Developmental diversity in an endemic family of Patagonian frogs (Anura: Batrachylidae)

Abstract

The Patagonian rainforest has environmental conditions that may have been appropriate for the evolution of different reproductive strategies in anurans. Despite its low species richness, the endemic family Batrachylidae has a wide diversity of reproductive modes. All species have exotrophic tadpoles, but oviposition sites may vary from lakes/ponds to the forest floor and tree holes. Here we study the embryonic development of five species to explore the morphological diversity and heterochronic shifts related to aquatic vs. terrestrial development. The main differences concern the length of the intracapsular period, morphology at tailbud stage, and gut and hind-limb development. Terrestrial embryos of Batrachyla have some peculiar features also reported in species with endotrophic development, such as yolk-rich eggs, poorly developed gills, precocious development of hind limbs and delayed gut coiling. Furthermore, observations on embryos releasing from the jelly layers with the vitelline membrane intact plus the likely absence of hatching gland cells at hatching stages make it likely that differences can occur in the hatching mechanism. Our results highlight that batrachylids and other neoaustraranans offer an excellent opportunity to investigate the evolution and diversity of reproductive and developmental strategies divergent from aquatic/exotrophic development.