ABNORMAL CIRCULATORY DEVELOPMENT IN MEDAKA CAUSED BY THE INSECTICIDES CARBARYL, MALATHION AND PARATHION

Three insecticides, carbaryl, malathion and parathion were tested for teratogenic effects in developing medaka eggs. The concentrations of insecticides ranged from 0.5 to 40.0 parts per million (ppm). The insecticides, dissolved in acetone, were added to dishes containing 10 newly fertilized eggs and 10 ml of embryo rearing solution. Circulatory anomalies which resulted in‐cluded defects in heart morphology, pericardial edema, irregular heart beat, blood clots and oscillating blood in the heart. The ED50 (effective dose) for cabaryl was 2.5 ppm; malathion, 10.0 ppm and parathion, 2.0 ppm. Limited exposure experiments were undertaken to determine possible sensitivity periods during development. These experiments, using 10 ppm carbaryl were initiated on days 0–7. Exposure lasted 24 to 96 hours. No periods of sensitivity were observed in these experiments. In a slightly varied experiment, eggs developed normally for 0–5 days, but were not removed from the insecticide once exposed. These results showed that carbaryl could cause circulatory abnormalities in 92% of the embryos which had completed cardiac morphogenesis before exposure. Combinations of malathion and carbaryl were administered to determine possible interactions. Twenty‐five different combinations ranging from 0.0 to 25.0 ppm were employed. At low concentrations, combinations had slightly greater than additive effects. At higher concentrations additive and antagonistic effects were observed. The above experiments show that (a) these insecticides are teratogenic, (b) carbaryl at 10 ppm does not disrupt developmental events but rather affects‐cell physiology and (c) combinations of some insecticides have an additive effect. Copyright © 1979 Wiley‐Liss, Inc., A Wiley Company