High-density Farming Research Articles

Optimal conditions for cryopreservation by vitrification of largemouth bass (Micropterus salmoides) embryos

The largemouth bass (Micropterus salmoides) is one of the important freshwater aquaculture species in the world. However, due to limitations on introduction scale, high-density farming, inbreeding, and species hybridization, the germplasm resources of largemouth bass face threats such as degradation and susceptibility to diseases. Therefore, it is urgent to conduct research on the conservation of its original and good germplasm resources. We optimized the conditions of cryopreservation to vitrify and revive largemouth bass embryos, including the mixing ratio of cryoprotectants, embryo stage, equilibration step and temperature, and washing regent. The results showed that the least toxic single, binary, and ternary mixed permeating cryoprotectants were PG, PM (PG: MeOH = 2:1), and PMD (PM: DMSO = 3:1), respectively. The least toxic non-permeating cryoprotectant was 5 % glucose. The optimal vitrification solution selected was PMDG (30 % PMD + 5 % glucose) with an 80.67 % survival rate of embryos. Embryos at the heartbeat stage exhibited strong tolerance to the PMDG solution, which is the optimal embryo stage for cryopreservation. During the equilibration process, either the five-step equilibration method or pre-cooling the cryoprotectant to 4°C could reduce its toxicity. During the washing process, a 0.125 mol·L−1 sucrose solution yielded the best results. Based on the optimized conditions, 650 embryos at the heartbeat stage were subjected to cryopreservation by vitrification, resulting in a total of 350 intact transparent eggs, two of which hatched successfully. The results provide a reference for further improving the efficiency of cryopreservation by vitrification of largemouth bass and other fish species.

Agricultural extension and farm entrepreneurship: evidence from small-scale farmers of high-density plantations in Kashmir

ABSTRACT Purpose The study examines the transformative trends in agriculture by analysing the adoption patterns of high-density plantations (HDP) among small-scale apple farmers in Kashmir. It explores the factors shaping the adoption process and the role played by extension services in fostering this adoption. Design Employing a mixed-method approach, this study investigates how extension services influence the adoption of high-density farming and farm entrepreneurship. Utilising cross-sectional data from 160 small-scale farmer households, the research employs a recursive bivariate probit regression model to unveil the relationship between extension services and the adoption of high-density farming. Findings The findings reveal a crucial link between small-scale farmers’ adoption decisions and their access to agricultural extension services. Land size, credit, and subsidies play key roles in influencing both HDP adoption and extension service accessibility, highlighting the interconnectedness of financial support in promoting sustainable agriculture. Furthermore, early adopters showcase innovative behaviour driven by production advantages and sustainability concerns. Practical implications It underscores the need for targeted interventions to promote sustainable agricultural practices and enhance extension service accessibility. Recognising the positive impact of credit and subsidy availability on both HDP adoption and access to extension services emphasises the interconnected role of financial support in driving sustainable practices. Theoretical implications The paper integrates theoretical frameworks from agricultural adoption, extension and entrepreneurship while contributing a more comprehensive understanding of sustainable and transformed food systems. Originality This study develops a crucial framework that underscores the significance of public extension services for small-scale farmers in the Himalayan regions. Additionally, it enhances understanding of the potential benefits of high-density farming and farm entrepreneurship for sustainable agriculture and transforming food systems for rural development globally.

Epidemiological investigation on diseases of Larimichthys crocea in Ningbo culture area.

