Comparison of the Intestinal Structure and Intestinal Microbiome between Two Geographically Isolated Populations of Culter alburnus

SIMPLE SUMMARY: Population differentiation usually forms between geographically isolated populations. We compared the intestinal structures, digestive enzyme activities, and intestinal microbiomes in the Xingkai (XK) Lake and Dianshan (DS) Lake populations of Culter alburnus. We sought to discover the differentiated intestinal structure and functional divergence in the two geographically isolated populations. Our study indicated that significantly different intestinal structures, digestive enzymes activities, and intestinal microbiomes were presented in the two populations, which may have been due to adaptative evolution caused by the long-term geographical isolation. ABSTRACT: Geographical populations of Culter alburnus inhabiting different regions of China present substantial differences in their reproduction and development characters. This study compared the intestinal structures, digestive enzyme activities, and intestinal microbiomes in the Xingkai (XK) Lake and the Dianshan (DS) Lake populations of C. alburnus collected in two isolated and contrasting river systems. We wanted to discover whether the intestinal structure and functional divergence were formed in the two populations due to adaptive evolution caused by geographical isolation. Our study indicated that higher intestinal villi, thicker intestinal mucosa layer and intestinal muscle layer, and significantly higher activity of α-amylase were identified in the XK population. Moreover, quite different intestinal microbiomes were presented in the two populations, with the higher abundance of Bacteroidetes and Firmicutes in the XK population. The significantly different intestinal microbiome in the XK population was functionally enriched in carbohydrate, lipid, and amino acid metabolism by Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. Our findings indicated that substantial adaptative divergence in the intestinal structures and intestine microbiomes was formed in the two populations due to long-term geographical isolation, which may have strongly affected the digestion and absorption ability of the XK population compared with the DS population.