Stress In Fish – Hematological And Immunological Effects Of Heavy Metals
of Animal Physiology,
Abstract: The aim of present study was to evaluate whether short-term exposures to high concentrations of heavy metals may induce stress symptoms in fish blood. Common carp were subjected for 3 hours to 10, 5, 10 or 20 mg/l of lead, copper, cadmium or zinc, respectively, and subsequently transferred to clean water. Blood was sampled immediately after the end of exposures, and then daily until 96 hours post exposures. In red blood cell system transient changes were observed such as an increase in hematocrit value without a substantial changes in red blood cell count (which indicates swelling of the cells), and an increase in erythropoietic rate (indicated by an increase in percentage of immature cells in circulation). In the white blood cell system – a decrease in total leukocyte count took place caused by a considerable drop in lymphocyte count. In some cases (particularly in Pb and Cd-intoxicated fish) percentage of neutrophils increased. However, metal exposures (Cd, Zn) resulted in a reduced ability of intracellular killing by these cells (a decrease in reactive oxygen radical production). The changes gradually developed with time after the end of exposure, and no recovery was observed until 96 hours from transfer of fish to clean water. The obtained data show that a short-term exposures to high levels heavy metals induced stress reactions in fish. In the red blood cell system adaptive changes prevailed, preparing the organism to an increased energy expense, while the changes observed in the white blood cell system indicate a considerable immunosuppressive effect of stress. Therefore, even a short-term exposure to heavy metals induces a persistent stress in fish which may render them more susceptible to diseases.
Key words: carp, stress, heavy metals, blood