PHYSIOLOGICAL ENERGETICS OF 4 SOUTH-AFRICAN MUSSEL SPECIES IN RELATION TO BODY SIZE, RATION AND TEMPERATURE

1. Filtration, respiration, ammonia excretion, absorption efficiency and scope for growth are compared in four South African mussel species. 2. Mytilus galloprovincialis and Choromytilus meridionalis have the fastest feeding and metabolic rates, while Aulacomya ater combines very slow filtration with intermediate respiration and excretion rates. 3. As ration increases all species show increased filtration, respiration and excretion combined with declining absorption efficiency, thus maintaining relatively steady scope for growth. 4. Increasing the temperature from 10 to 20-degrees-C accelerates filtration in M. galloprovincialis and Perna perna, but slows it in C. meridionalis and A. ater. Absorption is little affected, while respiration and excretion increase. 5. Scope for growth thus remains consistently high in M. galloprovincialis, increases with temperature in P. perna, but decreases in C. meridionalis and particularly A. ater.