Patterns of allometric and heterochronic changes in the early ontogeny of species of Physalaemus (Anura: Leptodactylidae)

Abstract

We studied the relationship between shape, size, and developmental timein the embryonic ontogeny of 15 species of the frog genus Physalaemus. As in otheranuran exotrophic embryos, shape changes are correlated with size increase and mainlyconcern tail elongation, decrease in body height, and increase in fin height. Size rangesand developmental times vary interspecifically. Embryos of the P. signifer Clade andthe P. gracilis Group are among the largest, are slightly peramorphic, and developfast regarding congeneric species. Embryos of P. cicada combine the smallest sizeswith fast development and the most peramorphic shapes. The paedomorphic shapesof embryos of P. biligonigerus and P. henselii groups are correlated with fast vs. slowdevelopmental times respectively. Trajectories in the P. cuvieri Group are diverse and ingeneral differ in size and developmental time. The embryos of P. cristinae and from theArgentinean lineage of P. cuvieri stand out with the longest development. Sequences ofdevelopmental events are overall conserved in the genus, and main differences concernmouthpart ontogeny. This study constitutes the first attempt to evaluate morphological,allometric, and heterochronic parameters of the early ontogeny of anurans and howthese can vary and contribute to diversification in taxonomic groups.