Characterizing Gut Microbiota Composition and Its Correlation with Growth Variation in Sea Cucumber Apostichopus japonicus.

Sea cucumber Apostichopus japonicus is one of the key aquaculture species in China, possessing high nutritional and medicinal value. However, significant variations in growth are commonly observed among individuals during their development. This study investigates the differences in gut microbiota composition, digestive capacity, and metabolic pathways in A. japonicus, aiming to elucidate the underlying relations contributing to growth rate discrepancies from the perspective of gut microbiota. Intestinal tissues were collected from individuals exhibiting marked growth differences, but Sharing the same genetic background And growth environment, for 16S rRNA sequencing analysis. Although no significant differences were observed in alpha diversity at the ASV level, differences in phylum level proportions suggest potential functional variations. We found significant differences in the gut microbiota between fast-growing and slow-growing A. japonicus by LEfSe analysis. The abundance of fast-growing individuals in Verrucomicrobiota, Verrucomicrobiaceae, and Haloferula was significantly increased. Additionally, significant differences in the enrichment of gut microbiota metabolic pathways were observed; the fast-growing group demonstrated higher overall metabolic activity, and body weight showed a significant positive correlation with glyoxylate and dicarboxylate metabolism and purine metabolism. The digestive capacity of fast-growing A. japonicus was significantly enhanced. Furthermore, fast-growing individuals exhibit a more complex metabolic network involving various biomolecular synthesis and metabolic pathways. These findings suggest that the differences in the growth rate of A. japonicus are primarily related to the functional activity of the gut microbiota; in particular, the improvement of digestive capacity and the activation of specific metabolic pathways may play a key role in promoting the growth of the host. Understanding these microbial influences provides valuable insights into the biological mechanisms underlying growth variation and may contribute to the development of strategies for optimizing sea cucumber aquaculture.