Endotrophy and morphology: cranial features and heterochronic development in non-feeding tadpoles of Eupsophus (Anura, Cycloramphidae)

VERA CANDIOTI, MF

Congreso; IX International Congress of Vertebrate Morphology; 2010

Endotrophic nidicolous tadpoles are characteristic of several species of modern anurans. These tadpoles do not feed actively, but obtain their nutrients from the vitellum. They include a wide morphological diversity that ranges from an entire tadpole morphotype to embryos that progressively lack typical tadpole features. We studied the larval morphology and development of two species of Eupsophus (Cycloramphidae, Alsodinae), a Patagonian genus unique in the subfamily in having nidicolous tadpoles. These tadpoles show an interesting combination of some traits shared with other alsodines (e.g., four lingual and infralabial papillae, quadratoethmoid process, and the configuration of the m. rectus cervicis) and some traits exclusive to the genus (e.g., absence of the pseudopterygoid process and quadrato-orbital commissure, and m. subarcualis rectus I with two slips). The development and metamorphosis include some characters that develop later (e.g., degeneration of mouthparts and chondrocranium shape and minimum calcification), characters that develop earlier (e.g., hindlimb appearance and jaw and suspensorium ossification), and characters that develop at the same time (e.g., most external features, cranial muscles) compared to most exotrophic species. Some Eupsophus distinctive characters (e.g., third lower labial ridge absent, general configuration of the hyobranchial skeleton, and skeletal development with retention of larval traits) resemble those of other endotrophic species, and the precocious ossification of jaws and suspensorium is shared with several direct-developing species among recent amphibians.