Some populations of turtle-headed sea snake have lost their stripes.
The turtle-headed sea snake (Emydocephalus annulatus) is adapting to increases in specific pollution in the South Pacific by becoming darker in coloration, according to a new study that was published last month in Current Biology.
The study, “Industrial Melanism in the Seasnake Emydocephalus annulatus,” says that some populations of the reptile are literally losing their dark and light stripes and are becoming dominated by dark pigmented snakes.
The researchers attribute the change in coloration to nickel, from mining runoff near New Caledonia. They note that the snakes in this area accumulate trace elements that are removed when the snake sheds its skin.
The researchers measured the trace elements in these snakes with that of snakes with less exposure to the nickel pollution and found that more algae grew on the darker patches of skin which caused the snakes to shed more frequently. This gave the darker colored snakes an advantage over the snakes with stripes.
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“That algal cover reduces the snake’s swimming speed by about 20 percent, and makes it slough its skin more often (to get rid of the algae),” study coauthor Rick Shine, a university of Sydney researcher, told Gizmodo. “Until the idea about trace elements came along, I thought that black color was a disadvantage—but now it looks like the advantage of excreting trace-element pollutants may be great enough to overcome the algal-fouling problem.”
Some question if pollution is the sole cause of the change in coloration of certain populations of the sea snake.
“I have no problems in accepting that the dark areas in the skin have a higher concentration of pollution,” Arne Rasmussen, a herpetologist at the Schools of Architecture, Design and Conservation at the Royal Danish Academy of Fine Arts in Copenhagen, told Nature. Rasmussen notes that other factors may have caused the snake to lose its stripes, such as temperature, which have Shine has covered with land snakes. “If you could use a sea snake to indicate how much pollution there is in an area, that would be great,” Rasmussen said.
An abstract of the study can be found on the Current Biology website.