COMPARATIVE RESPONSE OF THE ZEBRA MUSSEL, DREISSENA-POLYMORPHA, AND THE ASIAN CLAM, CORBICULA-FLUMINEA, TO DGH QUAT, A NONOXIDIZING MOLLUSCICIDE/

In a series of laboratory and held experiments, zebra mussels, Dreisse na polymorpha, and Asian clams, Corbicula fluminea, were exposed to th e cationic surfactant-based molluscicide DGH/QUAT under both static an d flow-through conditions. Cumulative mortality of the two bivalves wa s comparable after 24-h treatments, but zebra mussels experienced sign ificantly higher mortality in 6-h exposures conducted at 20-25 degrees C. The rate at which mortality occurred was greater for the zebra mus sel in all experiments. The molluscicide induced an increase in tissue water and a decrease in whole body glycogen levels of both organisms, although these changes occurred at a faster rate in the zebra mussel. While greater sensitivity of zebra mussels to DGH/QUAT may have been due to a longer time spent siphoning during the exposure periods, it m ay also indicate an enhanced ability of the Asian clam to tolerate the biochemical stress associated with exposure.