Abstract
This study was conducted to investigate the long‐term effect of a low fish meal (FM) diet comprising plant‐based protein sources (PPS) on changes of gut microbial diversity in olive flounder (Paralichthys olivaceus) over the course of life. Two experimental diets were prepared to contain 74% FM (control) or 52% FM with 22% PPS (30% FM replacement, FM30). Fish were fed one of the two experimental diets for 8 months, and we collected the midgut contents to analyze the gut bacterial community by Illumina MiSeq based on the metagenomic sequences in the V3–V4 regions of 16S rRNA. We found that there were nine dominant phyla, which in turn presented Proteobacteria, Firmicutes, and Actinobacteria as the three major phyla in the gut microbiota of the flounder. At genus level, the dominant genera were Delftia, Prevotella, and Chthoniobacter at the juvenile stage (below 100 g/fish); Chthoniobacter, Bacillus, and Bradyrhizobium at the grower stage (400 g/fish); Chthoniobacter, Bacillus, and Delftia at the subadult stage (800 g/fish); and Lactobacillus and Prevotella at the adult stage (over 1,000 g/fish). The microbial diversity in olive flounders arched from the juvenile and subadult stage and reached a plateau thereafter. The fish fed the FM30 diet significantly had an increased abundance of Lactobacillus and Photobacterium and had less abundance of Prevotella and Paraprevotella than the control. However, the effect of dietary PPS was not significant on total microbial richness, indicating no negative effect as feed sources on the intestinal microbiota in olive flounder. These results indicate that the life stage of olive flounder is more important in modulating intestinal microbiota than is the diet. It could also be concluded that dietary PPS might be used as a potential fish meal alternative without any compromising effects on microbial diversity of olive flounder for long‐term feeding.
Highlights
Olive flounder (Paralichthys olivaceus) is the most economically important carnivorous marine fish cultured in Republic of Korea, which has achieved more than 45% of all fish production (KOSTAT, 2017)
The six most dominant genera were Chthoniobacter (5.42 ± 0.93%), Prevotella (4.77 ± 1.40%), Bacillus (4.18 ± 0.59%), Delftia (3.44 ± 1.05%), Photobacterium (3.02 ± 1.99%), and Lactobacillus (2.51 ± 0.98%) in fish fed with the control diet (Con) diet and Photobacterium (10.90 ± 4.96%), Lactobacillus (7.40 ± 3.20%), Chthoniobacter (4.49 ± 0.99%), Bacillus (3.54 ± 0.56%), Prevotella (3.12 ± 0.80%), Delftia (2.71 ± 0.78%) in fish fed with the FM30 diet (Table 3)
Firmicutes and Proteobacteria were identified as biomarkers in different developmental stages in relation to low fish meal (FM) diet, suggesting that these phyla were prevalent in the gut microbiota of olive flounder and different species of these phyla may perform different functions in the gut ecosystem
Summary
Olive flounder (Paralichthys olivaceus) is the most economically important carnivorous marine fish cultured in Republic of Korea, which has achieved more than 45% of all fish production (KOSTAT, 2017). The NGS technique has been used to explore the dietary effects on gut microbiota of different fish species, including rainbow trout (Oncorhynchus mykiss; Desai et al, 2012), sea bream (Sparus aurata; Estruch et al, 2015), Arctic charr (Salvelinus alpinus; Nyman, Huyben, Lundh, & Dicksved, 2017), field eel (Monopterus albus; Peng et al, 2019), yellowtail kingfish (Serio lalalandi; Soriano et al, 2018), and channel catfish (Ictalurus punctatus; Wang et al, 2019) Most of these studies investigated the dietary effects on fish gut microbiota for a short-term administration, but the long-term dietary effects at different growth stages have generally been overlooked. We investigated the gut microbiota of olive flounder at different growth stages with long-term dietary administration of plant-based low FM and practical FM diets by a culture-independent metagenomic approach
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
