The Herpetological Journal

pp. 121-132

Authors: Grisel Navarro Acosta, Diego Baldo, Francisco Kolenc, Claudio Borteiro
& Florencia Vera Candioti

Abstract: Research concerning the early development of anuran tadpoles has sparked new interest, ever since comparative studies
revealed structural and temporal variations of embryonic stages within different taxonomic groups. In this paper we studied
the early ontogeny of five species of the hylid genus Hypsiboas: H. curupi, H. pulchellus, H. riojanus and H. sp. from the H.
pulchellus group, and H. faber from the homonymous group. We analyse the development of typical larval structures (oral
disc), and of embryonic transient structures (external gills, ciliated cells, hatching glands and adhesive glands). The diversity
in structural patterns is mainly related to the number and size of external gills, size of the adhesive glands, ciliation density
and number of labial tooth ridges. In turn, heterochronic shifts mostly concern the time of adhesive gland division, and the
regression of the hatching gland and ciliated cells. In some cases these variations appear to be related with oviposition sites
and environments where embryos and larvae develop. Hypsiboas faber embryos, which develop in small nests outside water
bodies, exhibit the largest hatching gland and large, densely ciliated and highly branched external gills as a possible response
to low oxygen environments. The large and persistent adhesive glands of H. curupi and H. sp. gr. pulchellus might be related
to the development of embryos and larvae in small streams. Within the same intrageneric group, certain embryonic traits
of H. pulchellus (e.g., tooth row formula 2/3, minute external gills, low body ciliation) appear to be paedomorphic regarding
ancestral ontogenies, but the ecological/functional correlation (if any) of these features is uncertain.

Keywords: adhesive glands, ciliation, external gills, hatching gland, oral disc