Finding a pathway through the rocks: the role of development on the evolution of quasi-terrestriality and the origin of endotrophism in cycloramphids (Anura)

Abstract

Abstract Anurans have served as models in evolutionary studies on reproduction and development. Several generalizations have emerged but it is unclear whether they represent the diversity of the entire group. We studied the development of two species of the Neotropical family Cycloramphidae. Frogs in this family have peculiar spawning sites and developmental biologies. Whereas some cycloramphid tadpoles are exotrophic, quasi-terrestrial and thrive in films of water that flow over rocky outcrops, others are endotrophic, terrestrial and complete their development outside the eggs laid on the forest floor, under logs or in crevices. Cycloramphid tadpoles have aspects of their morphology distinct from those of pond and stream dwellers; they hatch in more advanced stages of development and have typical tadpole structures, either in a modified form or absent. Herein we present a study of the tadpoles of C. lithomimeticus and T. miliaris, in order to document and discuss alterations in the ontogeny of several larval structures. These changes seem to be associated with adaptations to life in the peculiar habitats where the tadpoles thrive. We infer that the observations we present are explained by development being associated with aspects of terrestrialization and endotrophism.