CONICET | Buscador de Institutos y Recursos Humanos

In Leptodactylus has been described at least five different reproductive modes, all of them involving foam nest. In this paper we analyzed the early ontogeny of five species of L. fuscus group that lay the eggs in terrestrial chambers; and of two species of L. latrans group that, in contrast, construct floating nest over lentic waters. The ontogenetic period described here?between 17 and 26 Gosner stage?includes the occurrence of transient, exclusively embryonic structures, and the initial stages of development of larval features. Species of the Leptodactylus fuscus group have large, not pigmented and kyphotic tailbud embryos; the body lengths, at tailbud stage, ranging 2?3 mm and yolk provision representing >50% of the whole body area; the external gills are present in two or three pairs lateral to the body, poorly developed, and scarcely ciliated; the larval oral discs have a LTRF 2(1)/3(1) and a single row of marginal papillae in alternated direction; the adhesive glands are absent; and the hatching glands are present like a T-pattern that continues on a short line over the dorsal head. Main differences with the species of L. latrans group concern the morphology at tailbud stage, smaller with comparatively less amount of yolk, highly pigmented, and with no dorsal curvature; the external gills are larger, more branched, highly ciliated and are folded ventrally; the presence of adhesive glands type D, is unique among gland morphogenetic patterns described so far for anurans; and the tooth ridges are undivided. Additionally the analysis of sequence heterochronies showed, between others, an early development of the hind limb in Leptodactylus except L. latrans, even before the spiracle is formed; and a comparatively delay in the development of the second and third gill pairs in L. latrans group.

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