How urban seasnakes lost their stripes

August 10, 2017, Cell Press
A photograph of a turtle-headed seasnake. Credit: Claire Goiran

Researchers studying turtle-headed seasnakes living on coral reefs in the Indo-Pacific noticed something unusual about the snakes' color patterns: seasnakes living in more pristine parts of the reef were decorated with black-and-white bands or blotches. Those in places with more human activity—near the city or military activity—were black.

As reported in Current Biology on August 10, those color differences are explained by differences in the snakes' exposure to pollution. The blacker skin of urban seasnakes allows the animals to more effectively bind and rid their bodies of contaminants, including arsenic and zinc, each time they shed their skins. The findings add seasnakes to a growing list of species that show industrial melanism, a greater prevalence of dark-colored varieties in industrial areas.

"The animals I study continue to astonish me," says Rick Shine at the University of Sydney in Australia. "I think it's remarkable to find industrial melanism in organisms as different as moths and seasnakes!"

Claire Goiran, the study's lead author, at Labex Corail & Université de la Nouvelle-Calédonie got the idea that blacker skin might be related to pollutant exposure after learning that the darker feathers of urban pigeons in Paris store more zinc than lighter feathers. Goiran and her colleagues wondered whether a similar thing might be happening in the seasnakes.

A photograph of a turtle-headed seasnake. Credit: Claire Goiran

To find out, the researchers measured trace elements in the sloughed skins of seasnakes from urban-industrial versus other areas and in dark versus light skin. As predicted, they report, concentrations of trace elements were higher in snakes from urban-industrial areas. Trace element concentrations were also higher in darker than in paler skin.

The researchers further found that darker snakes slough their skins more often. As a result, it appears that seasnakes whose is more heavily pigmented with melanin have an advantage over their lighter relatives in polluted areas.

Shine says that the findings are yet another example of rapid adaptive evolutionary change in action. For him, it's also a more sinister reminder that "even on an apparently pristine coral reef, human activities can pose very real problems for the animals that live there."

A photograph of a turtle-headed seasnake. Credit: Claire Goiran

Explore further: Study shows urban birds with darker feathers may be better at removing metal toxins

More information: Current Biology, Goiran et al.: "Industrial Melanism in the Seasnake Emydocephalus annulatus" , DOI: 10.1016/j.cub.2017.06.073

Related Stories

Recommended for you

World's first known manta ray nursery discovered

June 19, 2018

A graduate student at Scripps Institution of Oceanography at the University of California San Diego and colleagues from NOAA's Office of National Marine Sanctuaries have discovered the world's first known manta ray nursery.

Scientists see human immune response in the fruit fly

June 19, 2018

Washington State University researchers have seen how both humans and fruit flies deploy a protein that a plays a critical role in their immune responses to invading bacteria. The discovery gives scientists evolutionary insight ...

Road rules for gene transfer are written in DNA

June 19, 2018

A new discovery suggests that bacteria's ability to transfer genes, like those associated with antibiotic resistance, are governed by a previously unknown set of rules that are written in the DNA of the recipient.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.