Search Results (57)

Aquaculture expansion to meet global protein demand has intensified concerns over nutrient pollution and greenhouse gas (GHG) emissions. While floating treatment wetlands (FTWs) are proven for water quality improvement, their potential to mitigate GHG emissions in marine aquaculture remains poorly understood. This study quantitatively evaluated the dual capacity of Sesuvium portulacastrum FTWs to (a) regulate dissolved inorganic nitrogen (DIN) and (b) reduce CO₂/N₂O emissions in grouper aquaculture systems. DIN speciation (NH₄⁺, NO₂⁻, NO₃⁻) and CO₂/N₂O fluxes of six controlled ponds (three FTW and three control) were monitored for 44 days. DIN in the FTW group was approximately 90 μmol/L lower than that in the control group, and the water in the plant group was more “oxidative” than that in the control group. The former groups were dominated by NO₃⁻, with lower dissolved inorganic carbon (DIC) and N₂O concentrations, whereas the latter were dominated by NH₄⁺ during the first 20 days of the experiment and by NO₂⁻ at the end of the experiment, with higher DIC and N₂O concentrations on average. Higher primary production may be the reason that the DIC concentration was lower in the plant group than in the control group, whereas efficient nitrification and uptake by plants reduced the availability of NH₄⁺ in the plant group, thereby reducing the production of N₂O. A comparison of the CO₂ and N₂O flux potentials in the plant group and control group revealed that, in the presence of FTWs, the CO₂ and N₂O emissions decreased by 14% and 36%, respectively. This showed that S. portulacastrum FTWs effectively couple DIN removal with GHG mitigation, offering a nature-based solution for sustainable aquaculture. Their low biomass requirement enhances practical scalability. Full article

Background: Aquaculture increasingly seeks sustainable alternatives to fishmeal, a key protein source in fish diets. Black Soldier Fly Larvae (BSFL) meal is a promising substitute, but its effects on fish growth, immunity, and gut health need further investigation. This study aimed to evaluate the impact of varying BSFL inclusion levels on juvenile hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂), a widely farmed species in tropical aquaculture. Methods: Juvenile hybrid grouper were fed diets with four levels of BSFL substitution (0%, 10%, 30%, and 50%) over 56 days. Key metrics such as growth performance, immune function, antioxidant capacity, and gut transcriptome were analyzed. Results: Replacing fish meal with BSFL meal had no significant effect on the survival rate of hybrid grouper (p > 0.05) but significantly affected growth performance, immune function, and antioxidant capacity (p < 0.05). BSFL10 and BSFL30 groups showed good growth and elevated immune enzyme activity, with significantly higher HIS levels (p < 0.05); the Wf of the BSFL10 group was comparable to the control. However, excessive replacement (BSFL50) led to reduced growth (Wf significantly lower, p < 0.05) and increased oxidative stress, as indicated by higher CAT activity (p < 0.05). Transcriptomic analysis revealed upregulation of immune- and metabolism-related genes with increasing BSFL levels, with immune pathways notably activated in the BSFL50 group. Conclusions: BSFL meal is a promising alternative to fishmeal in juvenile hybrid grouper diets, with moderate inclusion (10–30%) being most beneficial. Excessive BSFL substitution (50%) may impair fish health, highlighting the need for careful formulation in aquaculture diets. Full article

Groupers are important aquaculture species, and hybridization is an effective breeding method for genetic improvement and to enhance production efficiency in groupers. The ShanHu grouper (Epinephelus fuscoguttatus ♀ × Epinephelus polyphekadion ♂) is a hybrid grouper with potential for aquaculture development and research value. Using Illumina and PacBio sequencing platforms, as well as PacBio SMRT technology and Hi-C auxiliary mounting technology, the whole genome sequencing and assembly of the ShanHu grouper were completed, resulting in a chromosome-level genome information for this hybrid grouper. The genome assembly has a total length of 1.17 Gb with a scaffold N50 of 46.12 Mb, and 171 contigs were anchored into 24 chromosomes. Additionally, its repeat sequences and non-coding RNAs were annotated and 26,102 genes were predicted. Through comparative genomic analysis of the hybrid species ShanHu grouper and its parents, we found that comparative genomic analyses revealed centric inversion structural variations on the chromosomes of the hybrid ShanHu grouper in relation to the brown-marbled grouper and the camouflage grouper. Furthermore, the gene families of the hybrid species have expanded in pathways related to immunity and growth development. This study is the first to provide complete genomic information for a hybrid grouper, offering its full genetic information, exploring the genetic variations in the genomes of hybrid offspring, and providing data references for foundational theoretical research and grouper production practices. Full article

