Immunostimulants for shrimp aquaculture: paving pathway towards shrimp sustainability

Litopeidin28-51, a novel antimicrobial peptide from Litopenaeus vannamei, combats white spot syndrome virus infection through direct virus lysis and immunomodulatory effects

White spot syndrome virus (WSSV) poses a critical threat to crustacean aquaculture, particularly shrimp, causing widespread pandemics. In crustaceans, hemocytes function as a key component of the innate immune system and play a pivotal role in both cellular and humoral immune responses by producing various immune factors, such as antimicrobial peptides (AMPs), to defend against pathogenic microorganisms. In this study, an uncharacterized functional gene named Litopeidin was identified in Pacific white shrimp (Litopenaeus vannamei). It exhibited heightened expression in hemocytes and demonstrated a significant response to WSSV infection. Further, a truncated peptide, Litopeidin28-51, derived from this gene, was characterized and identified as a novel AMP with robust antibacterial and antifungal properties, especially against common aquatic pathogens, including Vibrio spp. Moreover, Litopeidin28-51 significantly suppressed the expression of viral genes (IE1 and VP28, WSSV replication-related genes) and the VP28 protein, as well as reduced viral copy numbers in hematopoietic tissue (Hpt) cells following WSSV infection. Mechanistic studies revealed that Litopeidin28-51 exhibited a direct virucidal effect on WSSV and significantly upregulated immune-related gene expression (including Relish, ALF, Crustin, and LYZ1) in Hpt cells. Notably, in Cherax quadricarinatus and L. vannamei, either co- or pre-treatment with Litopeidin28-51 markedly reduced animal mortality and viral replication in tissues. Collectively, the findings suggest that Litopeidin28-51, a newly identified AMP with potent antibacterial activity, effectively inhibits WSSV replication by disrupting the viral envelope and regulating the cellular antiviral responses, making it a promising candidate for developing anti-infective agents or immunostimulants in aquaculture.

Probiotic modulation of key immune macromolecules in shrimp

The rapid expansion of shrimp aquaculture has been accompanied by significant disease challenges, driving the need for innovative prevention strategies. Probiotics, which are live microorganisms that confer health benefits to the host, have shown promise in controlling diseases in aquatic environments. Shrimp rely on their innate immune system, including physical barriers, and cellular and humoral defenses, for protection against pathogens. Physical barriers include the exoskeleton and the digestive tract, while cellular defenses involve hemocytes that engage in encapsulation, phagocytosis, and nodulation. Humoral defenses include the prophenoloxidase (proPO) system, lectins, agglutinins, and antimicrobial peptides (AMPs). Recent studies suggest that shrimp innate immunity can exhibit immunological memory, primarily through the actions of phagocytic cells. This review explores the use of probiotics in shrimp aquaculture, with a focus on their interaction with the shrimp immune system and their potential role in probiotic selection, either through environmental adaptation or as feed additives. Probiotics that enhance shrimp immunity by boosting phagocytosis, modulating the proPO system, and interacting with key signaling pathways such as Toll, IMD, and JAK/STAT offer a promising means of improving disease resistance. Probiotics play a critical role in modulating the infection process, influencing pathogen virulence factors, and shaping host-pathogen interactions. Further research into emerging immune pathways in shrimp could deepen our understanding of crustacean immunity and its applications in aquaculture.

Involvement of nerve cord-expressed SVWC2 in pathogen recognition and defense in Macrobrachium nipponense

The single von Willebrand factor C-domain proteins (SVWCs) are primarily found in arthropods and are involved in responding to environmental stress, nutritional availability, and pathogen infection. In this study, an SVWC family member from the Macrobrachium nipponense was identified that contains a conserved single von Willebrand factor C domain that is highly expressed in the nerve cord (designated MnSVWC2). The role of MnSVWC2 in resistance to bacteria and viruses was investigated. MnSVWC2 is upregulated in response to both bacterial challenge and viral infection. The recombinant MnSVWC2 (rMnSVWC2) exhibited binding activity to a range of pathogen-associated molecular patterns (PAMPs). Furthermore, it exhibited Ca2+-dependent binding and agglutination capabilities against Gram-negative, Gram-positive bacteria and yeast. The co-incubation of rMnSVWC2 with E. coli, followed by injection into prawns, resulted in an increase in the phagocytosis of E. coli by hemocytes in vivo. ELISA analysis indicated that rMnSVWC2 can bind to white spot syndrome virus. Knockdown of MnSVWC2 by RNA interference (RNAi) resulted in an increase in virus copies in prawns and a significant decrease in survival rate following viral infection. These findings provide important insights into the function of MnSVWC2 in the innate immunity of M. nipponense and the mechanisms of defense against pathogens.