Due to the high-density farming of Larimichthys crocea over the years, diseases caused by pathogens such as bacteria, viruses, and parasites frequently occur in Ningbo, posing a huge threat and challenge to the sustainable and healthy development of the L. crocea's bay farming industry. In order to understand the diseases occurrence in L. crocea farming in Ningbo area, an epidemiological investigation of L. crocea diseases was carried out through regular sampling in 2023. From April to October 2023, routine sampling of L. crocea was conducted monthly in various farming areas in Ningbo. Each time, live or dying L. crocea with obvious clinical symptoms were sampled, with a total number of 55 L. crocea collected. The samples were preserved in ice bags and transported to the laboratory for pathogen detection(including bacterial isolation and identification,virus identification, and parasites detection). A total of fifty-five fish dying L. crocea with obvious clinical symptoms were collected in this study, of which 78.18% (43/55) were detected with symptoms caused by pathogenic infection, while 21.82% (12/55) did not have identified pathogens, which were presumed to be breeding abrasions, nutritional metabolic disorders, unconventional pathogens infection or other reasons. A total of twenty-five pathogenic bacteria strains were isolated, which mainly were Pseudomonas plecoglossicida and Vibrio harveyi, accounting for 52% (13/25) and 32% (8/25) of the pathogenic bacteria strains, respectively. Among them, both V. harveyi and Streptococcus. iniae co-infected one fish. Additionally, three other bacterial strains including Nocardia seriolae, Staphylococcus Saprophyticus, and Photobacterium damselae subsp.damselae were isolated. Microscopic examination mainly observed two parasites, Cryptocaryon irritans and Neobenedenia girellae. In virus detection, the red sea bream iridovirus (RSIV) was mainly detected in L. crocea. Statistical analysis showed that among the fish with detected pathogens, 55.81% (24/43) had bacterial infections, 37.21% (16/43) had parasitic infections, and 37.21% (16/43) had RSIV infections. Among them, five fish had mixed infections of bacteria and parasites, three had mixed infections of bacteria and viruses, three had mixed infections of parasites and viruses, and one L. crocea had mixed infections of viruses, bacteria, and parasites. These findings indicate that these three major types of diseases are very common in the L. crocea farming area in Ningbo, implying the complexity of mixed infections of multiple diseases.

Prevalence, Risk Factors, and Molecular Epidemiology of Anaplasma phagocytophilum in Sheep Raising in Khuzestan Province, Iran

Background: Anaplasma sp. is a blood protozoon that causes economic damage to the livestock industry. Therefore, studying this disease’s epidemiology and distribution pattern in different regions is essential. Objectives: This study aimed to investigate the variety of infections of the Anaplasma sp. in the sheep population of Khuzestan Province in Iran. Methods: A total of 200 sheep blood samples were randomly collected and examined using specific nested polymerase chain reaction (nPCR) based on the 16S rRNA gene. Results: The prevalence of Anaplasma phagocytophilum was 17%, and infected sheep had no clinical signs. The effective risk factors in the spread of infection in Khuzestan Province include sheep aged 3-5 years, low sanitation, high-density farms, use of acaricides in the field, and hot season (P≤0.05). There was no significant association between the occurrence of A. phagocytophilum infection and variables of altitude, farm type, vectors, distance from other farms, and sex. Conclusion: Since the infection often has no clinical symptoms, identifying the risk factors and epidemiology is essential to develop control and prevention planning.

DISCUSSION ON ECOLOGICAL AQUACULTURE AND INNOVATIVE OPERATION STRATEGY

This study aims to improve the problems faced by Taiwan's aquaculture industry, such as the increased risk of drug residues caused by excessive use of water and soil resources and high-density farming, and to improve its competitiveness. Improve regional production and marketing operations, increase environmental protection production methods, and increase young people's willingness to return to their hometowns to invest. In order to increase consumers' trust in aquaculture aquatic products, basic safety requirements can be achieved through production and sales history labels, vacuum-sealed packaging, and clear labels, thereby enhancing consumer loyalty. Brand features and product discounts can also enhance loyalty. This study uses the focus group interview method to understand the problems of regional farming and the expected future prospects. Results found that it is possible to integrate regional farmers, establish sales channels for agricultural and fishery products in Chiayi, achieve sustainable development and improve competitiveness, and increase the willingness of young people to return to their hometowns to invest. To sum up, there are the following three propositions: (1) Construct cooperation channels to increase the added value of production and sales. (2) Introduce friendly breeding and increase product differentiation. (3) Establish an intelligent platform to train young people to return hometown. In addition, it is also suggested to combine the promotion of local recreational fishery and the characteristics of e-commerce distribution and sales to establish an operation model of online distribution and sales; and widely publicize Taiwan's seafood and aquatic product certification and inspection system to promote friendly farming methods to improve the existing breeding environment. Protect the sustainable environment and increase production value.

Resveratrol impacts on aquatic animals: a review.

