Effects of low salinity on hemolymph osmolality and transcriptome of the Iwagaki oyster, Crassostrea nippona

Crassostrea nippona is a kind of oysters with great development value as it can be edible in summer for its late reproductive period. Salinity is one of the important limiting abiotic factors to the survival and distribution of this stenohaline species. To better understand the physiological and immunological response of C. nippona to varying environmental salinities, the effects of low salinity on the hemolymph osmolality and gill transcriptome were investigated in this study. The osmolality of hemolymph in vivo and surrounding water were assessed regularly over one week at five test salinities ranging from 5 ps mu to 30 ps mu. They reached osmotic equilibrium within hours above 15 ps mu but remained hyperosmotic at 10 and 5 ps mu for the whole sampling period. Through comparative transcriptome analysis, there were less differentially expressed genes (DEGs) in pairwise comparison of S1 (10 ps mu) vs S3 (30 ps mu) than in S2 (20 ps mu) vs S3. KEGG enrichment analysis identified ubiquitin-mediated proteolysis and mitochondrial apoptosis pathway specifically enriched at 10 ps mu. This study gained comprehensive insights on the low salinity response of C. nippona at the molecular level, which provide a theoretical basis for understanding the immune mechanism under low salinity stress.

Automated summary

This study investigated the physiological and immunological response of Crassostrea nippona to low salinity. The results showed that low salinity led to hyperosmolality in the hemolymph and differential gene expression in the gill transcriptome. The study provides insights into the immune mechanism of C. nippona under low salinity stress.