Effects of the insecticide endosulfan and presence of congeneric tadpoles on Australian treefrog (Litoria freycineti) tadpoles

The organochlorine insecticide endosulfan is extensively used in Australia and can often contaminate aquatic environments. However, its effects on Australian frog species are unknown. We exposed tadpoles of the Australian treefrog Litoria freycineti to endosulfan for 96 hours. Tadpoles exposed to 0.03 or 1.3 mug/L endosulfan grew more slowly than control tadpoles. Furthermore, feeding was inhibited in L. freycineti when the animals were observed halfway through their exposure to a concentration of 1.3 mug/L endosulfan for 96 h. This concentration (which periodically occurs in natural water bodies and rivers) also caused 17% tadpole mortality, and the survivors were more vulnerable to invertebrate (odonate) predation when tested 15 days after transfer to clean water. The presence of a sympatric species of tadpole, Litoria peronii, did not affect survivorship of L. freycineti, but reduced growth rates. Thus, short-term exposure to endosulfan in natural water bodies may influence tadpole viability either immediately or over an extended period.