Aquaculture has intensified tremendously with the increasing demand for protein sources as the global population grows. However, this industry is plagued with major challenges such as poor growth performance, the lack of a proper environment, and immune system impairment, thus creating stress for the aquaculture species and risking disease outbreaks. Currently, prophylactics such as antibiotics, vaccines, prebiotics, probiotics, and phytobiotics are utilized to minimize the negative impacts of high-density farming. One of the promising prophylactic agents incorporated in fish feed is resveratrol, a commercial phytophenol derived via the methanol extraction method. Recent studies have revealed many beneficial effects of resveratrol in aquatic animals. Therefore, this review discusses and summarizes the roles of resveratrol in improving growth performance, flesh quality, immune system, antioxidant capacity, disease resistance, stress mitigation, and potential combination with other prophylactic agents for aquatic animals.

Assessing the Interactive Effects of High Salinity and Stocking Density on the Growth and Stress Physiology of the Pacific White Shrimp Litopenaeus vannamei

This study was conducted to evaluate the effects of high salinity combined with stocking density on Litopenaeus vannamei. Three salinity gradients, namely, 28 g/L, 36 g/L, and 44 g/L, and two stocking densities, namely, 300 and 600 shrimp/m3, were used to analyze the synergistic effect of high salinity and stocking density on the growth performance, digestibility, and energy budgets of L. vannamei. The experimental testing period lasted 45 days. The research results showed that a salinity level of 36 g/L was the most suitable salinity level for shrimp growth under both high and low stocking densities. The body weight, specific growth rate, and relative weight gain of the shrimp in the 36 g/L salinity group were significantly higher than those in the other two salinity groups under both high and low stocking densities. The high-density farming group with 600 shrimp/m3 exhibited a significant inhibition of shrimp growth compared to the low-density group under the same salinity conditions. The activities of amylase, lipase, and protease in the high-density-group shrimp gradually decreased with an increase in salinity, and the three digestive enzymes had the same overall effect of changing trends. This indicates that under high-density farming conditions, the increase in salinity is not conducive to the digestive function of shrimps. At the same time, the proportion of respiratory energy to feeding energy gradually decreased in the high-density group and with the increase in salinity. However, under the same salinity conditions, the higher the stocking density, the higher the energy consumed by respiration compared to the low-density group. In addition, the expression of the growth-related gene’s small nuclear ribonucleoprotein polypeptide G (SNRPG) under high stocking density was significantly lower than that in the low-density group at a salinity of 28 g/L, and ribosomal protein L7 (RPL7) expression was also significantly lower under high stocking density than that in the low-density group at a salinity of 44 g/L. The expression levels of molting-related genes retinoid X receptor (RXR), ecdysone receptor (ECR), and ecdysone-induced protein 75 (E75) were significantly higher in the 36 g/L salinity group compared with the other two salinity groups under high-stocking-density treatment. The findings indicate that the synergistic effects of salinity and stocking density have a significant impact on the growth of L. vannamei, and excessive salinity would inhibit its growth in the process of high-density culturing.

Mechanical abrasion stimulation: Altered epidermal mucus composition and microbial community in grass carp (Ctenopharyngodon idella)

In modern high-density farming, seasonal change, fishing, transportation, and other conditions easily cause mechanical abrasion of fish skin. This leads to alterations in the material balance of the epidermal mucus composition of fish, preventing normal immune function. Subsequently, the risk of disease increases. In this study, grass carp (Ctenopharyngodon idella) was used as an object to investigate immune-related enzyme activities, structural characteristics, and physiological changes of its epidermal mucous cells caused by mechanical abrasion. Furthermore, we explored the changes in body surface mucus composition and microbial community diversity and structure. Our results showed that mechanical abrasion stimulation, significantly changed the activities of immune-related enzymes, such as lysozyme (LZM), alkaline phosphatase (AKP), and acid phosphatase (ACP) were within 24 h (P < 0.05). Their levels gradually recovered after 48 h. In contrast, no significant change was observed in superoxide dismutase (SOD) levels. The number of mucous cells increased, especially those of type I and type II mucous cells in the dorsal skin, which were significantly increased (P < 0.05). Meanwhile, the stimulation changed the metabolites composition of the fish epidermal mucus in the short term, upregulating 12-OPDA, indole, quinic acid and GSH, which are beneficial to antibacterial and anti-inflammatory, and downregulating L-saccharopine, L-2-aminoadipic acid, spermine, GSSG and ribose 5-phosphate, which disrupt protein synthesis, energy production and DNA synthesis. Additionally, these metabolite changes further affect the composition of microorganism communities, rising the abundance of certain disease-associated microorganisms, such as Acidovorax, Rhizobiaceae, Aurantimicrobium, and Leifsonia, which increases the risk of disease in fish. The findings of the present study provide a deeper understanding of the role of mucus as a component of the immune system in fish and provide a scientific basis for effective grass carp culture management and disease control.

