[Heart rate variation patterns in some representatives of Bivalvia].

The pattern of heart rate variation was studied in bivalves sublittoral (aquaculture) and littoral mussels Mytilus edulis L. and Hiatella arctica L. in a long-term experiment at constant salinity (25 degrees C) and temperature (10 degrees C). Periodic changes in heart rate were observed in both littoral and sublittoral mussels. Heart activity could regularly decrease up to temporary cardiac arrest. Changes in H. arctica heart rate were much less pronounced compared to mussels and no cardiac arrest was observed.