Monopterus Albus Research Articles

Assessment of Swamp Eels’ (Monopterus albus) Diaspora and Presence at Remedios, Cervantes, Ilocos Sur

The Asian swamp eels (Monopterus albus) which is locally known as Kolukol have been found to be occupying the rice fields of Barangay Remedios, Cervantes, Ilocos Sur. Unfortunately, the diaspora and presence of these eels remain undocumented. In such context, this study was conducted to describe the diaspora and presence of these eels. Specifically, this study determined their characteristics, the farmers’ fishing activities, and the common Kolukol dishes as experienced and observed by the farmers. Through interviews with the farmers, the study revealed that Kolukols, which occupied an estimated 2,666-hectare of rice fields, have anguilliform body, do not have scales, slippery, no fins, with gill openings merged into single slit underneath the head, is red to brown with a sprinkling of dark flecks across their backs, have large mouths and small eyes, bloody when cut, and go out at night. The study also discovered that the farmers use machete, their hands, and spear to catch these eels. After one (1) or two (2) hours of fishing, they can bring home at least three (3) kilograms of Kolukol. With the caught Kolukols, the common dishes out of them are paksiw, tinuno, and prinito. Based on these findings, the study concludes that potential of Kolukol in food product development is yet to be explored. As such, studies should be conducted on developing products out of Kolukol.

Effects of metamifop on ammonia production and metabolism of Monopterus albus

The use of herbicides is believed to have an impact on the metabolism, physiology and biochemistry of fish. In this study, we studied the effects of metamifop on the production and metabolism of Monopterus. albus living in the water. According to the semi-lethal concentration of metamifop for 96 h, four MET concentration groups (0.2-, 0.4-, 0.6- and 0.8 mg L−1) were set up for 96 h exposure test. The ammonia discharge rate decreased, hemolymph ammonia content increased significantly, and hemolymph urea nitrogen content decreased at all time periods of metamifop exposure. In liver, the protein content decreased, the neutral protease content increased significantly (p < 0.01), amino acid content increased, and ATP content increased significantly (p < 0.01). In brain, the protein content increased, the activity of acid protease, neutral protease and alkaline protease all decreased, amino acid content decreased significantly (p < 0.01), and the content of ATP decreased. Glutamic-pyruvic transaminase (GPT) activity did not change in liver but decreased in brain. Glutamine synthetase (GS) activity decreased in liver and increased in brain. Glutaminase (GLS) activity decreased in liver and increased in brain. In conclusion, the liver and brain tissues of M. albus react differently to MET exposure. The liver mainly synthesizes energy through hydrolyzed protein, while the brain mainly synthesizes protein. Amino acids produced by protein hydrolysis cannot be converted to alanine for storage, and the degraded amino acids lead to the elevation of endogenous ammonia. MET inhibits the removal of ammonia from M. albus. Only liver tissue can detoxify the eel by converting ammonia into glutamine. Brain should have to tolerate high levels of endogenous ammonia.

Combined transcriptomics and metabolomics analysis reveals lipid metabolic disruption in swamp eel (Monopterus albus) under chronic waterborne copper exposure

Excessive copper can induce many adverse effects although it's an essential trace element in organisms. The effects of copper on the lipid metabolism have aroused increasing attention. This study investigated the liver lipid metabolism in swamp eel (Monopterus albus, M. albus) chronically exposed to 0, 10, 50, and 100 μg/L Cu2+ for 56 days. The results showed that copper increased the contents of triglyceride (TG), total cholesterol (T-CHO), non-esterified fatty acids (NEFA), and lipid droplets. Transcriptomic analysis found 1901 differentially expressed genes (DEGs) and 140 differential alternative splicing (DAS) genes in the 50 μg/L Cu2+ group, and 1787 DEGs and 184 DAS genes in the 100 μg/L Cu2+ group, respectively, which were enriched in peroxisome proliferator-activated receptor (PPAR), adenosine 5‘-monophosphate (AMP)-activated protein kinase (AMPK), and other signaling pathways. The expression levels of key genes related to PPAR and AMPK signaling pathways were significantly down-regulated after chronic exposure to Cu2+. Meanwhile, metabolomics analysis showed that 52 and 110 differentially expressed metabolites (DEMs) were identified, which were mainly enriched in glycerophospholipids metabolism and steroid synthesis. Moreover, combined analysis of transcriptome and metabolome showed that glycerophospholipid metabolism co-enriched 19 down-regulated DEGs and 4 down-regulated DEMs. Taken together, our results suggested that chronic waterborne copper exposure promoted lipid synthesis, disrupted the metabolic homeostasis of glycerophospholipid, and led to excessive hepatic lipid deposition in M. albus. The combined omics approach enhanced our understanding of copper pollution to lipid metabolism.

