Activities of three digestive enzymes during development in the crayfish Procambarus clarkii (Decapoda)

Enzyme extracts were used to characterize alpha -amylase-, trypsin-, and no nspecific-esterase-specific and total activities during the early life-hist ory stages of the red swamp crayfish Procambarus clarkii. Significant incre ases in the specific activities of all three digestive enzymes were observe d prior to the onset of feeding, suggesting that digestive competence is at tained prior to feeding and appears to be controlled genetically. After the onset of feeding, the digestive-enzyme-specific and total activity increas ed steadily through the 42(nd) day of development, after which point activi ty did not change significantly. We hypothesize that the observed increase in specific activity reflects the maturation of the hepatopancreas, as grea ter amounts of digestive enzymes are being: produced per unit weight of tis sue. As individuals exceeded approximately 100 mg in total weight, specific activity was variable and did not change substantially. Further increases in total enzyme activity (total digestive capacity) were dependent primaril y on increases in the weight gain of the individual. We suggest that the fi rst four to six weeks of development may represent a crucial stage in the d evelopment of the hepatopancreas and that perturbations that occur during t his stage of development may impact future growth. The pattern of digestive enzyme expression in Procambarus clarkii indicates little or no change in nutritional requirements and is different from the patterns observed in dec apod crustaceans that have planktotrophic life-history stages. The digestiv e enzyme activities indicate that crayfish can digest and utilize primarily carbohydrates, proteins and, to a lesser extent, lipids as macronutrients during early growth.