Abstract
In this experiment, the effects of a sudden drop in salinity on the antioxidant defense system and related gene expression of the ark shell Scapharca subcrenata were examined. The sudden drop in seawater salinity after a rainstorm was simulated, and subsequently differentially expressed metabolic markers were identified by LC-MS non-targeted metabolomics. When the salinity dropped to 14‰ (S14), the total anti-oxidant content, activity of Na+/K+-ATPase, superoxide dismutase (SOD), and catalase (CAT), content of malondialdehyde, and expression levels of Mn-SOD, CAT, and C-type lectin of S. subcrenata were significantly higher than in groups with salinity of 22‰ (S22) or 30‰ (S30) (P < 0.05). The activity of glutathione peroxidase (GPx), the content of reduced glutathione, and the expression levels of GPx were not significantly different between S14 and S22, but the values in each group were significantly higher than those in S30 (P < 0.05). Using the metabolomics technique, 361, 271, and 264 metabolites with significant differences were identified from S22 vs. S14, S30 vs. S14, and S30 vs. S22, respectively. The drop in salinity was accompanied by up-regulation of phosphatidylcholine (PC) (20:4 (5Z, 8Z, 11Z, 14Z)/P-18: 1 (11Z)), PC (16:0/22: 6 (4Z, 7Z, 10Z, 13Z, 16Z, 19Z)), phosphatidylethanolamine (PE) (18:4 (6Z, 9Z, 12Z, 15Z)/24:1 (15Z)), phosphatidylinositol (PI) (20:1 (11Z)/0:0), phalluside-1, C16 sphinganine, and LacCer (d18:0/14:0) and by significant down-regulation of PI-Cer (d18:1/14:0) and PE (14:0/16:1(9Z). The results of this study illustrate how these nine metabolites can be used as metabolic markers for the response of S. subcrenata to a sudden drop in salinity. They also provide the theoretical groundwork for selection of bottom areas with salinity that is optimal for release and proliferation of S. subcrenata, which is needed to restore the declining populations of this species.
Highlights
Www.nature.com/scientificreports at a fast rate and slowly recover their normal body volume over time
In the simulation that mimicked the sudden drop of salinity in seawater after a rainstorm, phagocytic activity of blood lymphocytes, O2– levels produced from respiratory burst, and the activity of lysozyme and acid phosphatase were significantly higher in the 14‰ group compared to the 30‰ and 22‰ group
When the salinity decreased from 30‰ to 22‰, no significant difference in total antioxidant capacity (T-AOC) was identified between the two groups
Summary
Www.nature.com/scientificreports at a fast rate and slowly recover their normal body volume over time. Under hypotonic conditions, when an organism has more dilute blood, cells retain ions and transport amino acids from the cell into the blood to reduce the osmotic gradient[10] In this way, salinity can significantly affect various physiological functions of marine organisms. In the simulation that mimicked the sudden drop of salinity in seawater after a rainstorm, phagocytic activity of blood lymphocytes, O2– levels produced from respiratory burst, and the activity of lysozyme and acid phosphatase were significantly higher in the 14‰ group compared to the 30‰ and 22‰ group These results indicate that the immune defense mechanism of S. subcrenata was activated in response to salinity stress[16]. Results of this study provide an understanding of the physiological adaptation process of marine invertebrates in response to low salinity
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