Baby sea turtles are born genderless: study

Is it a boy or a girl? For baby sea turtles it is not that cut and dry as their sex is defined during development by the incubation environment, a new study has found.
Baby sea turtles do not have an X or Y chromosome. The nest's thermal environment determines whether an embryo will develop as a male or female.
Warmer sand temperatures produce more females and cooler sand temperatures produce more males, researchers from Florida Atlantic University in the US said.
With the increase of global temperatures and climate change, sea turtle nests tend to produce more female-biased sex ratios further increasing their risk of extinction.

Despite this risk, very few studies actually verify the sex of individual sea turtles and then compare that data to predictions of sex ratios based on the incubation environment.
A crucial step in the conservation of these animals is estimating hatchling sex ratios, which remains imprecise because of their anatomical makeup, researchers said.

Scientists rely mainly upon laparoscopic procedures to verify neonate turtle sex. However, in some species, anatomical sex can be ambiguous even down to the histological level.
Researchers modified an immunohistochemical (IHC) approach used in freshwater turtles and tested its accuracy in identifying the sex in hatchling loggerhead and leatherback turtles.

They hypothesised that CIRPB - a RNA-binding protein known to respond to temperature - may show differential gene expression in marine turtle hatchlings that are both well-differentiated and those that are not yet distinctly male or female.
To assess the utility of this new approach, they successfully tested the expression of CIRPB using IHC with loggerhead turtle hatchlings and post-hatchlings samples because that species' sex can be identified reliably via laparoscopy and standard histology.
Results showed a 93 per cent success agreement between the IHC method and the established sex-identification techniques for loggerhead turtles.
They then used the technique with leatherback turtles and got a 100 per cent agreement between the IHC method and established sex-identification techniques.

"The high level of CIRPB expression found in the developing ovaries of marine turtle hatchlings and post-hatchlings also supports our hypothesis that CIRBP may play a role in the molecular pathways of sexual differentiation in marine turtles," said Boris M Tezak, FAU graduate student.
The study was published in The Anatomical Record journal.