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An 8-week feeding trial was conducted using the rice field eel (Monopterus albus) with six isonitrogenous and isoenergetic experimental diets of basic feed supplemented with different levels of methionine (0, 2, 4, 6, 8, or 10g/kg). This study built upon previous research findings that showed dietary methionine restriction (M0, 0 g/kg) inhibited hepatic fatty acid metabolism and intestinal fatty acid transportation, but both are improved by dietary supplementation with a suitable level of methionine (M8, 8g/kg). Hence, M0 and M8 were selected to investigate how methionine regulates the gut microbiota and lipidomics of M. albus. Compared with M0, values for gut bacterial Sobs, Shannon, ACE, and Chao1 indices of M8 were remarkably increased (p < 0.05), with Fusobacteria, Firmicutes, and Proteobacteria the dominant phyla and Cetobacterium, Plesiomonas, and Bacillus the main genera in the community under the M0 vs. M8 treatments. However, compared with M0, the proportion of phyla consisting of Fusobacteria decreased in M8, as did the Cetobacterium and Lactococcus at the genus level; conversely, the proportions corresponding to Firmicutes, Proteobacteria, and Chioroflexi phyla increased in M8, as did the Clostridium and Streptococcus genera. Many edges appeared in the circus and networks, demonstrating the interspecies interactions among different operational taxonomic units (OTUs). In addition, various OTUs within the same phylum were clustered within one module. Cooperative interactions were predominant in the two networks, while competitive interactions were prevalent in their submodules. Gut microbiota mainly played roles in nutrition (lipid, amino acid, and carbohydrate) transport and metabolism under the M0 vs. M8 treatments. The PLS-DA scores indicated a significant difference in the main lipidomic components between the M0 and M8 treatment groups. Namely, the TG(26:0/16:0/17:0), TG(28:0/16:0/16:0), TG(26:0/16:0/16:0), and TG(30:0/16:0/16:0)- among others-comprising the gut content were reduced under the M8 treatment (p<0.001). The genus Clostridium was positively correlated with TG(18:1/18:1/22:5), TG(16:0/17:0/18:1), TG(18:0/18:1/20:3), and other compounds, yet negatively correlated with TG(18:0/17:0/20:0), TG(16:0/17:0/24:0), and TG(16:0/16:0/24:0), among others as well. According to the lipidomics analysis, the predicted KEGG pathways mainly included lipid and glycan biosynthesis and metabolism, and digestive, sensory, and immune systems. In conclusion, methionine restriction disturbed the microbial community balance and induced microbial dysfunctions, whereas methionine supplementation improved the homeostasis of gut microbiota and lipid metabolism of the rice eel. [ABSTRACT FROM AUTHOR]

Simple Summary: Thyrotropin-releasing hormone (TRH) is an important upstream regulator in the hypothalamus-pituitary-thyroid (HPT) axis in mammals. In this study, we isolated and characterized trh gene from a protogynous hermaphrodite fish rice field eel Monopterus albus. TRH had no significant effect on serum thyroid hormone levels in rice field eel. However, we found that TRH was involved in the regulation gonadal differentiation-related gene expression and serum sex steroid hormone secretion. Our results indicated that TRH may play a novel role in gonadal differentiation in rice field eel. Rice field eel (Monopterus albus), a protogynous hermaphrodite fish, is a good model for the research of sex determination and gonadal differentiation in teleosts. In this study, we cloned the full-length cDNA sequence of trh, which encoded a predicted protein with 270 amino acids. Trh mainly expressed in the brain, followed by the ovary, testis, muscle and pituitary, and had low levels in other peripheral tissues. During natural sex reversal, trh mRNA expression levels exhibited a significant increase at the late intersexual stage in the hypothalamus. In the gonad, trh mRNA expression levels showed a trend of increase followed by decrease, and only increased significantly at the middle intersexual stage. No matter static incubation or intraperitoneal (IP) injection, TRH had no significant effect on trh and thyroid-stimulating hormone βsubunit (tshβ) mRNA expression levels, and serum T3, T4 and TRH release. After static incubation of ovarian fragments by TRH, the expression of gonadal soma derived factor (gsdf) was up-regulated significantly at both the doses of 10 and 100 nM. IP injection of TRH stimulated the expression of gsdf, and inhibited the expression of ovarian aromatase gene (cyp19a1a), accompanied by the increase of serum 11-KT levels. The results indicated that TRH may play a novel role in gonadal differentiation by the regulation of gonadal differentiation-related gene expression and sex steroid hormone secretion in rice field eel. [ABSTRACT FROM AUTHOR]

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Background: An increasing number of long noncoding RNAs (lncRNAs) have been found to play important roles in sex differentiation and gonad development by regulating gene expression at the epigenetic, transcriptional and posttranscriptional levels. The ricefield eel, Monopterus albus, is a protogynous hermaphroditic fish that undergoes a sequential sex change from female to male. However, the roles of lncRNA in the sex change is unclear. Results: Herein, we performed RNA sequencing to analyse lncRNA expression patterns in five different stages of M. albus development to investigate the roles of lncRNAs in the sex change process. A total of 12,746 lncRNAs (1503 known lncRNAs and 11,243 new lncRNAs) and 2901 differentially expressed lncRNAs (DE-lncRNAs) were identified in the gonads. The target genes of the DE-lncRNAs included foxo1, foxm1, smad3, foxr1, camk4, ar and tgfb3, which were mainly enriched in signalling pathways related to gonadal development, such as the insulin signalling pathway, MAPK signalling pathway, and calcium signalling pathway. We selected 5 highly expressed DE-lncRNAs (LOC109952131, LOC109953466, LOC109954337, LOC109954360 and LOC109958454) for full length amplification and expression pattern verification. They were all expressed at higher levels in ovaries and intersex gonads than in testes, and exhibited specific time-dependent expression in ovarian tissue incubated with follicle-stimulating hormone (FSH) and human chorionic gonadotropin (hCG). The results of quantitative real-time PCR (qRT-PCR) analysis and a dual-luciferase assay showed that znf207, as the gene targeted by LOC109958454, was expressed in multiple tissues and gonadal developmental stages of M. albus, and its expression was also inhibited by the hormones FSH and hCG. Conclusions: These results provide new insights into the role of lncRNAs in gonad development, especially regarding natural sex changes in fish, which will be useful for enhancing our understanding of sequential hermaphroditism and sex changes in the ricefield eel (M. albus) and other teleosts. [ABSTRACT FROM AUTHOR]

The Asian swamp eel (Monopterus albus) is an excellent model species for studying sex change and chromosome evolution. M. albus is also widely reared in East Asia and South-East Asia because of its great nutritional value. The low fecundity of this species (about 300 eggs per fish) greatly hinders fries production and breeding programs. Interestingly, about 3–5% of the eels could remain as females for 3 years and lay more than 3,000 eggs per fish, which are referred to as non-sex-reversal (NSR) females. Here, we presented a new chromosome-level genome assembly of such NSR females using Illumina, HiFi, and Hi-C sequencing technologies. The new assembly (Mal.V2_NSR) is 838.39 Mb in length, and the N50 of the contigs is 49.8 Mb. Compared with the previous assembly obtained using the continuous long-read sequencing technology (Mal.V1_CLR), we found a remarkable increase of continuity in the new assembly Mal.V2_NSR with a 20-times longer contig N50. Chromosomes 2 and 12 were assembled into a single contig, respectively. Meanwhile, two highly contiguous haplotype assemblies were also obtained, with contig N50 being 14.54 and 12.13 Mb, respectively. BUSCO and Merqury analyses indicate completeness and high accuracy of these three assemblies. A comparative genomic analysis revealed substantial structural variations (SVs) between Mal.V2_NSR and Mal.V1_CLR and two phased haplotype assemblies, as well as whole chromosome fusion events when compared with the zig-zag eel. Additionally, our newly obtained assembly provides a genomic view of sex-related genes and a complete landscape of the MHC genes. Therefore, these high-quality genome assemblies would provide great help for future breeding works of the swamp eel, and it is a valuable new reference for genetic and genomic studies of this species. [ABSTRACT FROM AUTHOR]

