Alterations of oxygen consumption and gills morphology of Nile tilapia acclimatized to extreme warm ambient temperature

Abstract

Elevation of water temperature due to global warming influences the physiological properties of fish by increasing their rate of metabolic function and demand for oxygen. It is important to know how fish respond to changing environments for indicating and predicting the impacts of climate change on fish populations, communities and for their sustainable management. Hence, the present study was aimed to investigate the effects of high water temperature on juvenile Nile tilapia, based on the oxygen consumption rate, blood physiology and gill morphology in different temperature (31 °C, 34 °C and 37 °C) in triplicates for a period of 28 days. Results showed that the oxygen consumption rate increased significantly at 37 °C, whereas no significant difference was observed at 31 °C and 34 °C. Hemoglobin (Hb) and red blood cell (RBC) were decreased significantly at 37 °C after 14 and 28 days of exposure, whereas blood glucose levels showed the opposite scenario. On the other hand, no significant changes were observed for white blood cell (WBC) on day 14, but a significant increase was observed on day 28 at 37 °C. Being the site of main gaseous exchange moderate to severe histopathological changes (epithelial lifting, epithelial necrosis, hypertrophy of chloride cell, lamella fusion, telangiectasia, vacuolation of epithelium and epithelial edema) were observed in the gill especially in the gill lamellae of the experimental fish at 37 °C. The findings of the study indicate the adaptive physiological strategy in changing climate despite being a thermal tolerant species, and the alteration in oxygen consumption rate, gill morphology and blood parameters could be used as an assessment strategy to know the condition of the fish and their surrounding environment.