Histology of the digestive system of larvae of African catfish (Clarias gariepinus): Implications on the timing of feeding transitions

Abstract

Clarias gariepinus is a dominant indigenous fresh water fish species most reared in Africa. Its dominance is attributed to; ability to tolerate extreme environment (swampy vegetation, drought and low oxygen areas), easy to cultivate, fast growth, and efficient feed conversion. . Many catfish farmers experience high larval mortalities especially during the first exogenous feeding. A descriptive study was conducted from November 2021 to February 2022 on African catfish larvae collected from Aquaculture experimental station at Kajjansi in Entebbe to describe the histology of digestive system of larvae of African catfish. A total of Sixty larvae of African catfish were collected at different age intervals (day; 3, 8, 15, 21, 30 and 42 post hatchings) from Kajjansi aquaculture station and put into sample bottle containing Bouin’s fixative, and embedded in paraffin. Serials sections of 5microns were made longitudinally and transversely, stained with H&E and Masson’s Trichome, and mounted for histological examination. Yolk reserves were available by 3dph, and completely depleted at 8dph. Stomach anlage was detected on 8dph, gastric glands observed in the fundic region on 15dph, and became fully functional with pylorus being surrounded by thick Tunica Muscularis on 21dph. The presence of gastric glands indicates the functional stomach and has been used as histological criterion to distinguish larvae from juveniles. Therefore, exogenous feeding should be started between 5-8post hatching. Weaning of larvae to micro diets should be done on 21dph. The findings from the histology of the digestive system of the African catfish larvae will provide knowledge on course of development of digestive structures in the larvae, which may be useful for improving current larval rearing techniques of this species.