Analysis of the Intestinal Flora in Male Versus Female Swamp Eels (Monopterus albus)

Abstract

This study aimed to analyze the intestinal flora of male versus female swamp eels, which have the unique characteristic of sex reversal. Same-aged swamp eels from the same parents, kept under the same conditions in terms of environment, diet, etc., were used as the study materials. After breeding for 1 year, 18 healthy swamp eels (nine males and nine females), weighing 39.4 ± 2.3 g, were selected. The intestinal contents of three swamp eels of the same sex were combined and labeled as follows: FM1-FM3 (n = 3) for females and MM1-MM3 (n = 3) for males. High-throughput sequencing was used to research the v3-v4 region of 16S rDNA in the intestinal flora. The results suggested significant differences in the structure, composition, and diversity of the intestinal flora of male versus female swamp eels. The relative abundances of Actinobacteria and Spirochaetes in female swamp eels were significantly higher (p < 0.05) than in male swamp eels at the phylum level. The relative abundances of Mycobacterium, Bacillus, and Vagococcus in female swamp eels were considerably higher (p < 0.05) than in male swamp eels at the genus level. The Alpha diversity of females was higher than that of males, and the Shannon index of females was also significantly higher (p < 0.05, Tukey's HSD) than that in males. Investigations of Beta diversity, including NMDS ordination, UPGMA cluster analysis, and PLS-DA analysis, showed that female and male swamp eels could be clearly distinguished based on significant differences in intestinal flora between the FM group and the MM group. LEfSe analysis showed that the dominant bacteria were Cetobacterium in male swamp eels and Clostridium_sp_ND2, Mycobacterium, Alphaproteobacteria, and Bacilli in female swamp eels. The results showed dramatic differences in the intestinal flora between the sexes, which indicates the need for a more in-depth study on sex reversal in the future.

Gonadal bacterial community composition is associated with sex-specific differences in swamp eels (Monopterus albus)

“…To further investigate the precise differences of gonadal microorganisms, the testis and ovaries of M. albus were collected for 16S rRNA sequencing and analyzed, respectively. In contrast to results reported for M. albus intestinal flora, this study found that gonadal tissues exhibited higher Alpha diversity in males than females ( 16 ). It supported that different tissues are inhabited by uniquely different microbial communities and proportions of specific bacteria ( 13 , 14 ).…”

“…At present, most studies have focused on the compositions of bacterial communities on teleost mucosal surfaces and found that different tissues are inhabited by unique microbial communities and proportions of specific bacteria (13,14). In addition, it was illustrated that gender was one of the factors influencing the intestinal microbial composition in D. rerio, M. albus, B. pectinirostris and C. guichenoti (15)(16)(17)(18). A recent study identified that the cloaca of Atlantic salmon (Salmon salar) was an additional teleost mucosa-associated lymphoid tissue (MALT), and we hypothesized that gonads connecting the cloaca also harbor abundant microbial communities as a matter of course (19,20).…”

Gut Bacterial Composition and Functional Potential of Tibetan Pigs Under Semi-Grazing

“…In addition, comparisons of the gut bacteria between Tibetan and Berkshire pigs, which were raised under semi-grazing conditions, and Landrace pigs raised in large-scale houses were conducted to understand the functions of the gut bacterial flora in Tibetan pigs. Besides, gut bacteria underwent dynamic changes in the process of growth ( Bäckhed et al, 2015 ), and were distinct in structure, composition, and diversity between male and female hosts ( Wang et al, 2020 ), which were also investigated in this study to gain an insight into functional gut bacteria in Tibetan pigs.…”

Effects of different protein and lipid levels on the growth performance and intestinal microflora of loach (Paramisgurnus dabryanus)

“…V3–V4 region of 16S rDNA was amplified by fusing primers with 338F and 806R barcodes and an Illumina MiSeq platform was used for high-throughput sequencing. According to barcode and primer sequencing, all raw data were screened by using Quantitative Insight into Microbial Ecology (QIIME) ( Han et al., 2019 ; Wang et al., 2020 ). All of the sequencing data are available in the Sequence Read Archive (SRA) database at NCBI under accession number SRP363340.…”

“…The raw data were demultiplexed, quality-filtered by Fastp (version 0.19.6) 1 and merged by FLASH (version 1.2.11). 2 Based on valid data, the operational taxonomic units (OTUs) were clustered by Upares (version 7.0.1090) 3 with 97% identity as the division standard ( Wang et al., 2020 ). The taxonomy of each OTU representative sequence was analyzed by RDP Classifier (version 2.11) 4 against the Silva Database (version 138), 5 using a confidence threshold of 0.7.…”