The study was to investigate the effect of corn gluten meal partial replacement of fish meal on growth performance and serum indexes of Monopterus albus. 108 young Monopterus albus weighing 13 g were selected and randomly divided into three groups with three replicates in each group, and 12 Monopterus albus in each replicate. The experimental treatment groups were equal in energy and nitrogen, control group (CON group) diet contained 68% fish meal, and the experimental group replaced 10% fish meal (R1 group) and 20% fish meal (R2 group) with corn gluten meal on basis of control group feed. The experiment lasted for 56 d. The results showed that compared with CON group, the weight gain rate, specific growth rate, crude protein apparent digestibility and crude protein content in muscle of Monopterus albus in R1 group and R2 group were reduced significantly (P<0.05), feed coefficient was significantly increased (P<0.05). Serum triglyceride levels and total protein in R1 group and R2 group were significantly lower than those in CON group (P<0.05). The catalase of liver of Monopterus albus was increased significantly in R1 group and R2 group (P<0.05). The experiment indicates that replacing part of fish meal with corn gluten meal can improve serum indexes of monopterus albus and has the potential to replace part of fish meal. [ABSTRACT FROM AUTHOR]

Toll-like receptors (TLRs) are a class of pattern recognition receptors (PRRs) that play a critical role in innate immune responses against pathogens. In the present study, a fish-specific TLR14 was identified and characterized from Monopterus albus (named Ma TLR14), which consisted of a 2658 bp open reading frame encoding a protein of 885 amino acids. Phylogenetic analysis revealed that Ma TLR14 belong to the TLR1 subfamily and shared the highest similarity to Paralichthys olivaceus TLR14. Immunohistochemistry assay showed that Ma TLR14 mainly located in intestinal epithelial cells of hindgut. Immunofluorescence revealed that Ma TLR14 largely localized to the intracellular region and partially co-localized with cell membrane of HeLa cells. The expression levels of Ma TLR14 were upregulated in the liver, spleen, foregut and hindgut post infection with Aeromonas hydrophila. When stimulated with LPS and Flagellin, the Ma TLR14 expression was elevated in isolated peripheral blood leukocytes. Further studies showed that recombinant Ma TLR14-LRR could bind to both the gram-negative and gram-positive bacteria and cause agglutination. Subsequently, the signaling pathway of Ma TLR14 was investigated. Confocal microscopy and co-immunoprecipitation assay demonstrated that Ma TLR14 recruited MyD88 as adaptor. When overexpressed, Ma TLR14 augmented the expression of TRAF6 and phosphorylation of ERK and p65, activated NF-κB and AP-1 and elicited the expression of il-6 and tnf-α. Collectively, Ma TLR14 plays an important role in the microorganism recognition and signaling transduction. • Ma TLR14 is expressed in the intestinal epithelium of hindgut and mainly localized to internal cellular compartments. • Ma TLR14 is upregulated at mRNA expression level after bacterial and PAMPs stimulation. • Ma TLR14 can bind gram-negative bacteria as well as gram-positive bacteria through the LRR domain. • Ma TLR14 significantly induces the expression of tnf-α and il-6 via NF-κB and MAPK pathways. [ABSTRACT FROM AUTHOR]

Objectives: The Asian swamp eel (Monopterus albus), is commonly distributed in Asian countries. However, its therapeutic potential has not been thoroughly investigated yet. The current study aimed to evaluate the in-vivo therapeutic properties of the skin mucus of this fish. Methods: The eel mucus was collected fleshly and topical gel with carbopol 934 was formulated to study the antibacterial activity on the infected skin of the rats. Sprague Dawley rats were used in the study and divided into 4 groups negative, positive, normal control, and treated groups. Results: Intracutaneous injections of pathogenic bacteria (Streptococcus pyogenes, Staphylococcus aureus) and fungi (Microsporum gypseum, Candida albicans) were injected into the rats. The development of tinea capitis, impetigo, and cutaneous candidiasis in the animal model was confirmed based on clinical and histopathological observations. To treat the infected rats, a formulated gel of eel skin mucus was applied on the infected rat’s skins topically. The histological analysis confirms a complete recovery in the skin tissues similar to commercial antifungal and antibacterial agents used in the positive control groups. Conclusion: The present novel eel skin mucus is an efficient therapeutic candidate in treating skin infections associated with pathogenic microbes.

The Asian swamp eel (Monopterus albus) is one of the most widely distributed freshwater fish in China. In this study, we identified the single nucleotide polymorphisms (SNPs) of M. albus from 19 wild populations in China using restriction-site associated DNA sequencing (RAD-seq), and used SNP markers to investigate the swamp eel the genetic diversity and population genetic structure. A total of 8941794 SNPs were identified. Phylogenetic and principal component analysis suggested that the 19 populations were clustered into four groups: The Jiaoling County (JL) and Poyang Lake (PYH)populations in Group Ⅰ; the Chengdu City (CD), Dali City (YN), Eli Village (EL), Dongting Lake (DTH), Huoqiu County (HQ), and Chaohu Lake (CH) populations in Group Ⅱ; the Puyang City (PY), Chongming Island (CM), Tai Lake (TH), Gaoyou Lake (GYH), Weishan Lake (WSH), Haimen City (HM), Hongze Lake (HZH), Baiyangdian Lake (BYD), Dagushan (DGS), and Pinghu City (PH) populations in group Ⅲ; and the Lingshui County (LS) populations in Group Ⅳ. All 19 populations may have evolved from four ancestors. The genetic diversity was relatively high in CM, GYH, and HM; and low in LS, EL, and JL. The LS, and CM populations had the highest and lowest differentiation from the other populations, respectively. These findings provide new insights for germplasm resources protection and artificial breeding of M. albus.

The Asian swamp eel (Monopterus albus) is an excellent model species for studying sex change and chromosome evolution. M. albus is also widely reared in East Asia and South-East Asia because of its great nutritional value. The low fecundity of this species (about 300 eggs per fish) greatly hinders fries production and breeding programs. Interestingly, about 3–5% of the eels could remain as females for 3 years and lay more than 3,000 eggs per fish, which are referred to as non-sex-reversal (NSR) females. Here, we presented a new chromosome-level genome assembly of such NSR females using Illumina, HiFi, and Hi-C sequencing technologies. The new assembly (Mal.V2_NSR) is 838.39 Mb in length, and the N50 of the contigs is 49.8 Mb. Compared with the previous assembly obtained using the continuous long-read sequencing technology (Mal.V1_CLR), we found a remarkable increase of continuity in the new assembly Mal.V2_NSR with a 20-times longer contig N50. Chromosomes 2 and 12 were assembled into a single contig, respectively. Meanwhile, two highly contiguous haplotype assemblies were also obtained, with contig N50 being 14.54 and 12.13 Mb, respectively. BUSCO and Merqury analyses indicate completeness and high accuracy of these three assemblies. A comparative genomic analysis revealed substantial structural variations (SVs) between Mal.V2_NSR and Mal.V1_CLR and two phased haplotype assemblies, as well as whole chromosome fusion events when compared with the zig-zag eel. Additionally, our newly obtained assembly provides a genomic view of sex-related genes and a complete landscape of the MHC genes. Therefore, these high-quality genome assemblies would provide great help for future breeding works of the swamp eel, and it is a valuable new reference for genetic and genomic studies of this species.