High-density farming of striped snakehead Channa striata (bloch, 1793) in artificial tanks

High-density farming of striped snakehead Channa striata (bloch, 1793) in artificial tanks

Captive Production of Bagrid Catfish, &lt;i&gt;Rita chrysea&lt;/i&gt; For Species Diversification in India

Catfish farming is getting more popular as an alternative to carp culture in India due to several advantages such as suitable for high-density farming, hardy species, more consumer preference, high market value, less pin-bones and higher economic returns. Catfishes are having a high regional preference and among many catfish species, the Mahanadi rita, Rita chrysea is one among the species having huge consumer preference in Odisha and Chhattisgarh region. The broodstock development, captive breeding, seed production and grow-out culture technology were successfully standardized by ICAR-Central Institute of Freshwater Aquaculture, Bhubaneswar. The study findings reveal that R. chrysea attains maturity in 1+ year and the ideal broodstock size of 90 g above is most suitable for induced breeding programme. The species breeds in monsoon season, June-August. The fecundity was found to be 10,000-13,000 per 90-130 g brooder. The fertilization and hatching percent were estimated in the range of 70-90% and 60-80%, respectively. The larval stocking density of 2 to 3 nos per litre of water is found to be ideal stocking density to get higher growth and improved larval survival. The fingerlings can be produced in tank system with the stocking density of 100-150 nos per m2 with the survival of 50-60 % and it reaches about 2-4 g in 2 months rearing period.

MicroRNA sequencing analysis reveals injury-induced immune responses of Scylla paramamosain against cheliped autotomy

During pond culture or intensive culture system of crabs (mainly Eriocheir sinensis, Portunus trituberculatus and Scylla paramamosain), high-density farming has typically contributed to a higher limb autotomy level in juvenile animals, especially in S. paramamosain which has a high level of cannibalism. Due to the high limb autotomy level, the survival and growth rates in S. paramamosain farming are restricted, which limit the growth of the mud crab farming industry. MicroRNAs (miRNAs) are small noncoding RNAs that regulate a series of biological processes including innate immune responses by post-transcriptional suppression of their target genes. MiRNAs are believed to be crucial for innate immune process of host wound healing. Many miRNAs have been verified to be required in host immune responses to repair wound and to defense pathogen after tissue damage. However, to our best knowledge, the miRNAs functions of crustacean innate immune reactions against injury induced by limb autotomy have not been studied yet. Here in this study, for the first time, miRNAs involved in the S. paramamosain immune reactions against injury induced by cheliped autotomy were obtained by high-throughput sequencing. A total of 575 miRNAs (518 known miRNAs and 57 novel predicted miRNAs) were obtained, of which 141 differentially expressed microRNAs (93 up-regulated microRNAs and 48 down-regulated microRNAs) were revealed to be modified against cheliped autotomy, and the qPCR results of randomly selected miRNAs confirmed the expression patterns in the miRNAs sequencing data. Numerous immune-related target genes associated with innate immune system were mediated by miRNAs to induce host humoral immune and cellular immune defense to minimize acute physical damage. Furthermore, the genes expression in hemolymph coagulation and melanization pathways, as well as Toll and Imd signaling pathways were mediated by miRNAs to activate host immune responses including melanization and antimicrobial peptides for rapid wound healing and killing invaded pathogens. These results will help to understand injury-induced immune responses in crabs and to develop an effective control strategy of autotomy rate in crabs farming.

