Histopathological effects of toxic alga Nostoc muscurum on juvenile grass carp fish (Ctenopharyngodon idella Val. 1844 )


In the present study, the grass carp fish (Ctenopharngodon idella) was divided into three groups, each of them was force feeding ; group (A)on toxic alga Nostoc muscurum only , group (B) on mixture of toxic alga N. muscurum and clover and group (C) served as the control group on clover only. The tissue sections which were made from fish organs that have been investigated a long two periods (after 24 h and after 15 days) , and they proved that the alga N. muscurum have toxic effect on the organs of grass carp fishes (gills , intestine , liver and kidney) in A and B groups and the degree of damage depend on the long time the experiment tacks. At first , the causal relationship of tissue damage with the presence of microcystin-containing (N. muscurum ) were investigated in grass carp fish . In gills filament the histopathological changes are represented by aneurism and congestion of capillaries , the adhesion and change in the shape of the secondary gill lamellae , increase in the number of epithelial cells and swelling of epithelial cells .These changes increased after 15 days , they were represented by detachment of epithelial layer of the secondary gill lamellae . The chondrodysplasia in the supporting cartilage of gill filament and atrophy and disappearance of the secondary gills lamellae were observed in mixture group only as changes. The histopathological changes of intestine were very severe after 15 days and were represented by the increase in the proliferation of columnar epithelial cells , necrosis of lining epithelial tissue and the vascular degeneration of smooth muscles cells in circular layer of tunica muscularis. after 24 hours, the histopathological changes in liver were confined by the congesting of sinusoid with the appearance of yellow patches through the liver cords. The hepatocytes in the liver of group A were seen as normal , but in the mixture group B the location of nucleolus of these cells appeared abnormal .While after 15 days the latter changes appeared in hepatocytes of both groups (A and B) and represented the beginning of necrosis which were described . In kidney , the histopathological changes occurred in all structures of the kidney of fish in the both groups (A and B) . In addition , after 24 hours , in renal tubules , the changes were represented by metaplasia in lining epithelial tissue and their hollow disappeared, the cells of that tubules are lost the polarization in tissue and a change in their nucleus . In glomerules , was noted the proliferative glomerionephritis then a disappearance of bowman's space . Also a necrosis occurred in hematopoietic tissue .However , after 15 days , all of that changes are also observe in two groups (A and B) , as well as the necrosis of some parts of the epithelial lining of renal tubules.