ON THE RESPIRATION IN SCALLOPS (LAMELLIBRANCHIATA)

1. The oxygen uptake and the percentage of oxygen withdrawn from the inhaled water, were determined in resting specimens of two species of lamellibranch molluscs which have a capacity for rapid swimming locomotion, vis. in the sea scallop (Pecten grandis Sol.) and in the bay scallop (Pecten irradians Lam.).2. In accordance with the absence of prolonged ventilation pauses common in several other species of Lamellibranchia, the oxygen uptake in the bay and sea scallop is quite uniform. In both species QO2 was found to be about 70 ml./kg./hr. at 20° C. This value is about half the QO2-value found in swimming species from the mediterranean and falls well within the range of QO2-values in boreal non-swimming types of lamellibranchs recorded in the literature.3. The oxygen uptake was independent of the oxygen tension down to a concentration of oxygen of about 1-½ ml. O2/L.4. The percentage of oxygen withdrawn from the inhaled water, in most cases, was low, ranging, approximately, from ½ to 13%. It was demonstrated that in the stream of water escaping from the cloacal chamber of the bay scallop considerable gradients in the concentration of oxygen occur.