Transcription factors Dmrt1a, Foxl2, and Nr5a1a potentially interact to regulate cyp19a1a transcription in ovarian follicles of ricefield eel (Monopterus albus)

Aromatase (encoded by Cyp19a1) in the ovarian follicular cells catalyzes the production of estradiol from testosterone, which plays important roles in the ovarian development of vertebrates. In the present study, the interaction of Dmrt1, Foxl2, and Nr5a1a on the regulation of cyp19a1a transcription in ovarian follicles was examined in a teleost, the ricefield eel Monopterus albus. The expression of dmrt1a, foxl2, and nr5a1a was detected in ovarian follicular cells together with cyp19a1a at the mRNA and/or protein levels. Sequence analysis identified one conserved Foxo binding site in the proximal promoter region of ricefield eel cyp19a1a. Transient transfection assay showed that Foxl2 may bind to the conserved Foxo site to activate cyp19a1a transcription and act synergistically with Nr5a1a. Mutation of either the conserved Nr5a1 site or Foxo site abolished or significantly decreased the synergistic effects of Nr5a1a and Foxl2 on cyp19a1a transcription. The sequence between Region III and I-box of Nr5a1a was critical to this synergistic effect. Dmrt1a modulated the Foxl2- and Nr5a1a-induced activation of cyp19a1a transcription and their synergistic effects in a biphasic manner, with inhibitory roles observed at lower doses (10–50 ng) but release of the inhibition or even potentiating effects observed at higher doses (100–200 ng). Collectively, data of the present study suggest that the interaction of Dmrt1a, Foxl2, and Nr5a1a in the ovarian follicular cells may facilitate the adequate expression of cyp19a1a and the production of estradiol, and contribute to the development and maturation of ovarian follicles in ricefield eels and other vertebrates as well.

Identification of fish spermatogenic cells through high-throughput immunofluorescence against testis with an antibody set.

Image-based identification and quantification of different types of spermatogenic cells is of great importance, not only for reproductive studies but also for genetic breeding. Here, we have developed antibodies against spermatogenesis-related proteins in zebrafish (Danio rerio), including Ddx4, Piwil1, Sycp3, and Pcna, and a high-throughput method for immunofluorescence analysis of zebrafish testicular sections. By immunofluorescence analysis of zebrafish testes, our results demonstrate that the expression of Ddx4 decreases progressively during spermatogenesis, Piwil1 is strongly expressed in type A spermatogonia and moderately expressed in type B spermatogonia, and Sycp3 has distinct expression patterns in different subtypes of spermatocytes. Additionally, we observed polar expression of Sycp3 and Pcna in primary spermatocytes at the leptotene stage. By a triple staining of Ddx4, Sycp3, and Pcna, different types/subtypes of spermatogenic cells were easily characterized. We further demonstrated the practicality of our antibodies in other fish species, including Chinese rare minnow (Gobiocypris rarus), common carp (Cyprinus carpio), blunt snout bream (Megalobrama amblycephala), rice field eel (Monopterus albus) and grass carp (Ctenopharyngodon idella). Finally, we proposed an integrated criterion for identifying different types/subtypes of spermatogenic cells in zebrafish and other fishes using this high-throughput immunofluorescence approach based on these antibodies. Therefore, our study provides a simple, practical, and efficient tool for the study of spermatogenesis in fish species.

Genetic diversity of Toll-like receptor 9 in swamp eels (Monopterus albus).

