Gill Reaction to Pollutants from the Tamiš River in Three Freshwater Fish Species,<i>Esox lucius</i>L. 1758,<i>Sander lucioperca</i>(L. 1758) and<i>Silurus glanis</i>L. 1758: A Comparative Study

The study evaluated the effects of waterborne pollutants from the Tamiš River on gill histology and possible differences in gill reaction patterns between three freshwater fish species, pike Esox lucius L. 1758, pike-perch Sander lucioperca (L. 1758) and wels catfish Silurus glanis L. 1758 from the Tamiš River. Gills from analysed fish species showed moderate to intense histopathological alterations. The most frequent progressive alteration was hyperplasia of epithelium, whereas the most frequent regressive alteration was epithelial lifting. Circulatory disturbances were most often manifested in the form of hyperaemia. During comparative analysis, differences in gill indices, reaction and alteration indices, as well as in gill and filament prevalence between analysed species, were observed. Although all analysed fish species did show both progressive and regressive alterations, there was a significant difference in the level of expression of these reaction patterns. Gill index obtained for pike clearly stands out as the lowest. Wels catfish showed the highest progressive reaction index, significantly higher in comparison with the other two species (P < 0.05), while pike-perch showed the highest regressive reaction index, also significantly higher in comparison with the other species (P < 0.001). These results may implicate species-specific gill reactions and thus present a useful tool for better understanding toxic mechanisms of various pollutants.