Meeting Abstract
Mangrove rivulus (Kryptolebias marmoratus) are self-fertilizing hermaphroditic teleost fish that range from Central Florida to Central America and that make occasional forays onto land in search of prey, to escape poor water conditions, or to thermoregulate. In a previous study, we observed that terrestrial behaviors varied considerably among animals originating from different geographical regions. In an attempt to study how regular training would affect jumping performance of individuals from different populations throughout the range, we conducted exercise trials once per week. These trials consisted of a fish being placed into a shallow pool (110 cm diameter) with wetted bench liner and induced to jump via tail-flipping by chasing it for one minute with the end of a blunt dowel. Within a few weeks, some specimens from particular populations in the Florida Keys began to change color from mottled brown to orange, indicative of the fish transitioning sex from hermaphrodite to male. Interestingly, we observed these phenotypic color changes to occur at different temporal intervals and different intensities across different lineages. Environments in which males experience greatest fitness and/or environments that shift the cost:benefit ratio of being one sex or the other, should favor sex change. The proximate mechanisms underlying exercise-induced sexual transitions are unknown but we hypothesize a shift in sex steroid hormone profiles accompanying phenotypic color changes. Understanding the plasticity of gene expression and physiology that initiate sex change will help us understand how the environment affects life history strategies of this self-fertilizing fish.
