Short-term feeding response of the scallop Argopecten purpuratus exposed to two di¡erent diets

5 páginas, 2 tablas, 2 figurasArgopecten purpuratus was exposed to two di¡erent diets which re£ected short term variations in quantity and quality of the natural food supply typical in bays of southern Chile. No signi¢cant di¡erences of clearance rate were observed over di¡erent time periods at either of two food concentrations. The scallop reduced its clearance rate signi¢cantly when it was exposed to the higher food concentration. Pseudofaeces production occurred only at this high diet and the time factor had no signi¢cant e¡ect on this process. The organic content of pseudofaeces was signi¢cantly lower than the organic content of the food, suggesting a pre-ingestive selection mechanism. Based on this capacity for particle selection, A. purpuratus was able to compensate for the di¡erences in food quality of the experimental diets and ingesting particulate material containing 38% organic matter as a result of the selection process when fed at the higher food concentration. Absorption e⁄ciency was lower following exposure to the high food concentration, suggesting that the experimental time of 72 h was not su⁄cient to acclimate the digestive response to a food supply signi¢cantly di¡erent from that of its habitat of origin. Phytoplankton form the principal nutritional source for this epibenthic species, and resuspended detritus, although occurring in large quantities, may only be of importance once digestive processes become acclimated to processing them.Thanks are also due to the Programa de Cooperación Cientifica Internacional CONICYT/CSIC grant no. 2002 3 212/2003CL0030, Chile y MICYT. REN2001-0501/MAR, España.Peer reviewe