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To determine the impacts of housefly larvae (Musca domestica) on the Chinese soft‐shelled turtle (Pelodiscus sinensis), sixty‐three turtles with an initial body weight of 65.33±7.35 g were randomly distributed into nine 120‐L tanks to three diet groups (three replicates each group), each group containing 21 turtles: basal diet every day (PBD), housefly larvae fed once weekly (PFL7, six‐day basal diet and one‐day housefly larvae), housefly larvae fed every third day (PFL3, two‐day basal diet and one‐day housefly larvae). We investigated their growth performance, immunity and intestinal microbiota. We found that the weight gain and specific growth rate were significantly higher in the larvae‐supplemented groups than in the PBD group (p < 0.05), whereas the lipid accumulation in the liver was lower. Expression levels of IgD and IgM (immune genes) were significantly increased in the gut samples of PFL7 group (p < 0.05). Meanwhile, the larvae supplementation influenced the composition and diversity of gut microbiota of turtles; the abundance of Bacillus and Bacteroides increased significantly. PICRUSt functional prediction indicated that both larvae‐supplemented groups exhibited upregulation of genes involved in lipid metabolism and carbohydrate metabolism, and downregulation of genes associated with infectious and cardiovascular diseases. In conclusion, dietary supplementation of housefly larvae had positive effects on the growth, liver health, immunity and intestinal microbiota of P. sinensis, suggesting that housefly larvae are a promising dietary supplement for the Chinese soft‐shelled turtle. [ABSTRACT FROM AUTHOR]

Herbivorous grass carp (Ctenopharyngodon idellus) has a powerful capability to digest cellulose from aquatic plants, depending on the cellulase complex produced by the cellulolytic bacterial community in the gastrointestinal (GI) tract. However, it remains uncertain which bacteria taxa may actively participate in the digestion of food fibre. In this study, a total of 499 cellulolytic bacteria from the gut content of grass carp fed on Sudan grass (242 strains) and artificial feedstuffs (257 strains) were randomly isolated and characterized using carboxymethyl-cellulose, microcrystalline cellulose and cellobiose agar media. The results showed that more than half of the isolates were capable of degrading carboxymethyl-cellulose and cellobiose, while the remaining isolates were restricted to microcrystalline cellulose decomposition, exclusively. The cellulolytic bacterial community was dominated by Aeromonas, followed by Enterobacter, Enterococcus, Citrobacter, Bacillus, Raoultella, Klebsiella, Hydrotalea, Pseudomonas, Brevibacillus and some unclassified bacteria, as revealed by 16S rDNA sequence analysis. Notably, grass carp fed on grass with high-fibre content harboured a higher diversity of cellulolytic bacteria than the ones fed on low-fibre feedstuffs. Our results provided evidence for a positive correlation between the content of food fibre and the diversity of cellulolytic bacteria in grass carp intestines. Thus, improving growth conditions and cellulase activities for GI cellulolytic microorganisms in grass carp intestines are critical for effective utilization of feedstuffs containing high fibre levels. [ABSTRACT FROM AUTHOR]

Bacterial communities in eggs and larvae of grass carp were analysed. During the early-developmental stages, grass carp harboured five bacterial phyla, i.e. Proteobacteria, Bacteroidetes, Verrucomicrobia, Planctomycetes and Firmicutes. However, the composition of bacterial communities varied among the different developmental stages. In eggs, the bacterial communities were dominated by Proteobacteria, while in larvae the dominant bacterial community was Bacterioidetes. With the exception of a large proportion (>50%) of uncultured bacteria, Sphingobacterium (14.75%) and Acinetobacter (13.11%) were the most abundant groups in eggs at the fertilization stage ( FS). However, Aermonas was the most abundant group, ranging from 40.54% to 61.76% in eggs at the cleavage ( CS), blastula ( BS), organ differentiation ( ODS) and hatching stages ( HS). In larvae after first ingestion ( OW), Chitinophagaceae (79.41%) formed the predominant bacterial community. Changes in the bacterial community were further confirmed by statistical analysis, which demonstrated significant differences in the bacterial communities of eggs at FS, eggs from CS to HS and OW. However, no significant difference was found in bacterial communities of eggs from CS to HS. Furthermore, the present study revealed that bacteria related to Chitinophagaceae persisted from CS to OW, suggesting that these bacteria form part of the autochthonous microbiota of the fish. [ABSTRACT FROM AUTHOR]

Traditional culture-based technique and 16S rDNA sequencing method were used to investigate the mucosa-associated autochthonous microbiota of grass carp ( Ctenopharyngodon idellus). Twenty-one phylotypes were detected from culturable microbiota, with Aeromonas, Shewanella, Lactococcus, Serratia, Brevibacillus, Delftia, Pseudomonas, Pantoea, Enterobacter, Buttiauxella and Yersinia as their closest relatives. Genomic DNA was directly extracted from the gut mucosa of C. idellus originating from six different geographical regions, and used to generate 609 random bacterial clones from six clone libraries and 99 archaeal clones from one library, which were grouped into 67 bacterial and four archaeal phylotypes. Sequence analysis revealed that the intestinal mucosa harboured a diversified bacterial microbiota, where Proteobacteria, Firmicutes and Bacteroidetes were dominant, followed by Actinobacteria, Verrucomicrobia and Deinococcus- Thermus. The autochthonous bacterial communities in the gut mucosa of fish from different aquatic environments were not similar (Cs < 0.80), but γ- Proteobacteria was a common bacterial class. In comparison to bacterial communities, the archaeal community obtained from one library consisted of Crenarchaeota and Euryarchaeota. These results demonstrate that molecular methods facilitate culture-independent studies, and that fish gut mucosa harbours a larger bacterial diversity than previously recognized. The grass carp intestinal habitat selects for specific bacterial taxa despite pronounced differences in host environments. [ABSTRACT FROM AUTHOR]