New Evidence Characterizing Temperature-dependent Sex Determination in Broad-snouted Caiman, Caiman latirostris

Abstract

Temperature-dependent sex determination (TSD) occurs in all three families of the Crocodylia. This study explored the sex ratio of hatchlings under incubation temperatures not previously tested in Caiman latirostris to delineate the transitional range of temperature (TRT) between male- and female-producing temperatures. We also estimated the pivotal temperature (Tpiv) of C. latirostris from our study site. We incubated eggs at various temperatures (31°, 32°, 33°, and 34° C). Incubation temperature had a significant effect on sex determination, but had no effect in hatching success. Eggs incubated at 31° C produced 100% females, 32° C produced approximately 70% females, and incubation at 33° C and 34° C produced only males. The TRT was > 31° to < 33° C for female to male transitions, and > 34° C and a temperature > 34.5° C male to female. Results indicate that the limits of Tpiv should be between 32–33° C (lower Tpiv), and between 34–34.5° C (upper Tpiv) for the population of C. latirostris in Santa Fe, Argentina. Our analysis support the female-male-female (FMF) pattern, but higher temperature females may be rarely seen in wild because survival of females incubated at such high temperatures is very low.