Toxicity of tetrachlorvinphos to Rana temporaria L

1. Changes in the erythrocyte system of frogs poisoned with tetrachlorwinfos depend on the sex of the animals and the dose of pesticide applied. They are a result of the pathomorphological changes due to translocation of fluids from the tissues to the circulation and swelling of the blood cells. 2. Changes in the leucocyte system of frogs are caused by several mechanisms: lytic action of the pesticide on the blood cell membrane, the stressogenic effect of the agent and enhanced activity of the reticuloendothelial system. 3. The appearance of typical changes due to stress, after even the lowest dose of tetrachlorwinfos, and low LD50 values indicate that this pesticide is highly toxic for frogs. 4. The relatively high susceptibility of frogs to intoxication with tetrachlorwinfos is probably the result of a high affinity of cholinesterase to this pesticide, because of the presence of the P = O bond in its molecule.