1 Nature 2006 Vol: 440(7086):926-929. DOI: 10.1038/nature04403

Parental investment by skin feeding in a caecilian amphibian

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 offspring1. Providing offspring with additional nutrition should be favoured by natural selection when the consequent increased fitness of the young offsets any corresponding reduction in fecundity2. 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 caecilian3, 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.

Mentions
Figures
Figure 1: Skin feeding in B. taitanus.a, Female with unpigmented young. b, Various stills from video footage of a young animal peeling and eating the outermost layer of its mother's skin. c, Changes in mean total length (n = 66, P < 0.001; t-test) of young (top) and mean body mass (n = 15, P < 0.001; paired t-test) of mothers (bottom) between a first (1) and a second (2) measurement after one week of parental care. Error bars show s.e.m. Figure 2: Comparison of the skin of non-brooding and brooding female B. taitanus, showing differences in skin colour, structure and histochemistry.a, Non-brooding; b, brooding. Sections on the left were stained with haemotoxylin and eosin; those on the right were stained (dark) for lipids with sudan black. E, epidermis; D, dermis; Sc, stratum corneum. Scale bars, 50 m. Figure 3: Dentition of adult and young B. taitanus.a, Anterior view of two monocuspid, adult premaxillary teeth. b, Labial view of three bicuspid, adult vomerine teeth. c, Lateral view of a lower jaw of a young specimen (total length 69 mm), showing different dentary tooth crown morphologies. d, Labial view of a posterior dentary tooth of this young specimen. e, Anterior premaxillary tooth of the same specimen. f, Anterior premaxillary tooth of a smaller specimen (total length 57 mm) resembling a grappling hook. Scale bars, 30 m.
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References
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    • . . . Here we report detailed observations of Boulengerula taitanus, another oviparous3 caecilian species that has altricial15 young (see Fig. 1a) equipped with ‘fetal-like’ teeth, including observations of several bouts of feeding . . .
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