Copyright of Journal of Food Safety & Quality is the property of Journal of Food Safety & Quality Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Primordial germ cells (PGCs) play an important role in sexual fate determination and gonadal development in gonochoristic fish, such as zebrafish and medaka. However, little is known about the function of PGCs in hermaphroditic fish. Rice field eel (Monopterus albus), a protogynous hermaphroditic fish, is an economically valuable aquaculture species. We eliminated PGCs in rice field eels during embryogenesis via morpholino-mediated knockdown dead end (dnd). The PGCs-depleted gonads developed into testis-like structures with Sertoli cells and Leydig cells. The gene expression pattern of 15-month-old PGCs-depleted gonads showed that male-biased genes, dmrt1, sox9a, gsdf, and amh, were significantly higher than that of the WT, whereas female-biased genes, foxl2 and cyp19a1a, were significantly decreased. These results indicate that PGCs are essential for ovarian differentiation in rice field eel, and PGCs-depleted gonads develop into sterile males without undergoing the female and intersex stages. Our study is the first to identify the role of PGCs in sex differentiation in rice field eel, a protogynous hermaphrodite teleost. And it is of great significance in rice field eel for discovering the underlying mechanism of sex differentiation and establishing sex control technology. [ABSTRACT FROM AUTHOR]

Quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) has become a popular technique to assess gene expression. Suitable reference genes are normally identified first to ensure accurate normalization. The aim of the present study was to select the most stable genes in embryonic developmental stages, the early development of immune organs, and cells infected with Chinese rice-field eel rhabdovirus (CrERV) of the rice-field eel (Monopterus albus). Four reference genes, including those encoding 18S ribosomal RNA (18SrRNA), beta actin (β-actin), elongation factor 1 alpha (EF1ɑ), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were assessed using geNorm, NormFinder, BestKeeper, and RefFinder software. Analyses indicated the stability ranking was 18SrRNA > β-actin > GAPDH > EF1α in the embryonic stage, with 18SrRNA as the most stable reference gene. For immunity-related organs at different developmental stages, the order in the thymus was β-actin > GAPDH > EF1α > 18SrRNA , with β-actin as the most stable gene. In both spleen and kidney tissues, the rank order was EF1ɑ > GAPDH > β-actin > 18SrRNA , with EF1α as the most stable gene. Furthermore, in rice-field eel kidney (CrE-K) cells infected with CrERV, the ranking was EF1ɑ > β-actin > GAPDH > 18SrRNA , with EF1α as the most stable gene. The results for cells infected with CrERV were verified by testing signaling pathway genes catenin beta 1 (CTNNB1) and NOTCH1 based on the above four genes after virus infection in CrE-K cells. This study laid the foundation for choosing suitable reference genes for immunity-related gene expression analysis in rice-field eel. • Selection of suitable reference genes is fundamental to ensure accurate normalization in qRT-PCR. • Four reference genes（ 18SrRNA , β‑actin , EF1ɑ , and GAPDH ）were assessed using geNorm, NormFinder, BestKeeper, and RefFinder. • The most stable reference genes were first identified in embryonic stages, immune organs, and cells in the rice-field eel. • This study laid the foundation for choosing suitable reference genes for immunity expression analysis in rice-field eel. [ABSTRACT FROM AUTHOR]

The dead end gene has been identified as a essential factor for Primordial germ cells (PGCs) migration and survival in many species, but its role in Monopterus albus is unclear. In order to clarify the function of dead end gene in M.albus PGCs migration and survival, we first characterized the expression profile of M.albus dead end (Madnd) in developing embryos and various tissues. qRT-PCR revealed that Madnd transcripts were exclusively detected in gonad, including ovary, testis and ovotestis.Embryos injected with a Madnd morpholino (Madnd-MO) exhibited down-regulation of the vasa gene. Furthermore, the GFP signal show the PGCs migration in control group were injected with GFP-nanos3 3′-UTR mRNA for visualization, as described in a previous study, yet it was disappeared after embryos injected with Madnd-MO.Finally, we characterized the genomics sequence of the Madnd gene and designed five gRNAs for genome editing. Three gRNAs were selected for microinjection according to the results of in vitro tests. gRNAd1 was used for microinjection with the Cas9 protein and was confirmed to be effective. Our analysis in this study suggested that Madnd play a key role in PGCs migration and survival in M. albus. These data provide the basis for the production of fast-growing and reproductively M.albus sterile. • Expression profile of Madnd gene in developing embryos and tissues was reported. • Madnd was crucial for PGCs migration and survival in embryos. • Genome editing technology was developed for the further studies in the future. [ABSTRACT FROM AUTHOR]

The ricefield eel (Monopterus albus), a protogynous hermaphroditic Synbranchiform species, is one of the most economically valuable freshwater fish in China. Studies on the sexual change of the ricefield eel will contribute to artificial culture and understanding the sex determination and differentiation in fish. In this study, the whole‐genome DNA methylation and transcriptomes of ovary and testis were analysed in ricefield eel. An elevated methylation level in the genome was observed in the testis compared with the ovary. A total of 457 genes showed a negative correlation between DNA methylation status and expression level in the testis compared with the ovary. Of these genes, 16 candidates were screened on the basis of their vital roles reported in gonadal development. The methylation statuses and expression levels of dnmt3a, piwil1, tdrd1, sox30, nanos2, socs2, mei4 and zmiz1 were further validated using bisulphite sequencing PCR and quantitative real‐time PCR respectively. These potential vital genes would be useful for future studies on the molecular mechanism of sex reversal in ricefield eel. Besides, the integrated analysis of DNA methylation and expression level of gonads provides basic information for epigenetic regulation in the process of sexual reversal in ricefield eel. [ABSTRACT FROM AUTHOR]

Bmpr2 plays a central role in the regulation of reproductive development in mammals, but its role during ovarian development in fish is still unclear. To ascertain the function of bmpr2 in ovarian development in the ricefield eel, we isolated and characterized the bmpr2 cDNA sequence; the localization of Bmpr2 protein was determined by immunohistochemical staining; and the expression patterns of bmpr2 in ovarian tissue incubated with FSH and hCG in vitro were analyzed. The full-length bmpr2 cDNA was 3311 bp, with 1061 amino acids encoded. Compared to other tissues, bmpr2 was abundantly expressed in the ovary and highly expressed in the early yolk accumulation (EV) stages of the ovary. In addition, a positive signal for Bmpr2 was detected in the cytoplasm of oocytes in primary growth (PG) and EV stages. In vitro, the expression level of gdf9, the ligand of bmpr2, in the 10 ng/mL FSH treatment group was significantly higher after incubation for 4 h than after incubation for different durations. However, bmpr2 expression in the 10 ng/mL FSH treatment group at 2 h, 4 h and 10 h was significantly lower. Importantly, the expression level of bmpr2 and gdf9 in the 100 IU/mL hCG group had similar changes that were significantly decreased at 4 h and 10 h. In summary, Bmpr2 might play a pivotal role in ovarian growth in the ricefield eel, and these results provide a better understanding of the function of bmpr2 in ovarian development and the basic data for further exploration of the regulatory mechanism of gdf9 in oocyte development.

The objective was to assess the impact of melatonin supplementation on the growth performance and intestinal health of rice field eel, Monopterus albus. Three hundred and sixty fish (28.46 ± 0.24 g) were fed five diets supplemented with melatonin of 0, 30, 60, 120, and 240 mg/kg for 70 days. The study found that the variables FBW, WGR, SGR, and FCR exhibited a statistically significant quadratic relationship (P < 0.05) with the dietary melatonin concentrations, and the highest FBW, WGR and SGR as well as lowest FCR were observed in the 120 mg/kg melatonin group, digestive enzymes activities (such as amylase, trypsin, and lipase) also had significant quadratic relationship (P < 0.05), and the highest intestinal villus height and goblet cells were found in the 120 mg/kg diet (P < 0.01), melatonin in diets significantly increased SOD and CAT activities in serum, up-regulated the expression of anti-inflammatory factors (IL-10) and tight junction protein (ZO-1), and down-regulated the expression of pro-inflammatory factors (IL-1β, IL-8, IL-15, and TNF-α) in the gut, dietary melatonin improved the intestinal microflora compositions, in the group that supplementation a dosage of 120 mg/kg, there was a noticeable rise in the abundance of Firmicutes and the ratio of Firmicutes/Bacteroidota, compared with control group (P < 0.1). Conclusively, dietary supplementation of melatonin promoted growth performance, enhanced intestinal immune capacity and serum antioxidant level, and improved intestinal morphology properties and intestinal flora composition in M. albus. In conclusion, based on quadratic broken-line regression analysis of WGR and FCR, the optimal concentration of melatonin to be supplied is predicted to be 146-148 mg/kg., Competing Interests: Declaration of competing interest The authors declare that they have no conflict of interest., (Copyright © 2024. Published by Elsevier Inc.)

