Temperature-driven shifts in haematology and erythrocyte morphology of Nile tilapia Oreochromis niloticus

The present study investigated the haematological responses of Oreochromis niloticus to seasonal temperature variations, critical to understanding their physiological health under changing environmental conditions.Fish were acclimatised in controlled laboratory settings, and blood samples were analysed during the summer and winter seasons.The results indicated significant reductions in total erythrocyte counts (7.22%), total leukocyte counts (14.28%), haemoglobin (20.20%), haematocrit (8.84%), mean corpuscular volume (2.04%), mean corpuscular haemoglobin concentration (12.38%), and mean corpuscular haemoglobin (14.24%) during the winter compared to summer.Additionally, erythrocyte cellular and nuclear changes, such as crenation, tear-drop shaped, sickle-shaped and elongated cells, notched nucleus and vacuolation in cytoplasm, were observed, indicating low temperature induced stress and bioresponses.The results emphasised the necessity of monitoring haematological parameters as vital indicators of fish health and environmental stress.