Some species of sea snake have developed "comically small" heads as a result of nosing around in sand eel burrows.

A research team led by zoologist Kate Sanders of the University of Adelaide discovered that while some sea snakes require a larger skull in order to indulge their diet of larger spiny fish, others prefer to forage in narrow sand eel burrows for food thus benefitting from a more slender cranium.

"We noticed that the blue-banded sea snake (Hydrophis cyanocinctus) and the slender-necked sea snake (Hydrophis melanocephalus) were almost indistinguishable genetically, despite being drastically different in size and shape," said Mike Lee from the South Australian Museum. "The slender-necked sea snake is half the size, and has a much smaller head, than the blue-banded sea snake."

He continued: "This suggested they separated very recently from a common ancestral species and had rapidly evolved their different appearances. One way this could have happened is if the ancestral species was large-headed, and a population rapidly evolved small heads to probe eel burrows -- and subsequently stopped interbreeding with the large-headed forms."

Sanders points out that aside from being of interest to students of sea snake biology, the results imply that the creatures may be valuable in terms of studying how speciation works in marine life.

The study is published in the journal Molecular Ecology.


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