THE EFFECT OF FOOD QUANTITY ON PHYSIOLOGICAL RESPONSES OF THE BEARDED HORSE MUSSEL MODIOLUS BARBATUSAND THE NOAH?S ARK SHELL ARCA NOAE.

The aim of the work was to investigate oxygen consumption, ammonia excretion, O:N ratio derived from oxygen consumption and ammonia excretion, and the clearance rate of the bearded horse mussel Modiolusbarbatus(Linnaeus, 1758) and the Noah\'s Ark shell ArcanoaeLinnaeus, 1758with regard to different food availability (100%, 50% and starving) during a fifteen day experiment. In this study, food quantity significantly affected ammonia excretion and O:N ratio for both species. Time spent under feeding regime resulted to increasing oxygen consumption and clearance rate values of the bearded horse mussel and the ammonia excretion values and O:N ratios of both species. Clearance rate and ammonia excretion followed a similar increasing trend over time. The consequence of increasing ammonia excretion over time was the concomitant reduction of the O:Nratio.Both species showed high values of clearance rate, an important information when choosing the farming site. Metabolic cost of respiration for starving animals was higher for M. barbatus than for A. noae, which suggests that A. noae would be a better choice for farming in oligotrophic environments.