Fish intestinal health under intensive aquaculture mode plays an important role in growth, development, and immune function. The present study was aimed to systematically investigate the differences of intestinal health between wild and cultured Monopterus albus by biochemical parameters, histomorphology, and molecular biology. A total of 15 healthy M. albus per group, with an average body weight of 45 g, were sampled to analyze intestinal health parameters. Compared with wild fish, the cultured M. albus in the foregut had lower trypsin, lipase, SOD, CAT, T-AOC, and GSH-Px activities ( P < 0.05) and higher amylase activity and MDA content ( P < 0.05). The villus circumference and goblet cells in the cultured group were significantly lower than those in the wild group ( P < 0.05). In addition, the cultured fish showed lower relative expression levels of occludin , zo-1 , zo-2 , claudin-12 , claudin-15 , mucin5 , mucin15 , lysozyme , complement 3 , il-10 , tgf-β1 , tgf-β2 , and tgf-β3 ( P < 0.05) and higher il-1β , il-6 , il-8 , tnf-a , and ifnγ mRNA expressions than those of wild fish ( P < 0.05). In terms of gut microbiota, the cultured group at the phylum level displayed higher percentages of Chlamydiae and Spirochaetes and lower percentages of Firmicutes , Bacteroidetes , Actinobacteria , Cyanobacteria , and Verrucomicrobia compared to the wild group ( P < 0.05). At the genus level, higher abundances of Pseudomonadaceae&#95;Pseudomonas and Spironema and lower abundances of Lactococcus and Cetobacterium were observed in the cultured group than in the wild group ( P < 0.05). To our knowledge, this is the first investigation of the intestinal health status between wild and cultured M. albus in terms of biochemistry, histology, and molecular biology levels. Overall, the present study showed significant differences in intestinal health between wild and cultured M. albus and the main manifestations that wild M. albus had higher intestinal digestion, antioxidant capacity, and intestinal barrier functions than cultured M. albus. These results would provide theoretical basis for the subsequent upgrading of healthy aquaculture technology and nutrient regulation of intestinal health of cultured M. albus., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Yang, Yuan, Rahman, Lv, Huang, Hu and Zhou.)

An 8‐week trial investigated how andrographolide effected lipopolysaccharide (LPS)‐induced serum biochemical indices, immune responses and the intestinal inflammatory response of Monopterus albus. The study included control and andrographolide groups (150 mg/kg andrographolide) with three replicates per group. Samples were taken 0, 3, 6, 12, 24 and 48 h after LPS injection. The results showed that the levels of GLU, COR, AST, ALT, IgM, LZM, AKP, C3 and C4 in serum showed an initial increasing that then decreased. Compared with that of the control group, the levels of serum LZM, AKP, IgM, C3 and C4 in the andrographolide group increased quicker after LPS injection, while the levels of GLU, COR, AST and ALT increased more slowly; further, these indices recovered to normal levels quicker. The expression of several genes in the intestine first increased and then decreased after LPS injection. Compared with that of the control group, il‐10, tgf‐β1, tgf‐β2 and tgf‐β3 gene expression in the andrographolide group increased quicker after LPS injection, while that of il‐1β, il‐8, il‐12β, nf‐κb, tlr‐3, tlr‐7 and tlr‐8 increased more slowly; these indices recovered to normal levels more quickly. In conclusion, LPS injection induced immune stress and inflammatory response in M. albus. Dietary supplementation with 150 mg/kg andrographolide effectively alleviated these responses. [ABSTRACT FROM AUTHOR]

Copyright of South China Fisheries Science is the property of South China Fisheries Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Objectives: Swamp eel is one model species for sexual reversion and an aquaculture fish in China. One local strain with deep yellow and big spots of Monopterus albus has been selected for consecutive selective breeding. The objectives of this study were characterizing the Simple Sequence Repeats (SSRs) of M. albus in the assembled genome obtained recently, and developing polymorphic SSRs for future breeding programs. Methods: The genome wide SSRs were mined by using MISA software, and their types and genomic distribution patterns were investigated. Based on the available flanking sequences, primer pairs were batched developed, and Polymorphic SSRs were identified by using Polymorphic SSR Retrieval tool. The obtained polymorphic SSRs were validated by using e-PCR and capillary electrophoresis, then they were used to investigate genetic diversity of one breeding population. Results: A total of 364,802 SSRs were identified in assembled M. albus genome. The total length, density and frequency of SSRs were 8,204,641 bp, 10,259 bp/Mb, and 456.16 loci/Mb, respectively. Mononucleotide repeats were predominant among SSRs (33.33%), and AC and AAT repeats were the most abundant di- and tri-nucleotide repeats motifs. A total of 287,189 primer pairs were designed, and a high-density physical map was constructed (359.11 markers per Mb). A total of 871 polymorphic SSRs were identified, and 38 SSRs of 101 randomly selected ones were validated by using e-PCR and capillary electrophoresis. Using these 38 polymorphic SSRs, 201 alleles were detected and genetic diversity level (Na, PIC, H O, and H e) was evaluated. Conclusions: The genome-wide SSRs and newly developed SSR markers will provide a useful tool for genetic mapping, diversity analysis studies in swamp eel in the future. The high level of genetic diversity (Na = 5.29, PIC = 0.5068, H O = 0.4665, H e = 0.5525) but excess of homozygotes (F IS = 0.155) in one breeding population provide baseline information for future breeding program. [ABSTRACT FROM AUTHOR]

Discoveries of new Hemiclepsis species (Hirudinea: Glossiphoniidae) in East and Southeast Asia were expected. A peculiar freshwater leech was found on the body surface of Asian Swamp Eel Monopterus albus (Synbranchiformes: Synbranchidae) in Jingzhou, Hubei Province, China. Here, we describe this leech species as Hemiclepsis yangtzenensissp. nov. It could be distinguished from other congeners based on a combination of morphological features such as very small size, translucent body with dense green reticulate markings throughout dorsum, very large posterior sucker with a characteristic reticulate pattern, and two pairs of well-developed drop-like eyespots. It also represents a phylogenetic lineage that is distant from other members of the genus based on the COI and 18S rRNA sequences. This leech species seems to be a specialized fish parasite that could negatively affect farming and wild stocks of Asian Swamp Eel in China. [ABSTRACT FROM AUTHOR]

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Aeromonas hydrophila causes sepsis and is responsible for significant economic losses in Asian finless eel (Monopterus albus) aquaculture. Previous studies have found that macrophage migration inhibitory factor (MIF) and Cathepsin B (CTSB) may be expressed in many vertebrate tissues and organs. However, there have been no reports discussing the importance of MIF and CTSB in Asian swamp eel. The complete ORF sequences of MAMIF and MACTSB were found to be 348 and 993 bp, respectively. The adaptive analysis showed that the sequences of MAMIF and MACTSB were highly conserved, and only two positive selection sites were identified in MAMIF. Quantitative real time polymerase chain reaction (qRT‐PCR) demonstrated that MAMIF and MACTSB genes were expressed in all tissues evaluated with the highest expression occurring in the head kidney, spleen and liver. Challenge with Aeromonas hydrophila resulted in a significant increase in the expression of MAMIF and MACTSB in skin, liver, head kidney and spleen that peaked at 12‐h post‐infection. The results show that MAMIF and MACTSB play important roles in the immune function of Monopterus albus. [ABSTRACT FROM AUTHOR]

Apoptosis plays a key role in the effective removal of excessive and defective germ cells, which is essential for sequential hermaphroditism and sex change in vertebrates. The ricefield eel, Monopterus albus is a protogynous hermaphroditic fish that undergoes a sequential sex change from female to male. Previous studies have demonstrated that apoptosis is involved in sex change in M. albus. However, the apoptotic signaling pathway is unclear. In the current study, we explored the underlying mechanism of apoptosis during gonadal development and focused on the role of the mitochondrial apoptosis signaling pathway in sex change in M. albus. Flow cytometry was performed to detect apoptosis in gonads at five sexual stages and ovary tissues exposed to hydrogen peroxide (H2O2) in vitro. Then the expression patterns of key genes and proteins in the mitochondrial pathway, death receptor pathway and endoplasmic reticulum (ER) pathway were examined. The results showed that the apoptosis rate was significantly increased in the early intersexual stage and then decreased with the natural sex change from female to male. Quantitative real-time PCR revealed that bax, tnfr1, and calpain were mainly expressed in the five stages. ELISA demonstrated that the relative content of cytochrome-c (cyt-c) in the mitochondrial pathway was significantly higher than that of caspase8 and caspase12, with a peak in the early intersexual stage, while the levels of caspase8 and caspase12 peaked in the late intersexual stage. Interestingly, the Pearson’s coefficient between cyt-c and the apoptosis rate was 0.705, which suggests that these factors are closely related during the gonadal development of M. albus. Furthermore, the cyt-c signal was found to be increased in the intersexual stage by immunohistochemistry. After incubation with H2O2, the mRNA expression of mitochondrial pathway molecules such as bax, apaf-1, and caspase3 increased in ovary tissues. In conclusion, the present results suggest that the mitochondrial apoptotic pathway may play a more important role than the other apoptotic pathways in sex change in M. albus.

