WIBBELS, T.*; MURDOCK, C.: Interclutch variability of sex ratios produced at pivotal temperature in a turtle with temperature-dependent sex determination
The red-eared slider turtle, Trachemy scripta, has a Male/Female (MF) pattern of temperature-dependent sex determination in which cooler incubation temperatures produce males and warmer temperatures produce females. The pivotal temperature (temperature producing a 1:1 sex ratio) has been suggested to be near 29.4oC. In the current study, 20 clutches of eggs were incubated at 29.4oC. All of the clutches were laid during the same 24 hour period and average clutch size was approximately 8 eggs. Individual clutches were kept separate throughout incubation and were rotated within incubators. Of the 20 clutches, 19 produced viable hatchlings. The sex of hatchlings was assessed by examining the structure of the gonads. Overall, an approximate 1:1 sex ratio was produced (79 males:78 females). However, the results reveal significant interclutch variation in sex ratios. Clutch sex ratios varied from 100% male to 100% female. The results support the hypothesis that pivotal temperatures may vary due to clutch-specific factors.