Effects of Low Salinity on the Physiological Indices, Stress-Related Gene Expression, and Histological Changes in Phasolosma Esculenta

Acute saline stress can cause death of Phasolosma esculenta, an important aquaculture species in China. Hence, investigating the sensitivity and physiological responses of P. esculenta to saline stress is important. The molecular, physiological, and immune responses of the intestine and body wall of P. esculenta upon saline stress were investigated in this study. The mortality rate of P. esculenta increased with the decreasing salinity. The Na+/K+-ATPase and acid phosphatase activity peaked at 6 h and 12 h, respectively, in the intestine and body wall, and subsequently stabilized at a higher level than control group. Further, superoxide dismutase activity significantly decreased within 12 h and then increased slowly, while its genes expression decreased and reached its lowest level at 6 h. In the intestine and body wall of P. esculenta, saline stress induced the transcription of Heat Shock Protein-70, Heat Shock Protein-90, and ferritin, along with the enlargement and loosening of connective tissue cells. Moreover, saline stress induced a more prominent adaptive response in the intestine than body wall. This research indicated that the enzymatic system, nonenzymatic system, and gene expressions of P. esculenta changed under low saline stress and provided references for the further research on the low saline stress response in P. esculenta.