The swamp eel, Monopterus albus, is an important aquaculture species in Asia (mainly China) whose production has seriously suffered from infectious diseases. In spite of the critical requirement for aquaculture practices, to date there is scant information on its immune defence. Here, the genetic characteristics of Toll-like receptor 9 (TLR9), which plays crucial roles in the initiation of host defence against microbial invasion, were analysed. It exhibits a striking lack of genetic variation resulting from a recent demographic bottleneck. A comparison with the homologue of M. javanensis revealed that replacement but not silent differences have nonrandomly accumulated in the coding sequences at the early stage following their split from a common ancestor. Furthermore, the replacements relevant to the type II functional divergence have mainly occurred in structural motifs mediating ligand recognition and receptor homodimerization. These results provide hints to understand the diversity-based strategy of TLR9 in the arms race against pathogens. Furthermore, the findings reported here give credence to the importance of basic immunology knowledge, especially for the key elements, in genetic engineering and breeding for disease resistance in the eel and other fishes.

Methionine-Mediated Regulation of Intestinal Lipid Transportation Induced by High-Fat Diet in Rice Field Eel (Monopterus Albus).

An eight-week feeding trial explored the mechanism that supplemented methionine (0 g/kg, 4 g/kg, 8 g/kg, and 12 g/kg) in a high-fat diet (120 g/kg fat) on intestinal lipid transportation and gut microbiota of M. Albus (initial weight 25.03 ± 0.13 g) based on the diet (60 g/kg fat), named as Con, HFD+M0, HFD+M4, HFD+M8, and HFD+M12, respectively. Compared with Con, gastric amylase, lipase, trypsin (P < 0.05), and intestinal lipase, amylase, trypsin, Na+/K+ -Adenosinetriphosphatase, depth of gastric fovea, and the number of intestinal villus goblet cells of HFD+M0 were markedly declined (P < 0.05), while intestinal high-density lipoprotein-cholesterol, very low-density lipoprotein-cholesterol and microsomal triglyceride transfer protein of HFD+M0 were markedly enhanced (P < 0.05); compared with HFD+M0, gastric lipase, amylase, trypsin, and intestinal lipase, trypsin, Na+/K+ -Adenosinetriphosphatase, microsomal triglyceride transfer protein, very low-density lipoprotein-cholesterol, and apolipoprotein -A, the height of intestinal villus and the number of intestinal villus goblet cells of HFD+M8 were remarkably enhanced (P < 0.05). Compared with Con, intestinal occ, cl12, cl15, zo-1, zo-2 of HFD + M0 were markedly down-regulated (P <0.05), while intestinal vldlr, npc1l1, cd36, fatp1, fatp2, fatp6, fatp7, apo, apoa, apob, apof, apoo, mct1, mct2, mct4, mct7, mct12, lpl, mttp, moat2, dgat2 of HFD M0 were remarkably upregulated (P < 0.05); compared with HFD+M0, intestinal gcn2 and eif2α of HFD+M8 were remarkably downregulated (P < 0.05), intestinal occ, cl12, cl15, zo-1, zo-2, hdlbp, ldlrap, vldlr, cd36, fatp1, fatp2, fatp6, apo, apoa, apob, apof, apoo, mct1, mct2, mct8, mct12, lpl, mttp, moat2, and dgat2 were remarkably upregulated (P < 0.05). Compared with Con, the diversity of gut microbiota of HFD+M0 was significantly declined (P < 0.05), while the diversity of gut microbiota in HFD+M8 was significantly higher than that in HFD+M0 (P < 0.05). In conclusion, a high-fat methionine deficiency diet destroyed the intestinal barrier, reduced the capacity of intestinal digestion and absorption, and disrupted the balance of gut microbiota; supplemented methionine promoted the digestion and absorption of lipids, and also improved the balance of gut microbiota.

Integrated analysis of the digestive tract bacterial community on individual growth in sibling generation of Swamp Eels (Monopterus albus)

Integrated analysis of the digestive tract bacterial community on individual growth in sibling generation of Swamp Eels (Monopterus albus)

Protease inhibitory activity profile of Indonesia wild swamp eel (Monopterus albus)

A protease inhibitor is a compound that potentially could inhibit the activity of a protease or some protease enzymes. It has a significant role in fish processing to prevent quality deterioration. The study aimed to investigate the inhibitory activity of wild swamp eel (Monopterus albus) plasma fractionated with ethanol to papain enzyme. The parameters analyzed were protein content, inhibitory activity to papain enzyme, and sodium dodecyl sulphate-polyacrylamide gel electrophoresis to demonstrate the protein profile. The result showed that the amount of protein in the plasma fractionated with ethanol was decreased. The effectiveness in inhibiting papain enzyme was increased when compared to that of the crude plasma, from 65 to 128.56% per mg protein. Analysis by sodium dodecyl sulfatepolyacrylamide gel electrophoresis demonstrated that the protein complex alpha-2- macroglobulin in wild swamp eel plasma consists of two different subunits of 120 kDa and 110 kDa. This study suggested that plasma fractionated with ethanol showed inhibitory activity to papain enzyme greater than that of the crude plasma.

