Hatchling sex is not correlated with the maternal allocation of sex steroids at oviposition in the lizard, calotes versicolor

In reptiles exhibiting temperature-dependent sex determination (TSD), maternally derived yolk steroids may play a role in the sex determination. The present study explores the correlation, if any, existing between hatchling sex ratio and maternally derived yolk steroid hormone concentrations [17β-estradiol (E2) and testosterone (T)] in the lizard, Calotes versicolor, which exhibits a unique FMFM (Female-Male-Female-Male) pattern of temperature-dependent sex determination. Ten clutches of C. versicolor eggs were collected and incubated at two male-producing (MPTs) (25.5±0.5°C & 34±0.5°C), two female-producing temperatures (FPTs) (23.5±0.5°C & 31.5±0.5°C) and at pivotal temperature (28.5±0.5°C). The yolk material was collected from eggs at oviposition (stage 27) as well as at hatching (stage 42) and homogenized. Subsequent to extraction of steroids from yolk, the concentrations of E2 & T were measured by ELISA using specific antibodies for each hormone. Results reveal a noteworthy within season inter-clutch and negligible intraclutch variation in both the yolk steroid hormone (E2 &T) concentrations among the 10 clutches. At oviposition, the steroid profile reveals that the level of T was much higher than that of E2 in all the clutches examined. However, at hatching concentration of E2 was greater than that of T. Eggs incubated at low FPT (23.5±0.5°C) and low MPT (25.5±0.5°C) had low steroid hormone concentrations when compared to the eggs incubated at high FPT (31.5±0.5°C) and MPT (34±0.5°C). Intermediate levels of yolk steroids were observed in eggs incubated at pivotal temperature (28.5±0.5°C). Hence, it is emphasized that high temperature has stimulatory effect on yolk steroid levels in this species. Therefore, based on these findings we conclude that the sex ratios are rather temperature dependent than on the maternal allocation of steroids at oviposition