Wednesday 28 May 2014

A new species of Caecilian from French Guiana.

Caecilians (Gymnophiona) are a group of Amphibians only distantly related to Frogs and Salamanders. They have lost all limbs, and live a burrowing lifestyle in moist tropical forests. Caecilians have banded scales around their bodies and many species lack external eyes, making them superficially resemble Annelid Worms (Earthworms), though they are true Vertebrates with visible jawbones, which all Worms lack.

In a paper published in the journal PLoS One on 6 March 2013, Mark Wilkinson of the Department of Zoology at The Natural History Museum in London, Emma Sherratt also of the Department of Zoology at The Natural History Museum in London and the Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology at Harvard University, Fausto Starace of Saint Laurent du Maroni in French Guiana and David Gower, also of the Department of Zoology at The Natural History Museum in London, describe a new species of Caecilian from French Guiana.

The new species is placed in the genus Microcaecilia, which already contains eight species, all native to South America. These are small Caecilians with closed skulls and eyes covered over by a layer of bone, which is thought to be an adaptation to burrowing, although it is unclear if the level of bone growth seen is necessary for the digging style employed by the animals (which used the head to shovel aside sediment); on the whole the ecology of these animals is poorly known.

It is named Microcaecilia dermatophaga, meaning ‘skin-eater’ a reference to its reproductive behaviour. One of the specimens studied during the discovery of this species produced a string of five eggs, and a few days later was discovered to have two young, which fed by consuming lipid-rich skin from around the mid-section of the mother’s body. 

Reproductive mode of Microcaecilia dermatophaga. Presumed mother with a connected string of five eggs (top) and with two hatchlings during the period of extended post-hatching parental care and maternal dermatophagy (bottom). Wilkinson et al. (2013).

This mode of juvenile feeding has been observed twice before in Caecilians, firstly in the African species Boulengerula taitanus, and secondly in the South American Siphonops annulatus. These two species are only very distantly related (it is thought that their most recent common ancestor lived over 100 million years ago), and it is therefore thought that the trait is likely to be widely found in Caecilians, a theory which the discovery of such behaviour in Microcaecilia dermatophaga supports.

Microcaecilia dermatophaga is a small Caecilian, the largest specimen discovered reaching 183 mm in length. It is somewhat flattened, and the head is more ‘U’-shaped than ‘V’-shaped when seen in dorsal view. Its teeth are pointed and curved backwards, lacking blades or serrations. The juveniles lacked pigmentation and were pinkish, the adults a darker lilac colour. The smallest free living specimens found in the study were 75-84 mm in length, a size achieved by the hatchlings in 26 days, when they also showed an ability to burrow for themselves and a willingness to take Invertebrate prey. Based upon this Wilkinson et al. conclude that reproduction may begin as early as March or April (the hatchlings in the study were produced in July), and that sexual maturity is reached in about a year.

Adult specimen of Microcaecilia dermatophaga. Wilkinson et al. (2013).

One of the specimens discovered during the study was found within a rotten log, alongside large numbers of Termites, and subsequently fed happily on Termites in captivity. Other specimens consumed Crickets and Earthworms when these were offered, suggesting the species will take a variety of prey. Pieces of what appear to be termite jaws were found embedded in the heads of several specimens, suggesting that this may be a common food item for the species, and also that the extensive bone development in the head of all members of the genus Microcaecilia may be an adaptation enabling feeding on aggressive Termites and Ants, rather than for digging.

Typical environment for Microcaecilia dermatophaga. Forest close to the Mana River (at Angoulême, French Guiana)Wilkinson et al. (2013).

See also…

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...

Follow Sciency Thoughts on Facebook.