CHARACTERIZATION OF THE DIGESTIVE PROTEINASES OF THE REDCLAW CRAYFISH Cherax quadricarinatus IN RESPONSE TO DIFFERENT DIETS.

SACRISTÁN HJ; FERNÁNDEZ GIMENEZ A; CHAULET A; FENUCCI J; RODRÍGUEZ E & LÓPEZ GRECO LS*

NATAL

Congreso; WORDL AQUACULTURE SOCIETY MEETING 2011; 2011

WAS

The crayfish Cherax quadricarinatus is endemic to freshwater systems of northern Australia and southern Papua New Guinea. The biology of this species is well known and the culture techniques are well established, but its capacity to digest dietary nutrients, such as proteins, carbohydrates and lipids is not yet completely understood. Crustaceans adapt quite well to changes in feed composition by the induction of digestive enzymes synthesized and secreted in the midgut gland. A better comprehension of its nutritional requirements is essential to ensure profitable production and long-term sustainability of the culture. The aim of the present work was to determine the proteinase activities of juvenile C. quadricarinatus fed two fish-based diets: a commercial, non-specific diet usually used in cultures (Diet 1), and a diet formulated for this species (Diet 2).   The composition of the diets was: 16.03 and 4.40% of lipids, 3.85 and 37.45% of protein, 72.69 and 51.37% of carbohydrates, for Diet 1 and Diet 2, respectively. Juveniles of two sizes (7.07±1.13g and 1.35±0.32g) were fed both diets. Table shows that proteinase activity and the percentage of trypsin inhibition were higher for individuals fed Diet 1, regardless of size. Trypsin activity was higher in the smaller juveniles fed with Diet 1 (lower percentage of proteins). The percentage of specific trypsin inhibition depended on size and type of diet while the inhibition percentage of trypsin belonging to the serine class did not depend on diet or size. Enzyme activity varies with modifications to feeds and its analysis allows a more accurate definition of an animal´s capacity to utilize nutrients. Diet 1 induced the highest proteinase and trypsin activities, indicating an ability of the crayfish to compensate for low quality dietary protein. Digestive activity can increase in crustaceans given feed with low nutritional quality.