Blood analytes of clinically normal and diseased neonatal and weaned farmed white-tailed deer (Odocoileus virginianus) fawns

Recent research focused on farmed deer has exposed many knowledge gaps regarding health assessment protocols for white-tailed deer (WTD). The objectives of this study were to establish de novo blood analyte reference intervals for farmed WTD fawns at birth (1–2 days of age; n = 84) and again at weaning (76–125 days of age; n = 28), to compare data at birth and at weaning to understand how these analytes are affected by the intrinsic factors age and sex in clinically normal WTD fawns, and to compare between clinically normal and sick WTD weanlings (respiratory disease n = 12; orbivirus-infected n = 6). Reference intervals were established for WTD fawns at birth and weaning. Female WTD neonates had significantly higher red blood cell counts, hematocrit, and hemoglobin compared to males. Most blood analytes were significantly different in clinically normal WTD neonates compared to weanlings, suggesting an effect of age. The observed sex- and age-related variations in WTD highlight the need to establish reference intervals that account for intrinsic factors. The comparison of clinically normal and sick WTD weanlings in this study identified higher MCHC and absolute monocytes in sick weanlings but these findings were presumably not biologically relevant given the small sample size for sick fawns. While the reference interval data presented herein will be useful for the veterinary care of WTD fawns at critical time periods in a high-density farm setting, this study also demonstrates the need to identify more sensitive and specific biomarkers for the assessment of health status in farmed WTD with specific underlying diseases.

Cooperative adaptation strategies of different tissues in blunt snout bream (Megalobrama amblycephala) juvenile to acute ammonia nitrogen stress.

Ammonia-nitrogen is a common stress factor for aquatic organisms in their habitation environment, which is enriched in water due to high-density farming and environmental pollution. Ammonia nitrogen can enter fish body through gill, epidermis, digestive tract, and other tissues, causing fish ammonia poisoning. In the present study, juvenile blunt snout bream (average weight, 45 ± 5g) were exposed to high concentrations of ammonia-nitrogen stress (25.0 ± 0.5mg/L) for six different treatment times (0, 3, 6, 12, 24, 48, and 72h); the tissue ultrastructure, mRNA levels of antioxidation system, and apoptosis patterns were studied. The antioxidant systems of malondialdehyde (MDA), catalase (CAT), acid phosphatase (ACP), and reduced glutathione (GSH) in various tissues were highly transcripted at 6 or 12h (hpt) after treatment under high ammonia-nitrogen, which may play a role in preventing cells from being attacked by highly toxic reactive oxygen species (ROS). After 24 hpt, the antioxidant capacity threshold is breached, followed by the decline of antioxidant enzyme activity. Thus, with the prolonging of high ammonia-nitrogen processing time, ammonia-nitrogen stress caused irreversible damage of organs (gill, liver, and kidney). Furthermore, the expression of caspase-3 apoptotic pathway was highly induced in different tissues, implying the apoptotic system is activated, which causes extensive cell apoptosis in different tissues as shown using TUNEL analysis. In conclusion, we observed that, in response to acute ammonia-nitrogen stress, blunt snout bream enhances antioxidant capacity and cell apoptosis.

Dynamic and systemic regulatory mechanisms in rainbow trout (Oncorhynchus mykiss) in response to acute hypoxia and reoxygenation stress

Hypoxia frequently occurs in natural aquatic systems and aquaculture environments due to extreme climate fluctuations, high-density farming, environmental pollution and global warming, resulting in serious ecological damage and enormous economic losses. Rainbow trout (Oncorhynchus mykiss), a key economic fish species worldwide, is extremely sensitive to hypoxia. However, the regulatory mechanisms in response to environmental hypoxia and reoxygenation stress remain unknown. Herein, rainbow trout liver transcriptomes and biochemical parameters were investigated in response to hypoxia for different durations (3, 12 and 24 h), reoxygenation (hypoxia for 24 h followed by reoxygenation for 3 h) and normoxia to highlight dynamic changes in molecular regulation and oxidative stress. In RNA-seq analysis, 5906 differentially expressed genes, two significantly expressed gene sets (profiles 10 and 12) and two hypoxia specific modules (MEgreen and MEturquoise) were screened by differential expression analysis, short time-series expression miner (STEM) and weighted gene co-expression network analysis (WGCNA), respectively. The intersection of the above analyses further identified several key hub genes related to hypoxia, including hif-1α, epo, igfbp1, ddit4, pck1, g6pc, cyp1a1 and dusp1. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses revealed different metabolic strategies at different stress stages; signal transmission and protein synthesis process were strongly influenced by hypoxia. The immune system was inhibited, and a switch from programmed to pathological cell death was observed from hypoxia for 12 h to 24 h. After reoxygenation for 3 h, mitochondrial oxidative phosphorylation was strongly activated to provide more cellular ATP. Enzymatic and non-enzymatic antioxidant systems clearly coordinate to alleviate oxidative stress injury caused by hypoxia. This study reveals dynamic and systemic regulatory mechanisms in rainbow trout liver, and lays a foundation for further study on the molecular mechanisms governing responses to environmental hypoxia and reoxygenation stress.

