Digestive enzyme system of larvae of different freshwater teleosts and its differentiation during the initial phase of exogenous feeding

Abstract

Activities of digestive enzymes and main histological characteristics of the intestine were investigated in larvae of three salmonid species (Coregonus maraena, C. atterensis, Thymallus thymallus), of burbot (Lota lota), and pikeperch (Sander lucioperca) at the onset of exogenous feeding (0 day degrees (°d)) and at 250°d thereafter. At the onset of exogenous feeding the activities of proteolytic, lipolytic, and carbohydrate splitting enzymes were detected in the intestines of all species. The enzymatic activities showed significant species specific differences indicating specializations in functionality and digestion ability. In C. atterensis and L. lota the activities of most enzymes were low in comparison to the other investigated species and therefore their digestive system was only poorly developed. In S. lucioperca it was moderately developed and in T. thymallus and C. maraena well-developed. After 250°d, the activities of the investigated enzymes changed in a very species specific way. Histologically, the intestines of the investigated species revealed no species specific differentiations at the onset of the first feeding with the exception of the absence of goblet cells in L. lota and C. atterensis. These differentiated after 250°d.