Nav: Home

Is it a boy or is it a girl? New method to ID baby sea turtles' sex

March 30, 2017

Is it a boy or is it a girl? For baby sea turtles it's not that cut and dry. Because they don't have an X or Y chromosome, baby sea turtles' sex is defined during development by the incubation environment. 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. To make things even more complicated, in some species of sea turtles, their sexual anatomy is not physically apparent until about a decade or so when they approach sexual maturity.

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 preservation and conversation of these animals is estimating hatchling sex ratios, which remains imprecise because of their anatomical makeup.

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. To overcome the uncertainties of current methods used to determine the sex of sea turtles, scientists from Florida Atlantic University modified an immunohistochemical (IHC) approach used in freshwater turtles and tested its accuracy in identifying the sex in hatchling loggerhead and leatherback turtles. Results of this study, published in the journal The Anatomical Record, show that this method provides a valuable step toward a more reliable method for sex identification of particular importance for leatherback turtles.

"Our IHC approach minimizes the shortfalls of other techniques, especially in the case of leatherback turtles. It adds a reliable character, increases the utility of available samples, identifies the sex of the turtle without the need to sacrifice imperiled species, and does not make assumptions about the relationship between incubation conditions and the sex ratio," said Jeanette Wyneken, Ph.D., co-author of the study and a professor of biological sciences in FAU's Charles E. Schmidt College of Science who collaborated on the study with Boris M. Tezak, first author and a FAU graduate student, and Kathleen Guthrie, Ph.D., associate professor of biomedical science in FAU's Charles E. Schmidt College of Medicine.

The researchers hypothesized 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 from their study showed a 93 percent success agreement between the IHC method and the established sex-identification techniques for loggerhead turtles. When they then used the technique with leatherback turtles, they got a 100-percent 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 Tezak.

Currently, the most common practices for estimating sex ratios from nesting beaches use nest temperature, beach temperatures, or incubation duration and empirically derived relationships from laboratory data. However, there is little evidence supporting the assumption that these proxies indeed match the primary sex ratios from natural sea turtle nests or rookeries. In fact, sample sex ratios collected for loggerhead turtles for more than 10 years in Palm Beach County, Fla. show significant variability, with highly female-biased ratios being produced over a wider range of temperatures than are found in many well-controlled laboratory studies. In addition, in some nests, more males occur than would be predicted by nest temperature alone.

"Evidence suggests that the temperature-sex relationship found in the laboratory is less tight in nature and verification of sex ratios is often insufficient or absent," said Wyneken. "Our IHC method is a breakthrough in hatchling sex identification in leatherback turtles, a species whose reproductive system differentiates more slowly than on other sea turtle species."

According to the Sea Turtle Conservancy, the leatherback sea turtle is listed as endangered (in danger of extinction within the foreseeable future) under the U.S. Federal Endangered Species Act and worldwide it is listed as vulnerable in 2013 (facing a high risk of extinction in the wild in the immediate future) by the International Union for Conservation of Nature and Natural Resources. The loggerhead sea turtle is listed as threatened (likely to become endangered, in danger of extinction, within the foreseeable future) under the U.S. Federal Endangered Species Act and internationally it is listed as endangered (facing a very high risk of extinction in the wild in the near future) by the International Union for Conservation of Nature and Natural Resources.
-end-
This research is supported by the Gumbo Limbo Gordon J. Gilbert Graduate Scholarships (Tezak), the National Save the Sea Turtle Foundation and the FAU Foundation's Nelligan Sea Turtle Research Support Fund (Wyneken).

About Florida Atlantic University:

Florida Atlantic University, established in 1961, officially opened its doors in 1964 as the fifth public university in Florida. Today, the University, with an annual economic impact of $6.3 billion, serves more than 30,000 undergraduate and graduate students at sites throughout its six-county service region in southeast Florida. FAU's world-class teaching and research faculty serves students through 10 colleges: the Dorothy F. Schmidt College of Arts and Letters, the College of Business, the College for Design and Social Inquiry, the College of Education, the College of Engineering and Computer Science, the Graduate College, the Harriet L. Wilkes Honors College, the Charles E. Schmidt College of Medicine, the Christine E. Lynn College of Nursing and the Charles E. Schmidt College of Science. FAU is ranked as a High Research Activity institution by the Carnegie Foundation for the Advancement of Teaching. The University is placing special focus on the rapid development of critical areas that form the basis of its strategic plan: Healthy aging, biotech, coastal and marine issues, neuroscience, regenerative medicine, informatics, lifespan and the environment. These areas provide opportunities for faculty and students to build upon FAU's existing strengths in research and scholarship. For more information, visit http://www.fau.edu.

Florida Atlantic University

Related Climate Change Articles:

Fairy-wrens change breeding habits to cope with climate change
Warmer temperatures linked to climate change are having a big impact on the breeding habits of one of Australia's most recognisable bird species, according to researchers at The Australian National University (ANU).
Believing in climate change doesn't mean you are preparing for climate change, study finds
Notre Dame researchers found that although coastal homeowners may perceive a worsening of climate change-related hazards, these attitudes are largely unrelated to a homeowner's expectations of actual home damage.
Older forests resist change -- climate change, that is
Older forests in eastern North America are less vulnerable to climate change than younger forests, particularly for carbon storage, timber production, and biodiversity, new research finds.
Could climate change cause infertility?
A number of plant and animal species could find it increasingly difficult to reproduce if climate change worsens and global temperatures become more extreme -- a stark warning highlighted by new scientific research.
Predicting climate change
Thomas Crowther, ETH Zurich identifies long-disappeared forests available for restoration across the world.
Historical climate important for soil responses to future climate change
Researchers at Lund University in Sweden, in collaboration with colleagues from the University of Amsterdam, examined how 18 years of drought affect the billions of vital bacteria that are hidden in the soil beneath our feet.
Can forests save us from climate change?
Additional climate benefits through sustainable forest management will be modest and local rather than global.
From crystals to climate: 'Gold standard' timeline links flood basalts to climate change
Princeton geologists used tiny zircon crystals found in volcanic ash to rewrite the timeline for the eruptions of the Columbia River flood basalts, a series of massive lava flows that coincided with an ancient global warming period 16 million years ago.
Think pink for a better view of climate change
A new study says pink noise may be the key to separating out natural climate variability from climate change that is influenced by human activity.
Climate taxes on agriculture could lead to more food insecurity than climate change itself
New IIASA-led research has found that a single climate mitigation scheme applied to all sectors, such as a global carbon tax, could have a serious impact on agriculture and result in far more widespread hunger and food insecurity than the direct impacts of climate change.
More Climate Change News and Climate Change Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#538 Nobels and Astrophysics
This week we start with this year's physics Nobel Prize awarded to Jim Peebles, Michel Mayor, and Didier Queloz and finish with a discussion of the Nobel Prizes as a way to award and highlight important science. Are they still relevant? When science breakthroughs are built on the backs of hundreds -- and sometimes thousands -- of people's hard work, how do you pick just three to highlight? Join host Rachelle Saunders and astrophysicist, author, and science communicator Ethan Siegel for their chat about astrophysics and Nobel Prizes.