Dynamic regulation of brain aromatase and isotocin receptor gene expression depends on parenting status.

Fathering behavior is critical for offspring survival in many species across diverse taxa, but our understanding of the neuroendocrine mechanisms regulating paternal care is limited in part because of the few primarily paternal species among the common animal models. However, many teleosts display primarily paternal care, and among the teleosts, anemonefish species are particularly well suited for isolating molecular mechanisms of fathering as they perform parental care in isolation of many other typically competing behaviors such as territorial defense and nest building. The goal of this study was to determine the extent to which whole brain gene expression levels of isotocin receptors, arginine vasotocin receptors, and aromatase as well as circulating levels of the bioactive sex steroid hormones estradiol (E2) and 11-ketotestosterone (11KT) vary in association with parenting behavior in Amphiprion ocellaris. Brain aromatase and IT receptor gene expression were higher in both males and females that were parenting versus not. IT receptor expression was overall higher in males than females, which we interpret is a reflection of the greater parental effort that males display. Aromatase was overall higher in females than males, which we conclude is related to the higher circulating E2, which crosses into the brain and increases aromatase transcription. Results suggest both aromatase and IT receptors are dynamically upregulated in the brains of A. ocellaris males and females to support high levels of parental effort.