This study establishes that ovulated female goldfish release F type prostaglandins (PGFs) to the water where they stimulate male spawning behavior and comprise the goldfish postovulatory pheromone. We first demonstrated that ovulated and prostaglandin-injected female goldfish release immunoreactive PGFs to the water. Next, using electro-olfactogram recording (EOG), we determined that waterborne prostaglandins function as potent olfactory stimulants for mature male goldfish. Prostaglandin F2 alpha (PGF2 alpha) and its metabolite 15-keto-prostaglandin F2 alpha (15K-PGF2 alpha) were the most potent prostaglandins; the former had a detection threshold of 10(-10) M and the latter a detection threshold of 10(-12) M. Studies of prostaglandin-injected fish indicated that PGF metabolites are an important component of the pheromone. Cross-adaptation experiments using the EOG demonstrated that goldfish have separate olfactory receptor sites for PGF2 alpha and 15K-PGF2 alpha that are independent from those that detect other olfactory stimulants. Finally, we established that male goldfish exposed to low concentrations of waterborne PGFs exhibit reproductive behaviors similar to those elicited by exposure to the odor of ovulated fish. Together with our recent discovery that a steroidal maturational hormone functions as a preovulatory "priming" pheromone for goldfish, these findings suggest that hormones and their metabolites may commonly serve as reproductive pheromones in fish.

No abstract

No abstract

Prostaglandins (PGs) have been identified in gonads, semen, ovarian fluid, blood, and in vitro ovarian incubates from a variety of teleosts. In teleosts, PGs appear to be involved in ovulation (follicular rupture) and female sexual behavior, and possibly in gonadotropin (GtH) secretion. An increase in prostaglandin F (PGF) levels associated with GtH-induced ovulation occurs in vivo in the pond loach (Misgurnus anguillicaudatus) and goldfish (Carassius auratus). Indomethacin (PG synthesis inhibitor) blocks ovulation in these species and, in goldfish, PG injection reverses this blockade. PGF2α stimulates in vitro ovulation in rainbow trout (Salmo gairdneri), brook trout (Salvelinus fontinalis), and yellow perch (Perca flavescens); however, in perch, PGE2 is the most potent prostaglandin. Addition of melatonin to incubation medium both inhibits ovulation and decreases PGE and PGF synthesis in yellow perch, while addition of epinephrine and theophylline both enhances ovulation and increases PGE and PGF synthesis. Several studies indicate that PG, released from the ovaries or oviduct in response to the presence of ovulated oocytes, acts on the brain to stimulate female spawning behavior in the goldfish. Other externally fertilizing teleosts may use similar mechanisms to synchronize female sexual behavior with ovulation.Key words: prostaglandins, fish reproduction, ovulation, sexual behavior

No abstract