Differential Sensitivities of Neurotoxic and Enzymatic Responses in the Endemic Snail Chilina

KRISTOFF, GISELA; MENGONI, CAROLINA; HERBERT, LUCILA THOMSETT; WOLANSKY, MARCELO; PAINEFILU, JULIO; LUQUET, CARLOS; COSSI, PAULA FANNY

San Pablo, Santos

Congreso; SETAC Latin America 12th Biennial Meeting; 2017

Chilina gibbosa is a freshwater snail endemic to southern Argentina and Chile, vulnerable to the presence of toxic contaminants in surface water. In Argentina, it is commonly found in rivers, lakes and reservoirs of the Río Negro and Neuquén provinces, where fruit production is one of the main economic activities and large amounts of pesticides of different chemical nature have been found in the surrounding water.Our aim was to characterize the acute effect of carbaryl (CAR, carbamate) and acetamiprid (ACP, neonicotinoid) on C. gibbosa neurotoxic response and enzymatic activities. We define neurotoxic response as the protrusion of the entire head-foot region of the snails. Measured enzymes were cholinesterases (ChE), carboxylesterases (CE) using p-nitrophenyl acetate (p-NPA) and p-nitrophenyl butyrate (p-NPB) as substrates, and glutathione S-transferase (GST). We exposed snails for 48 h to a range of 0.05 to 500 µg L-1 CAR. Separately, we exposed snails for 48 h to a range of 10 to 1000 µg L-1 ACP. These ranges include maximum concentrations reported as found in the environment and national guidelines for the protection of the aquatic biota.In the case of CAR, we obtained similar sensitivities between the activities of ChE (NOEC 5 µg L-1; LOEC 13 µg L-1; IC50 37 µg L-1; 75% inhibition at 500 µg L-1) and CE measured using p-NPB (IC50 11 µg L-1; 88% inhibition at 500 µg L-1; no dose response relationship found ≤ 5 µg L-1). These values are above the national guidelines for aquatic biota protection (0.5 µg L-1). We did not find any effects on the activities of CE using p-NPA and GST. For ACP, we found an increase in CE activity using p-NPA and no effect on the activities of ChE, CE using p-NFB and GST. Neurotoxic response was not observed for either pesticide.A previous study from our laboratory reported C. gibbosa neurotoxic response and ChE activity as very sensitive biomarkers for acute toxicity of azinphos-methyl (AZM, organophosphate) with an IC50 value of 0.02 µg L−1, equal to national guidelines, and NOEC 0.001 µg L-1. CE activity was only inhibited at much higher concentrations (IC50 1000 µg L−1; NOEC 500 µg L−1 p-NPB; NOEC p-NPA 1000 µg L−1). Contrastingly, ChE activity is less sensitive for CAR and is not altered by ACP.Our results provide further information on the adverse effects of two different pesticides on an endemic species of South America and aid towards a better ecological risk assessment of pesticides on non-standard organisms.