Unveiling a new hemocyte subpopulation in white shrimp (Penaeus vannamei) and the characterization of immune response in hemocyte subpopulation

Hemocytes are the primary cellular components of the shrimp immune system, playing a crucial role in host defense. However, a comprehensive understanding of their subpopulations and specific functions remains incomplete. In this study, four hemocyte subpopulations, designated as H1, H2, H3, and H4, were identified in Penaeus vannamei using transmission electron microscopy (TEM) and flow cytometry. The H1 subpopulation was the most abundant cells, the smallest in size, lacked granules, and had the highest nucleus-to-cytoplasm (N:C) ratio, identifying it as prohemocytes (immature cells). The H2 subpopulation fits the criteria of hyaline hemocytes. They are relatively small, have a large nucleus, and contain no or very few cytoplasmic granules. The H3 subpopulation was the least abundant cell. These cells are larger than HCs, have a moderate N:C ratio, and contain a few granules, identifying them as semi-granulocytes. The H4 subpopulation, representing granulocytes, had the largest cell size and the lowest N:C ratio and was characterized by the presence of large granules in the cytoplasm. Non-specific immune responses were investigated through various parameters and gene expression profiling. Each hemocyte subpopulation exhibited distinct immune functions. Prohemocytes strongly expressed notch-1, suggesting a role in hemocyte proliferation. Hyalinocytes exhibited strong phagocytic activity and produced superoxide anions. Semigranulocytes exhibited high expression of lysozyme and anti-lipopolysaccharide factor. Granulocytes showed high expression of propo-1, propo-2, and antimicrobial peptide genes. Following Vibrio parahaemolyticus injection, the H1 subpopulation significantly increased at 6 h post-infection before returning to baseline levels, whereas the H4 subpopulation followed an opposite trend. These findings suggest that both H1 and H4 hemocytes play critical roles in the immune response against V. parahaemolyticus.

Transcriptome analyses of mRNA and circular RNA reveal dietary supplementation with freeze-dried Lactiplantibacillus plantarum primes immune memory of Whiteleg shrimp (Penaeus vannamei) against pathogens

The lack of a classical adaptive immunity renders the development of disease control and prevention measures in shrimp challenging. In this study, the concept of trained immunity was exploited in the development of a feed supplement. Penaeus vannamei shrimp was fed with feed supplemented with freeze-dried whole culture of Lactiplantibacillus plantarum (FD-LAB) for 15 days. RNA sequencing using Illumina platform was performed on the gill and stomach tissues collected at specific time points during the feeding period (0th day, 8th day, 15th day). Differentially-expressed genes (DEGs) previously reported to have innate immunity- and immune memory-related functions were selected for validation. Additionally, the differential expression of putatively immune-related circular RNAs (DECs) were also explored as these noncoding regulatory RNAs may also influence host immunity. Challenge tests with either the acute hepatopancreatic necrosis disease-causing strain Vibrio parahaemolyticus D6 or White Spot Syndrome Virus (WSSV) were conducted. Transcriptome analyses showed that FD-LAB supplementation resulted to DEGs and DECs related to pathogen recognition, antimicrobial peptides, transcription regulation, and immune memory. Challenge tests performed immediately after 15 days and 8 days of feeding showed protection on P. vannamei by FD-LAB against bacterial and viral pathogens. Increase in survival rates were also observed upon challenge with both pathogens 7 days and 14 days after last intake of FD-LAB, indicating trained immunity in shrimp. Our study highlighted the effects of FD-LAB on the innate immunity and immune memory of P. vannamei against bacterial and viral pathogens. These findings emphasize the possibility of immunostimulants inducing lasting enhanced immunity against infections despite the lack of a classical adaptive immunity in shrimp.