Dietary Cinnamaldehyde Enhances Growth Performance, Digestion, Immunity, and Lipid Metabolism in Juvenile Fat Greenling (Hexagrammos otakii).

Fat greenling (Hexagrammos otakii) is a kind of economic fish that is widely consumed by human, and its intensive farming technology is making important progress. However, high-density farming may cause the occurrence of diseases in H. otakii. Cinnamaldehyde (CNE) is a new feed additive for aquatic animals and has a positive effect on disease resistance. In the study, dietary CNE was evaluated on the growth performance, digestion, immune response, and lipid metabolism of juvenile H. otakii (6.21 ± 0.19 g). Six experimental diets were formulated containing CNE at levels of 0, 200, 400, 600, 800, and 1000 mg/kg for 8 weeks. The percent weight gain (PWG), specific growth rate (SGR), survival (SR), and feeding rate (FR) were significantly increased by including CNE in fish diets regardless of the inclusion level (P < 0.05). The feed conversion ratio (FCR) was significantly decreased among the groups fed CNE supplemented diets (P < 0.05). A significant decrease in hepatosomatic index (HSI) was observed in fish fed 400 mg/kg-1000 mg/kg CNE compared to the control diet (P < 0.05). Fish-fed diets containing 400 mg/kg and 600 mg/kg CNE had a higher level of crude protein in muscles than the control diet (P < 0.05). Moreover, the activities of lipase (LPS) and pepsin (PEP) in the intestinal were markedly increased in juvenile H. otakii-fed dietary CNE (P < 0.05). Apparent digestibility coefficient (ADC) of dry matter, protein, and lipid was significantly increased with CNE supplement (P < 0.05). The activities of catalase (CAT) and acid phosphatase (ACP) in the liver were markedly enhanced by including CNE in juvenile H. otakii diets compared with the control (P < 0.05). The activities of superoxide dismutase (SOD) and alkaline phosphatase (AKP) in the liver were markedly enhanced in juvenile H. otakii treated with CNE supplements 400 mg/kg-1000 mg/kg (P < 0.05). Additionally, the levels of total protein (TP) in the serum were markedly increased by including CNE in juvenile H. otakii diets compared with the control (P < 0.05). In the CNE200, CNE400, and CNE600 groups, albumin (ALB) levels in the serum were markedly higher compared with that in the control (P < 0.05). In the CNE200 and CNE400 groups, the levels of immunoglobulin G (IgG) in the serum were significantly increased compared with that the control group (P < 0.05). The juvenile H. otakii-fed dietary CNE had lower triglycerides (TG) and total cholesterol (TCHO) levels in the serum than fish-fed CNE-free diets (P < 0.05). The gene expression of peroxisome proliferator-activated receptor alpha (PPAR-α), hormone-sensitive lipase (HSL), and carnitine O-palmitoyltransferase 1 (CPT1) in the liver was significantly increased by including CNE in fish diets regardless of the inclusion level (P < 0.05). However, fatty acid synthase (FAS), peroxisome proliferator-activated receptor gamma (PPAR-γ), and acetyl-CoA carboxylase alpha (ACCα) in the liver were markedly decreased with CNE supplements 400 mg/kg-1000 mg/kg (P < 0.05). The glucose-6-phosphate1-dehydrogenase (G6PD) gene expression levels in the liver were markedly decreased compared with the control (P < 0.05). The optimal supplementation level of CNE was shown by curve equation analysis to be 590.90 mg/kg.

