Effect of some pesticides on the rhythmic adductor muscle activity of fresh-water mussel larvae.

The effect of some pesticides on the spontaneous and tryptamine (TA)-induced adductor muscle activity of glochidiae of the fresh-water mussel Anodonta cygnea was examined in short-term experiments. The pesticides used were: Bi-58 EC, Novenda, Malathion, Shell-DD, Dikonirt and pure 2,4-D the active ingredient of Dikonirt. High concentrations (greater than or equal to 10(-1) g/l) of the examined substances have a short, slight excitatory influence on the spontaneous rhythmic adductor activity of larvae, in addition their effect results in lasting closure of some specimens. In lower concentrations, they inhibit the TA-induced adductor activity. The threshold of inhibitory concentrations may be lower with prolonged exposure time.