Amphibian vocalizations: novel ecotoxicological bioindicators

TRUDEAU V. L.; SALGADO COSTA C.; ZHANG W.S. ; NATALE G. S.; FARMER E.J.

Quebec

Workshop; Canadian Ecotoxicology Workshop; 2019

The vocalizations of male frogs and toads are critical for attracting mates and reproducing. Consequently, disruption of such vocalizations by pollutants have been of concern since Rachel Carson?s 1962 book ?Silent Spring?. Two case studies of disrupted amphibian vocalization will be presented. Adult male Silurana (Xenopus) tropicalis were exposed to control conditions or a commercial mixture of naphthenic acids (NAs), an industrial contaminant from petroleum. Mating calls were induced by injection of human chorionic gonadotropin (an analog of luteinizing hormone) and recorded using underwater microphones. The NAs reduced or completely inhibited calling. We also studied premetamorphic tadpoles of Ceratophrys ornata (Argentinian horned frog), the first vertebrate known to vocalize as larvae. Sounds are emitted during conspecific interactions and when touched to experimentally simulate an interaction, perhaps to avoid siblicide in this highly aggressive, carnivorous, and cannibalistic species. Exposure to the acetylcholinesterase inhibitor chlorpyriphos (CPF; insecticide) disrupted this unique behaviour. In addition to standard ecotoxicological endpoints in C. ornatatadpoles (mortality, swimming, abnormalities and growth inhibition), we show that sound production is extremely sensitive to water-borne CPF. For both examples, potential mechanisms of disruption will be discussed.