# Seasonal Breeding Alters Fecal Microbiota and Metabolome in the Male Captive Yangtze Finless Porpoise (Neophocaena asiaeorientalis asiaeorientalis)

## TL;DR

This study shows how seasonal breeding affects the gut microbes and metabolites in Yangtze finless porpoises, offering insights into their reproductive biology.

## Contribution

The study reveals novel seasonal shifts in gut microbiota and metabolites linked to breeding in Yangtze finless porpoises.

## Key findings

- Firmicutes dominate in nonbreeding seasons, while Actinobacteria, Proteobacteria, and Fusobacteriota increase in breeding seasons.
- Metabolic pathways like phenylalanine metabolism and bile secretion change significantly between seasons.
- Strong correlations exist between gut microbiota and metabolite profiles during breeding and nonbreeding periods.

## Abstract

The Yangtze finless porpoise (YFP) is a critically endangered freshwater cetacean endemic to China. Understanding seasonal breeding patterns is critical for the effective conservation of critically endangered species. The current study was designed to examine the function and taxonomic characteristics of fecal microbiota and their metabolites in male captive YFPs during both nonbreeding (NB) and breeding (B) seasons, analyzing 20 fecal samples using both UHPLC–MS/MS and 16S rRNA gene sequencing approaches. The present study revealed that Firmicutes were increased in the NB season, while Actinobacteria, Proteobacteria, and Fusobacteriota were increased in the B season at the phylum level. At the genus level, Paeniclostridium, Clostridium_sensu_stricto_13, and Mycobacterium were increased in the NB season, while Romboutsia, Plesiomonas, and Cetobacterium were increased in the B season. LEfSe analysis revealed that Staphylococcus, Comamonas, and Tetrasphaera were significantly increased in the B season, while the genus Terrisporobacter was substantially increased in the NB season. The fecal metabolome undergoes significant changes during the B and NB seasons, altering metabolic pathways such as phenylalanine metabolism, protein digestion, taurine and hypotaurine metabolism, lysine degradation, tryptophan biosynthesis, tyrosine metabolism, and bile secretion. Moreover, there was a significant correlation between the fecal metabolome and microbiome in the captive YFPs in the B and NB seasons. This study explores the impact of seasonal reproduction on gut microbes and their metabolites, providing insights into animal seasonal reproductive behavior and providing a theoretical basis for studying gut microbiota and metabolites in cetaceans, both in captivity and in the wild.

This study investigates the seasonal variations in fecal microbiota and metabolites of captive Yangtze finless porpoises (YFP) during breeding (B) and nonbreeding (NB) seasons using 16S rRNA gene sequencing and UHPLC–MS/MS analysis. Firmicutes were dominant in NB, while Actinobacteria, Proteobacteria, and Fusobacteriota increased in B. Significant shifts in microbial composition and metabolic pathways, including phenylalanine metabolism and bile secretion, were observed. Correlations between microbiota and metabolites highlight the influence of seasonal reproduction on gut ecology, providing insights into cetacean reproductive biology in captivity and the wild.