Uptake and excretion of organophosphorus and carbamate insecticides by fresh water fish, motsugo,Pseudorasbora parva

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Abstract
Fresh water fish, motsugo, were reared in aquarium water containing about 1 ppm of 3 organophosphorus and 3 carbamate insecticides for about 30 days. The persistance of these insecticides in water and uptake and excretion of insecticides by fish were examined. Among organophosphorus insecticides, malathion is the most unstable in water, and was degraded more than 99% in 7 days. Fenitrothion is moderately stable, and was degraded 97% in 29 days. Diazinon is the most stable, and was degraded 72% in 30 days. Among carbamates, carbaryl is the most unstable in water, and was degraded more than 95% in 6 days. BPMC [2-sec-butylphenyl N-methylcarbamate] is moderately stable, and was degraded 80% in 32 days. XMC [3,5-dimethylphenyl N-methylcarbamate] is the most stable, and was degraded 45% in 34 days. As for the uptake of the pesticides by fish, organophosphorus insecticides were generally higher than carbamate insecticides. The concentration of diazinon in fish reached 211 ppm, the maximum level, after 3 days, and that of fenitrothion reached 162 ppm, the maximum level, after 4 days. Afterwards, the concentration of both the insecticides decreased gradually due to the metabolism and excretion of the insecticides in fish. Uptake of malathion was very low and it was metabolized rapidly; its concentration became less than 0.01 ppm after 7 days. Among carbamate insecticides, the concentration of carbaryl in fish after 1 day reached 7.5 ppm which was the maximum level of uptake. The concentration of BPMC in fish after 4 days became 4.8 ppm, which was the maximum level, and decreased gradually. The concentration of XMC in fish was only 1.4 ppm after 1 day, but the metabolism rate of XMC in fish was fairly slow. Therefore, 0.55 ppm of XMC in fish remained even after 34 days. Moreover, in the test tanks of diazinon, fenitrothion and BPMC, the appearance of deformed fish with spinal curvature appeared at the rate of 10-30%.