Effects of aquatic hypoxia on growth rate and lung development in four tropical anuran species

Anuran species breeding in temporary ponds face environmental challenges, including fluctuating dissolved oxygen levels, high temperatures, and limited water volume. We examined the effects of aquatic hypoxia on the development of four Neotropical anurans: Leptodactylus labyrinthicus, Physalaemus nattereri, Physalaemus cuvieri, and Elachistocleis cesarii. Clutches were reared under normoxic or hypoxic conditions, and developmental parameters—mortality rates, time to metamorphosis, body mass, snout-vent length, tail length, and total body length—were measured at intervals of 2, 5, 10, 20, 30, 40, and 50-days post-hatching. Lung length was also assessed. Elachistocleis cesarii tadpoles in hypoxia exhibited accelerated growth, advanced developmental stages, and earlier metamorphosis compared to normoxia. In contrast, the other species showed no significant differences in developmental parameters under hypoxia. Mortality rates were highest for E. cesarii and P. cuvieri. Lungs were present from early stages, but no significant differences in lung length were observed between treatments. However, structural differences in lung morphology, observed qualitatively, may suggest potential adaptive variations. These findings highlight species-specific responses to hypoxia and the importance of developmental plasticity in adapting to challenging environments.