Índices hematológicos y celulares como bioindicadores de estrés en Oreochromis aureus Steindachner (tilapia) de cultivo

Tilapia, several species and their hybrids of Oreochromis, are the second most important group of farm raised fish in the world, reason why it is necessary to have diagnosis tools to evaluate its health state in culture conditions. Since haematological variables can be used to asses the health state in cultured fishes, a haematological characterization of clinically healthy Oreochromis aureus was done to established the references indices of this species. Fish were subjected to different stressed conditions (biological, environmental and physical stressors). The reference indices for the haemoglobin, haematocrit, and red blood cell count and erythrocytes indexes were determined. Six types of cells in peripheral blood were identified: mature and young erythrocytes, thrombocytes, monocytes, neutrophil and lymphocytes. The biological stressors Corynebacterium sp. and Aeromonas hydrophila caused decrease of the haemoglobin, Mean Corpuscular Haemoglobin (MCH), Mean Corpuscular Haemoglobin Concentration (MCHC), Mean Corpuscular Volume (MCV) and Red Blood Cell Count (RBCC) and poikilocytosis. It was observed that for both pathogens the fish showed neutrophilia, increase of the young lymphocytes and reduction of mature lymphocytes. Anesthetic MS 222 caused haematocrit increase and MCHC diminution after 2h post-anesthesia and to the 24 hours was observed haematocrit diminution. Anesthetic benzocaine caused in O. aureus, lymphocytopenia and neutrophilia. A decrease of the haemoglobin, erythrocyte counts and haematocrit was observed in fish with nitrite intoxication, but 48h the haematocrit and MCV increased significantly. In O. aureus exposed to sublethal lead concentrations was observed haemoglobin, RBCC and MCHC diminution; in the white cells it was observed young lymphocytes and neutrophil increase, as well as mature lymphocytes diminution and thrombocytopenia. The use of high doses of green malachite caused, haematocrit increase, as well as MCHC, was observed neutrophilia. Oreochromis aureus exposed to Trichlorphon presented neutrophilia, mature lymphocytes diminution and thrombocytopenia. The stress proteins Hsp 70 expression response in O. aureus under physical stress, appears at 2 hours with an increase of these proteins in liver and hematologicals indicators response begin at 24 hours. In the comparison of O. aureus with other tilapia species, the values of the haematological indexes analyzed were significantly different when the three Oreochromis species were analyzed. Hybrid O. aureus x O.niloticus showed higher erythrocyte and haemoglobin concentration than the parental O. niloticus but lower concentration than O. aureus, while the average corpuscle value was lower than that of the O. niloticus and higher than that of O. aureus. The values of the mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration were not significantly different for O. niloticus and hybrid O. aureus x O. niloticus, while O. aureus exhibited the highest values in these two indexes. With these results we can enrich the applied investigation and basic, and contribute to the practical necessities of the culture with a tool that helps to determine the optimal physiological state in the fish and with it to mitigate the economic losses by diseases or environmental changes.