Evaluating the interaction between dissolved oxygen (DO) and feeding rates (FRs) in fish is crucial for the precise regulation of aquaculture water environments. This study established four treatment groups: the CK group (DO = 6 mg/L, FR = 2% of body weight), the HFR group (DO = 6 mg/L, FR = 3.5% of body weight), the HDO group (DO = 9 mg/L, FR = 2% of body weight), and the MIX group (DO = 6 mg/L, FR = 3.5% of body weight). The combined effects of dissolved oxygen and feeding levels on oxidative stress, biochemical indicators, and growth in the hybrid grouper were evaluated. The results showed that mild hyperoxia significantly upregulates the expression of antioxidant enzyme genes (cat, cu/zn-sod, and gpx1a). Under conditions of mild hyperoxia, an increased feed rate can significantly downregulate the expression of cat and gpx1a. Additionally, serum levels of carnosine and cndp1 in muscle tissue are significantly elevated. Furthermore, a high FR mitigates the downregulation of glucose, triglycerides, and alanine aminotransferase (ALT) induced by mild hyperoxia while alleviating the upregulation of aspartate aminotransferase (AST). The combined effects of mild hyperoxia and high FR significantly enhance final body weight and specific growth rate (SGR), with notable interactions observed. Mild hyperoxia reduces serum levels of bile acids and glycocholic acid under high feeding conditions while significantly downregulating the expression of ghrb in both liver and brain tissues. In summary, high FRs alleviate oxidative stress and energy substrate deficiency in juvenile hybrid grouper under mild-hyperoxia environments. Moreover, the synergistic effect between mild hyperoxia and high FR promotes growth by improving bile acid enterohepatic circulation. This study provides a reference for the regulation of DO and feeding in modern industrial intensive mariculture. Full article

Enterospora epinepheli poses a severe threat to grouper aquaculture due to the absence of effective prevention and treatment strategies. To address this challenge, we developed and validated two isothermal diagnostic tools, the real-time enzymatic recombinase amplification (RT-ERA) assay and the enzymatic recombinase amplification combined with a lateral flow dipstick (ERA-LFD) assay, targeting the 18S rDNA gene of the parasite. These assays operate under isothermal conditions at ≤40 °C and offer rapid detection, with RT-ERA yielding results in 14~20 min and ERA-LFD in approximately 10 min. The RT-ERA assay demonstrated a strong linear relationship between plasmid copy numbers and cycle threshold (Ct) values (y = −2.1226x + 19.562, R² = 0.9915), enabling accurate quantification. Both methods displayed a detection limit of 2 × 10⁰ copies/μL and no cross-reactivity with other aquaculture pathogens. Validation using grouper tissue and water samples from Hainan, China, demonstrated 100% concordance rates with basic ERA and outperformed compared to conventional PCR. These assays provide sensitive, specific, and rapid detection tools for effective monitoring and pathogen load assessment of E. epinepheli, with broad applicability to pathogen detection in aquaculture systems. Full article

In this work, a novel molecularly imprinted electrochemical sensor was proposed based on molecular imprinting technology for the detection of sulfamethazine. A glassy carbon electrode was modified with a composite material of carbon nanotubes and graphene quantum dots to effectively improve sensitivity. The molecularly imprinted electrochemical sensor was then prepared by electropolymerization using sulfamethazine as the template and o-phenylenediamine as the functional monomer on the modified electrode. Under optimal measurement conditions, electrochemical tests of different sulfamethazine concentrations (0.5 μM–200 μM) showed excellent linearity and a detection limit of 0.068 μM. In addition, the sensor demonstrated satisfactory selectivity, stability, and reusability. Furthermore, the sensor was applied to the spiked analysis of sulfamethazine in grouper aquaculture water, achieving recovery rates between 95.4% and 104.8%, with a relative standard deviation (RSD) of less than 4.14%. These results indicated that the developed method was effective for the analysis of sulfamethazine in aquaculture seawater, providing a new approach for the detection of antibiotic residues in seawater samples. Full article

