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

VERA CANDIOTI, MF; GROSSO, J; HAAD, B; PEREYRA, M; BORNSCHEIN, M; BORTEIRO, C; NOGUEIRA COSTA, P; KOLENC, F; PIE, M; PROAÑO, B; RON, S; BALDO, D

HERPETOLOGICAL MONOGRAPHS

HERPETOLOGISTS LEAGUE

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

0733-1347

In recent decades, a renewed interest in comparative studies of embryonic ontogeny in anurans is taking place. Toad embryos areoften employed as model organisms, and scarce attention has been put on interspecific variations. In this work we analyze the development oftransient embryonic and larval structures in 21 species in five genera of Bufonidae. These species vary in their ovipositional mode and the type ofenvironments where the embryos and tadpoles develop, including ponds, streams, and axils of leaves of terrestrial or epiphytic plants.Comparative anatomical studies and sequence heterochrony analyses show that primary morphological variations occur in the morphology at thetail-bud stage, the arrangement and development of the external gills, adhesive gland type and division timing, growth of the dorsal hatching glandon the head, configuration of the oral disc, emergence and development of the hind limbs, and presence of the abdominal sucker. Some of thesetransformations are best explained by phylogeny (e.g., early divergent taxa of bufonids have embryos with kyphotic body curvature, Type Cadhesive glands, and a very small third pair of gills). Other traits might be correlated with reproductive modes (e.g., phytotelmata embryos hatchcomparatively late and show an accelerated development of hind limbs). Because these actual variations are not well studied (e.g., less than the10% of the known diversity of bufonids has been studied from this perspective), comprehensive analyses are required to interpret characterevolution and the relationship with reproductive modes within the family.