CHANGES OF INTESTINAL EPITHELIAL STRUCTURE AND CELL TURNOVER IN CARP CYPRINUS-CARPIO INFECTED WITH GOUSSIA-CARPELLI (PROTOZOA, APICOMPLEXA)

Epithelial cell turnover in the intestine of common carp Cyprinus carp io infected with the coccidian parasite Goussia carpelli (Leger & Stan kovitch, 1921) was investigated during laboratory infection using hist ological and electron microscopical techniques. During the development of the parasite an increased number of mitotic enterocytes, identifie d by bromodeoxyuridine (BRDU) uptake, were observed at the base of inf ected mucosal folds. During the merogonic and gamogonic development of the parasite, severe damage to infected epithelium occurred, and conc omitantly BRDU-positive cells spread along the mucosal folds. These ce lls exhibited immature characteristics, including a squamous to cuboid al shape, nuclear apolarity, a high number of ribosomes, and short or reduced microvilli. Contact with adjoining cells was formed by tight j unctions and desmosomes, indicating the epithelial origin of these cel ls. These cells covered gut segments with damaged epithelium within a few days, suggesting a high regenerative capacity of the carp intestin e, and this could explain the mild clinical symptoms in fish affected by G. carpelli-coccidiosis Our study for the first time describes epit helial cell. responses to injuries caused by enteric protozoa in pisci ne hosts.