Quirks & Quarks

Sea snake adapts to pollution by turning black

The turtle-headed sea snake has become jet black in colour in some environments as an evolutionary adaptation to deal with pollution.
An all black turtle-headed sea snake sheds its skin. (Claire Goiran)

The turtle-headed sea snake is found on and around coral reefs throughout the Indo-Pacific Ocean. It is about a metre long and usually covered in black and white bands or speckles.

Banded turtle-headed sea snake. (Claire Goiran)

But lately, scientists, including Dr. Richard Shine from the School of Life and Environmental Sciences at the University of Sydney in Australia, have been puzzled for years about a population of turtle-headed sea snakes that are jet black. This population was first observed in the waters of a tourist region of New Caledonia, a French archipelago in the southern Pacific Ocean.

After ruling out camouflage and mate attraction, the researchers hypothesized the black skin may be an adaptation that helps the snake deal with the pollution as a result of human activity in that environment.

In an experiment, it was determined that the black skin attracted more potentially harmful minerals including zinc, nickel and arsenic, than the skin of the banded or speckled snakes. The colour black also attracts more algae, which slows the snakes as they swim. As a result, the jet black turtle-headed sea snake has evolved to shed its skin more frequently to remove the algae, but in doing so also removes the harmful pollutants.      

Paper in the journal Current Biology, "Industrial Melanism in the Seasnake Emydocephalus annulatus"