Endocrine changes during natural spawning in the white sucker, Catostomus commersoni: I. Gonadotropin, growth hormone, and thyroid hormones☆

摘要: White suckers (Catostomus commersoni; Cypriniformes, Teleosteii) spawning in a small stream central Alberta were captured during different stages of their migrations 1981 and 1982, blood was sampled, the fish examined to determine reproductive condition. Blood samples analyzed for gonadotropin (GtH), growth hormone (GH), triiodothyronine (T3), thyroxine (T4) by radioimmunoassay. GtH levels both sexes lowest prior onset spawning, increased significantly males, females which germinal vesicle migration had begun, ovulated then dropped spent sexes. GH prespawning females, at ovulation, remained high females. In contrast, males relatively constant throughout spawning. sexes, highest T4 found fish, decreased fish. Although similar decline seen T3 1981, 1982 there no changes associated with No significant diurnal variations detected or T3; appeared vary on basis only. Spawning activity therefore appears be increases occurring ovulation initiation males. may also related condition but not The relationship thyroid is less clear, however, these reflect endocrine environmental influences function.