Correlation between levels of sex hormones (progesterone, testosterone, and estrogen) and ecophysiological-behavior stages in two species of desert snails (Sphincterochila zonata and Sphincterochila prophetarum) in the Northern Negev Desert

The steroidal hormonal profiles of two sympatric species of desert snails, Sphincterochila zonata and Sphincterochila prophetarium were determined at three ecophysiological-behavior stages, i.e., aestivation, cryptobiosis, and active-feeding phases. Live snails were collected in their natural habitat every month for 13 months, the corpi removed and extracted with organic solvents and the progesterone, testosterone, and estrogen concentrations determined by radioimmunoassay. In both these hermaphroditic species during aestivation, a peak of testosterone followed by a peak of estrogen was observed. During the brief active intervals, minor peaks of estrogen were also observed but these were much lower than seen during aestivation. Although the two species have different microhabitats during aestivation, there was little difference in the hormonal profile, although S. prophetarum had about two fold higher progesterone concentration than S. zonata.