A Novel Approach To Identify The Sex Of Marine Turtles

Marine turtles exhibit temperature dependent sex determination (TSD). During critical periods of embryonic development, the nest's thermal environment directs whether an embryo will develop as a male or a female. Nests that incubate at warmer sand temperatures tend to produce female-biased sex ratios. The rapid increase of global temperature highlights the need for a clear assessment of effects on sea turtle sex ratios. However, identifying hatchling sex ratios at rookeries remain as coarse estimates because the mechanisms that trigger male vs. female development are understood only in part. We currently rely mainly upon laparoscopic procedures to verify hatchling sex; however, in some species, morphological sex can be ambiguous even at the histological level. Recent studies using immunohistochemical techniques identified that red-eared slider (Trachemys scripta) embryos over-expressed a cold-induced RNA binding protein in the ovary when compared to developing testes. We developed a variation of this technique and successfully identified the sexes of loggerhead sea turtle (Caretta caretta) hatchlings, a species that can also be identified reliably using standard histological and laparoscopic methods. We then tested the technique with a more challenging species, the leatherback turtle (Dermochelys coriacea), species that retains many neotenic features. The morphology of leatherback hatchling gonads remains difficult to interpret, particularly when dead-in-nest hatchlings and embryos are the source tissues. Our purpose is to introduce the modified procedure and its efficacy. This new technique has the potential to greatly enhance our ability to verify hatchling sex ratios and identify baseline sex ratios; both fundamental steps in assessing global climate change on sea turtle populations.