| Salinity is one of the important environmental factors that directly influence the survival, growth and other physiological functions such as osmoregulation of crustaceans. The paper studies the effects of salinity on osmoregulation parameters, immune signal transduction factors and immune defense parameters of the swimming crab Portunus trituberculatus, preliminary discussed the penetration physiological adaptability and immune response mechanisms under salinity stress, mainly including three aspects:(1)the penetration physiological adaptability of Portunus trituberculatus under salinity stress; (2) the effects of salinity stress on the immune signal transduction pathway; (3) the effects of salinity stress on immune defense parameters. The main results were as follows:1 The study on penetration physiological adaptability of P. trituberculatus under salinity stressIn the study, salinity experiments were set up by three different salinity grades:21, 26 and 31 ppt (as control), and sampled tissues of hemolymph and gills at 0,3,6,12, 24,72 and 144 h. Osmotic pressure, hemocyanin content, ion transportation enzyme activity and biogenic amine content in gills were measured. The results indicated that salinity stress had significant effects (.P<0.05) on osmotic pressure, ion transportation enzyme activity and biogenic amine contents in gills, but there were no significant effects in the control group. Osmotic pressure decreased significantly (P<0.05) in the treatment groups and reached the lowest levels at 24 h, then tended to be stable after 72 h, but was significantly lower than the control group. The Na+-K+-ATPase activity increased significantly (P<0.05) in the treatment groups and reached the highest levels at 12 h, then tended to be stable after 72 h, but here were no significant effects on V-ATPase and HCO3--ATPase activities. Salinity stress had significant effects (P<0.05) on biogenic amine (BA) contents in gills, DA content increased significantly (P<0.05) at 3,6 h and 12 h in the treatment groups, and reached the peak at 12 h, then recovered to control level and kept、constant.5-HT content increased significantly (P<0.05) at 6,12 and 24 h in the treatment groups and reached the highest value at 12 h, then recovered to control level at 72 h. NE content increased significantly (P<0.05) at 3,6,12 and 24 h in the treatment groups and reached the highest value at 12 h, then recovered to control level after 72 h. These results suggest that the Na+-k+-ATPase plays a leading role in the process of adaptation to salinity. In addition, biogenic amine, as a kind of neuroregulators, plays an important role in the osmoregulation of crustaceans.2 Effects of salinity stress on the immune signaling transduction pathway in hemocyte of P. trituberculatusIn the study, salinity experiments were set up by three different salinity grades: 21,26 and 31 ppt (as control), and sampled tissues of hemolymph at 0,3,6,12,24,72 and 144 h. Biogenic amine (BA) contents in plasma, biogenic amines receptors relative mRNA expression levels, cAMP, protein kinase A (PKA), phospholipase C (PLC) and protein kinase C (PKC) content in hemocyte were measured. The results indicated that salinity stress had significant effects (P<0.05) on biogenic amine (BA) contents in plasma, biogenic amines receptors relative mRNA expression levels, cAMP, protein kinase A (PKA), phospholipase C (PLC) and protein kinase C (PKC) content in hemocyte in the control group. Salinity stress had significant effects (P<0.05) on dopamine (DA) content and 5-hydroxytryptamine (5-HT) content, but no significant effects on noradrenaline (NE) content. DA content increased significantly (P<0.05) at 3,6 and 12 h in the treatment groups, and reached the peak at 12 h, then recovered to control level and kept constant.5-HT content increased significantly (P<0.05) at 6 and 12 h in the treatment groups and reached the highest value at 12 h, then recovered to the control value level at 24 h. NE content had no significant change in the treatment groups during the experimental period. DA and 5-HT receptor was significantly up-regulated in the treatment groups (P<0.05). The highest value of mRNA expression level of DA and 5-HT receptor occurred at 12 h and recovered to the control level at 24 h. In contrast to the control group, salinity stress had significant effects (P<0.05) on cAMP, PKA, PLC and PKC content. The cAMP and PKA content increased significantly (P<0.05) at 3,6,12 and 24 h in the treatment groups, and reached the peak at 12 h, then recovered to control level at 72 h. The PLC and PKC content increased significantly (P<0.05) at 6,12 h and reached the peak at 12 h, and then resumed to the control level at 24 h and kept constant. These results suggest that the changing trends of biogenic amine content are almost consisitent with immune defense parameters. Biogenic amine plays an important role in regulating the immune defenses and could modulate immune responses via biogenic amines receptors/ cAMP/PKA signaling pathway or biogenic amines receptors/PLC/PKC signaling pathway when exposed to salinity stress.3 Effects of salinity stress on immune defense parameters of P. trituberculatusIn the study, salinity experiments were set up by three different salinity grades: 21,26 and 31 ppt (as control), and sampled tissues of hemolymph and gills at 0,3,6, 12,24,72 and 144 h. The THC, prophenoloxidase (ProPO) activity in hemocyte, phenoloxidase (PO) activity in plasma, phagocytic activity in hemocyte, antibacterial activity and bacteriolytic activity in plasma were measured. The results indicated that salinity stress had significant effects (P<0.05) on THC, prophenoloxidase (ProPO) activity in hemocyte, phenoloxidase (PO) activity in plasma, phagocytic activity in hemocyte, antibacterial activity and bacteriolytic activity in plasma. The THC decreased significantly (P<0.05) in the treatment groups after 6 h and reached the lowest levels at 12 h, then tended to be stable after 24 h, but was significantly lower (P<0.05) than the control group. The prophenoloxidase (proPO) activity in hemocyte of the treatment groups decreased significantly (P<0.05) at 3,6,12 and 24 h, reached the lowest levels at 12 h, then resumed to the control level and remained stable after 24 h, while the phenoloxidase (PO) activity in plasma increased significantly (P<0.05) at 6,12 and 24 h in the treatment groups, and peaked at 12 h, then recovered to control level and kept stable after 24 h. The phagocytic activity in hemocyte, antibacterial activity and bacteriolytic activities in plasma decreased significantly (P<0.05) at 6,12 and 24 h in the treatment groups, and reached the lowest levels at 12 h, then recovered to control level after 72 h. These results suggest that crabs have a strong stress response on salinity stress and the immune defense factor activities are suppressed under low salinity. In addition, these changes had a significant time-dependent relationship under salinity stress. |
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