Use of Immunostimulants in Shrimp Farming-A Bioeconomic Perspective

Aquaculture is the fastest-growing food industry worldwide because it allows faster intensive production in a limited space and short time. However, the trade-off of this production scheme has led to infectious disease outbreaks that harm food production with economic impacts. Immunostimulants have entered the industry to fight against diseases by enhancing the immune system and conferring better protection against pathogens. In this regard, dietary immunostimulants have been tested at the farm level, such as carbohydrates and proteins known to enhance immunity and improve survival rates under experimental conditions. Despite the success of immunostimulant inclusion in experimental aquaculture, economic evaluation is an innovative avenue to be integrated when a novel immunostimulant is developed. The bioeconomic analysis permits the accurate demonstration of advantages or disadvantages regarding survival and yield performance upon immunostimulant application through mathematical and statistical estimates. An integrative bioeconomic model for testing a novel immunostimulant should contemplate technological, biological, and economic submodels at least; thus, financial variables, such as revenue, costs, and profitability, should also be considered for proper decision-making. Therefore, this perspective briefly describes the most relevant immunostimulants used in shrimp farms and offers bioeconomic elements that should be considered for affordable immunostimulant development and inclusion in shrimp aquaculture.

Effects of Fermented Pomegranate Peel Polyphenols on the Growth Performance, Immune Response, Hepatopancreatic Health, and Disease Resistance in White Shrimp (Litopenaeus vannamei)

This study evaluated the growth performance, immune response, hepatopancreatic health, and disease resistance in Litopenaeus vannamei fed diets supplemented with fermented pomegranate peel polyphenols (FPPP) for 45 days. Five diets were formulated to contain various levels of FPPP: FP0 (no FPPP), FPPP inclusion at 0.015% (FP1), 0.030% (FP2), 0.060% (FP3), and 0.120% (FP4). The results indicated there were no significant variations in weight gain rate (WGR), specific growth rate (SGR), and feed conversion rate (FCR) of shrimp in all treatment groups (p > 0.05), but the survival (SR) of shrimp was significantly higher in all groups with the addition of FPPP (p < 0.05). Compared with FP0 group, the contents of total protein (TP) and globulin (GLB) in serum biochemical indexes of FP3 and FP4 groups were significantly increased, and the content of blood urea nitrogen (BUN) was significantly decreased (p < 0.05). Compared with FP0 group, the activities of superoxide dismutase (SOD), catalase (CAT), alkaline phosphatase (AKP), acid phosphatase (ACP), and lysozyme (LZM) in the hepatopancreas and serum of FP3 and FP4 groups were significantly increased (p < 0.05). Similarly, the activities of glutathione peroxidase (GSH-Px), total antioxidant capacity (T-AOC), and phenoloxidase (PO) in the hepatopancreas and serum of FP2 group were significantly higher than those of FP0 group (p < 0.05). In addition, the content of malondialdehyde (MDA) in the hepatopancreas and serum of shrimp in FPPP-added groups was decreased (p < 0.05). Compared with FP0 group, the expression levels of SOD, CAT, glutathione S-transferase (GST), LZM, prophenoloxidase (ProPO), penaeidin-3 (Pen3), Crustin, immune deficiency (Imd), Toll, and Relish genes were significantly upregulated in the hepatopancreas of shrimp in FP3 and FP4 groups (p < 0.05). Additionally, increasing the addition level of FPPP resulted in a more compact hepatosomal arrangement of the shrimp's hepatopancreas, a more visible star-shaped lumen structure, and a significantly higher number of B cells. Finally, the cumulative SR of shrimp in FPPP groups was significantly higher than that in FP0 group after 7 days of infection with Vibrio alginolyticus (p < 0.05). In summary, dietary supplementation of FPPP can improve SR, immunity, and hepatopancreatic health and resistance to Vibrio alginolyticus of L. vannamei.