Disruption of mstn Gene by CRISPR/Cas9 in Large Yellow Croaker (Larimichthys crocea).

The large yellow croaker (Larimichthys crocea) plays an economically vital role in the marine aquaculture in China. Suffering from infection of bacteria and protozoon, effect of extreme weather and stress from high-density farming, genome editing is thought to be an important tool applied to L. croea for enhancing commercial traits such as growth rate, disease resistance, and nutrition component. In this study, we identified two mstn genes in L. croea and investigated the different phylogenetic clades, gene structures, and conserved syntenic relationships. To obtain fast-growing large yellow croaker, we specially selected two validated targets for mstnb knockout, which was homologous to mammalian myostatin gene (MSTN) and downregulated skeletal muscle growth and development. Five significant mutation types were generated in two mosaic mutants by transferring specific CRISPR/Cas9 RNPs (ribonucleoprotein) into the one-cell fertilized embryos based on CRISPR/Cas9 technology. Subsequently, we also elucidated the obstacles and possible measures to improve the success rate of inducing modified large yellow croaker. Our results would provide valuable method and reference for facilitating genome editing programs of the large yellow croaker in the future.

Liver transcriptome analysis reveals changes in energy metabolism, oxidative stress, and apoptosis in pearl gentian grouper exposed to acute hypoxia

Pearl gentian grouper is an important new breed of high-density farmed fish with high commercial value on the coast of southeast China. However, frequent hypoxia could suppress growth and increase the mortality of high-density farmed pearl gentian grouper, limiting the application and scope of this farming mode and obstructing the rapid development of grouper aquaculture. Thus, this study investigated liver transcriptional changes in pearl gentian grouper exposed to hypoxic conditions (dissolved oxygen: 0.5 ± 0.05 mg/L) for different durations (0 h, 1 h, 3 h, 6 h, and 9 h) using Illumina RNA-Seq technology. Based on a differential expression analysis, short time-series expression miner (STEM) clustering, and weighted gene co-expression network analysis (WGCNA), 2383 differentially expressed genes (DEGs), two gene sets (profiles 0 and 18) with obvious expression trends, and three hypoxia-specific modules (lightcyan1, tan, and antiquewhite4) were screened, respectively. Genes involved in glycolysis (SLC2A3, PFKP, ALDOB, TPI1, GAPDH, PK, and LDHA) and fatty acid β-oxidation (ACSL1, ACOX1, and EHHADH) were all up-regulated, whereas genes involved in aerobic glycolysis (PC) and fatty acid synthesis (ACACB, FASN, FADS2) were down-regulated during hypoxic exposure. The CHAC1, GGCT, and OPLAH genes, involved in glutathione decomposition, were up-regulated. Additionally, the PXMP4, MPV17, SOD1, and CAT genes, involved in peroxisome antioxidation, were up-regulated. Moreover, the up-regulation of apoptosis-related genes (AIFM1, ENDOG, TNFRSF10A, and MCL1) was also detected. The results revealed that anaerobic glycolysis, fatty acid β-oxidation, glutathione metabolism, peroxisome antioxidation, and apoptosis played crucial roles in the transcriptomic responses of pearl gentian grouper towards hypoxia. These findings provide an essential basis for understanding the molecular mechanism by which this grouper adapts to profound changes in dissolved oxygen, thereby reducing damage caused by acute hypoxia during high-density farming.

Comprehensive proteomic analysis to elucidate the anti-heat stress effects of nano-selenium in rainbow trout (Oncorhynchus mykiss)

