OF ZEBRA MUSSEL (DREISSENA-POLYMORPHA) LIFE STAGES TO CANDIDATE MOLLUSCICIDES

We developed methods for measuring the toxicity of candidate molluscicides to several life stages (preveliger, D-stage veliger, post-D stage veliger, plantigrade, and adult) of the zebra mussel Dreissena polymorpha: Veligers were obtained by inducing ripe adults to spawn in the laboratory and by field collection. Plantigrades were collected on slides suspended in Lake Erie. The toxicity of candidate molluscicides on all stages was evaluated in 24 hour static tests in hard standard reference water. The sensitivity of zebra mussel life stages to different chemicals varied. Veliger stages showed similar sensitivity to Bayer 73 and TFM, whereas plantigrades and adults were less sensitive. Sensitivity to Calgon H-130, Clamtrol CT-1, and Sal I decreased with each successive developmental stage; adults were most and preveligers were least sensitive to rotenone. In general, chemical concentrations that kill adults will also be effective against other life stages. However, because chemical minimization strategies require the use of the smallest amount of chemical possible, molluscicides should be tested on the life stage targeted for control.