Meeting Abstract
The amphibian pharyngeal arch (PA) skeleton is comprised of rod-, plate- and bar-shaped cartilages that support feeding and breathing in two habitats, an aquatic one followed by a terrestrial one. To accommodate its dual functions, the skeleton undergoes two periods of growth: larval and postmetamorphic, and two periods of development: embryogenesis and metamorphosis. Having multiple periods of growth and development suggests multiple opportunities for phylogenetic diversification. Functionally significant differences in PA skeletal shape arise in both embryogeny and metamorphosis, but how much allometric growth contributes to variation in larval and adult PA skeletons remains unclear. It is also unclear whether cylindrical cartilages adhere to fixed growth and static allometries in the way that bird and mammal long bones do. This study addresses these questions using developmental series of skeletally stained whole-mounts for 13 species of salamander belonging to eight families (Ambystomatidae, Salamandridae, Plethodontidae, Dicamptodontidae, Amphiumidae, Sirenidae, Proteidae, and Cryptobranchidae). PA skeletons including mandibles are dissected, photographed, and digitized to generate width and length measurements for all cartilages. The data for individual cartilages are averaged between sides, log-transformed and fitted to linear regression equations, the slopes of which are compared between larval and adult stages within species and between the same stages among species. Interspecific comparisons are also intended to reveal how variation in length of larval period and loss of metamorphosis affect the adult proportions of PA cartilages.
