Hormonal Regulation of Female Reproductive Behavior in Fish

SYNOPSIS. Fundamentally different mechanisms regulate femalesexual behavior in the ovoviviparous guppy and the oviparousgoldfish. In the female guppy, ovarian estrogen evidently synchronizescycles of sexual receptivity with endogenous cycles of ovarianmaturation and also increases female attractivity at the timeof maximum receptivity by stimulating the release of a sexualpheromone. In the goldfish, it appears that prostaglandin, releasedfrom the ovary or oviduct in conjunction with ovulation andthe presence of ovulated eggs, acts on the brain to stimulatespawning behavior. In contrast to the situation in the guppy,steroid treatments alone (in the absence of ovulated eggs) failto stimulate spawning behavior in the goldfish. It isproposedthat endocrine mechanisms regulating female sexual behaviorin the teleosts and in other vertebrates are less related tophylogeny than to the mode of reproduction employed. In thegoldfish and several other externally fertilizing teleosts,where sexual behavior involves oviposition, female sexual behaviorapparently is synchronized with ovulation by mechanisms whichrespond to elevated plasma prostaglandin as an indicator ofthe presence of ovulated eggs. In internally fertilizing species(guppy, reptiles, birds, mammals), where sexual behavior andfertilizationare temporally dissociated, female sexual behavior is synchronizedwith ovulation by mechanisms which anticipate either an imminentspontaneous ovulation, or the potential for reflex ovulation,by responding to increases in plasma estrogen associated withfolliculardevelopment.