SHORT-TERM AND LONG-TERM EFFECTS OF DELTAMETHRIN ON FILTERING ACTIVITY OF FRESH-WATER MUSSEL (ANODONTA-CYGNEA L.)

Bioindicator methods were used to study the effects of the pyrethroid insecticide deltamethrin on the filtering behavior of the freshwater m ussel Anodonta cygnea L in the laboratory, during short-term (30 min) and long-term (1 week) exposure, In the course of the short-term treat ment, the water flow through the outflow syphon was monitored, It was found that 1 and 5 mu g/liter deltamethrin caused an increase, whereas from 10 to 50 mu g/liter deltamethrin resulted in a depression, in th e open time of the outflow syphon and the water outflow, The inhibitor y response was concentration dependent, In the long-term experiments, the valve movement representing the activity of the adductor muscles w as recorded, At 1 mu g/liter, deltamethrin had no effect on the active period, but reduced the rest time, causing an increase in the filtrat ion; all higher concentrations (10-50 mu g/liter) caused inhibition of the filtration activity by reducing the active periods and lengthenin g the rest periods, The active periods were shortened on increase in d eltamethrin concentration, the reduction being 80% of the control at 5 0 mu g/liter. Lengthening of the rest periods led to a maximum (207% a s compared with the control) at 15 mu g/liter, with a subsequent decli ne to levels close to the control at 30 and 50 mu g/liter. Nevertheles s, due to the strong reduction of the active periods, the filtering ac tivity remained depressed at higher concentrations, The results provid e evidence that deltamethrin pollution may have an adverse effect on t he functioning of the bivalve community in the aquatic environment, wh ich should be considered when this chemical is used in agricultural ar eas near aquatic ecosystems, (C) 1997 Academic Press.