Effects of Chemical Fertilizer Application upon the Water Quality Parameters of a Rice–Eel (Monopterus albus) Coculture System

The excessive use of chemical fertilizers causes many problems for which solutions are being sought in a variety of agricultural production systems. From the perspective of paying attention to the health requirements of aquatic animals in terms of water quality, this study investigated the impact of chemical fertilizer application on water quality in a rice (Oryza sativa L.; Cultivar “Qingxiangruangeng,” accession number: 2014004)–eel (Monopterus albus) coculture system in Shanghai, China. Chemical fertilizer was applied four times—as base fertilizer, rejuvenated fertilizer, tiller fertilizer, and ear granule fertilizer—during the production process of a rice–eel coculture system (June to October 2020). Changes in the water quality parameters of rice field’s surface water and ring ditch water in the regular chemical fertilizer group (RF) and no chemical fertilizer group (NF, the control) were compared before and at 24 h, 48 h, and 72 h after the chemical fertilizer application. The results for the analyzed physical and chemical indexes of each water area before and after four fertilizations revealed several consistent trends. First, the pH, dissolved oxygen (DO), water temperature (T), and chemical oxygen demand (COD) of either water area were similar between the NF and RF groups, whereas their total nitrogen (TN), total ammonia nitrogen (TAN), and total phosphorus (TP) levels differed significantly. After adding the above fertilizer containing nitrogen and phosphorus, 24 h later, the TN, TAN, and TP content had already increased significantly in comparison with the control. The maximum average content of TAN and nitrite nitrogen (NO2−-N) in the ring ditch water reached 12.30 mg/L and 0.37 mg/L, respectively, at 24 h after the chemical fertilizer application. Nonlinear regression analysis results showed that there was a significant positive relationship TN (δTN) and TAN (δTAN) vis-à-vis the nitrogen content of the fertilizer. The results of this study provide a timely empirical reference and data support for improving fertilizer management in rice–eel coculture systems.

Effects of Dietary Arginine Level on Growth Performance and Immune Response in Monopterus albus

To assess the dietary arginine requirement of Monopterus albus (21 ± 0.03 g), we compared six diets containing different arginine levels (2.03%, 2.58%, 3.16%, 3.63%, 4.24%, and 4.88%). The results revealed that dietary arginine content had a significant effect on weight gain (WG), specific growth rate (SGR), IL-1β, IL-10, lysozyme, and complement C3 activity in Monopterus albus ( p &lt; 0.05 ). The WG and SGR increased with increasing dietary arginine levels, and the regression analysis found that the optimum dietary arginine level for growth of rice field eel was 4.28–4.35% of the dry diet. However, the C3 and LZM activities peaked in the 2.58% arginine diet group ( p &lt; 0.05 ). The dietary arginine level had no significant effect on the viscerosomatic index, hepatosomatic index, condition factor, survival rate, nitric oxide, total nitric oxide synthase, insulin, growth hormone, trypsin, lipase, or amylase activities ( p &gt; 0.05 ). Arginine can significantly promote Monopterus albus growth; however, the immunity of Monopterus albus decreases as the arginine level exceeds 2.58%. A comprehensive assessment of growth and immunity recommends the optimum arginine level for Monopterus albus was 3.16–3.63% of the dry diet, corresponding to 6.58–7.70% of the dietary protein.

Metamifop as an estrogen-like chemical affects the pituitary-hypothalamic-gonadal (HPG) axis of female rice field eels (Monopterus albus).

