Ethological principles predict the neuropeptides co-opted to influence parenting.

Abstract

Ethologists predicted that parental care evolves by modifying suitable behavioural precursors in the asocial ancestor, such as nest building, defensive and aggressive behaviours, and potentially shared resources. From this, we predicted that the evolved mechanistic changes would reside in genetic pathways underlying these behavioural precursors. We tested this by measuring differential expression of neuropeptides in female Nicrophorus vespilloides Parenting in this species is extensive and complex as caring adults regurgitate food to begging, dependent offspring. We identified neuropeptides associated with mating, feeding, aggression, and social interactions by sampling females in different behavioural states: solitary, actively parenting, or post-parenting and solitary. We measured peptide abundance in adult female brains and identified 130 peptides belonging to 17 neuropeptides. Of these 17, seven were differentially expressed. Six of the seven were up-regulated during parenting. None of the identified neuropeptides have previously been associated with parental care, but all have known roles in the behavioural precursors. Two, tachykinin and sulfakinin, influence multiple pathways. Our study supports the prediction that appropriate behavioural precursors are likely targets of selection during the evolution of parenting. Evolutionary principles predicted neuropeptides influencing social behaviour, and our results provide several new candidate neuropeptides underpinning parenting.