# Gut Microbiome Signatures Across Migratory, Sedentary, and Aquaculture Ecotypes of Coilia nasus

## TL;DR

This study explores how the gut microbiome of Coilia nasus varies across different ecological types, revealing insights into their adaptation and conservation.

## Contribution

The study identifies gut microbiome signatures linked to different ecotypes of Coilia nasus, offering new molecular markers for ecological tracing and conservation.

## Key findings

- The core gut microbiota of Coilia nasus includes Firmicutes, Proteobacteria, and Actinobacteria.
- Marine-adapted bacteria like Proteobacteria and Psychrobacter are enriched in migratory marine populations due to high salinity.
- Aquaculture-reared fish show higher Actinobacteria abundance, likely due to artificial feed.

## Abstract

This study constructed a database of intestinal microbiota for three ecological types of Coilia nasus, namely migratory type (comprising marine population and freshwater population), sedentary type and aquaculture-reared type, through 16S rRNA amplicon sequencing technology. This study investigates the ecological mechanisms underlying microbiota differentiation, focusing on three key drivers: environmental selection, host nutritional metabolism requirements, and host life history strategies. The results showed that the core flora of Coilia nasus consisted of Firmicutes, Proteobacteria, and Actinobacteria. Both the depletion of microbial taxa and the enrichment of marine-adapted bacterial lineages—including Proteobacteria and Psychrobacter—may be associated with elevated salinity in the migratory marine population of Coilia nasus. Significant variations in both richness and diversity of the intestinal microbiota were observed among the different ecological groups. In conclusion, this study not only provides potential molecular markers for the traceability of the genetic resources and the identification of ecological types of Coilia nasus, but also lays a theoretical foundation for understanding the co-evolutionary mechanism between fish hosts and microorganisms and for formulating conservation strategies for wild populations and aquaculture strategies based on microbiota regulation.

Coilia nasus, a typical species with migratory–sedentary polymorphism, shows different intestinal microbiota characteristics among its different ecotypes. This is attributed to differences in feeding habits and habitat environments (such as water temperature, salinity, etc.). This study constructed a database of intestinal microbiota for three ecological types of C. nasus, namely migratory type (comprising marine populations and freshwater populations), sedentary type and aquaculture-reared type, through 16S rRNA amplicon sequencing technology. This study investigates the ecological mechanisms underlying microbiota differentiation, focusing on three key drivers: environmental selection, host nutritional metabolism requirements, and host life history strategies. The results showed that the core flora of C. nasus consisted of Firmicutes, Proteobacteria, and Actinobacteria. Both the depletion of microbial taxa and the enrichment of marine-adapted bacterial lineages—including Proteobacteria and Psychrobacter—are associated with elevated salinity in the migratory marine population of C. nasus. In contrast, the elevated relative abundance of Actinobacteria in aquaculture-reared C. nasus is likely attributable to dietary supplementation with protein- and lipid-rich artificial feed. Functional correlation analysis holds promise for partially predicting the microbiota’s metabolic functional succession patterns. The dominance of Pseudomonas_E in the migratory freshwater population is consistent with its well-documented physiological versatility and adaptive capacity in dynamically fluctuating aquatic habitats. The elevated abundance of Cyanobacteria in the sedentary population C. nasus coincides with the water bloom in their habitat, suggesting that the structure of the microbiota may serve as a novel biomarker for indicating the ecosystem. In conclusion, this study identifies potential molecular markers for tracing genetic resources and distinguishing ecological types of C. nasus, while establishing a theoretical foundation for elucidating the co-evolutionary dynamics between fish hosts and their associated microbiota—and thereby informing both conservation strategies for wild populations and microbiota-informed aquaculture practices.