**3. Conclusion**

Teleost fishes possess a high compensatory potential for improving oxygen transport under the influence of adverse environmental factors [48]. It includes synthesis of erythrocytes and hemoglobin, amitotic division of erythrocytes, release of erythrocytes from blood depots (spleen and main kidney), as well as activation of hematopoiesis.

A low-cost response to oxygen deficiency is realized by increasing the MCV. The increase in cell volume, together with the increase in erythrocyte pH, improves oxygen transport under hypoxic conditions [3]. They result from adrenergic activation of Na+ /proton exchange across the erythrocyte membrane [49]. Knowledge, on the one hand, of anemic and genotoxic effects of aquatic pollutants, and on the other hand, of adaptive-compensatory responses to the action of aquatic toxicants, is a good basis for using a large set of freshwater bony fish for ecological biomonitoring purposes.
