverse social structures and ecological adaptations. The main goal of this study is to describe the diversity of shapes and relative volumes of calyces and their subregions broadly across ant genera (77 species, 8 subfamilies). We used micro-CT scanning and segmented the calyces of the workers into two main subregions: lip and collar. Our analysis reveals allometric scaling in both subregions: the collar scales more steeply with brain volume compared to the lip, which is caused by the lip’s larger contribution to the overall volume of the calyces compared to the collar. Additionally, the collar demonstrates greater variability in volume compared to the lip, suggesting that visual system investment is more variable across species. The retrieved data highlight a clear correlation between sensory investment and calyx structure, with the sizes of the collars and lips reflecting the relative emphasis on visual and olfactory processing across species.