The difference in salinity tolerance between cultured and wild sea cucumber <em>Apostichopus japonicus</em> Selenka based on survival, enzyme activity and transcriptome analyses

Abstract

Salinity is a critical environmental factor affecting the growth, survival, distribution, and physiological processes of the sea cucumber, <em>Apostichopus japonicus</em> (Selenka). In this study, we examined the survival rates, enzymatic activities, and transcriptomes of one cultured and two wild populations of the sea cucumber, <em>A. japonicus</em> Selenka to compare their tolerance across a range of salinities. Significant differences in survival rates were observed among the three populations when exposed to salinity levels of 45, 40, 23, 20, and 17 psu. As salinity decreased, the activities of catalase, Na+-K+-ATPase, amylase and superoxide dismutase in cultured sea cucumbers peaked at 23 psu, and declined at 20 psu. In contrast, the activities of these enzymes in wild sea cucumbers decreased at 23 psu. At 40 psu, the four enzymatic activities significantly decreased in cultured sea cucumbers but continued to increase significantly in wild populations (P < 0.05). Transcriptomic analysis based on Gene Ontology (GO) function revealed the terms “cellular process,” “membrane” and “binding” were most enriched in the biological process, cellular component, and molecular function categories, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis identified “Glycerophospholipid metabolism” and “Starch and sucrose metabolism” among the top 10 most enriched pathways. The findings of this study provide new insights into the salinity tolerance adaptation of cultured sea cucumbers.