Acute toxicity and biochemical effects of azinphos methyl in the amphipod Hyalella curvispina

ANGUIANO L; CASTRO C; VENTURINO A; FERRARI A

ENVIRONMENTAL TOXICOLOGY

JOHN WILEY & SONS INC

Lugar: New York; Año: 2014 vol. 29 p. 1043 - 1053

1520-4081

We evaluated the acute toxicity and biochemical effects of the organophosphorus (OP) pesticide azinphos methyl (AM) in the amphipod Hyalella curvispina, inhabiting ponds and irrigation channels of an intensive fruit-production region in Rio Negro and Neuquén valley, North Patagonia, Argentina. The analysis by non-linear regression of data from the 96-h acute toxicity tests indicated the coexistence of two subpopulations of H. curvispina with different susceptibility to AM. The 96h-LC50 for the resistant subpopulation (166 ± 56 µg/L) was 216 fold higher than the 96h-LC50 value for the susceptible one (0.77 ± 1.33 µg/L).The two subpopulations could not be distinguished based on the biochemical measurements in control amphipods. Cholinesterase activity was significantly inhibited in AM-exposed amphipods in a concentration-dependent manner. The IC50 value obtained after 96 h of in vivo exposure (2.18 ± 1.95 µg/L) was significantly lower than the 48h-IC50 value (29.6 ± 17.4 µg/L). Carboxylesterase activity was significantly inhibited after 48 h exposure to 12.5 μg/L and 62.5 μg/L AM (51% of inhibition). This enzyme was thus able to protect ChE from inhibition at 12.5 µg/L AM. Reduced glutathione (GSH) and catalase (CAT) showed a significant increase after 24 h of exposure as an adaptive response to AM, while GST activity was not significantly modified. The analysis of species sensitivity distribution showed that both subpopulations of H. curvispina were more tolerant to AM than most amphipod species, and that the susceptible subpopulation was more sensitive to AM than the other local aquatic species analyzed. The maximum concentration of AM in drainage water within the fruit-producing area would affect most of amphipod species (99%) and also a 44% of local aquatic ones. The results obtained in this work point out the usefulness of including amphipods like H. curvispina in ecotoxicity studies and monitoring programs to perform pesticide risk assessments.