Comparison of fungal community composition within different intestinal segments of tilapia and bighead carp

Although intestinal fungi play important roles in host health and disease, the composition and diversity of fungal communities remain poorly reported in fish. In this study, fungi in the fore-, mid-, and hind-intestine of tilapia (Oreochromis mossambicus) and bighead carp (Aristichthys nobilis) from Hongchaojiang Reservoir in Guangxi, China were investigated by ITS sequencing. Based on this, we obtained 1 763 478 high-quality tags, which clustered into 1 089 operational taxonomic units (OTUs). In total, 404 OTUs were annotated, of which 310, 68, and 26 belonged to Ascomycota, Basidiomycota, and other, respectively. Results show significant differences in the community composition of intestinal fungi between tilapia and bighead carp but not within their different intestinal segments. Furthermore, 154 of the 404 annotated OTUs were considered reliable and were classified into three trophic modes and nine guilds. The three trophic modes consisted of 108 OTUs of saprotrophic fungi, 41 OTUs of pathotrophic fungi, and five OTUs of symbiotrophic fungi. The top three most abundant OTUs overall (i.e., Otu000002, Scopulariopsis acremonium; Otu000018, Alternaria palandui; Otu000034, Aureobasidium pullulans) showed lower abundance in the hind-intestinal segments of bighead carp, suggesting uneven distribution of these fungi in this species. In addition, saprotrophic and pathotrophic fungi were markedly decreased in the hind-intestine. It is indicated that the fungal community was not only related to host species specificity but also to the respective physiological functions of different intestinal segments. These findings provide valuable information on the composition, structure, and potential function of the intestinal fungi community associated with different intestinal segments in tilapia and bighead carp under natural conditions, thus highlighting the importance of fungi as an integral part of the intestinal microbiota in maintaining host health.

Automated summary

This study investigated the composition and diversity of fungal communities in different intestinal segments of tilapia and bighead carp from Hongchaojiang Reservoir in Guangxi, China. Significant differences were found between the intestinal fungal communities of the two fish species, but not within their different intestinal segments. The fungal communities were classified into three trophic modes and nine guilds, highlighting the importance of fungi as a part of the intestinal microbiota in maintaining host health.