The use of histological, histochemical and ultramorphological techniques to detect gill alterations in Oreochromis niloticus reared in treated polluted waters.

Fish gills are constituted by primary filaments and secondary lamellae, which are formed, basically, by three different cell types: pillar cells, respiratory cells and erythrocytes that circulate in the lamellae interior. This respiratory organ is very appreciated in environmental studies since it is constantly in contact with the water, accomplishing exchanges; besides this, it presents a high adaptation capacity. In this work, some fishes were reared in polluted waters treated by the flotation method (treated group) and compared with others that were reared in clean waters (control group). The ultramorphological, histological and histochemical analyses were used. The fishes from the treated group presented morphological alterations when compared with the control groups, such as lamellar fusion, aneurism and detachment of the respiratory epithelium. These alterations demonstrate the several adaptations, as morphologic as physiologic, that fishes can present when exposed to an inappropriate environment. The techniques employed are good tools to detect morphological biomarkers in gills of Oreochromis niloticus submitted to polluted waters.