Divergent brain gene expression profiles between alternative behavioural helper types in a cooperative breeder, Neolamprologus pulcher. Neolamprologus pulcher

Juveniles of the cooperatively-breeding cichlid fish Neolamprologus pulcher either consistently provide help in form of alloparental egg care ('cleaners') or consistently abstain from helping ('non-cleaners'). These phenotypes are not based on heritable genetic differences. Instead they arise during ontogeny, which should lead to differences in brain structure or physiology, a currently untested prediction. We compared brain gene expression profiles of cleaners and non-cleaners in two experimental conditions, a helping opportunity and a control condition. We aimed to identify (i) expression differences between cleaners and non-cleaners in the control, (ii) changes in gene expression induced by the opportunity, and (iii) differences in plasticity of gene expression between cleaners and non-cleaners. Control cleaners and non-cleaners differed in the expression of a single gene, irx2, which regulates neural differentiation.