Metamifop (MET) is a widely used herbicide. It is likely for it to enter water environment when utilized, thus potential impacts may be produced on aquatic animals. Little information is available about its effects on the endocrine system of fish to date. In the current study, female rice field eels (Monopterus albus) were exposed to different MET concentrations (0, 0.2, 0.4, 0.6, 0.8mgL -1) for 96h to examine the effect of MET on the hypothalamic-pituitary-gonadal (HPG) axis and sexual reversal. The results showed that high concentrations of MET exposure increased vitellogenin (VTG) levels in liver and plasma, but plasma sex hormone levels were not affected by MET exposure. MET exposure increased the expression of CYP19A1b and CYP17 that regulate sex hormone production in the brain, but the expression of genes (CYP19A1a, CYP17, FSHR, LHCGR, hsd11b2, 3β-HSD) associated with sex hormone secretion in the ovary and the estrogen receptor genes (esr1, esr2a, esr2b) in the liver were all suppressed. In addition, the expression of sex-related gene (Dmrt1) was suppressed. This study revealed for the first time that MET has estrogen-like effects and has a strong interference with the expression of HPG axis genes. MET did not show the ability to promote the sexual reversal in M. albus, on the contrary, the genes expression showed that the occurrence of male pathway was inhibited.

Animals ethnozoology as traditional medicine in the Dayak Tamambaloh Tribe, Labian Ira'ang Village, Kapuas Hulu District, Indonesia

Abstract. Supiandi MI, Syafruddin D, Gandasari A, Mahanal S, Zubaidah S. 2023. Animals ethnozoology as traditional medicine in the Dayak Tamambaloh Tribe, Labian Ira'ang Village, Kapuas Hulu District, Indonesia. Biodiversitas 24: 26-33. The Dayak Tamambaloh community in Labian Ira'ang Village, Kapuas Hulu District, Indonesia, is a community that has traditional knowledge of the use of fauna. However, at this time this knowledge has been reduced or relegated by the times and the use of animals and has never had a written document. This study aimed to obtain the types of animals used by the Dayak Tamambaloh people for treatment. The method used was a survey. Data was collected through literature studies, semi-structured interviews, and field observations. Data on using animals as traditional medicine was obtained from main informants, key informants, and recommendation informants. Data analysis was descriptive and qualitative, including data collection, data reduction, data presentation, and conclusions. The results obtained 13 types of animals in 13 families that are used as traditional medicine by the Tamambaloh Dayak people. The types of animals used in traditional medicine were wanyi (Apis cerana), asu (Canis lupus familiaris), kandalak (Channa striata), panang (Clarias sp.), bunsok (Gekko gecko), dingkawat (Hipposideros larvatus), lati loman (Lumbricus terrestris), tangkiling (Manis javanica), takiung (Sulcospira testudinaria), manuk (Gallus gallus domesticus), ular sawa (Malayopython reticulatus), lundung (Monopterus albus), and beruang (Ursus thibetanus). Animal families used as traditional medicine were Apidae (1 spesies), Canidae (1 spesies), Channidae (1 spesies), Clariidae (1 spesies), Gekkonidae (1 spesies), Hipposideridae (1 spesies), Lumbricidae (1 spesies), Manidae (1 spesies), Pachychilidae (1 spesies), Phasianidae (1 spesies), Pythonidae (1 spesies), Synbranchidae (1 spesies), and Ursidae (1 spesies). The Dayak Tamambaloh people use meat, bile, scales, shells, egg whites, wax, and all parts of animals for traditional medicine.

Hydrology-mediated ecological function of a large wetland threatened by an invasive predator.

Invasive species are one of the greatest threats to ecosystems, disrupting ecosystem function and leading to the collapse and extinction of native species. While populations of native fishes in the Everglades are tied to the system's natural hydrological dynamics, Asian Swamp Eels (Monopterus albus/javanensis) are drought-resistant fish first reported from Florida in 1997 and the Everglades in 2007. Using a 26-year dataset that included a 13-year baseline period prior to swamp eel arrival in Taylor Slough, we assessed population changes of common small fishes and decapods that are important prey for larger vertebrate predators. After invasion, populations of two crayfishes collapsed by >95 %, two fishes declined by >80 %, two fishes had intermediate declines of 44-66 %, and three species remained unchanged. Species most strongly reduced were those dependent on predator-free habitats at the onset of the wet season, indicating drought-resistant swamp eels have introduced novel predator effects and disrupted the hydrology-mediated production of aquatic animals that are prey for many larger predators. Ongoing Everglades restoration is designed to restore hydrological conditions that support production of crayfishes and fishes, and nesting wading birds reliant on them. Water management may have facilitated the invasion of swamp eels. Our results suggest that the continued spread of swamp eels may result in adverse consequences for Everglades trophic dynamics and potentially diminish benefits expected from the $20B+ restoration.

