© 1996 by The Society for Integrative and Comparative Biology
The Physiological Ecology of the Zebra Mussel, Dreissena polymorpha, in North America and Europe1
Center for Biological Macrofouling Research, Department of Biology, Box 19498, The University of Texas at Arlington Arlington, Texas 76019
SYNOPSIS. The zebra mussel, Dreissena polymorpha (Pallas), was introduced into North America in 1986. Initial North American (N.A.) studies suggested that physiological responses varied between N.A. and European populations. However, literature review indicates agreement on most aspects of physiological adaptation including: respiratory responses; hypoxia/anoxia tolerance; salinity limits; emersion tolerance; freezing resistance; environmental pH limits; calcium limits; starvation responses; and bioenergetic partitioning. The main differences among N.A. and European mussels appear to be elevated upper thermal limits and temperatures for optimum growth among N.A. populations. N.A. zebra mussels probably originated from the northern shore of the Black Sea in the warmest portion of the mussel's European range. However, most European physiological data come from northern Europe where populations may be adapted to colder temperatures. Alternatively, N.A. research suggests that mussels may have a capacity for seasonal temperature acclimatization such that responses recorded in warmer N.A. waters may be different from those recorded in northern Europe even after short-term laboratory acclimation. Studies of genetic variation and physiological response among European and N.A. D. polymorpha populations are required to elucidate the basis for physiological differentiation. Recently evolved D. polymorpha has poor resistance adaptations compared to unionacean and sphaeriid bivalves with longer freshwater fossil histories. Poor resistance adaptations make it less suited for stable habitats, instead, its high fecundities, early maturity, and rapid growth are adaptations to unstable habitats where extensive resistance adaptations are of little value.