Effects of short-term salinity exposure on haemolymph osmolality, gill morphology and Na+/K+ - ATPase activity in Solenaia oleivora

In order to explore the physiological reaction to hyperosmotic environment, Solenaia oleivora were exposed to 2.23‰ salinity. In 48h, the hemolymph osmolality kept increasing, and the hemolymph protein concentration increased in the first 6h and then decreased significantly, while the free amino acid content increased in the first 24h and then kept stable ( P < 0.05). The activity of Na+/K+-ATPase at 0h was significantly higher than other times in most organs except intestine, which was highest at 3h ( P < 0.05). The ions concentration were also influenced. The concentration of Na+ rose in haemolymph, axe foot and intestine, but decreased in gill and hepatopancreas. In hemolymph, gill, hepatopancreases and adductor muscle, the K+ concentration was the highest at 0h, while in axe foot and intestine, it showed a positive tendency. The concentration of Cl- in haemolymph, adductor muscle, intestine and axe foot were positively correlated with treatment time, while hepatopancreas showed opposite tendency. High salinity stress caused a difference in the gill histological structure, the gill structure shrunk, the gill lamellas space and shrinking degree showed an enlarging trend with salinity treatment time. ### Competing Interest Statement The authors have declared no competing interest.