Ontogenic Development of Digestive Enzymes of Mud Crab (Scylla paramamosain) During Larval Stages

Abstract

Scylla paramamosain have been considered as an economic candidate for aquaculture, however, high mortality during early larval stages exhibits a significant bottleneck to their mass seed production. Operational enzymatic variables were investigated for further studies on feeding optimization. Ontogenetic change of the digestive system of S. paramamosain was enzymatically (trypsin, chymotrypsin, pepsin, amylase and alkaline phosphatase) evaluated. Results showed that these enzymes were already presented in the larvae before exogenous feeding. The first detection after hatching was low activity and gradually increased from Z3 except trypsin, and chymotrypsin activity increased from Z5 stage. Alkaline phosphatase activity peaked at Z2 and Z4, followed by a sharp fall in Z5 and megalope. Trypsin and Chymotrypsin activities were also decreased from Z3 to Z5, then sharply increased from Z5; however, Chymotrypsin activity decreased after megalope stage. Pepsin activity was detectable after hatching and regularly increased through the larval development. Amylase activity was low from hatching to Z3 and then suddenly increased. Alkaline phosphatase activity was recorded with the highest activity at Z2 and Z4, then complex variation, particularly at Z3 and megalope stage. The study constitutes physiological information on ontogenic development as well as the digestive abilities of mud crab larvae further, facilitates feeding diet formulation and larviculture of this species.