Nghiên cứu được thực hiện nhằm xác định phương pháp nuôi kết hợp lươn Monopterus albus với rau ngổ Enhydra fluctuans phù hợp nhằm góp phần giảm ô nhiễm nitrogen trong môi trường và tăng năng suất trong mô hình nuôi lươn và rau. Thí nghiệm được bố trí ngẫu nhiên gồm 3 nghiệm thức (NT) với 3 hình thức nuôi khác nhau gồm: 1) kết hợp gián tiếp bằng cách hàng tuần sử dụng 100% nước từ bể lươn cung cấp cho bể rau (NT1_lươn, rau); 2) kết hợp trực tiếp lươn với rau trong cùng một bể (NT2_lươn+rau); và 3) nuôi lươn kết hợp rau theo hệ thống aquaponic (NT3_aqua.lươn, rau). Lươn (52 g/con) được bố trí với mật độ 1,5 kg/bể (9,4 kg/m3) và rể rau ngổ giống ban đầu là 1,0 kg/bể. Lươn được cho ăn thức ăn viên 2 lần/ngày theo nhu cầu. Thời gian thí nghiệm là 90 ngày. Kết quả cho thấy các chỉ tiêu môi trường TAN (0,25-7,41mg/L), NO2- (0,27-1,91 mg/L), NO3- (31,28-57,69 mg/L), PO43- (8,54-9,83 mg/L), trong đó NT3 luôn thấp và ổn định hơn các NT còn lại. Tăng trưởng (0,124 g/ngày) và chiều dài (0,011 cm/ngày) của lươn cao nhất là ở NT2 nhưng khác biệt không có ý nghĩa thống kê so với các NT còn lại. Tương tự sinh khối rau ngổ ở NT3 là cao nhất 3,4 kg/m2 khác biệt có ý nghĩa thống kê (p

Three experimental diets including frozen trash fish (Diet 1), the equal mixture of frozen trash fish and formulated pellets (Diet 2), and formulated pellets (Diet 3) were prepared and fed to the female broodstocks of Monopterus albus for 6 weeks. Swamp eels fed with Diet 3 exhibited lower values of weight gain and specific growth rate (p < 0.05). Plasma concentrations of total protein, total cholesterol and estradiol were higher in fish fed Diet 1. Fish fed with Diet 3 had higher values of crude protein (CP) and ash, together with lower moisture concentration in muscle. Concentrations tendency of CP, ash and moisture in the ovary were completely opposite to that in the muscle. The concentration of total n−3 fatty acids was highest in both the muscle and ovary of fish fed Diet 1. Fertilization of eggs in fish fed Diet 3 was blocked. It suggested that the insufficiency of plasma estradiol, and n−3 fatty acids in the muscle and ovary, together with the impediment of protein mobilization from muscle to ovary, caused the fertilization failure of M. albus fed with formulated feeds. Equal mixture of trash fish and formulated pellets was appropriate for the successful propagation of swamp eels. [ABSTRACT FROM AUTHOR]

Polyploid fish have valuable applications in aquaculture, and artificial breeding of polyploids is an important field of aquatic research. In this study, fertilized eggs (65–100 min post-fertilization (mpf)) were treated with 650–750 kg/cm2 hydrostatic pressure for 3–6 min to induce tetraploidy. The optimal rates for hatching and tetraploidization of embryos were achieved at 4.70% and 23.33%, correspondingly. Flow cytometry analysis revealed that the DNA content of tetraploidized embryo cells was approximately twice that of the wild-type. The chromosome number of the tetraploidized rice field eels was 48. In this study, artificially induced tetraploid rice field eels were able to survive, with four of them reaching 20 months of age. Measurement of erythrocyte nuclei revealed that the nuclear area of erythrocytes from tetraploids increased and was approximately twice that of the diploids. Histological analysis showed that the gonads of tetraploids developed into testes, and spermatogenetic germ cells were observed. In conclusion, a technique to induce tetraploidization has been developed for rice field eels by applying 700 or 750 kg/cm2 hydrostatic pressure on 85 mpf embryos for 5 min. The viable tetraploidized rice field eels were produced using this approach. • A method for hydrostatic pressure shock-induced tetraploid rice field eel was established. • Artificially induced tetraploid rice field eels survived and grow up to adult. • The gonad of tetraploid rice field eel developed into testis and may be fertile. [ABSTRACT FROM AUTHOR]

Teknologi akuaponik merupakan teknologi kombinasi akuakultur dan hidroponik yang bertujuan untuk memelihara ikan dan tanaman dalam satu sistem yang saling terhubung (Sibarani, 2013). Limbah yang dihasilkan oleh ikan seperti feses dan pakan, digunakan sebagai pupuk untuk tanaman. Kemudian air yang dialirkan dari media pemeliharaan dibersihkan olah tanaman sehingga dapat digunakan kembali oleh ikan (Wahap,2010). Menurut Rokocy (2010) interaksi antara ikan dan tanaman menghasilkan lingkungan yang ideal untuk tumbuh sehingga lebih produktif dari metode tradisional.Tujuan penelitian ini adalah untuk mengetahui pengaruh media tanam terhadap pertumbuhan belut (Monopterus albus) dalam sistem akuaponik. Penelitian ini dilakukan pada bulan Agustus sampai September 2016 di Fakultas Perikanan dan Kelautan Universitas Airlangga. Percobaan terdiri dari empat perlakuan dan lima ulangan, tanpa media tanam sebagai kontrol ( P0), media tanam zeolit (P1), media tanam batu apung (P2) dan media tanam pecahan batu bata (P3). Hasil pengamatan yang didapatkan dari penggunaan teknologi akuaponik dengan media tanam selada terbaik yang dapat mempengaruhi pertumbuhan belut yaitu media tanam zeolit. Pada pengamatan menunjukkan laju pertumbuhan spesifik dengan media tanam zeolit (1,19%/hari), kelulushidupan belut dengan media tanam zeolit (70%), Penambahan tinggi selada pada media tanam zeolit ( 11,39 cm), dan kandungan amonia terendah pada media tanam zeolit pada hari ke-28 (0,03 mg/L).

In immature lymphocytes, recombination activating genes 1 and 2 are necessary for antigen receptor V (D) J recombination, representing immature lymphocyte biomarkers. Herein, we cloned and sequenced rice-field eel rag1 and rag2 genes. Their expressions in the thymus, liver, and kidney were significant from 0 days post hatching (dph) to 45 dph, peaking at 45 dph in these three tissues. In situ hybridization detected high rag1 and rag2 expressions in the liver, kidney, and thymus of rice-field eel from 2 to 45 dph, suggesting that multiple tissues of rice-field eel contain lymphocyte lineage cells and undergo lymphopoiesis. Tissue morphology was used to observe lymphopoiesis development in these three tissues. The thymus primordium began to develop at 2 dph, while the kidney and liver have generated. Our findings verified that the thymus is the primary lymphopoietic tissue and suggested that, in rice-field eel, lymphocyte differentiation also occurs in the liver and kidney.

