Effects of salinity stress on physiological behavior, respiratory metabolism, and intestinal transcriptome of juvenile Stichopus monotuberculatus

Abstract

This study investigated the impacts of salinity stress on the physiological behavior, respiratory metabolism, and transcriptome of artificially cultured juvenile Stichopus monotuberculatus (S. monotuberculatus) (with a body weight of 3.23 ± 0.60 g). S. monotuberculatus individuals cultured in artificial seawater were transferred to artificial seawater with salinities of 20‰, 30‰, and 40‰ for salinity stress treatment. The physiological behavior of S. monotuberculatus was observed, and their ammonia discharge rates, oxygen consumption rates, and oxygen/nitrogen (O/N) ratios were measured. After 24 h of stress, the intestines of S. monotuberculatus were collected for transcriptome sequencing. The results showed that both hyper-salinity and hypo-salinity stresses significantly affected the physiological status of S. monotuberculatus. The oxygen consumption and ammonia discharge rates of the hyper-salinity group (40‰) and hypo-salinity (20‰) group were remarkably higher than those of the control group (P<0.05), and the O/N ratios of the two groups were significantly lower than those of the control group (P<0.05). Sequencing identified a total of 3840 differentially expressed genes (DEGs) from the salinity-stress groups and the control group. GO analysis revealed that DEGs were mainly enriched in biological processes, cellular components, and molecular functional categories, with the highest enrichment observed in cellular processes, metabolic processes, membranes, binding, and catalytic activities. KEGG analysis showed that the DEGs of hyper-salinity and hypo-salinity groups were enriched in different secondary pathways, with the expressions of related genes significantly upregulated, indicating that S. monotuberculatus may adapt to hyper-salinity and hypo-salinity environments through various regulatory mechanisms. The results verify that salinity stress significantly affects the physiological behavior and respiratory metabolism of S. monotuberculatus. S. monotuberculatus respond to hyper-salinity and hypo-salinity stresses by increasing protein consumption and adopting different adaptation mechanisms. Furthermore, S. monotuberculatus exhibits stronger tolerance to hypo-salinity environments compared to hyper-salinity ones.