Scientists dig up new branch of amphibian family tree

02 March 2012

Long and limbless and with a scientific name meaning naked snakes, caecilians are the least well-known of the major amphibian groups, the others being frogs, toads, newts and salamanders. However, scientists discovered a lot more about caecilians last month when a whole new family was identified in northeast India.

Digging for caecilians in northeast India is Rachunliu G. Kamei (University of Delhi

Digging for caecilians at 1 of the more than 200 sites in northeast India is Rachunliu G Kamei from the  University of Delhi.

The new caecilian family is called Chikilidae, after their local Indian name, chikila. They make up a major new branch of the amphibian tree of life.

An international team carried out the research, which was led by the University of Delhi, India, and included 4 scientists from the Natural History Museum, London.

Lots of digging

So, how did scientists find this new group, given that they spend their lives hidden beneath the soil?

The first step involved lots of digging. More than 1,000 hours in fact, over 5 years, at 238 sites in the little-explored northeast region of India. This was the largest caecilian survey ever.

Caecilians are adapted to a life burrowing in soil. They have very strong and bony skulls. Although their eyes are reduced, they have a pair of sensory organs on the snout called tentacles that 'taste' the environment around them. 

Identifying the animals
CT scans reveal details of skull and jaws of caecilian from newly identified family.

CT scans reveal details of the skull and jaws of a caecilian from the newly identified family.

The team found more than 500 specimens. Since caecilians have few external features that can be used to easily identify them, the team used X-ray CT (computed tomography), a non-destructive imaging technique, to see under the caecilian’s skin. 

The team also analysed the DNA of the new specimens and discovered that most of them belonged to species new to science. They had found not only new species, but a new genus (Chilika) and a new family, one of only 9 other caecilian families in the world.

Chikilidae is the first vertebrate family known to be endemic (found nowhere else) to northeast India.

Interestingly, a very old specimen from the Zoological Survey, India, prompted scientists to take another look at the area. It was misidentified, in bad condition and had not been studied in detail. 

Museum zoologist Dr David Gower who was part of the research says, 'It's exciting that a group of amphibians previously known from only a single grotty specimen collected more than 100 years ago, actually represents a whole (previously unrecognised) family of several (previously unrecognised) species.'

Under-explored areas

The habitats of northeast India are under-explored and undocumented and many areas are threatened with pressures from deforestation and an increasing human population.

The caecilian research highlights the fact that there may be greater and more unique biodiversity in this region than previously thought. It is likely there is much more to discover there.

Ancient relatives
Map showing where the team surveyed for caecilians in northeast India (in box)

Map showing the northeast Indian region where scientists surveyed 238 sites for caecilians (in box). The coloured areas are biodiversity hotspots - regions of the world that are biologically rich and threatened.

The team got another surprising result from the DNA analysis, as Gower explains. 'This newly discovered family, although restricted as far as we know to northeast India, has its closest known relatives living today in Africa'.

They were separated from their African relatives about 140 million years ago in the Early Cretaceous Period when the Indian plate broke off from the super-continent of Gondwana.

Amphibians in India

India is an important country for amphibians, which are among the planet’s most threatened animals. As a centre for global amphibian diversity, India has more endemic amphibian families than any other country.

Until now, these endemic Indian families had all been found in the Western Ghats area of peninsular India. This new research has identified Chikilidae as northeast India's first endemic amphibian family and raises the likelihood that many more discoveries are to come.

The research was a collaboration between University of Delhi, Systematics Lab, University of Brussels and the Natural History Museum. The Museum scientists were David Gower, Diego San Mauro, Emma Sherratt and Mark Wilkinson.

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Publication

Kamei, R. G., San Mauro, D., Gower, D. J., van Bocxlaer, I., Sherratt, E., Thomas, A., Babu, S., Bossuyt, F., Wilkinson, M. & Biju, S. D. (2012) 

Discovery of a new family of amphibians from Northeast India with ancient links to Africa. Proceedings of the Royal Society 
[doi: 10.1098/rspb.2012.0150]