The effect of different salinities on the gill morphology and related gene expression of larval Scylla paramamosain Estampador, 1950 (Brachyura, Portunidae)

In the present study, histopathological changes in the gills and the expression of genes related to osmotic pressure regulation in larval mud crab, Scylla paramamosain , were examined under different conditions of salinity stress. Notable alterations in gill tissue were observed in low salinity environments (5 ppt) compared to normal salinity (20 ppt). The gill filaments from the low salinity stress groups became shorter and thicker over time, resulting in severe morphological damage. Quantitative real time PCR (qRT-PCR) analysis indicated a reduction in NKCC (Na + -K + -Cl − -cotransporter) expression under both low and high salinity conditions. NKCC expression gradually decreased over time in low salinity conditions. However, expression was only slightly elevated at 2 hours in high salinity conditions. These findings suggest that the NKCC transport function is inhibited to prevent salinity-induced damage. Conversely, CA gene expression levels increased after 2 hours across all salinity conditions and the highest levels were observed in the 5 ppt group. Regardless of salinity levels, CA showed a positive response to salinity changes, which supported the maintenance of normal physiological functions. This experiment would be helpful for understanding the impact of salinity stress on osmotic pressure and ion regulation under different salinity conditions in S. paramamosain .