Investigating the Mechanism of Low-Salinity Environmental Adaptation in Sepia esculenta Larvae through Transcriptome Profiling

SIMPLE SUMMARY: The cuttlefish, Sepia esculenta, is both a valuable economic resource and a creature of scientific interest. Our study investigated how changes in ocean salinity, a factor subject to environmental shifts, affect young, more responsive cuttlefish. We examined the gene expression of cuttlefish when exposed to lower levels of salinity. Using transcriptomic and enrichment analysis, we identified over a thousand genes that were differentially expressed under these circumstances. The images created from the results of these analyses can be used to visualize the content of the analyses. Interestingly, we discovered that low salinity could trigger harmful cell proliferation in juvenile cuttlefish, thus disrupting their normal functions. This information is valuable as it can inform potential measures to reduce the mortality rate of hatchling cuttlefish in artificially controlled conditions. ABSTRACT: Sepia esculenta is an economically important mollusk distributed in the coastal waters of China. Juveniles are more susceptible to stimulation by the external environment than mature individuals. The ocean salinity fluctuates due to environmental changes. However, there is a lack of research on the salinity adaptations of S. esculenta. Therefore, in this study, we investigated the differential expression of genes in S. esculenta larvae after stimulation by low salinity. RNA samples were sequenced and 1039 differentially expressed genes (DEGs) were identified. Then, enrichment analysis was performed using the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. Finally, a protein–protein interaction network (PPI) was constructed, and the functions of key genes in S. esculenta larvae after low-salinity stimulation were explored. We suggest that low salinity leads to an excess proliferation of cells in S. esculenta larvae that, in turn, affects normal physiological activities. The results of this study can aid in the artificial incubation of S. esculenta and reduce the mortality of larvae.