Parental investment by skin feeding in a caecilian amphibian

Yummy mummy A highly unusual form of parental care has been identified in a mysterious group of tropical vertebrates. In the oviparous amphibian Boulengerula taitanus , the young use specialized teeth to peel and eat the outer layer of their mother's modified skin, thereby ensuring a good start in life. This bizarre behaviour can be seen as an evolutionary link paving the way for fetal feeding on the oviduct lining of related viviparous amphibians. The movies, in the Supplementary Information on http://www.nature.com , are pretty gory. Although the initial growth and development of most multicellular animals depends on the provision of yolk, there are many varied contrivances by which animals provide additional or alternative investment in their offspring 1 . Providing offspring with additional nutrition should be favoured by natural selection when the consequent increased fitness of the young offsets any corresponding reduction in fecundity 2 . Alternative forms of nutrition may allow parents to delay and potentially redirect their investment. Here we report a remarkable form of parental care and mechanism of parent–offspring nutrient transfer in a caecilian amphibian. Boulengerula taitanus is a direct-developing, oviparous caecilian 3 , the skin of which is transformed in brooding females to provide a rich supply of nutrients for the developing offspring. Young animals are equipped with a specialized dentition, which they use to peel and eat the outer layer of their mother's modified skin. This new form of parental care provides a plausible intermediate stage in the evolution of viviparity in caecilians. At independence, offspring of viviparous and of oviparous dermatotrophic caecilians are relatively large despite being provided with relatively little yolk. The specialized dentition of skin-feeding (dermatophagous) caecilians may constitute a preadaptation to the fetal feeding on the oviduct lining of viviparous caecilians.