STUDIES ON SEX DETERMINATION IN THE AMERICAN ALLIGATOR ALLIGATOR-MISSISSIPPIENSIS

Estradiol-17 beta was measured in the plasma and urogenital tissues of male and female alligator embryos. Hormone levels were generally very low and there was no significant differences between the sexes. There were no significant changes in estrogen levels during the period of g onadal differentiation in either sex. Alligator embryos incubated at m ale producing temperatures were feminized by small doses of estrogen a pplied to the egg shell. The antiestrogen, tamoxifen, masculinizes tur tle and bird embryos, but, paradoxically, feminized alligator embryos at male producing temperatures. The contraceptive steroid, norethindro ne, a progestin that is claimed to block estrogen synthesis, is the mo st potent estrogenic steroid tested on alligator embryos. A single dos e of norethindrone applied to the egg shell caused massive hypertrophy of the Mullerian duct and feminized embryos at male producing tempera tures. The androgen, dihydrotestosterone, had no detectable effect on male or female embryos at the doses tested. Undifferentiated urogenita l tracts of embryos were cultured at 30 and 33 degrees C in the presen ce of steroids, tamoxifen, or antibodies to steroids. None of the trea tments had any effect on tissue differentiation. Tissues survived for up to 6 weeks, but there was no evidence of gonadal differential in vi tro. (C) 1994 Wiley-Liss, Inc.