Comparative toxicity of seven neonicotinoid insecticides and their two metabolites to juveniles of the marine crustacean kuruma prawn (Marsupenaeus japonicas)

Abstract

This study was performed to investigate the toxicological effects of seven neonicotinoid insecticides and their two metabolites on juvenile (approximate total length of 10-15 mm) kuruma prawn Marsupenaeus japonicas, settled in estuary areas for nursery establishment. Following neonicotinoid insecticide treatment for 96 h under semi-static exposure, the effective concentration (mean 96 h-EC₅₀ with 95% credible intervals in parenthesis) was 31 (25-37) μg/L, 14 (9.0-18) μg/L, 530 (410-660) μg/L, 50 (36-63) μg/L, 490 (270-720) μg/L, 20 (11-29) μg/L, and 940 (420-1500) μg/L, for acetamiprid, clothianidin, dinotefuran, imidacloprid, nitenpyram, thiacloprid and thiamethoxam, respectively. IM-2-1, a metabolite of acetamiprid and IC-O, a metabolite of neonicotinoid insecticides with chloronicotinic group had 96 h-EC₅₀ of 1300 (1100-1500) μg/L and >12000 μg/L, respectively. These results indicate the substantial variation in the toxicity of the insecticides to the crustacean species and the correlation of their magnitude with the logarithm of the octanol water partition coefficient (Log K_ow). Furthermore, for some insecticides, molting frequency significantly decreased with increasing concentrations, implying that the insecticide delayed molting of the organism. In summary, the present study provides the first demonstration that neonicotinoid insecticides adversely affect kuruma prawn and that two metabolites were less toxic than the parent compounds. Future research will be necessary to investigate marine contamination of the insecticides, especially in estuaries.