Ingestion of horseradish peroxidase by the intestinal cells in larvae or juveniles of some teleosts.

The ability to ingest protein molecules by the intestinal cells of larval or juvenile fishes was investigated with five teleost species; Oncorhynchus masou, Hypomesus olidus, Cottus nozawae, Tilapia nilotica, and Carasius auratus, using horseradish peroxidase (HRP) as a marker substance. Histological characteristics of the intestine were also described. The intestine of all fishes examined was divided into the anteromedian intestine and the rectum on the basis of morphological and functional characteristics of the epithelial cells. The columnar cells of the anteromedian intestine showed the cytoplasm deeply stained with hematoxylin. The supranuclear region in the columnar cells of the rectum was characterized by the extensive chromophobic (O. masou, H. olidus), or vacuolated (C. nozawae, T. nilotica, C. auratus), appearance . HRP ingestion was found only in the rectal cells. Ingested HRP was accumulated forming granules in the supranuclear area of the rectal cells.