Hormones, pheromones and reproductive behavior

Fish commonly use reproductive hormones ( steroids and prostaglandins) both as endogenous signals between reproductive tract and brain and as exogenous signals (hormonal pheromones) that synchronize gamete maturation and/or spawning interactions between and among conspecifics. This dual function for hormonal products not only extends traditional concepts that sex hormone actions are limited to reproductive synchrony within the individual, but also implies we are unlikely to achieve a comprehensive understanding of reproductive function in any fish without knowledge of both the endogenous and exogenous actions of its hormones and related released compounds. Such knowledge is beginning to accumulate for several species ( e. g. goldfish, Atlantic salmon), but even here is far from complete. Moreover, because hormonal pheromone studies have focused on oviparous gonochorists with relatively simple reproductive strategies, we know nothing about the potential hormonal pheromone functions of the numerous species with sequential hermaphroditism or alternative male strategies, or the possible changes in pheromone function associated with the numerous transitions from oviparity to viviparity. Given the insights we have gained from studies of traditional species, it seems certain that expanding hormonal pheromone research to nontraditional species exemplifying the diverse nature of fish mating systems will similarly enrich our understanding of fish reproductive function.