Biochemical and histological studies on juvenile tilapia, Oreochromis mossambicus exposed to salinity stress

Abstract

The secondary stress response of juvenile Tilapia, Oreochromis mossambicus after direct transfer to saline water was evaluated by assessing the levels of plasma glucose, plasma protein, hepatosomatic index and liver histology. After an acclimation period of 6 days, fishes were transferred directly to different experimental salinities (2, 4, 8 and 10 ppt) for a period of 5 days. Plasma glucose increased, plasma protein and hepatosomatic index showed slight decrease. However, liver histology did not exhibit any marked variation from that of the control. These alterations at the molecular and biochemical levels are measures of processes that are a normal component of an organism’s attempt to maintain a constant internal environment, and may be regarded as biological markers of exposure to salinity stress. Considering the parameters measured in this study Oreochromis mossambicus appeared to exhibit a stress response to direct transfer to saline water, nevertheless, the magnitude of stress response was related to salinity level.