Influence of Diet and Starvation on Toxicity of Endrin to Fathead Minnows (Pimephales promelas)

摘要

Endrin toxicity to fathead minnows, Pimephales promelas, was determined in flow-through toxicity tests at 25 C for periods of up to 30 days. Three months prior to endrin exposure six groups of fish were fed artificial diets containing an increasing percentage of fat, and two groups were fed either a high or low ration of frozen brine shrimp. Fish fed frozen brine shrimp showed better growth, survival and fewer deformities (hemorrhagic kidney lesions and lordosis) than fish fed artificial diets. Based on 96-hr LC50 values, fish fed diets low in dietary fat were 2.4 times more susceptible to endrin than fish fed frozen brine shrimp. On the same basis (96-hr LC50) fish fed a low ration level of brine shrimp were 2.0 times more susceptible to endrin than fish fed an unrestricted ration level of brine shrimp. In another series of experiments, adult fathead minnows starved for 80 days were 2.0 times more susceptible to endrin than recently fed fish. Fathead minnows captured in a small pond on April 30 were also about 2.2 times more susceptible than recently fed fish. There was no detectable relationship between body weight and susceptibility of fathead minnows to acute endrin toxicity. The reduced tolerances of endrin caused by a low percentage of dietary fat, reduced ration level and starvation were correlated to an increased total body water content. The underlying reason is assumed to be a concomitantly decreased total body lipid content.