Toxicity of mosquitocides on freshwater mussel larvae.

The effect of four insecticides also used for mosquito-killing (Fyfanon ULV, K-Othrin ULV, Unitox 7 ULV and Unitox 20 ULV) was studied on the larvae (glochidia) of two freshwater mussel species, Anodonta cygnea and Anodonta anatina. In addition to the determination of the 24-96 h LC50 values of the insecticides, studies were also performed on their effect exerted on a physiological process, the tryptamine-(TA)-induced activation of the larvae in normal and 24 h test. On the basis of the LC50 values, Fyfanon and Unitox 20 were found to be the most toxic to the studied mussel larvae, however, the TA-induced adductor muscle activity, as physiological process, was also inhibited by Unitox 7 in relatively low concentrations. This effect may reduce the chance of further development of the larvae, by exerting harmful effect on the number of freshwater mussels.