Kupfer Alexander, Müller Hendrik, Antoniazzi Marta M, Jared Carlos, Greven Hartmut, Nussbaum Ronald A, Wilkinson Mark
Department of Zoology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK.
Nature. 2006 Apr 13;440(7086):926-9. doi: 10.1038/nature04403.
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. 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. 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, 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.
尽管大多数多细胞动物的初始生长和发育依赖于卵黄的供应，但动物有许多不同的方式为其后代提供额外的或替代的投入。当由此带来的幼体适应性增加抵消了繁殖力的任何相应降低时，自然选择会倾向于为后代提供额外的营养。替代的营养形式可能使亲代能够延迟并可能重新调整它们的投入。在此，我们报告了一种无足目两栖动物中显著的亲代抚育形式以及亲代与子代间营养转移的机制。泰氏无足蚓是一种直接发育、卵生的无足目动物，其在抱卵雌体中皮肤会发生转变，为发育中的后代提供丰富的营养供应。幼体具有专门的齿列，它们用此来剥下并吃掉母亲经过改造的皮肤外层。这种新的亲代抚育形式为无足目动物胎生进化过程中一个合理的中间阶段提供了依据。在独立时，胎生和卵生的皮肤营养型无足目动物的后代尽管所获卵黄相对较少，但体型相对较大。以皮肤为食（食皮性）的无足目动物的专门齿列可能构成了对胎生无足目动物以输卵管内壁为食的一种预适应。
