ACUTE PHYSIOLOGICAL-EFFECTS OF ZEBRA MUSSEL (DREISSENA-POLYMORPHA) INFESTATION ON 2 UNIONID MUSSELS, ACTINONAIAS-LIGAMENTINA AND AMBLEMA-PLICATA

Our laboratory studies of the physiological effects of zebra mussel (D reissena polymorpha) infestation on the freshwater mussels Actinonaias ligamentina and Amblema plicata (Unionidae) show that (i) zebra musse l infestation causes stress and symptoms of starvation in unionid muss els, (ii) unionid species are affected unequally, and (iii) symptoms o f starvation are greater when initial condition is low. Nutritive stre ss in infested unionid mussels was indicated by shifts to lower metabo lic rates, more protein-based metabolism (lower O:N ratios), and compe nsatory increases in grazing rates. Starvation may be the result of lo cal food depletion and (or) increased metabolic cost. Actinonaias liga mentina (subfamily Lampsilinae) was more sensitive to infestation than Amblema plicata (subfamily Ambleminae), as indicated especially by ch anges in oxygen uptake rate and grazing rate. The effects of infestati on were greater in mussels that were already in low condition. Our res ults indicate that the decline in diversity of unionid mussels since t he introduction of zebra mussels is due to species-specific rates of s tarvation.