These icons share a common trait: tiny changes that didn’t last very long.
Now, a paper published in the journal Current Biology features another case of industrial melanism.
Rick Shine at the University of Sydney and colleagues found that the turtle-headed sea snake (Emydocephalus annulatus) is turning black due to pollution.
Reporting on the story, New Scientist says:
“The group already knew that pollutants such as arsenic or lead can bind to melanin, a dark pigment in the skin, and they wondered whether this might explain the black snakes. To find out, they collected and analysed the skins naturally shed by these snakes in industrial and non-industrial waters. The sea snakes typically shed – or slough – their skin a few times a year.”
The NS story goes on to say:
“Looking at 17 sloughs, Shine’s group found that the concentrations of 13 trace elements – particularly cobalt, manganese, lead, zinc and nickel – were higher in snakes near urban areas, and higher in darker skin. Shine says similar concentrations of those trace elements have been reported to cause severe health problems in many domesticated species, from cattle to poultry.
What’s more, Shine’s group found that the black sea snakes shed their skins twice as often as their lighter counterparts. This suggests that the black sea snakes are, indeed, adapting to deal with the pollution in the water they inhabit – both by developing skin with a better capacity to bind potentially harmful trace elements, and by shedding that skin more often to reduce the trace element load they must deal with.”
Instead of invoking evolution, a more credible explanation would rely on design. Sea snakes were designed with the ability to survive in hazardous environments.