Structural and heterochronic variations during the early ontogeny in toads (Anura: Bufonidae)

VERA CANDIOTI, MARÍA FLORENCIA; GROSSO, JIMENA RENEÉ; HAAD, BELÉN; PEREYRA, MARTÍN; BORNSCHEIN, MARCOS; BORTEIRO, CLAUDIO; COSTA, PAULO; KOLENC, FRANCISCO; PIE, MARCIO; PROAÑO, BELÉN; RON, SANTIAGO; STANESCU, FLORINA; BALDO, DIEGO

HERPETOLOGICAL MONOGRAPHS

HERPETOLOGISTS LEAGUE

Lugar: Lawrence; Año: 2016 vol. 30 p. 79 - 118

0733-1347

In the last decades, a renewed interest in comparative studies of embryonic ontogeny in anurans is taking place. Toad embryos are often employed as model organisms, and scarce attention has been put on interspecific variations. In this work we analyze the development of transient embryonic and larval structures in 21 species belonging to five genera of Bufonidae. These species vary in their ovipositional mode and the type of environments where the embryos and tadpoles develop, including ponds, streams, and axils of leaves of terrestrial or epiphytic plants. Comparative anatomy studies and sequence heterochrony analyses show that main variations are recorded in the morphology at tailbud stage, arrangement and development of the external gills, adhesive gland type and division timing, extension of the dorsal hatching gland, configuration of the oral disc, emergence and development of the hind limbs, and presence of the abdominal sucker. Some of these transformations are best explained by phylogeny (e.g., early divergent taxa of Bufonidae have embryos with kyphotic dorsal curvature, type C adhesive glands, and a very small third gill pair), whereas others can be correlated to reproductive modes (e.g., phytotelmata embryos hatch comparatively late and show an accelerated development of hind limbs). Because the actual variation is clearly underrepresented, since only less than the 10% of the known diversity of Bufonidae has been studied from this perspective, further comprehensive analyses are required to interpret character evolution and their relationship with reproductive modes within the family.