Direct Development in Desmognathus aeneus (Caudata: Plethodontidae): A Staging Table

We describe development of the salamander Desmognathus aeneus (Plethodontidae: Desmognathinae) from fertilization to hatching. Embryonic development is divided into 33 stages on the basis of external morphology. Frontand hind-limb buds appear nearly simultaneously. This feature is characteristic of desmognathines, as well as direct-developing plethodontids (e.g., Ensatina and Batrachoseps). Previous workers have characterized the developmental mode of D. aeneus as intermediate between larval and direct development. Based on features of the embryo and hatchling, we contend that D. aeneus is a true direct developer. First, prominent endolymphatic calcium deposits are present during embryonic development, a feature thought to be correlated with direct development in salamanders and frogs. Second, D. aeneus shows no evidence of a desmognathine larval pigment pattern during development. Third, hatchlings have eyelids, nasolabial grooves, tiny gill stubs that disappear soon after hatching, an adult color pattern, and no tail fin. These features are characteristic of hatchlings of other direct-developing plethodontids. Fourth, the skull and hyobranchial apparatus are essentially adult in morphology. The initial characterization of D. aeneus as semimetamorphosed probably was based on hatchlings that were induced to hatch prematurely in the lab.