부산대학교 도서관

Milt volume in goldfish (Carassius auratus) is known to increase in response to both spawning interactions with prostaglandin F2α‐injected females (spawning stimuli) and a steroidal pheromone, 17α,20β‐dihydroxy‐4‐pregnen‐3‐one (17,20β‐P). In this study, we sought evidence that spawning stimuli and 17,20β‐P increase milt volume via different mechanisms, by determining latency of the milt response, and by comparing the effects of water temperature, hypophysectomy, and human chorionic gonadotropin (hCG) injection on milt response. At both 21 and 11°C, spawning stimuli increased milt volume within 2 hr, whereas 17,20β‐P exposure or hCG injection did not increase milt volume until 4‐6 hr at 21°C and 12‐24 hr at 11°C. Hypophysectomy did not block spawning‐induced milt increase but did block 17,20β‐P‐induced milt increase, consistent with earlier studies showing that pheromonal 17,20β‐P acts by increasing blood gonadotropin‐II (GtH‐II) level. Furthermore, in males injected with hCG to swamp the effect of 17,20β‐P‐induced GtH‐II increase, milt increase was observed in response to spawning stimuli but not to 17,20β‐P exposure. These results indicate that distinct mechanisms mediate the effects of spawning stimuli and 17,20β‐P on milt volume in goldfish. 17,20β‐P evidently acts by releasing pituitary GtH‐II, whereas the mechanism mediating the effect of spawning stimuli is unknown. The role of these two mechanisms in made reproductive function is discussed. © 1996 Wiley‐Liss, Inc.