VALVE MOVEMENT OF FRESH-WATER MUSSEL ANODONTA-ANATINA - A RECIPROCAL TRANSPLANT EXPERIMENT BETWEEN 2 LAKES

The effects of caging and source on the valve movements of freshwater mussel Anodonta anatina were studied in two different lakes. Caged mussels were compared with those in their natural environment on the lake bottom. In both lakes, the mussels from the study lake and the mussels from the other lake were monitored. Caging was found to increase the valve openness. The source effect was demonstrated in a few treatments. The overall level of valve openness did not differ very much between the lakes. The water temperature was negatively correlated with valve openness in one of the lakes. The correlations between the rate of valve movements and water temperature were of different signs in the two lakes. The particle concentrations, measured by water transparency, had little effect on valve movement. The daily rhythm of valve movement was different between animals at the bottom of the lake and in cages, while the effects of source or study lake were smaller.