For years, the scientific community has expressed concern about the marked feminization of sea turtle hatchlings, a phenomenon linked to the incubation temperature of the eggs. On certain beaches in northern Australia, it had been detected that up to 99% of young green turtles were female, fueling fears of extinction due to a lack of males.
However, a recent study led by Chris Eizaguirre and his team from the Queen Mary University of London, published by New Scientist, offers a more optimistic perspective: sea turtles possess epigenetic adaptation mechanisms that allow them to maintain a balance in sex ratios, even under higher temperatures.
The experiment in Florida and Cape Verde
The team collected 240 loggerhead turtle eggs (Caretta caretta) on Florida beaches and incubated them at three different temperatures: 27°C, 30°C, and 32°C.
- At 27°C, males predominated.
- At 30°C, a balance was achieved.
- At 32°C, the proportion of females increased.
Through blood analysis, the researchers sequenced the genomes of the hatchlings and discovered DNA methylation patterns in hundreds of genes, confirming the existence of epigenetic regulation associated with sexual development.
The experiment was replicated on Sal Island (Cape Verde), burying eggs at different depths to simulate cooler or warmer environments. The analysis of 116 hatchlings showed that more males were born than predicted by traditional models, which overestimated female production by 50% to 60%.
Epigenetic adaptation and behavior
The results show that sea turtles can modulate heat sensitivity during the development of reproductive organs. In females, 383 hypermethylated genes were found, and in males 394, allowing genetic activity to be regulated and maintaining some stability in sex ratios.
In addition to epigenetics, turtles have behavioral strategies to face global warming:
- Migrate to new nesting areas.
- Advance the egg-laying season.
- Vary the pivotal temperature (threshold of balance between males and females) according to local conditions.
Ecological perspective
The study acknowledges that climate change still poses a risk, with a trend towards feminization. However, it warns that in large populations with high genetic diversity, sea turtles have a margin for evolutionary adjustments.
According to researcher Graeme Hays (Deakin University, Australia), reproductive patterns also help balance the sex ratio: females do not reproduce every year, while males visit breeding areas more frequently, compensating for the difference.
The findings show that sea turtles are not as vulnerable as previously thought: they have biological and epigenetic resources that allow them to adapt to higher temperatures and maintain viable populations.
Although the risk of feminization persists, the combination of genetic, behavioral, and ecological mechanisms offers hope for the survival of these species in the face of climate change.
