Pathological changes in the midgut epithelium of grayling, Thymallus thymallus L., larvae reared on different kinds of food, and their relation to mortality and growth

Abstract. The histological differentiation of the digestive tract in grayling, Thymallus thymallus L., larvae was studied during the first 20 days after hatching. The normal development was assessed in larvae fed with nauplii of two Anemia strains. These results were compared with a starved control....
Ausführliche Beschreibung

Abstract. The histological differentiation of the digestive tract in grayling, Thymallus thymallus L., larvae was studied during the first 20 days after hatching. The normal development was assessed in larvae fed with nauplii of two Anemia strains. These results were compared with a starved control. Grayling larvae reared on lake zoo-plankton suffered mortality which was ten times higher than that in the Artemia-fed groups. The histopathology of the zooplankton-fed larvae was characterized by excessive fat accumulation in the apices of columnar absorptive cells, complete absence of fat transport into the villus lamina propria, and disintegration of enterocyte cell membranes. This pathology is compared with the clinical findings in human abetalipoproteinaemia. It is concluded that the histopathological manifestations and the resulting elevated mortality in larval grayling were provoked by a disturbance of the fat absorption process in the enterocytes. This disturbance is likely to be due to the inability to synthesize chylomicrons. It is further hypothesized that lake plankton either contains a toxic agent which interferes with the build-up of chylomicrons or is deficient in some lipoprotein moiety which is essential for chylomicron synthesis. Ausführliche Beschreibung