Triploid fish sometimes grow faster and larger than diploids, making them valuable in aquaculture. Their underdeveloped gonads redirect energy from reproduction to muscle growth. This study compared embryonic development and antioxidant responses between allotriploid and hybrid diploid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂) after cold shock, aiming to support large-scale allotriploid production. The diploid group had a 99.08% fertilization rate and 82.87% hatching rate, while the triploid group had lower rates (95.71% fertilization, 39.63% hatching, 11.52% deformity). Triploids developed later, with higher incidences of abnormalities and mortality, especially in the gastrula and neuro-embryo stages. Triploid larvae exhibited shortened tails, abnormal yolk sacs, and impaired swimming. Flow cytometry showed triploids that had 1.55 times more DNA and larger red blood cells. Triploids had lower midgut trypsin and lipase levels than diploids (p < 0.05) but similar glucose, liver malondialdehyde, and total cholesterol levels (p > 0.05). However, they had higher liver and spleen lactate dehydrogenase, catalase, and alkaline phosphatase, along with lower spleen malondialdehyde and liver superoxide dismutase (p < 0.05). These findings offer insights into reducing mortality in allotriploid grouper aquaculture, aiding large-scale production efforts. Full article

This study examined the diversity and responses of intestinal microbiota in hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂) fed diets with varying levels of fishmeal replaced by black soldier fly larvae (BSFL). The 10% BSFL substitution (BSFL10) group showed the highest levels of trypsin and amylase. Substituting fishmeal with 30% and 50% BSFL weakened the intestinal wall, resulting in vacuoles, sparse striatal boundaries, and fewer villi. Microbiota diversity, measured through Shannon’s index, was higher in the BSFL10 and BSFL50 groups than in the control. 16S rRNA amplicon data revealed the dominance of Firmicutes, Proteobacteria, Bacteroidetes, Spirochaetota, and Verrucomicrobia phyla. The BSFL-replacement groups showed an increase in Proteobacteria, Bacteroidetes, and Spirochaetota compared to the control, but fewer Firmicutes. PICRUSt analysis indicated significant alterations in microbial function, particularly enhanced protein, carbohydrate, lipid, and energy metabolisms in the BSFL-fed group. Substituting 10% fishmeal with BSFL enhanced nutrient metabolism and gut microbiota in juvenile hybrid grouper. Further research is needed to explore factors affecting the efficacy of insect feed as a sustainable aquaculture diet. Full article

Sesuvium portulacastrum floating treatment wetlands (FTWs) are effective at removing nitrogen and phosphorus, adsorbing heavy metals, and removing organic pollutants from aquaculture wastewater, and thus improve fish farming productivity. In this study, an S. portulacastrum FTW was used in a simulated grouper aquaculture experiment for 40 days. The FTW removed 1~3 mg/L of dissolved inorganic nitrogen (DIN) throughout the experimental period as well as the following toxic nitrogen species: 88% NO₂⁻-N in the middle stage and 90% TAN (total ammonia nitrogen) in the middle stage. The health of the groupers was promoted and the weight of each grouper was 8% higher than those in the control group in the end. Compared with that of the control group, the carbon sequestration of the aquaculture ecosystem was also increased by S. portulacastrum FTW because more carbon was held in the biomass, including through the growth of the plant mass of the FTW, 109 g C/pond, and a reduction in fishing catch losses, 442 g C/pond. Therefore, S. portulacastrum FTW can serve as a potential technology for improving the water environment quality of feeding ponds and contributing to carbon sequestration in aquaculture systems. Full article

Humpback grouper (Cromileptes altivelis) is an economically important fish, but the increasing density of its farming has led to more severe disease outbreaks. To address this challenge, we established brain (CAB) and kidney (CAK) cell lines in our laboratory previously, providing a valuable tool for in vitro studies on immune responses. In this study, we used quantitative real-time polymerase chain reaction (qRT-PCR) to identify the optimal reference gene from six reference genes for CAB and CAK cells, under both normal conditions and after stimulation with LPS or Poly I: C. The qRT-PCR data were analyzed using geNorm, NormFinder, and BestKeeper software (Version 3.5) to ensure comprehensve evaluation. The results showed that RPL13 was the most stable reference gene for both CAB and CAK cells under normal conditions. Following LPS stimulation, TTLL1 was the best reference gene for CAB cells, while RPL13 remained the most suitable for CAK cells. For Poly I: C stimulation, EF1A and Actin were identified as the most stable reference genes for CAB and CAK cells, respectively. To confirm the reliability of the selected reference genes, we analyzed the expression of the cytokine genes IL-6 and IFN-h, demonstrating the dependability of these reference genes. This study lays a solid foundation for exploring gene expression patterns in humpback grouper cell lines under various experimental conditions, providing essential insights for future research into immune processes and disease control strategies in aquaculture. Full article

