A remarkable form of parental care, where young amphibians feed on their mother's skin, is revealed today in the journal Nature.
Alexander Kupfer, Hendrik Müller and Mark Wilkinson at the Natural History Museum, with researchers from Brazil, Germany and the USA, witnessed the unusual behaviour when studying a group of worm-like amphibians called caecilians.
The species is called Boulengerula taitanus. The females transform their outer skin into a thick, nutrient-rich meal for their babies. The young crawl over their mother and peel and eat the skin with their specialised teeth.
This highly unusual method of parental care is called dermatotropy and was previously unknown in animals.
'That this amazing behaviour has never been seen before shows how much we still have to learn about the diversity of these animals,' said Mark Wilkinson, zoologist at the Museum.
Caecilians are snake-like amphibians related to frogs and newts. They mostly burrow in tropical soil and their underground behaviour is rarely seen. B. taitanus is from Kenya and can grow up to 30cm long.
B. taitanus young hatch from eggs and this new form of parenting may provide a missing link between egg-laying and live-bearing caecilians.
The foetuses of live-bearing caecilians feed on the lining of the womb-like oviduct using similar teeth to B. taitanus . This behaviour may have developed from external skin-feeding as shown in egg-hatching caecilians.
Wilkinson explains how biologists use comparisons between animal groups to test predictions about evolution. 'Studying neglected groups, like caecilians, is one of the best ways of testing evolutionary theory, and it's the surest way to discovering the un-dreamt products of evolution', he said.
'You can draw parallels between skin feeding in these creatures and lactation in mammals, so studying how this form of parenting evolved might shed light on how parenting developed in mammals.'
The project was carried out with funding from the Natural Environment Research Council and an EU Marie Curie Fellowship. It builds on research by H. W. Parker, a Natural History Museum zoologist, who reported the discovery of the specialised teeth in the foetuses of live-bearing caecilians in Nature fifty years ago.