Development and Evolution of Caecilians (Amphibia: Gymnophiona)

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9527681 Wake A general hypothesis in evolutionary biology is that modification of a developmental pattern may be correlated with a change in reproductive mode. Analysis of development of the skeleton, and some elements of the muscular and nervous systems, in a monophyletic lineage, the amphibian Order Gymnophiona, will test the general hypothesis of correlation of reproductive and developmental patterns. Development in three focal species representing three families will be analyzed. One species represents a basal family with an oviparous, free-living larval life history, the other two are viviparous (live-bearing with maternal nutrition). One viviparous species is terrestrial, the other fossorial, and their developmental patterns and, consequently, adult morphologies differ significantly. Consequently, interactions of phylogenetic history, life history, habitat, development and function can be approached and analyzed. Comparative development of the skull will be examined to ascertain the basis of homology of structural elements, and the degree to which modification of development is correlated with the factors mentioned above. The microstructure of tooth development will be examined to understand the development and evolution of the unique fetal dentition of viviparous forms. The development of the vertebrae will be studied to test the hypothesis that resegmentation is a fundamental property of development, and to determine the process by which it occurs. The development of specific neural and muscular elements associated with the skeletal ontogeny, such as the jaw musculature and the hypoglossal nerve, will be studied. A diversity of techniques will be employed: immunohistochemistry, scanning and transmission electron microscopy, clearing and staining, and others. A program t o breed caecilians in captivity will be established in order to: (1) provide means of examining the diversity of reproductive modes in the lineage; (2) provide embryos at crucial developmental stages for study; and (3) assure the maintenance of species threatened in their natural habitats. This is an integrative study that should lead to significant advancement in the search to understand the relationship between reproduction, development and evolution