Feeding and digestive response of Argopecten purpuratus to short-term variation in food quality and quantity

Changes in differential absorption of biochemical components and enzymatic digestive activity of Argopecten purpuratus were observed using two different diets over a short-term experiment (24 and 72 h). One diet was below the threshold of A. purpuratus pseudofaeces production (low diet 3.93 mg l(-1)) and had high organic content (42.5%). The second diet was above the threshold (high diet = 20.8 mg l(-1)), but with low organic content (26%). The effect of the diet and acclimation time on assimilation and on the enzymatic behaviour was studied with a two-way ANOVA. The response of the carbohydrase activity to changes in the food offered (low- versus high-diet concentration) was abrupt in the crystalline style where greater investment in enzymes was detected after 72 h. However, in the digestive gland, the processes were slower over the study period. The proteases in the gland showed no significant differences between the two diets. Although the preingestive selection of A. purpuratus allowed the organic ingestion rate to equilibrate with diets of high concentration and low organic content, the digestive response in enzymatic behaviour did not permit adequate acclimation, as observed in the assimilation of biochemical components. From an ecological standpoint, A. purpuratus is unable to maximise energy gain in areas where rapid increase in suspended particulate material occurs, such as in the bays of southern Chile. (C) 2004 Elsevier B.V. All rights reserved.