Pseudomonas plecoglossicida infection, which causes visceral white spot disease, is a significant and economically devastating disease in aquaculture. In this study, we investigated the impact of bacterial infection on the protein composition of exosomes derived from the surface mucus of the hybrid grouper Epinephelus fuscoguttatus♀ × E. lanceolatus♂. Two hundred healthy fish were randomly separated into challenge and control groups. Fish from the challenge group received 10³ CFU/g of the bacterial pathogen P. plecoglossicida via intraperitoneal injection, while sterile PBS was used as a negative control. After injection, the mucus was collected and the exosomes were extracted for proteomic analysis. The results of proteomic analysis revealed that P. plecoglossicida infection significantly increased the levels of innate immune proteins, including lysosomal and peroxisomal proteins, within the exosomes. Furthermore, the CAD protein was found to play a pivotal role in the protein interaction networks involved in the response to P. plecoglossicida infection. Intriguingly, we also observed a significant increase in the levels of metal-binding proteins within the exosomes, providing important evidence of nutritional immunity on the surfaces of the fish hosts. Notably, several proteins, such as plasma kallikrein, Annexin A5, eukaryotic translation initiation factor 3 subunit M, and S-methyl-5-thioadenosine phosphorylase, exhibited a remarkable increase in abundance in exosomes after infection. These proteins show promising potential as noninvasive biomarkers for the diagnosis of visceral white spot disease. The study contributes to the understanding of the host response to P. plecoglossicida infection and may aid policymakers in implementing appropriate intervention measures for effective risk management of this devastating disease. Full article

Vibrio harveyi is a major bacterial pathogen that causes disease in aquaculture animals worldwide. Although V. harveyi consistently harbors a range of traditional virulence genes, it remains unclear which specific genes are crucial for virulence at different infection stages. Dual RNA-seq is a cutting-edge RNA sequencing technology that is ideal for investigating the gene expression patterns of pathogens within the host, which is highly effective in identifying key virulence genes. In previous artificial infection experiments, we have identified the liver of hybrid grouper (♀ Epinephelus polyphekadion × ♂ E. fuscoguttatus) as the main target organ for pathogenic V. harveyi GDH11385 during the initial infection phase. To further explore the key virulence factors of V. harveyi at the early stage of infection, the liver of the hybrid grouper infected with strain GDH11385 was analyzed here by dual RNA-seq. The transcriptome data were compared with that of in vitro cultured bacteria. The results showed that 326 and 1140 DEGs (differentially expressed genes) were significantly up- and down-regulated, respectively, at 4 h post-infection (hpi). Further pathway enrichment analyses revealed that these up-regulated DEGs in vivo were mainly enriched in siderophore biosynthesis and transport, type VI secretion system (T6SS), flagellar assembly, glycolysis/gluconeogenesis, and ribosome. Notably, all genes involved in the metabolism and utilization of vibrioferrin (a carboxylate class of siderophore produced by Vibrio), and most of the genes within one of three T6SSs, were significantly up-regulated in vivo. This indicates that siderophore-dependent iron competition and T6SS-mediated delivery of virulence factors are vital for the successful colonization of V. harveyi at the early stage of infection. This study provides more precise clues to reveal the virulence mechanism of V. harveyi during the initial phase of infection. Full article

