Digestive enzymes of the shrimp Penaeus japonicus - II. Effect of short-necked clam diets on shrimp growth and digestive enzyme activities.

The effects of feeding live short-necked clam (L-SNC) , freeze-dried short-necked clam ( F-SNC), and a compounded dry diet (CDD) made of mimic live clam , on the growth, survival, and digestive enzyme activities of Penaeus japonicus were compared .Exogenous digestive enzymes from the live food source seemed to affect the shrimps' protease and amylase activities.The L-SNC group showed an increase in amylase and protease activities , whereas the F-SNC group exhibited decreased amylase and protease activities .These changes seemed to be an adaptation of endogenous enzyme activity to the diet's enzymic content , and are supported by the positive growth effect in the L-SNC group relative to the F-SNC group.The amylase activity in the F-SNC group increased greatly when L-ascorbic acid was added to the extract solution, which may indicate that an insufficient amount of vitamin C was available for maximal expression of amylase activity.It is not clear whether the negative effect on growth in the F-SNC group was entirely due to the inactivation of amylase and protease activities, as a dietary deficiency of some vitamin(s) or other metabolic cofactors may have occurred during storage of the freeze-dried diet.