Abstract:

To understand the microbial composition and structure of the intestinal tract of three fish species in the Nujiang River basin in Xizang, the study was conducted to analyze the species composition, abundance and diversity of intestinal microorganisms of three fish species in the Nujiang River basin by sequencing of the V3-V4 region of 16S rRNA. A total of 1153446 valid sequences and 1754 OTUs were obtained from all samples. These microorganisms of Schizothorax nukiangensis were determined to belong to 27 phyla, 56 classes, 154 orders, 297 families and 634 genera. The microorganisms of Schizopygopsis thermalis were determined to belong to 29 phyla, 59 classes, 165 orders, 308 families and 659 genera. The microorganisms of Triplophysa stenura were determined to belong to 29 phyla, 62 classes, 161 orders, 306 families and 647 genera. At the phylum level, Proteobacteria and Firmicutes were the dominant microflora of all three species of fishes, accounted for more than 70% of the total. At the genus level, Aeromonas was the dominant genus in the intestinal microbiota of S. nukiangensis, Pseudorhodobacter was the dominant genus in the intestinal microbiota of S. thermalis, Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium was the dominant genus in the intestinal microbiota of T. stenura. Diversity analysis showed that Shannon's index was higher in the samples of S. thermalis than in the samples of S. nukiangensis and T. stenura, but the difference was not significant (P>0.05). The community composition and proportions of the three fishes were relatively similar at the phylum level. However, at the genus level, although the community structure was similar, the species proportions were significantly different. PCoA analysis showed even smaller differences between S. nukiangensis and S. thermalis in gut microflora.

Key words: Xizang Nujiang River basin, Schizothorax nukiangensis, Schizopygopsis thermalis, Triplophysa stenura, Gut microorganism, High-throughput sequencing, fish gut microbiota, 16s rRNA sequencing, species diversity, community structure