Gonadal steroid levels in the turtle Emys orbicularis L.: A preliminary study in embryos, hatchlings, and young as a function of the incubation temperature of eggs

Abstract

Eggs of Emys orbicularis L. were incubated at either 25° (100% male-producing temperature) or at 30° (100% female-producing temperature). Gonadal levels of seven steroids were subsequently measured in embryos (stage 24), hatchlings, and young (3 and 9 months). According to the stage, 22–80 gonads were first removed and cultured in synthetic medium for 2 hr. They were then pooled and homogenized in this medium for steroid assay (RIA). The total steroid levels were weak (10–30 pg/gonad) in embryos and hatchlings and increased in the young turtles. In embryos, total steroid level was higher in males than in females, while at 9 months it was higher in females. As for the different steroids, the main following results were obtained. In embryos, progesterone (Prog), dehydroepiandrosterone (DHA), and testosterone (Testo) were not detected in either testes at 25° or ovaries at 30°, while Δ 4-androstenedione (Δ4A), dihydrotestosterone (DHT), and estrone (E1) were found in higher levels in testes (chiefly E1). Low levels in testes or traces in ovaries of estradiol (E2) were present. At hatching, E2 was no longer detectable, while DHA in both sexes and Testo in males were measurable. At this time, the other hormones displayed either minor variations in females or were decreased in males. At 3 months, Prog and E2 were still missing and only traces of E1 were detected. DHA decreased in males, while it increased in females. Levels of the other steroids, mainly Testo (in both sexes) and DHT (in males) increased. At 9 months, all steroids except E2 were detected. The total steroid content increased markedly, with the highest levels being found for Prog and Δ4A, chiefly in ovaries. This latter increase could be related to the posthatching differentiation of interstitial gland (Leydig cells) in testes and to follicle growth in ovaries.