The orange-spotted grouper (Epinephelus coioides) is an important mariculture fish in China. However, in recent years, with the rapid development of aquaculture activities, outbreaks of viral diseases have affected the grouper aquaculture industry, causing severe economic losses. In the present study, we isolated and identified a virus from diseased, orange-spotted groupers from an aquaculture farm in Hainan Province, China. The isolated virus was identified as orange-spotted grouper iridovirus, hence named the orange-spotted grouper iridovirus Hainan strain (OSGIV-HN-2018-001). OSGIV-HN-2018-001 induces a cytopathic effect after the infection of mandarin fish (Siniperca chuatsi) brain clonal passage (SBC) cells. In addition, the cytoplasm of the OSGIV-HN-2018-001-infected SBC cells was found to contain a large number of hexagonal virus particles with a diameter of approximately 134 nm. Using the Illumina NovaSeq system, we assembled the sequence data and annotated the complete genome of OSGIV-HN-2018-001 (GenBank accession number: PP974677), which consisted of 110,699 bp and contained 122 open reading frames (ORFs). Phylogenetic tree analysis showed that OSGIV-HN-2018-001 was most closely related to ISKNV-ASB-23. The cumulative mortality rate of groupers infected with OSGIV-HN-2018-001 reached 100% on day 8. The spleens were enlarged and blackened after the dissection of the dying groupers. These results contribute to the understanding of the molecular regulatory mechanism of the iridovirus infection and provide a basis for iridovirus prevention. Full article

Heterosis of growth traits in economic fish has benefited the production of aquaculture for many years, yet its genetic and molecular basis has remained obscure. Nowadays, a new germplasm of hybrid Jinhu grouper (Epinephelus fuscoguttatus ♀ × E. tukula ♂), abbreviated as EFT, exhibiting paternal-biased growth heterosis, has provided an excellent model for investigating the potential regulatory mechanisms of heterosis. We integrated transcriptome and methylome to unravel the changes of gene expression, epigenetic modification, and subgenome dominance in EFT compared with maternal E. fuscoguttatus. Integration analyses showed that the heterotic hybrids showed lower genomic DNA methylation levels than the purebred parent, and the up-regulated genes were mostly DNA hypomethylation. Furthermore, allele-specific expression (ASE) detected paternal subgenome dominance-regulated paternal-biased heterosis, and paternal bias differentially expressed genes (DEGs) were wholly up-regulated in the muscle. Multi-omics results highlighted the role of lipid metabolism, particularly “Fatty acid synthesis”, “EPA biosynthesis”, and “Signaling lipids”, in EFT heterosis formation. Coherently, our studies have proved that the eicosapentaenoic acid (EPA) of EFT was greater than that of maternal E. fuscoguttatus (8.46% vs. 7.46%). Finally, we constructed a potential regulatory network for control of the heterosis formation in EFT. Among them, fasn, pparg, dgat1, igf1, pomca, fgf8a, and fgfr4 were identified as key genes. Our results provide new and valuable clues for understanding paternal-biased growth heterosis in EFT, taking a significant step towards the molecular basis of heterosis. Full article

Several exogenous probiotics are applicable in fish culture; however, challenges in isolation and verification have hindered the full utilization of numerous host probiotics. Therefore, this study aimed to apply the host probiotic Exiguobacterium acetylicum G1-33 to hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂) cultures and explore its mechanism of action. In total, 360 hybrid grouper were divided into four groups, which were fed the following for 60 days: three received commercial feed with varying concentrations of E. acetylicum G1-33 (10⁶, 10⁸, and 10¹⁰ CFU/g), while a control group received commercial feed. The results showed that supplementation with 10⁶ and 10⁸ CFU/g of E. acetylicum G1-33 enhanced gut morphology, upregulated growth-related genes (ghr1, igf-2, s6k1, tor), and promoted growth, with supplementation with 10⁸ CFU/g resulting in the most notable enhancement. However, supplementation with 10¹⁰ CFU/g inhibited growth, possibly because of changes in intestinal morphology. Additionally, supplementation with E. acetylicum G1-33 upregulated the expression of immune-related genes (c3, myd88, Cu/Zn-sod, tlr3, and tnf2) in the liver and head kidney but led to an increase in malondialdehyde content, as well as a decrease in alkaline phosphatase and acid phosphatase activities, in the liver and serum, indicating increased oxidative stress. Moreover, supplementation with 10⁶ and 10⁸ CFU/g E. acetylicum G1-33 enhanced the widespread expression of immune-related genes in the head kidney and liver, respectively, and improved resistance to Vibrio harveyi, whereas supplementation with 10¹⁰ CFU/g weakened this resistance. In conclusion, E. acetylicum G1-33, particularly at 10⁸ CFU/g, emerged as an effective probiotic, optimizing growth performance and immunity in hybrid grouper. This research is pioneering in its application of E. acetylicum in mariculture, potentially broadening the range of probiotic strategies in aquaculture. Full article