Integrated chromatin accessibility and DNA methylation analysis to reveal the critical epigenetic modification and regulatory mechanism in gonadal differentiation of the sequentially hermaphroditic fish, Monopterus albus

BackgroundMonopterus albus is a hermaphroditic and economically farmed fish that undergoes sex reversal from ovary to testis via ovotestis during gonadal development. The epigenetic changes that are associated with gonadal development in this species remain unclear.MethodsWe produced DNA methylome, transcriptome, and chromatin accessibility maps of the key stages of gonad development: ovary, ovotestis, and testis. The expression of the key candidate genes was detected using qRT-PCR and in situ hybridization and the methylation levels were analysed using bisulphite sequencing PCR. Promoter activity and regulation were assessed using dual-luciferase reporter assays.ResultsGonadal development exhibits highly dynamic transcriptomic, DNA methylation, and chromatin accessibility changes. We found that DNA methylation status, especially of the transcription start site, was significantly negatively correlated with gene expression while chromatin accessibility exhibited no correlation with gene expression during gonadal development. The epigenetic signatures revealed many novel regulatory elements and genes involved in sex reversal, which were validated. DNA methylation detection and site mutation of plastin-2 promoter, as a candidate gene, revealed that DNA methylation could impact the binding of transcription factor dmrt1 and foxl2 through methylation and demethylation to regulate plastin-2 expression during gonadal development.ConclusionsThese data provide novel insights into epigenetic modification and help elucidate the potential molecular mechanism by which dynamic modification of DNA methylation plays a crucial role in gonadal development.

Multi-locus gene editing effectively knocked out cyp19a1a and foxl2 in Monopterus albus, a hermaphroditic fish

Homozygous mutant populations are typically obtained when studying gene function using gene editing. However, because of asynchronous testicular and ovarian development, it is difficult to obtain homozygous mutant offspring of hermaphrodite fish by mating males and females. The rice field eel (Monopterus albus) was the first hermaphrodite teleost to be identified. Natural sex change characteristics render M. albus a good model for studying vertebrate sex differentiation. Rice field eels are also an economically important aquaculture species in East and Southeast Asia. In this study, we established a highly efficient multi-locus gene editing method for rice field eels. We selected cyp19a1a and foxl2 for editing and targeted seven and 11 sites in the coding regions of these genes, respectively. Fertilized eggs were co-injected with the Cas9 protein and the guide RNAs of each gene. The efficiency of gene editing–induced mutations in cyp19a1a and foxl2 was approximately 100% in the microinjected embryos and adult fish tissues. In cyp19a1a mutants, serum E2 levels were decreased, and ovarian development was blocked. Only germ stem cells or oogonia were present in the gonads of the 12-month-old cyp19a1a mutant fish. These results suggest that cyp19a1a plays a key role in regulating primary gonadal development in the ovaries of rice field eels. In foxl2 mutants, cyp19a1a transcription and serum E2 levels were minimally decreased, whereas the transcription of foxl2-l, foxl3, and dmrt1 was increased. Nevertheless, the gonads of foxl2 mutant fish differentiated into ovaries, thereby indicating that foxl2 does not directly affect ovarian development in rice field eels. The multi-locus gene editing method established in this study provides an effective approach for studying gene function study and improving the genetic traits in rice field eels.

Expression Patterns and Gonadotropin Regulation of the TGF-β II Receptor (Bmpr2) during Ovarian Development in the Ricefield Eel Monopterus albus

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 ontogenic gonadal transcriptomes provide insights into sex change in the ricefield eel Monopterus albus

