AbstractThe fecal microbiome is an integral part of aquatic mammals, like an inner organ. But we know very little about this inner organ of the threatened aquatic species, Yangtze finless porpoise (YFP). Four YFPs were placed into a purse seine for skin ulceration treatment, and this opportunity was taken to nurse the animals closer. In particular, we collected the feces of the YFPs before and after the paired healing and therapeutic treatment, along with samples of their fish diet and water habitat, to explore the changes in their fecal microbiome. Firmicutes (20.9–96.1%), Proteobacteria (3.8–78.7%), Actinobacteria (0.1–35.0%) and Tenericutes (0.8–17.1%) were the most dominant phyla present in the feces. The proportion of Proteobacteria and Actinobacteria increased after the treatment. Firmicutes showed a significant decrease, and most potential pathogens were absent, which reflected the administration of ciprofloxacin hydrochloride. Moreover, environmental shifts can also contribute to changes in the fecal microbiome. These results indicate that certain microbial interactions can be affected by environmental shifts, dietary changes and health-care treatments, which can also help maintain the internal environment of YFPs. These findings will inform the future enhanced protection and management of endangered YFPs and other vulnerable aquatic animals.

Bacteria play an essential role in the health of marine mammals, and the bacteria of marine mammals are widely concerned, but less is known about freshwater mammals. In this study, we investigated the bacteria of various body sites of Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) and analyzed their association with freshwater environmental bacteria. The bacterial community and function of Yangtze finless porpoise showed apparent site-specificity. Various body sites have distinct differences in bacteria and have their dominant bacteria. Romboutsia, Plesiomonas, Actinobacillus, Candidatus Arthromitus dominated in the intestine (fecal and rectal samples). Fusobacterium, Streptococcus, and Acinetobacter dominated in the oral. The dominant genera in the blowhole include Suttonella, Psychrobacter, and two uncultured genera. Psychrobacter, Flavobacterium, and Acinetobacter were dominant in the skin. The alpha diversity of intestinal (fecal and rectal) bacteria was the lowest, while that of skin was the highest. The oral and skin bacteria of Yangtze finless porpoise significantly differed between the natural and semi-natural conditions, but no sex difference was observed. A clear boundary was found between the animal and the freshwater environmental bacteria. Even the skin bacteria, which are more affected by the environment, are significantly different from the environmental bacteria and harbor indigenous bacteria. Our results provide a comprehensive preliminary exploration of the bacteria of Yangtze finless porpoise and its association with bacteria in the freshwater environment.

Early development, when many important developmental events occur, is a critical period for fish. However, research on the early development of clearhead icefish is very limited, especially in molecular research. In this study, we aimed to explore the dynamic changes in the biological functions of five key periods in clearhead icefish early development, namely the YL (embryonic), PM (first day after hatching), KK (fourth day after hatching), LC (seventh day after hatching), and SL (tenth day after hatching) stages, through transcriptome sequencing and different analysis strategies. A trend expression analysis and an enrichment analysis revealed that the expression ofgenes encoding G protein-coupled receptors and their ligands, i.e., prss1_2_3, pomc, npy, npb, sst, rln3, crh, gh, and prl that are associated with digestion and feeding regulation gradually increased during early development. In addition, a weighted gene co-expression network analysis (WGCNA) showed that eleven modules were significantly associated with early development, among which nine modules were significantly positively correlated. Through the enrichment analysis and hub gene identification results of these nine modules, it was found that the pathways related to eye, bone, and heart development were significantly enriched in the YL stage, and the ccnd2, seh1l, kdm6a, arf4, and ankrd28 genes that are associated with cell proliferation and differentiation played important roles in these developmental processes; the pak3, dlx3, dgat2, and tas1r1 genes that are associated with jaw and tooth development, TG (triacylglycerol) synthesis, and umami amino acid receptors were identified as hub genes for the PM stage; the pathways associated with aerobic metabolism and unsaturated fatty acid synthesis were significantly enriched in the KK stage, with the foxk, slc13a2_3_5, ndufa5, and lsc2 genes playing important roles; the pathways related to visual perception were significantly enriched in the LC stage; and the bile acid biosynthetic and serine-type peptidase activity pathways were significantly enriched in the SL stage. These results provide a more detailed understanding of the processes of early development of clearhead icefish.