Scientists Uncover How Sea Snakes Develop Shrunken Heads

First Posted: Mar 20, 2013 09:19 AM EDT

An international team of scientist has uncovered the mystery behind how certain sea snakes develop shrunken heads or other small physical features when compared to related species.

This study was conducted by researchers from the University of Adelaide including the South Australian Museum.

According to the study, larger heads would have helped sea snakes to swallow large spiny fish. But for certain sea snakes these big head aren't that useful. In places where they have to probe into narrow sand eel burrows, a big head does not help.  This is why sea snakes have evolved comically small heads.

Apart from this, the team has shown that the normal shaped sea snake can develop shrunken heads very rapidly. This process can lead to speciation where one species splits into two, according to the press release.

When compared to its ancestors, the small head snake population is smaller in size and the difference in the shape and size indicates that it is more likely to avoid interbreeding with large headed snakes.

This study was led by Dr Kate Sanders from the University of Adelaide and Dr Mike Lee from the South Australian Museum.

Dr Sanders has been investigating the genetic differences in all sea snakes. Shee noticed that a genetic similarity between blue-banded sea snakes and the slender-necked sea snakes despite them being different in size and shape.

 When compared to the blue-banded sea snake, the slender-necked sea snake is half the size and has a smaller head. This indicates that they were recently disconnected from the common ancestral speices and rapidly evolved different features.

Dr Lee says," 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."

Dr Sanders says "Our results highlight the viviparous sea snakes as a promising system for studies of speciation and adaptive radiation in marine environments."

The study is published in the journal Molecular Ecology.

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