Embryonic morphology in two species of the Physalaemus signifer clade (Anura: Leptodactylidae).

We studied the embryonic morphology of Physalaemus camacan and P. signifer, two small foam-nesting frogs endemic to the Atlantic Forest. We analysed the development of transient embryonic structures and of the larval oral disc. These embryos have features typical of most congeneric species, such as the kyphotic dorsal curvature, three pairs of gills and the configuration of hatching and adhesive glands. Main differences regarding embryos of the P. cuvieri clade are the larger size and yolk provision at tailbud stage, less developed external gills and an apparently novel pattern of oral marginal papilla ontogeny. While some shifts could be correlated with variant modes of oviposition, others appear to be developmental modifications not related with ecomorphological aspects. [ABSTRACT FROM AUTHOR]