A. Salamemendez et al., RESPONSE OF DIENCEPHALON BUT NOT THE GONAD TO FEMALE-PROMOTING TEMPERATURE WITH ELEVATED ESTRADIOL LEVELS IN THE SEA-TURTLE LEPIDOCHELYS OLIVACEA, The Journal of experimental zoology, 280(4), 1998, pp. 304-313
Although temperature sex determination is well known in several reptil
e species, the physiological mechanism underlying this process remains
to be elucidated. In the current work, we analyzed the levels of test
osterone (T) and estradiol (E2) in the gonads; two brain regions-telen
cephalon (Te) and diencephalon/mesencephalon (Di)-and the serum of dev
eloping embryos of the olive ridley Lepidochelys olivacea incubated at
male-or female-promoting temperatures. (C)onversion of pregnenolone (
P5) to T and T to E2 were studied in the gonads and brain. The analyse
s were performed during three periods: the thermosensitive period (TSP
), histologically undifferentiated gonads (UDG), and differentiated go
nads (DG). In the gonads, serum, and brain, T concentrations were high
er at the female-promoting temperature during the three periods, where
as in the gonads and serum, E2 levels were similar at the female and m
ale-promoting temperature. In Di, the concentration of E2 was signific
antly higher at the female-promoting temperature. Biotransformation of
P5 to T in gonadal tissues were slightly higher at the female-promoti
ng temperature in TSP and increased during UDC; and DG. Conversion of
T to E2, however, was similar at the two temperatures during the three
periods. In the brain, the Di showed a higher efficiency for transfor
ming T to E2 at the female-promoting temperature. Our present results
do not allow us to decide whether the diencephalon is the cause or the
effect, but they conclusively demonstrate that, in L. olivacea, this
region of the brain senses temperature during sex determination. (C) 1
998 Wiley-Liss, Inc.