Bisazir as a chemosterilant to control invasive vertebrates: ecotoxicity and efficacy to induce male sterility in Lithobates catesbeianus

Abstract

Chemical sterilisation is a way to control populations of invasive exotic species. To investigate the potential to control populations of invasive American bullfrog (Lithobates catesbeianus), 26 adult male individuals were caught and injected with a dose of 0, 12.5, 25, 50, 100 mg/kg bisazir in order to induce DNA fragmentation in sperm cells and subsequent induce sterility. The results indicate that injecting 50 mg/kg bisazir causes significant fragmentation in the sperm of Lithobates catesbeianus. Before using chemicals in situ their potential risk for the environment should be documented. As a first step the inherent ecotoxic properties of bisazir were evaluated in both acute and chronic aquatic tests: microtox (Aliivibrio fischeri), microalga (Raphidocelis subcapitata), duckweed (Lemna minor), waterflea (Daphnia magna). The no effect concentration (NOEC) was 1 mg/l for Daphnia reproduction. Based on these results the predicted no effect concentration (PNEC) value was 20 µg/l. These results show the inherent ecotoxic properties of the compound and raise questions on the safe applicability in aquatic habitats.