Wednesday, 22 February 2012

New Amphibians from Northeast India.

Caecilians are limbless burrowing Amphibians found in tropical regions of Asia, Africa and South America. They resemble Earthworms, with circular folds on their skin which make them look segmented and skin covering their eyes (though they can see). Unlike snakes they have greatly reduced or even absent tails with their anus close to or at the tips of their bodies. Caecilians are predatory with a well developed sense of smell.

In a paper published in the Proceedings of the Royal Society B on 22 February 2012, a team of scientists led by Rachunliu Kamei of the Department of Environmental Studies at the University of Delhi, describe the discovery of a new family of previously undescribed Caecilians from the Northwest of India, named as the Chikilidae comprising the single genus Chikila (a local name for the animals)

Specimen of Chikila fulleri brooding eggs in captivity. From Kamei et al. (2012).

The Chikilidae were found to be quite widespread across Northeast India, though genetic studies suggested that their closest relatives were in fact African Caecilians, from which they probably diverged about 140 million years ago. This ties up well with predictions based upon the breakup of the ancient continent of Gondwana, during which India separated from Africa between 160 and 120 million years ago. Caecilians like other Amphibians cannot tolerate salt water, so they cannot have made the crossing after the continents separated. In addition they are restricted to wet tropical climates, and therefore cannot have crossed any colder or drier climatic zones during their history.

Elevation map of Northeast India showing locations where the new Caecilians were found. Different coloured circles represent different species of Chikilidaen. From Kamei et al. (2012).

Kamei et al. suggest that the Chikilidae were probably more widespread in India, and became more restricted as a result of the Deccan Traps volcanic eruptions, that covered much of India in volcanic basalt 65 million years ago at the end of the Cretaceous. Other formerly widespread groups have been shown to have become restricted to the better studied Western Ghats biozone in Southeast India and Sri Lanka at this time, and Kamei et al. suggest that further studies of the far Northwest of India may well uncover other unexpected endemic groups of animals. They also note that many of the forests of the area are currently under threat from a rapidly growing human population, and increasing deforestation.

Map of India and South Asia, showing the study area (square) and the main biogeographical zones. From Kamei et al. (2012).

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