BackgroundThe ricefield eel is a freshwater protogynous hermaphrodite fish and has become an important aquaculture species in China. The sex change of ricefield eel is impeding its aquaculture practice, particularly the large-scale artificial breeding. Many studies including transcriptomes of mixed gonadal samples from different individuals have been aimed to elucidate mechanisms underlying the sex change. However, the key physiological factors involved in the initiation of sex change remain to be identified. ResultsThe present study performed transcriptomic analysis on gonadal samples of different sexual stages obtained through biopsy from the same fish undergoing sex change. A total of 539,764,816 high-quality reads were generated from twelve cDNA libraries of gonadal tissues at female (F), early intersexual (EI), mid-intersexual (MI), and late intersexual (LI) stages of three individual sex-changing fish. Pairwise comparisons between EI and F, MI and EI, and LI and MI identified 886, 319, and 10,767 differentially expressed genes (DEGs), respectively. Realtime quantitative PCR analysis of 12 representative DEGs showed similar expression profiles to those inferred from transcriptome data, suggesting the reliability of RNA-seq data for gene expression analysis. The expression of apoeb, csl2, and enpp2 was dramatically increased and peaked at EI while that of cyp19a1a, wnt4a, fgf16, and foxl2a significantly downregulated from F to EI and remained at very low levels during subsequent development until LI, which suggests that apoeb, csl2, enpp2, cyp19a1a, wnt4a, fgf16, and foxl2a may be closely associated with the initiation of sex change of ricefield eels.ConclusionsCollectively, results of the present study confirmed that the down-regulation of female-related genes, such as cyp19a1a, wnt4a, fgf16, and foxl2a, is important for the sex change of ricefield eels. More importantly, some novel genes, including apoeb, csl2, and enpp2, were shown to be expressed with peak values at EI, which are potentially involved in the initiation of sex change. The present transcriptomic data may provide an important research resource for further unraveling the mechanisms underlying the sex change and testicular development in ricefield eels as well as other teleosts.

FEASIBILITY SIMULATION OF EEL (Monopterus albus) CULTIVATION IN CLEAR WATER

Before undertaking the cultivation of eel (Monopterus albus) in clear water to obtain optimal results, it is necessary to conduct a business feasibility analysis simulation study. This study aims to determine the feasibility analysis simulation of eel cultivation in clear water as an illustration to start aquaculture business. The method used in this study is a literature review or library research, where the data collection method is entirely with secondary data or literature study. Secondary data is collected by reviewing from references in the form of journals, books and online articles that are still related. The calculation of business feasibility analysis is carried out by calculating investment costs, fixed costs, variable costs, calculating production costs, revenues, R/C Ratio and PBP. The results of the calculation of the business feasibility simulation show that the production cost is Rp. 12,921,000/year, revenue of Rp. 25,350,000/year, a profit of Rp. 21,043,000, R/C Ratio of 1.6 and PBP (Payback Period) of 0.008 where the investment capital for eel cultivation will return in less than 1 year. Therefore, the eel cultivation business in the first quarter of 2022 can be said to be profitable and feasible.

Taurine improves health of juvenile rice field eel (Monopterus albus) fed with oxidized fish oil: Involvement of lipid metabolism, antioxidant capacity, inflammatory response

An 8-weeks feeding experiment was performed to evaluate the potential effect of dietary taurine on the growth, liver oxidative stress and lipid metabolism, intestinal integrity and inflammatory response as well as the skin pigments of Monopterus albus fed with the oxidized fish oil diet. With that purpose, four iso-nitrogenous and iso-lipid experimental diets were formulated, including FO (2% fresh fish oil), OO (2% oxidized fish oil completely replacing the fresh fish oil in FO group) supplemented with 0%, 0.2% (OOT0.2) and 0.5% (OOT0.5) taurine. Each diet was randomly fed to triplicate groups of 50 fish (average initial weight 30.09 ± 0.06 g). The results showed that long-term feeding of OO diet did not affect the growth performance, while decreased the contents of serum immune parameters, lowered the liver antioxidative enzymes activities and induced oxidative stress, caused abnormal fat deposition in liver by interfering lipid metabolism-related genes mRNA express profile, simultaneously accompanied by hepatocyte atrophy, destroyed the intestinal mucosal barrier through dysregulation of the mRNA expression of tight junction proteins and raised the inflammatory response by elevating the pro-inflammatory cytokines mRNA abundance, and generated undesirable skin hyperpigmentation via boosting tyrosinase activity. Notably, taurine administration improved the growth performance and partially mitigated the negative impacts in M. albus subjected to the oxidized fish oil. Taken together, it was supposed that taurine exerted its anti-oxidative and anti-inflammatory properties to confer protection against oxidized fish oil. These findings would provide a theoretical basis for the application of taurine in aquatic feed.