Site-related differences in the feeding physiology of the green mussel Perna viridis : A reciprocal transplantation experiment

Differences in the feeding physiology of the green mussel Perna viridis between 2 aquaculture sites with contrasting hydrographies in Hong Kong were demonstrated. One site, Kat O, is oceanic and characterized by low seston concentrations and high organic contents. The other, Ma Wan, is under the influence of the Pearl River Estuary, hence the water is more turbid and has a low organic content. To determine the extent to which differences in mussel feeding responses were caused by environmental factors, a reciprocal transplantation experiment between the 2 sites was undertaken. Feeding rates (clearance rate, rejection rate, absorption rate and absorption efficiency) and enzyme activities (amylase and cellulase) were determined at various times, up to 8 mo post-transplantation. Complete acclimatization of the physiological responses of transplanted mussels occured 30 d post-transplantation. Transplanted individuals also showed complete morphological acclimatization in terms of palp area and palp:ctenidial area ratio 150 d post-transplantation, with higher ratios being obtained at Kat O, where suspended solid levels were lower, which is in contrast to other mytilids. The physiological differences between the 2 populations are thus largely environmentally induced.