Laboratory exposure of Oreochromis niloticus to crude microcystins (containing microcystin-LR) extracted from Egyptian locally isolated strain (Microcystis aeruginosa Kützing): biological and biochemical studies.

Cyanobacterial blooms exert negative impacts on fisheries and water management authorities. Recently, it has gained global attention, as elevated earth warming and environmental pollution are accelerating algal growth. Oreochromis niloticus (O. niloticus) is a worldwide and the most commonly cultured fish in Egypt. The biological interaction of the living organisms to the surrounding environment must continuously be assessed to predict future effects of the ongoing hazards on fish. The study was designed to examine the possible biological and biochemical response of O. niloticus exposed to different concentrations of microcystins crude extract (containing microcystin-LR). Three equal groups of O. niloticus were assigned for intraperitoneal injection of three different doses: 100, 200, and 400 μg m(-1) dried aqueous microcystins extract, for 10 days. Clinical, condition factor (K) and hepatosomatic index (HIS) were estimated. Biochemical alterations were evaluated via lipid peroxidation, DNA fragmentation assay and electrophoretic analysis of fragmented DNA using agarose gel electrophoresis. The results showed that there were discernible behavioral and clinical alterations. Significant differences in K and HIS were observed between treatments. Also, significant elevations were observed in lipid peroxidation level and in the DNA fragmentation percentage in the exposed fish to the doses of 200 and 400 μg m(-1) of microcystins crude extract. The current study addresses the possible toxic effects of microcystins crude extract to O. niloticus. The results cleared that microcystins crude extract (containing MC-LR) is toxic to O. niloticus in time- and dose-dependent manners.