Habitat and Respiratory Strategy Effects on Hypoxia Performance in Anuran Tadpoles.

This article investigates how natural habitat type and lung presence affect the physiological resilience of anuran (frog) tadpoles to acute hypoxia (low dissolved oxygen) in aquatic environments. Using experimental tests on 475 wild-caught tadpoles from 15 genera and 10 families in South Africa, the study found that stream-living tadpoles, especially those lacking lungs, exhibit significantly reduced responsiveness and tolerance to hypoxia compared to pond-living tadpoles. Pond-living, lunged tadpoles increased air-breathing rates under hypoxia, whereas stream-living tadpoles did not, and some lungless species displayed alternative respiratory behaviors. These findings suggest that stream habitats, which are typically well-oxygenated, may relax selection for hypoxia tolerance and pulmonary respiration, making stream-living, lungless tadpoles particularly vulnerable to anthropogenic disturbances that reduce stream flow and oxygen availability, with important implications for amphibian conservation strategies.