ENZYMATIC ACTIVITY AS AN INDEX OF TROPHIC RESOURCE UTILIZATION BY THE SNOW CRAB CHIONOECETES OPILIO (O. FABRICIUS)

Abstract

In order to assess the food utilization of Chionoecetes opilio, we measured the activity of 5 enzymes in the digestive gland: 2 metabolize animal products (chitinase and phosphorylase-a), and 3 digest vegetal products (cellulose, alpha-amylase, and laminarinase). The analysis was made on 18 morphometrically mature males and 2 mature females. Chitinase had a high activity level (mean = 6.728 ± 1.689 units/mg of protein). Phosphorylase-a had a much lower activity level (mean = 0.114 ± 0.039 unit/mg). Alpha-amylase, while present in every crab, had a low activity level (mean = 0.102 ± 0.031 unit/mg). Cellulase was present in 85% of the crabs (mean = 0.115 ± 0.089 unit/mg). Laminarinase was hardly detected (maximum 0.002 unit/mg). The presence of active enzymes digesting vegetal products indicates that the snow crab is not a strict carnivore but is able to metabolize energy from various trophic sources, including vegetal detritus.