Alternate Title

Effects of Whole Drilling Mud and Selected Components on the Shell Movements of the Bay Scallop, Argopecten irradians


The shell movements of bay scallops (Argopecten irradlans) were electronically monitored before and after different amounts of whole drilling mud, barite, lignosulfonate, and calcium carbonate were added to their tanks. Movements were compared with those made by scallops exposed to seawater for the same duration using six response measures. For whole drilling mud, a graded dose-response relationship existed for two response measures: change In the number of major Rapid Valve Closures (RVCs) and change In the cumulative magnitude of all RVCs. Ejection of pseudofeces Is frequently associated with RVCs. Scallops tested simultaneously with barite, lignosulfonate, and calcium carbonate showed Irregular but similar dose-response relationships for these two response measures. Three other measures (changes In gape width, RVC magnitude, and number of all RVCs) were not reliable Indicators of responsiveness for any materials. None of the materials caused significant changes In the number of swimming attempts, but only one-third of the animals ever attempted to swim. Scallops exposed to seawater showed no significant change for any response measure.