Sea snakes are turning black to keep clean

Sea snakes are turning black t...
A turtle-headed sea snake in the waters of New Caledonia
A turtle-headed sea snake in the waters of New Caledonia
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A turtle-headed sea snake in the waters of New Caledonia
A turtle-headed sea snake in the waters of New Caledonia

Ordinarily, turtle-headed sea snakes have black skin with white bands or blotches. In a recent study conducted at the Pacific island of New Caledonia, however, it was discovered that snakes living on reefs near the city or military activity were almost pure black. It turns out that they've evolved to shed pollutants that bind to the melanin in black skin.

Study lead author Claire Goiran, of the University of New Caledonia, already knew that the darker feathers of pigeons in Paris store more zinc than lighter feathers. That zinc enters their bodies from the urban environment, binds with the melanin in their dark feathers, and is then shed along with them.

In order to determine if something similar was happening with the snakes, she and her colleagues analyzed their sloughed skins. Sure enough, it was found that the skins of darker "urban-industrial" snakes contained more trace elements of pollutants – including arsenic and zinc – than the skins of normally-colored snakes from more pristine areas.

Additionally, the darker the skin of the urban-industrial snakes, the higher the concentration of pollutants. What's more, those snakes also shed their skin more often than their black-and-white counterparts. All in all, an effective way of drawing pollutants out of their bodies, then getting rid of them.

A paper on the research was recently published in the journal Current Biology.

Source: Cell Press via EurekAlert

The snake sheds it's skin more often, the skin has higher levels of pollutants, and the skin is darker. Three interesting facts, but what is the reationship between them? Is one of them causal for the others? If so, what is the link and how does it function? Has there been a change in DNA that can be passed to offspring? Or is this an existing defence mechanism that is activated by toxins? Without this information this is both a poor piece of science and reporting.
It amazes me how these creatures "evolve" in such a short time,when it is apparent that it took millenia (or longer) for most animals to "evolve" to a point where they are today. Is it not possible that there have always been striped snakes AND black snakes? We just didn't see them yet.