PHYSIOLOGICAL ENERGETICS OF BROODING IN CHILEAN OYSTER OSTREA-CHILENSIS

The physiology of brooding and non-brooding individuals of the Chilean oyster Ostrea chilensis Philippi was compared. In this species, repro duction occurs once per year, during spring and early summer. The broo ding period lasts approximately 7 to 8 wk, during which time larvae li ve in the infrabranchial chamber of the brooder. In the experiments de scribed here. brooding resulted in significant decreases in the rates of particle clearance, ingestion, faeces production and excretion, alt hough there was no difference in oxygen uptake between brooding and no n-brooding oysters. Brooders partially compensated for reduced food in take by increasing absorption efficiency. The scope for growth was muc h lower in brooding oysters than in non-brooders, largely as a result of the reduced clearance rate of the brooders. The cost of brooding wa s 6 to 7 J h(-1). Meat weight decreased during the brooding process. A fter the larvae were liberated, the clearance rate of the brooder incr eased, reaching values close to those obtained for non-brooding Chilea n oysters.