Hematological importance of pseudoeosinophilic granulocytes in acclimation of common carp (Cyprinus carpio Linnaeus, 1758)

Adaptation mechanisms as response to water content, oxygen level and pollutants are very important and they can be interpreted by hematological analysis. The aim of this study was the analysis of hematological and immune adaptations of common carp (Cyprinus carpio Linnaeus, 1758) to thermal stress. All specimens were divided into a control and experimental group. The control group of fish was exposed to a constant water temperature of 10°C. We induced thermal stress in experimental fish by gradually heating water to 28°C, held for 30 minutes and then comparing the obtained results with the control fish. Short-term hyperthermia lead to an increase of the number of leukocytes, especially pseudoeosinophilic granulocytes and monocytes, while the number of neutrophils and lymphocytes was reduced. The analysis of the leukocyte number and differential blood count in the control group showed high individual variation of segmented granulocytes, monocytes and pseudoeosinophilic granulocytes. Statistically significant differences (p=0.00) were found for the white blood cells, nonsegmented neutrophils and pseudoeosinophils between the control and experimental group. The experimental group of males had an increased number of white blood cells, monocytes and pseudoeosinophils, where significant differences were found for nonsegmented and total neutrophils and also for pseudoeosinophils (p=0.00), lymphocytes (p=0.01) and monocytes (p=0.03). Females had an increased total number of white blood cells, lymphocytes, monocytes and pseudoeosinophils, while significant differences (p=0.00) were obtained in the number of white blood cells, non segmented and total neutrophils and pseudoeosinophils between the control and experimental group. Adaptation mechanisms in carp after water temperature heating are mostly reflected in the increase of pseudoeosinophils and the decrease of neutrophils.