Identification of sex pheromones from the anal gland of male blennies

Salaria pavo is small bottom living fish in the shallow littoral zone of the Mediterranean and adjacent Atlantic coast. The closely related freshwater species, S. fluviatilis, inhabits rivers and lakes in the vicinity of the Mediterranean. In both species, the mating system is promiscuous. Males occupy holes or crevices in the hard substrate where females come to spawn and the males subsequently guard the eggs. These are a good model fish species to investigate specialization in sex pheromone production. The males develop anal glands from the epidermis of the first two rays of the anal fin concurrent with development of the gonads, that is a source of substances that attract pre-ovulatory females and thereby promotes male reproductive success. This suggests that male blennies are “active signallers” in contrast with known pheromone systems in teleosts, where receivers are “chemical spies” detecting gonadal steroids or prostaglandins.