Biotoxicity of diclofenac on two larval amphibians: assessment of development, growth, cardiac function and rhythm, behavior and antioxidant system

Abstract

The non-steroidal anti-inflammatory drug diclofenac (DCF) threatens the health of aquatic animals and ecosystems. In the present study, different biological endpoints (mortality, development and growth, abnormalities, cardiotoxicity, neurotoxicity and antioxidant system) were used to characterize the acute and chronic effects of DCF (at concentrations ranging between 125 and 4000 μg L−1) on two amphibian species from Argentina (Trachycephalus typhonius and Physalaemus albonotatus). Results showed that the larval developmental, growthrates, and body condition of DCF-exposed individuals of both species were significantly reduced. DCF-exposed individuals also showed several morphological abnormalities, including significantly altered body axis, chondrocraniumand hyobranchial skeleton, and organ and visceral abnormalities including cardiac hypoplasia, malrotated guts, asymmetrically inverted guts, and cholecystitis. DCF also had a significant effect on the swimmingperformance of both species: at low concentrations (125 and 250 μg L−1), swimming distance, velocity and global activity decreased, whereas, at high concentrations (1000 and 2000 μg L−1), these behavioral responsesincreased. Regarding cardiac function and rhythm, at DCF concentrations higher than 1000 μg L−1, the heart frequency and ventricular systole interval of both specieswere significantly reduced. Regarding the antioxidantsystem, the activity of acetylcholinesterase indicated that DCF is neurotoxic and thus related to the changes in behavioral performance. The DCF concentrations studied produced a biochemical imbalance between radicaloxygen species production and antioxidant systems. The sensitivities to sublethal and chronic DCF exposure in both anuran specieswere similar, thus indicating the inherent complexity involved in understanding the biotoxiceffects of DCF.