The role of prolactin in fish reproduction

Abstract

Prolactin (PRL) has one of the broadest ranges of functions of any vertebrate hormone, and plays a critical role in regulating aspects of reproduction in widely divergent lineages. However, while PRL structure, mode of action and functions have been well-characterised in mammals, studies of other vertebrate lin- eages remain incomplete. As the most diverse group of vertebrates, fish offer a particularly valuable model system for the study of the evolution of reproductive endocrine function. Here, we review the cur- rent state of knowledge on the role of prolactin in fish reproduction, which extends to migration, repro- ductive development and cycling, brood care behaviour, pregnancy, and nutrient provisioning to young. We also highlight significant gaps in knowledge and advocate a specific bidirectional research method- ology including both observational and manipulative experiments. Focusing research efforts towards the thorough characterisation of a restricted number of reproductively diverse fish models will help to provide the foundation necessary for a more explicitly evolutionary analysis of PRL function.