Scheide, J. I. and A. Mihal, 1996.     Ion Balance Predictors of Physiological Stress in Zebra Mussels: Effect of Molluscicidal Conditions, Central Michigan University

Abstract from The Sixth International Zebra Mussel and Other Aquatic Nuisance Species Conference, Dearborn, Michigan, March 1996

Ion Balance Predictors of Physiological Stress in Zebra Mussels: Effect of Molluscicidal Conditions

The effects of various molluscicidal conditions on zebra mussel ion balance were examined. Dreissena polymorpha, collected from Lakes Erie, Huron and Michigan, were acclimated to the laboratory setting in artificial lake water. Mussels were exposed to molluscicidal conditions including: heat shock, Clamtrol^-1TM, niclosamide and CO₂. Mussels, which survived the molluscicidal treatment as determined with observations on controlled gaping and response to stimulus, showed stress with significant changes in hemolymph ion concentrations and net ionic fluxes. Heat shock stress was induced in zebra mussels with an immediate elevation of the bathing media 11-14 °C for 60 minutes. Hemolymph was withdrawn, by cardiac puncture, from surviving mussels and control mussels. Heat shock treatment resulted in significant decreases in mussel hemolymph Na and Cl concentrations coupled with increases in Ca and HCO₃ , while hemolymph pH became more alkaline. The changes resulting from heat shock are similar to those observed with nonspecific mussel death.

The short term exposure of mussels to Clamtrol^-1TM (20 ppm) and niclosamide (1 ppm) resulted in significant net loss of Na, Cl, Ca and K as observed with negative net fluxes of these ions. Hemolymph Na and Cl concentrations significantly decreased in treated mussels with a decrease of hemolymph pH. In addition, niclosamide exposure resulted in an elevation of hemolymph Ca and HCO₃.

Exposure of mussels to elevated CO₂ results in the significant changes in hemolymph Ca, HCO₃ and pH. Zebra mussels, exposed to 5% CO₂ in the bathing media, were observed to increase hemolymph Ca and HCO₃ concentrations while the hemolymph became more acidic. Exposure of mussels to higher levels of bathing media CO₂ resulted in depressed hemolymph Na and Cl concentrations.

Stressful situations result in a reduction of both hemolymph sodium and chloride with an elevation in hemolymph calcium and bicarbonate. These dramatic changes in hemolymph ion concentrations indicate physiological stress to the mussel and may be used as an indicator of non-lethal stress. Supported by a Michigan REF grant to JIS.

Keywords: Zebra_mussel, Chemical_control, Industry
Product Type: Publication, Proceedings
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