Abstract:A healthy microbial community in digestive tract is critically important during early life stages of fish. To examine the microbial diversity in the gastrointestinal tract of Japanese flounder (Paralichthys olivaceus), we surveyed the intestinal bacteria of P. olivaceus during the larvae and juvenile stages. In this study, Illumina MiSeq of 16S rRNA and biological information analysis method were used to explore the intestinal bacterial community composition in indoor tank-culture system. Sampling was carried out throughout the larvae and juvenile stages for six time points. The obtained 7462 operational taxonomic units (OTUs) were classified into 42 bacterial species and 972 genera. The results indicated that larval fish (1 day-post-hatch; dph) displayed a distinct and diversified gut microflora, with Proteobacteria, Bacteroidete and Firmicutes dominating the community structure. During the age of 9 and 21 dph, Proteobacteria population increased significantly and remained to be the main species. By comparison, Firmicutes had fast turnover rate and increased sharply at 45 dph after feeding formulated food. The change of intestinal dominant microflora genus was also significant. The relative abundance of Vibrio was the highest during the period of live feed (9 and 21 dph sampling), and was the lowest level after feeding formulated feed (115 dph). By contrast, the Bacteroides and Prevotella became the predominant intestinal bacteria at 80 dph, whereas Firmicutes became a core microbiota at 80 dph. Blautia and other related genus colonized in the intestinal tract of P. olivaceus and became the dominant microbiota between 80 and 115 dph. The results revealed the change and establishment of microbiota during the transition stages from larvae to juvenile in response to live and formulated feed. Our results provided a database for analyzing the role of the intestinal micro ecological system of P. olivaceus at larvae and juvenile stages and have important implication for larval production of P. olivaceus.
