Changes in Plasma Steroid Hormone Levels During Gonadal Maturation in Female Goldfish Carassius auraturs

Abstract

Levels of plasma estradiol-17β, testosterone, progesterone, 17α-hydroxyprogesterone (17α-OHprog) and 17α, 20β-dihydroxy-4-pregnen-3-one (17α, 20β-diOHprog) were assayed by radio-immunoassay during gonadal maturation in female goldfish Carassius auratus which have an asynchronous ovary in which oocytes are found at various stages of development. Estradiol-17β was maintained at low levels (below 3ng/ml) from December to February, reached a peak of about 7.5ng/ml in March which was maintained after ovulation. Plasma testosterone levels significantly increased in March and remained at high levels (8-14ng/ml) in ovulated fish and increased again in fish 15 days after ovulation (about 26ng/ml). Progestogens (progesterone, 17α-OHprog, 17α, 20β-diOHprog) were very low from December to February, rapidly increased just before or after ovulation and decreased 1 day after ovulation. Estradiol-17β levels and the gonadosomatic index (GSI) correlated well from December to March; the GSI was low from December to February (about 5), increased rapidly to about 13 in March and again increased to 18 on April 30. These results are discussed in relation to other studies on seasonal changes in plasma steroid levels in species in which the ovary is of the total synchronism or group synchronism type.