Abstract

The histopathological effects of sublethal doses of microcystin-LR, a hepatotoxin produced by Microcystis aeruginosa, on channel catfish (Ictalurus punctatus) were studied over a 7-day period. The goal of this study was to identify and characterize histopathological lesions that would prove useful as a diagnostic tool in catfish ponds where algal bloom toxicosis is suspected. Fish were injected intraperitoneally with various doses (2.5 ug kg-1, 25 ug kg-1 and 250 ug kg-1) and observed for behavioral changes (feeding rate and opercular rate). Necropsies were performed on sacrificed fish at 1, 2, 4 and 7 days post-inoculation. Toxic effects were evaluated through histopathological examination of vital organs (gills, liver, spleen, kidney, heart, intestine and brain). No mortalities were recorded at any of the doses. After seven days, all fish had returned to normal activity and feeding. Histopathological changes were limited to the liver of fish injected with the medium and high doses and included diffuse to regionally extensive hepatocellular dissociation, individualization, degeneration and necrosis. Hepatocyte regeneration was evident in all samplings by day 7. All other organs appeared unaffected.