Gut fungi of black-necked cranes (Grus nigricollis) respond to dietary changes during wintering.

BACKGROUND: Migratory birds exhibit heterogeneity in foraging strategies during wintering to cope with environmental and migratory pressures, and gut bacteria respond to changes in host diet. However, less is known about the dynamics of diet and gut fungi during the wintering period in black-necked cranes (Grus nigricollis). RESULTS: In this work, we performed amplicon sequencing of the trnL-P6 loop and ITS1 regions to characterize the dietary composition and gut fungal composition of black-necked cranes during wintering. Results indicated that during the wintering period, the plant-based diet of black-necked cranes mainly consisted of families Poaceae, Solanaceae, and Polygonaceae. Among them, the abundance of Solanaceae, Polygonaceae, Fabaceae, and Caryophyllaceae was significantly higher in the late wintering period, which also led to a more even consumption of various food types by black-necked cranes during this period. The diversity of gut fungal communities and the abundance of core fungi were more conserved during the wintering period, primarily dominated by Ascomycota and Basidiomycota. LEfSe analysis (P < 0.05, LDA > 2) found that Pyxidiophora, Pseudopeziza, Sporormiella, Geotrichum, and Papiliotrema were significantly enriched in early winter, Ramularia and Dendryphion were significantly enriched in mid-winter, Barnettozyma was significantly abundant in late winter, and Pleuroascus was significantly abundant in late winter. Finally, mantel test revealed a significant correlation between winter diet and gut fungal. CONCLUSIONS: This study revealed the dynamic changes in the food composition and gut fungal community of black-necked cranes during wintering in Dashanbao. In the late wintering period, their response to environmental and migratory pressures was to broaden their diet, increase the intake of non-preferred foods, and promote a more balanced consumption ratio of various foods. Balanced food composition played an important role in stabilizing the structure of the gut fungal community. While gut fungal effectively enhanced the host's food utilization rate, they may also faced potential risks of introducing pathogenic fungi. Additionally, we recongnized the limitations of fecal testing in studying the composition of animal gut fungal, as it cannot effectively distinguished between fungal taxa from food or soil inadvertently ingested and intestines. Future research on functions such as cultivation and metagenomics may further elucidate the role of fungi in the gut ecosystem.

Structural changes in the gut microbiota community of the black-necked crane (Grus nigricollis) in the wintering period.

During overwintering of black-necked cranes (Grus nigricollis), the composition and function of the gut microbiota changes are of considerable interest for understanding its environmental adaption mechanism. In this study, we characterized the structure of the gut microbiota from the black-necked crane in the Dashanbao wintering area, and compared the early-winter (November) microbiota to the late-winter (March of the next year) microbiota. The results showed that the gut microbiota diversity of black-necked crane in the early-overwintering stage was higher than that in the late-overwintering stage, but it did not reach a significant level. Gut microbiota taxonomic composition analysis showed that relative abundance of Bacteroidota increased significantly, and showed decreased Firmicutes to Bacteroidota ratio at the phylum level, meanwhile, the abundance of Lactobacillus decreased significantly at the genus level. Explain gut microbiota between the early- and late-wintering showed some differences in microbiota richness but maintained a relatively conservative microbiota structure. PICRUSt2 method was used to predict and analyze the KEGG functional abundance of 16S rDNA sequences of bacteria, it was found that the changes in gut microbiota composition increased the abundance of bacteria associated with amino acid biosynthesis and acid metabolism in the late stage of overwintering. This work provides basic data for black-necked crane gut microbiota study, which might further contribute to their protection.