The paradoxical frog Pseudis paradoxa: larval anatomical characteristics, including gonadal maturation

Abstract

The genus Pseudis is unique amongst anuran amphibians in that body growth occurs mostly or entirely in the larval phase, with huge tadpoles metamorphosing into smaller but adult-sized frogs. Selected organ systems were studied in tadpoles of the paradoxical frog Pseudis paradoxa in order to determine whether they have any special features associated with their large size and unique life history. Testes of large tadpoles were well developed with spermatogenesis proceeding before metamorphosis; ovaries were also well developed in later stage tadpoles with large pre-vitellogenic oocytes. In later stage tadpoles, unusually for anuran larvae, the intestine had developed longitudinal internal ridges, increasing the internal surface area. Lungs of later stage tadpoles showed internal septation, again an unusual feature for anuran larvae. Finally, later stage tadpoles had a considerably thickened epidermis compared to earlier stages, though no sign of adult-type glands. Overall, these results suggest that as Pseudis tadpoles grow in size beyond the norm for conventional anuran larvae, a suite of features normally associated with adult anurans begins to develop before metamorphosis.