Five isonitrogenous and isocaloric diets containing dietary lipid concentrations from 71.90 to 142.70 g/kg were formulated and fed to Chinese rice field eel Monopterus albus fingerlings (5.00 ± 0.50 g). The highest values of weight gain, specific growth rate (SGR), together with the lowest feed conversion ratio (FCR) were found in fish fed with 89.10 g/kg lipid diet. Fish fed with 71.90 g/kg diet (F1) had higher hepatosomatic index, viscerosomatic index and whole‐body crude lipid than fish in the other four treatments (p <.05). Plasma concentration of triacylglycerol and the activity of alanine aminotransferase were also higher in fish fed with F1 diet. Whole‐body fatty acid profile varied exclusively, but with a stable value of n−3/n−6 ratio. Gas chromatography–mass spectrometry‐based metabolomics identified eighteen differential metabolites (including idose, alanine, glutamic acid, serine and hypotaurine) in liver affected by dietary lipid content using PLS‐DA analysis. The subsequent pathway enrichment revealed ten affected pathways, with the top three pathways being glycine, serine and threonine metabolism; starch and sucrose metabolism; and D‐glutamine and D‐glutamate metabolism. The broken‐line model of SGR suggested that a dietary lipid concentration of 83.50 g/kg was appropriate for M. albus fingerlings. [ABSTRACT FROM AUTHOR]

The swamp eel (Monopterus albus) is one economically important fish in China and South-Eastern Asia and a good model species to study sex inversion. There are different genetic lineages and multiple local strains of swamp eel in China, and one local strain of M. albus with deep yellow and big spots has been selected for consecutive selective breeding due to superiority in growth rate and fecundity. A high-quality reference genome of the swamp eel would be a very useful resource for future selective breeding program. In the present study, we applied PacBio single-molecule sequencing technique (SMRT) and the high-throughput chromosome conformation capture (Hi-C) technologies to assemble the M. albus genome. A 799 Mb genome was obtained with the contig N50 length of 2.4 Mb and scaffold N50 length of 67.24 Mb, indicating 110-fold and ∼31.87-fold improvement compared to the earlier released assembly (∼22.24 Kb and 2.11 Mb, respectively). Aided with Hi‐C data, a total of 750 contigs were reliably assembled into 12 chromosomes. Using 22,373 protein-coding genes annotated here, the phylogenetic relationships of the swamp eel with other teleosts showed that swamp eel separated from the common ancestor of Zig-zag eel ∼49.9 million years ago, and 769 gene families were found expanded, which are mainly enriched in the immune system, sensory system, and transport and catabolism. This highly accurate, chromosome-level reference genome of M. albus obtained in this work will be used for the development of genome-scale selective breeding. [ABSTRACT FROM AUTHOR]

To investigate the impact of the effect of high temperature stimulation on Monopterus albus larvae after a certain period of time, five experimental groups were established at different temperatures. Then, the M. albus under high temperature stress was fed at 30°C for 70 days. After that, the growth index of the M. albus was counted and analyzed. In terms of growth index, high temperature stress had significant effects on FCR, FBW, WGR, and SGR of M. albus ( p < 0.05). The SR increased after being stimulated by temperature ( p < 0.1). The study revealed that liver cells of M. albus were harmed by elevated temperatures of 36°C and 38°C. In the experimental group, the activities of digestive enzymes changed in the same trend, reaching the highest point in the 32°C group and then decreasing, and the AMS activity in the 38°C group was significantly different from that in the 30°C group ( p < 0.05). The activities of antioxidase in liver reached the highest at 34°C, which was significantly different from those at 30°C ( p < 0.05). In addition, the expression levels of TLR1 , C3 , TNF-α , and other genes increased in the experimental group, reaching the highest point at 34°C, and the expression level of the IL-1β gene reached the highest point at 32°C, which was significantly different from that at 30°C ( p < 0.05). However, the expression level of the IRAK3 gene decreased in the experimental group and reached its lowest point at 34°C ( p < 0.05). The expression level of the HSP90α gene increased with the highest temperature stimulus and reached its highest point at 38°C ( p < 0.05). In the α diversity index of intestinal microorganisms in the experimental group, the observed species, Shannon, and Chao1 indexes in the 34°C group were the highest ( p < 0.05), and β diversity analysis revealed that the intestinal microbial community in the experimental group was separated after high temperature stimulation. At the phylum level, the three dominant flora are Proteus , Firmicutes , and Bacteroides . Bacteroides and Macrococcus abundance increased at the genus level, but Vibrio and Aeromonas abundance decreased. To sum up, appropriate high-temperature stress can enhance the immunity and adaptability of M. albus . These results show that the high temperature stimulation of 32°C-34°C is beneficial to the industrial culture of M. albus ., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Mao, Lv, Huang, Yuan, Yang, Zhou and Li.)

Swamp eel or rice field eel (Monopterus albus) is one of the most economically valuable freshwater fishes in China. Based on the body colour patterns, Chinese rice field eels are commonly classified into three strains, including deep‐yellow strain (DY), pale‐yellow strain (PY) and steel‐grey strain (SG). Reports have shown that DY strain is superior to the other two strains at growth rate and fecundity. In the present study, RNA‐Seq technology was employed to profile liver transcriptomes of these three strains, and differentially expressed genes (DEGs) were identified. The hierarchical clustering analysis showed that expression patterns of liver transcripts among the three strains were different. A total of 3,296 DEGs, 3,043 DEGs and 143 DEGs were identified, respectively, from DY versus SG, DY versus PY and PY versus SG. The three comparison groups shared three DEGs, of which one DEG (batf) played a vital role in immune system. Functional enrichment analyses of DEGs in DY versus PY and DY versus SG revealed that significantly enriched Gene Ontology terms and KEGG pathways were mainly involved in innate immune responses and lipid metabolism. Additionally, most of DEGs related to immunity were mainly up‐regulated in DY compared to PY and SG. The above results indicated that the DY strain might have strong adaptability and resistance to disease, which might support their superiority for better growth and reproduction. [ABSTRACT FROM AUTHOR]

At present, research into the impact of microplastic contamination on environmental and food safety in the eel farming industry is insufficient. Here, we investigated the occurrence of microplastics in eels (Monopterus albus), wastewater and soils from recycled‐water, cement‐pool, net‐cage and rice‐field rearing systems. Results showed that average microplastic abundances were 2.4 ± 0.8 items/individual, 1.0 ± 0.4 items/L, 27.1 ± 7.0 items/kg in eels, water and soils, respectively. A significant increase in microplastic abundances occurred in all diet‐fed eels (recycled‐water, cement‐pool and net‐cage eels) from their pre‐rearing to post‐rearing stages. Moreover, cluster analysis indicated high similarities in composition of microplastics between fish diets and eels. However, no significant differences in microplastic abundances were observed among the four types of reared eels. Most of the microplastics were found in the foreguts of eels. In addition, wastewater microplastic increased significantly in the cement‐pool, net‐cage and rice‐field farming during eel rearing. This study first revealed microplastic contamination and its characteristics in eels‐rearing environments, which suggests the eco‐environmental risk of microplastics in aquaculture. [ABSTRACT FROM AUTHOR]

Present study was performed to know the infection status of Gnathostoma sp. larvae in swamp eels from Cambodia. We purchased total 30 Asian swamp eels, Monopterus albus, from local markets in Pursat and Takeo Provinces and Phnom Penh on May and November 2017 and May 2018. All collected eels were transferred to our laboratory with ice and each of them was examined by artificial digestion method. A total of 15 larval gnathostomes (1-5 larvae) were detected from 55.6% (5/9) swamp eels in Pursat Province. No larval gnathostomes were found in 21 swamp eels in Takeo Province and Phnom Penh. The advanced third-stage larvae (AdL3) detected were 2.575-3.825 (3.250) mm in length and 0.375-0.425 (0.386) mm in width. They had the characteristic head bulb (av. 0.104-0.218 mm) with 4 rows of hooklets, long muscular esophagus (1.048 mm), and 2 pairs of cervical sacs (0.615 mm). The number of hooklets in 4 rows on the head bulb was 41, 44, 47, and 50. In scanning electron microscopy, characteristic features were 4 rows of hooklets on the head bulb, cervical papillae, tegumental spines regularly arranged in transverse striations, and anus. The larval gnathostomes were identified as AdL3 of Gnathostoma spinigerum based on the morphological characters. By the present study, it has been confirmed that G. spinigerum larvae are infected in Asian swamp eels, M. albus, in Pursat Province, Cambodia. [ABSTRACT FROM AUTHOR]

