Study On The Temperature-dependent Sexual Differentiation In Turtle (Chinemys Reevssii)

In many reptiles sexual differentiation is controlled by the incubating temperature of the embryo. With histological method, this paper studies the sexual differentiation and gonadal development of Chinemys reevesii under different incubating temperature and histological and cytological characteristics of its sexual gonads. Eggs of Chinemys reevesii were incubated at 26 , 33 and normal atmopheric temperature. Incubation at 33 resulted in females in 100% of the cases; Incubation at 26 resulted in males in 100% of the cases; Incubation at normal atmospheric temperature resulted in females, males and intersexualities. This study investigates the time when sexual differentiation is finished in Chinemys reevesii, using different combinations of incubation at a male-producing temperature(26 ) and at a female-producing temperature (33 ). Incubation at 33 , the female sexual differentiation is finished after 22-23 days (around stage 19), at 26 ,the male sexual differentiation is completed after 34-35 days (around stage 20). Once suxual differentiation is finished, the sex will not be reversed when the incubating temperature is changed.The females incubated at 33 , their ovarium has powerful cortex, the germinal epithlium produce oocyte, its medulla degenerate into ovarian cavity. During sexual differentiation, mitochondria and smooth endoplasmic reticulum in cells of ovary increase in quantity, they disintegrate after sexual differentiation. There are a lot of big grana in cells of ovary before sexual differentiation, in the course of sexual differentiation the quantity of the big grana decrease, while small grana increase and peakafter sexual differentiation. The males incubation at 26 , cortices of their testes degenerate into a thin albuginea. Medulla are formed by testicular cords in which scatter spermatogonium. During sexual differentiation, mitochondria and smooth endoplasmic reticulum in cells of testis also increase in quantity, but it is less than that in ovary, they disintegrate after sexual differentiation. The big grana always exsist in course of sexual differentiation, but small grana don't appear. The author consider that the grana are steroid hormone according to the studies of domestic and overseas scholars, the big grana should be androgens, the small grana should be estrogens. Estrogens are synthesized from androgens through the activity of aromatase. Besides fitting the own growth of gonad, the main function of the increase of mitochondria is to provide energy to the synthesis of estrogens, the main function of smooth endoplasmic reticulum is for the synthesis of the steroid hormone. But in differentiation of testis, estrogens are hardly synthesized from androgens, the increase of mitochondria and smooth endoplasmic reticulum is mainly used in the growth of gonad, so their quantities are less than that in ovary.Furthermore, this paper touches other problems such as factors influencing the development of embryonic, periods of gonad in sexual differentiation, histological and cytological characteristics of the primordial gonad, the sex determination influenced by incubating temperature, and the relationship of temperature and hormone, hormone and sexual differentiation, gene and sexual differentiation what are concerned by internal-external country in recent years.