Because of the continuous intensification of global warming, extreme climate fluctuations, and high-density farming, cold-water rainbow trout (Oncorhynchus mykiss) are exposed to conditions of heat stress, which has severely impacted their survival and yield. Nano-selenium (nano-Se) shows higher biological activity and lower toxicity and has emerged as an ideal and ecological Se formulation. Herein rainbow trout were fed either a basal diet (control group) or basal diet plus 5 mg/kg nano-Se (treatment group). Samples were collected before (18 °C for 9 days; CG18, Se18) and after (24 °C for 8 h; CG24, Se24) heat stress. The DIA/SWATH approach was then applied to compare changes at the proteome level. We found 223 and 269 differentially abundant proteins in the CG18-CG24 and Se18-Se24 groups, respectively, which mainly included apoptosis-, heat stress-, and lipid-related proteins. In comparison with the CG18-CG24 group, the Se18-Se24 group showed higher abundance of molecular chaperone, such as Hsp70, Hsp90a.1, Hspa8, Hsp30, DNAJA4, Dnajb1, Bag2 and Ahsa1; on nano-Se supplementation, the heat stress-induced decline in the abundance of the selenoprotein MsrB2 was partially restored. Furthermore, nano-Se supplementation downregulated the abundance of lipid-related (CYP51, EBP, DHCR7, DHCR24, and APOB) and pro-apoptotic (caspase-8 and Bad) proteins. Protein–protein interaction analyses suggested that nano-Se inhibits apoptosis by upregulating the expression of Hsp70, Hsp90a.1, Hspa8, and Dnajb1; further, Hsp70/Hspa8 and MsrB2 appear to play a synergistic role in antioxidant defense under heat stress. Overall, our findings provide novel insights into nano-Se-mediated tolerance of heat stress, demonstrating that nano-Se exerts its anti-heat stress effects in rainbow trout by promoting protein repair, enhancing recovery of antioxidant enzyme activity, and alleviating lipid metabolism and apoptosis.

Nile tilapia (Oreochromis niloticus) can be experimentally infected with both marine and freshwater fish trypanosomes

Trypanosomes are haemoflagellates found in vertebrate species and many of them can cause death in infected hosts including fish and humans. With the development of high-density farming in marine and freshwater fish aquaculture systems, severe disease or death, caused by trypanosomiasis, has been frequently reported. However, due to the lack of a model system, particularly for marine fish trypanosomes, and a paucity in the understanding of the biology and pathogenesis of these parasites, effective treatment for fish trypanosomiasis is significantly hampered. The goldfish is the common model system for freshwater fish trypanosomes, mainly of the species Trypanosoma carassii, while a similar model for marine fish trypanosomes has not yet been established. To address this issue, we found that Nile tilapia (Oreochromis niloticus) could be easily infected with a marine fish trypanosome, Trypanosoma epinepheli isolated from Lates calcarifer. Obvious clinical symptoms, associated with a high parasitemia (>108/ml), were found in the infected tilapias and more than 70% mortality was recorded in individuals within 20 days of infection. Interestingly, we also found that the Nile tilapia could also be infected with a freshwater fish trypanosome isolated from the largemouth bass (Micropterus salmoides) and caused significant death (more than 13%) in infected fish. This system not only provides an economical and effective laboratory model to study the biology and pathogenesis of marine and freshwater fish trypanosomes, but also provides a useful platform to develop vaccines and screen compounds for the protection and treatment of fish trypanosomiasis.

Exploring the garlic (Allium sativum) properties for fish aquaculture.

The aquaculture industry's rapid growth to meet commercial demand can trigger an outbreak of infectious diseases due to high-density farming. Antibiotic overuse and misuse in fish farming and its global health consequences have led to searching for more natural alternatives such as medicinal plants. In this sense, garlic (Allium sativum) has different bioactive compounds with biological properties for animal health. Among them are the ajoene, alliin, and allicin, which confer biological properties such as growth promotion, antimicrobial, antiviral, antioxidant, and antiparasitic. Ways to use garlic in aquaculture include oil, fresh mash, aqueous extract, and garlic powder. The powder presentation is the most used in aquaculture; it is generally applied by oral administration, adding to the feed, and the dose used ranges from 0.05 to 40g/kg of feed. Garlic has been used in the aquaculture of different species such as rainbow trout (Oncorhynchus mykiss), spotted grouper (Epinephelus coioides), catfish (Clarias gariepinus), tilapia (Oreochromis niloticus), guppy fish (Poecilia reticulata), goldfish (Carassius auratus), and barramundi (Lates calcarifer). In addition to its properties, garlic's usage became popular, thanks to its low cost, easy incorporation into food, and little environmental impact. Therefore, its application can be an effective solution to combat diseases, improve organisms' health using natural supplies, and as an alternative to antibiotics. This review reports and discusses plant-derived products' beneficial properties, emphasizing garlic and its usages in fish aquaculture.