Oxidative stress contributes a lot to initiation and progression of pathological conditions. Heme oxygenase 1 (HO1), a cytoprotective enzyme, is usually upregulated to alleviate oxidative stress in vivo. The function of teleost HO1 in the response to oxidative stress induced by heavy metal exposure and in pathogenic bacterial infection remains uncertain. In the present study, both complementary DNA and genomic sequence of a HO1-like gene cloned from the liver of swamp eel (Monopterus albus) are reported. Sequence analysis showed that the putative amino acid sequence contained a conserved heme oxygenase signature and displayed higher similarity to HO1 genes of other teleosts. Expression profile of swamp eel HO1 was investigated in healthy tissues and in tissues following stimulation with pathogenic bacteria (Aeromonas hydrophila) or cadmium chloride (CdCl2) exposure. Results demonstrated that HO1 messenger RNA (mRNA) was highly expressed in the liver and relatively less in other tissues. Bacterial infection with A. hydrophila significantly changed HO1 mRNA expression in the liver, spleen, and kidney, and the mRNA expression of HO1 and Nrf2 in the liver was elevated after the fish were exposed to CdCl2. Subsequently, the swamp eel HO1 was subcloned into a pET28a expression vector and transformed into Escherichia coli BL21 (DE3). Recombinant HO1 (rHO1) was successfully induced by 0.1 mmol/l IPTG and purified by Ni-NTA His Bind Resin purification system. To determine whether the rHO1 could confer stress tolerance in vitro, the viability of control and HO1-expressing E. coli under CdCl2 stress was compared by spot assay. The rHO1 protein significantly increased survival rates of the bacterial hosts. To evaluate whether intraperitoneal injection with rHO1 protected the liver of swamp eel against A. hydrophila-induced oxidative stress, mRNA expression of HO1, Nrf2, hepcidin, and IL-1β as well as the oxidative stress-related parameters (ROS and total antioxidant capacity (T-AOC)) in the liver were examined. The results showed that exogenous rHO1 could significantly upgrade the mRNA expression of HO1 and hepcidin, coupled with increased ROS and T-AOC levels. However, Nrf2 and IL-1β expression levels were significantly downregulated and upregulated, respectively. These results suggested that HO1 should not only play a protective role in oxidative stress response and its adverse effects deserved further investigation. [ABSTRACT FROM AUTHOR]

A ten-week feeding trial on Monopterus albus (initial weight 24.02 ± 0.02 g) was conducted to evaluate effects of four isonitrogenous and isoenergetic diets in which different proportions of fish meal (0, 2.5 %, 5% and 7.5 %) were substituted with Hermetia illucens (HI) larvae meal, corresponding to dietary inclusion levels of 0 (FM), 5.26 % (HI5.26), 10.52 % (HI10.52) and 15.78 % (HI15.78). Compared with FM, weight gain rate and condition factor of M. albus and gumminess and adhesiveness of its muscle tissue were significantly increased in HI5.26 and HI10.52 groups (P < 0.05); whereas feed conversion ratio was markedly decreased in HI5.26 (P < 0.05), and expression of hepatic FASD2 and ME2 was significantly upregulated in HI5.26 (P < 0.05). Compared with FM, cohesiveness of muscle was significantly decreased in HI groups, but hardness of muscle and expression of hepatic FAS were remarkably upregulated in HI groups (P < 0.05); ACC and ME1 mRNA levels were significantly upregulated in HI10.52 (P < 0.05); CPT2 mRNA levels were significantly upregulated in HI5.26 and HI15.78 (P < 0.05); PPARγ, G6PD and HSL mRNA levels were significantly upregulated in HI10.52 and HI15.78 (P < 0.05). Springiness and chewiness of muscle, activity of intestinal lipasewere, serum indexes (glutamic oxalacetic transaminase, catalase, malondialdehyde), several gut bacterial indices (shannon, chao1, ACE, OTUs abundance of proteobacterias) and abundance of hepatic PPARα mRNA in HI15.78 were remarkably lower than those in FM (P < 0.05), while content of crude lipid, gut firmicutes and hepatic Dgat2 mRNA were significantly lower than FM (P < 0.05). Results showed that HI improved growth performance and balance of gut bacteria of M. albus when supplemented at a rate below 15.78 %, but negative effects on lipid metabolism were observed when HI was supplemented at excessive levels.

The swamp eel (Monopterus albus) is a typical sex reversal fish with high economic value. Several phylogeographic studies have been performed using various markers but comparative research between mitochondrial and nuclear markers is rare. Here, a fine-scale study was performed across six sites along the Yangtze River including three sites on the main stem and three sites from tributaries. A total of 180 swamp eel individuals were collected. Genetic structure and demographic history were explored using data from two mitochondrial genes and eight microsatellite loci. The results revealed the samples from tributary sites formed three separate clades which contained site-specific lineages. Geographic isolation and the habitat patchiness caused by seasonal cutoff were inferred to be the reasons for this differentiation. Strong gene flow was detected among the sites along the main stem. Rapid flow of the river main stem may provide the dynamic for the migration of swamp eel. Interestingly, the comparative analyses between the two marker types was discordant. Mitochondrial results suggested samples from three tributary sites were highly differentiated. However, microsatellite analyses indicated the tributary samples were moderately differentiated. We conclude this discordance is mainly caused by the unique life history of sex reversal fish. Our study provides novel insights regarding the population genetics of sex reversal fish.

Eel mucus (Monopterus albus) contains bioactives such as glycoprotein, lectin, hemagglutinin and hemolysin. This bioactives are ejected through the mucus glands of the eel skin (Monopterus albums) and has an antibacterial effectivity. The aim of this study is to know the potential of eel mucus gel to treat burn wounds on rabbit. The method used on this study is laboratoric experimental method, thus randomized controlled design using 4 male rabbits divided into 4 groups equally that each group contain 1 male rabbit. The treatment of gel given differently to each group, which are F0, F1, F2 F3 also as positive control used Bioplacenton 0,1 gram. The data obtain are diameters of burn wounds. Data was analyze statistically using one way anova and then followed by LSD and Duncan test. The result of anova test showed there was a significant difference between the treatment group and control negative (p

Background The swamp eel (Monopterus albus) is a commercially important farmed species in China. The dysbiosis and homeostasis of gut microbiota has been suggested to be associated with the swamp eel’s disease pathogenesis and food digestion. Although the contributions of gut microbiome in fish growth and health has been increasingly recognized, little is known about the microbial community in the intestine of the swamp eel (Monopterus albus). Methods The intestinal microbiomes of the five distinct gut sections (midgut content and mucosa, hindgut content and mucosa, and stools) of swamp eel were compared using Illumina MiSeq sequencing of the bacterial 16S rRNA gene sequence and statistical analysis. Results The results showed that the number of observed OTUs in the intestine decreased proximally to distally. Principal coordinate analysis revealed significant separations among samples from different gut sections. There were 54 core OTUs shared by all gut sections and 36 of these core OTUs varied significantly in their abundances. Additionally, we discovered 66 section-specific enriched KEGG pathways. These section-specific enriched microbial taxa (e.g., Bacillus, Lactobacillus) and potential function capacities (e.g., amino acid metabolism, carbohydrate metabolism) might play vital roles in nutrient metabolism, immune modulation and host-microbe interactions of the swamp eel. Conclusions Our results showed that microbial diversity, composition and function capacity varied substantially across different gut sections. The gut section-specific enriched core microbial taxa and function capacities may perform important roles in swamp eel’s nutrient metabolism, immune modulation, and host-microbe interactions. This study should provide insights into the gut microbiome of the swamp eel.

Methionine restriction reduces animal lipid deposition. However, the molecular mechanism underlying how the body reacts to the condition and regulates lipid metabolism remains unknown. In this study, a feeding trial was performed on rice field eel Monopterus albus with six isonitrogenous and isoenergetic feeds that included different levels of methionine (0, 2, 4, 6, 8, and 10 g/kg). Compared with M0 (0 g/kg), the crude lipid and crude protein of M. albus increased markedly in M8 (8 g/kg) (p < 0.05), serum (total cholesterol, triglyceride, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and non-esterified free fatty acids), and hepatic contents (hepatic lipase, apolipoprotein-A, fatty acid synthetase, total cholesterol, triglyceride, and lipoprteinlipase). However, in the serum, very-low-density lipoprotein and hepatic contents (hormone-sensitive triglyceride lipase, Acetyl CoA carboxylase, carnitine palmitoyltransterase, and mirosomal triglygeride transfer protein) decreased markedly in M8 (p < 0.05). The contents of hepatic C18:2n-6, C22:6n-3, and n-3PUFA in the M8 group were significantly higher than those in M0 (p < 0.05), and the contents of lipid droplets in M8 were higher than those in M0. Compared with M0, the hepatic gcn2, eif2α, hsl, mttp, ldlrap, pparα, cpt1, and cpt2 were remarkably downregulated in M8, while srebf2, lpl, moat2, dgat2, hdlbp, srebf1, fas, fads2, me1, pfae, and icdh were markedly upregulated in M8. Moreover, hepatic SREBP1 and FAS protein expression were upregulated significantly in M8 (p < 0.01). In short, methionine restriction decreased the lipid deposition of M. albus, especially for hepatic lipid deposition, and mainly downregulated hepatic fatty acid metabolism. Besides, gcn2 could be activated under methionine restriction.

The paper reports a study of chromosome abnormalities (CA/s) in the Monopterus albus near a gold mine area compared to a non-affected area. The arsenic (As) concentrations were determined in the water, sediment and M. albus muscles. The average concentrations of As in the water and sediment samples near the gold mine were higher than allowable by Thailand's water quality standards. The average concentrations of As in the M. albus samples were lower than the standards. The diploid chromosome number of M. albus in both areas was 2n = 24. The percentage of CA of M. albus in the gold mine area was higher than in the non-affected area. Seven types of CA were single chromatid gap (SCG), fragmentation (F), sister chromatid gap, single chromatid breaks, deletion, sister chromatid fragmentation and centric fusion. In the affected area, the most common CAs in the samples were SCG and F. The specific CA in M. albus samples was SCG on chromosome pair 1. It can be concluded that As contamination caused structural CA, but did not affect the diploid chromosome number in the Asian swamp eel from the gold mine area. The accumulation of As in M. albus has potential effects on human health in consumers of M. albus from this contaminated area. [ABSTRACT FROM AUTHOR]

Housefly larvae are widely used in livestock breeding industry as a functional feed additive with immunostimulant properties, but their effects as dietary additive are poorly understood in aquatic animals. We conducted an eight‐week rearing experiment to determine the effects of housefly larvae (complete) on growth performance, immunity and intestinal microbiota in swamp eel (Monopterus albus). Dietary treatments were as follows: BD (control group, fed a basal diet), FL7 (fly larvae supplemented once weekly, i.e., 6‐day basal diet, 1‐day larvae) and FL3 (larvae supplemented every third day, i.e., 2‐day basal diet, 1‐day larvae). The final body weight (FBW) and weight gain (WG) of the FL3 group significantly (p <.05) increased. Hepatosomatic index (HSI) and malondialdehyde (MDA) concentration significantly decreased in FL3 and FL7 groups. The expression of immune‐related genes was also influenced by the fly larvae. Aeromonas hydrophila challenge experiment produced higher survival rates in the FL3 (75%) and FL7 (37.5%) groups. Fly larvae also affected the composition of gut microbiota: the abundance of Bacteroides increased, and Pseudomonas decreased, in the treatment groups. Dietary supplementation of housefly larvae has positive effects on the growth and immunity of swamp eel, and we suggest supplementing housefly larvae every third day. [ABSTRACT FROM AUTHOR]

Smad2, a receptor-activated Smad, plays a critical role in regulating gametogenesis. In this study, a smad2 homologue was identified and sequenced from ricefield eel ovary cDNA, and its mRNA and protein expression levels were analysed during oocyte development. The cDNA sequence of ricefield eel smad2 consisted of 1863 bp encoding a 467-amino acid protein that had high sequence homology with Smad proteins in other teleosts, especially in Poeciliopsis prolifica. The results of real-time quantitative PCR (RT-qPCR) analysis revealed that smad2 is expressed in the ovary during gonad development, increased continuously until the early vitellogenic stage in the ovaries, and then decreased with ovary maturation. Smad2 protein immunoreactivity was localized in the cytoplasm of follicular cells, oogonia, and primary growth stage oocytes. In vitro experiments revealed that follicle-stimulating hormone (FSH) and human chorionic gonadotropin (hCG) promoted smad2 expression in ovary tissue in a time- and dose-dependent manner, respectively. In summary, Smad2 plays a potentially vital role in ricefield eel ovary development. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Henan Agricultural Sciences is the property of Editorial Board of Journal of Henan Agricultural Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of South China Fisheries Science is the property of South China Fisheries Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A 10‐week feeding trial aimed to investigate the effects of dietary vitamin C (l‐ascorbic acid) on growth, antioxidant activity, and immunity in ricefield eel, Monopterus albus. Six diets were formulated with different levels of vitamin C supplementation (0.1, 17.5, 34.8, 68.6, 139.7, and 278.5 mg/kg). The results indicated that the weight gain (WG) of the M. albus fed the diets with vitamin C was remarkably higher than that of the M. albus fed the control diet (p <.05), and the quadratic analysis showed an optimal vitamin C level of 80.66 mg/kg. Compared with the control group, serum lysozyme activities, the complement pathway, red blood cell counts, white blood cell counts, immunoglobulin M, and phagocytosis percentage were significantly increased (p <.05) in the treatment groups, and superoxide dismutase activity, serum glucose, and malondialdehyde content were significantly decreased (p <.05) in the treatment groups. The challenge trial with Aeromonas hydrophila showed that the M. albus fed the diets with vitamin C had remarkably reduced cumulative mortality compared with those fed the control diet (p <.05), and mortality in the 68.60 mg/kg diet group was the lowest. Based on WG, the optimal vitamin C supplementation level for M. albus was estimated to be 80.66 mg/kg. [ABSTRACT FROM AUTHOR]

A 12‐week feeding trial was conducted to determine the influence of dietary protein levels on growth performance, body composition, haematological parameters and digestive enzyme activity of Chinese rice field eel (Monopterus albus) fingerlings. Six isolipidic experimental diets (27.89%, 32.23%, 35.95%, 40.06%, 43.31% and 46.53%) were formulated to randomly assign to triplicate groups of 50 rice field eel fingerlings (5.0 ± 0.5 g) cultured in plastic cages. Results indicated that the best growth performance of fish with the highest WG (158.68 ± 31.59%) and SGR (2.28 ± 0.21%) was obtained at 40.06% group. Significant alterations were demonstrated on whole‐body crude protein, crude lipid and amino acid profile by different dietary protein levels. Besides, haematological parameters including triacylglycerol, aspartate aminotransferase and alkaline phosphatase decreased with various levels by the increasing of dietary protein levels. The lowest pepsin activity was observed in 27.89% protein group, which suggested lower availability of protein as substrate for protease activity. Meanwhile, the highest amylase activity in fish of 27.89% group indicated higher carbohydrate level in this group. Based on the polynomial regression analysis of WG and SGR, the dietary protein requirement for fingerlings of Monopterus albus was estimated to be 386.4–390.8 g/kg, respectively, with the lipid level of 10.08%. [ABSTRACT FROM AUTHOR]

Swamp eel (Monopterus albus) is an economically important freshwater fish which has the potential to sustainable development. This species is considered as one of the taxonomically problematic spesies due to its complex characters and similar morphology to Monopterus cuchia and Monopterus javanensis that often lead to taxonomic dilemmas. Taxonomic certainty is an essential basis information in sustainable fisheries management, studies on morphometric characters, and genetic variability is a method which commonly used for species or stock identification. This study was aimed to validate the taxonomy certainty and evaluate the kinship of swamp eel from four populations (Indramayu, Subang, Tasikmalaya, and Garut distrik) in West Java. Morphometric analysis was conducted by measurement of 19 characters, whereas genetic analysis was conducted using PCR-Sequencing method of COI gene. The results from stepwise discriminant analysis showed that 7 morphometric characters ratio were powerful to classified the populations and the first two discriminant functions accounted 84.2% of the total variability. Genetic diversity indicated by alignment 14 sekuen of COI gene showed there were 11 haplotypes from 109 variable sites. Results of cluster and phylogenetic tree analysis indicated that swamp eel from four research populations were grouped into two major clusters. The first cluster consists of Indramayu and Subang population, the second cluster consists of Tasikmalaya and Garut population. This cluster is an evidence that swamp eel from West Java possesed morphometric and genetic diversity among populations and lead to assumption that at least there were two cryptic species from M. albus in West Java.