Safety Assessment of Camelid-Derived Single-Domain Antibody as Feed Additive for Juvenile Whiteleg Shrimp (Litopenaeus vannamei) Against White Spot Syndrome Virus

A six-week feeding trial was conducted to assess the safety of single-domain antibodies (sdAbs) derived from camelids against the white spot syndrome virus (WSSV) (WSSVvp28 was used as the antigen), focusing on the whole-organism responses and molecular-level changes in juvenile whiteleg shrimp (Litopenaeus vannamei). Five experimental diets with varying levels of sdAbs were formulated: CON (no sdAb supplementation); SDA8.2 (8.20% of sdAbs); SDA16.4 (16.40% of sdAbs); SDA24.6 (24.60% of sdAbs); and SDA32.8 (32.80% of sdAbs). In the CON diet, 450 mL of water per kg of diet (45%) was used to form a feed dough, while sdAbs were used to replace the water in the treatment diets. A total of 450 shrimp, with an initial body weight of 3.27 ± 0.02 g (mean ± SEM), were randomly distributed in 15 tanks (30 shrimp per tank; three tanks per treatment). Each tank was filled with 30 L of seawater (77 L capacity) in an indoor semi-recirculating system with a constant water flow rate of 1.2 L min-1. The photoperiod was maintained at 12 h of light and 12 h of dark. The water temperature, pH, salinity, and dissolved oxygen were 27.3 ± 0.1 °C, 7.61 ± 0.01, 34 ± 1 ppt, and 5.94 ± 0.04 mg L-1, respectively. During the feeding trial, the shrimp were fed the experimental diet (40% protein and 11% lipid) three times a day for six weeks. Following the feeding trial, an acute cold-water-temperature stress test was conducted by abruptly exposing the shrimp from each treatment to 15 °C for 4 h, down from 27 °C. The results showed no significant differences in the growth performance (weight gain, feed utilization efficiency, survival, etc.), plasma metabolites (aspartate aminotransferase activity, alanine aminotransferase activity, total protein, and glucose), or antioxidant enzymes (superoxide dismutase and glutathione peroxidase) among all the experimental diets (p > 0.05). In the acute cold-temperature stress test, there was no significant interaction between sdAb supplementation and temperature stress, nor any main effect from either factor, except for the main effect of temperature stress on the glucose levels, which was significantly higher in shrimp exposed to cold-temperature stress (p < 0.05). The next-generation sequencing of differentially expressed genes (DEGs) in the hepatopancreases of shrimp fed the CON, SDA16.4, and SDA32.8 diets, followed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses, indicated that DEGs were significantly enriched in signaling pathways associated with growth, cold stress, and antioxidant systems. Overall, the results from conventional measurements suggest that the use of sdAbs against the WSSV may be safe for juvenile whiteleg shrimp. However, findings from the sophisticated analysis indicate that further research is needed to understand the molecular mechanisms underlying the observed changes, and to evaluate the long-term effects of sdAb supplementation in shrimp diets.

Microbes and pathogens associated with shrimps - implications and review of possible control strategies

Shrimp aquaculture has been growing rapidly over the last three decades. However, high-density aquaculture together with environmental degradation has led to increased incidence of shrimp infections. Thus, devising and implementing effective strategies to predict, diagnose and control the spread of infections of shrimps are crucial, also to ensure biosecurity and sustainability of the food industry. With the recent advancements in biotechnology, more attention has been given to develop novel promising therapeutic tools with potential to prevent disease occurrence and better manage shrimp health. Furthermore, owing to the advent of the next-generation sequencing (NGS) platforms, it has become possible to analyze the genetic basis of susceptibility or resistance of different stocks of shrimps to infections and how sustainable aquaculture could be made free of shrimp diseases.

Effect of Diets Supplemented With Yeast, Chitin, and Chitosan on the Growth, Immune, and Antioxidant Responses of the Freshwater Prawn Cryphiops (Cryphiops) caementarius

The purpose of the present research was to evaluate the effect of diets supplemented with activated yeast, crude chitin, and chitosan on the growth, immune, and antioxidant response of freshwater prawn Cryphiops (Cryphiops) caementarius. Adult male prawns were kept in individual culture vessels installed in aquarium tanks. The basal diet (control) was supplemented with activated Saccharomyces cerevisiae yeast (60 g/kg), crude chitin (20 g/kg), and chitosan (1 g/kg). Each dietary treatment consisted of three replicates. The diet supplemented with activated yeast causes greater growth, as well as a greater number of total hemocytes (82.54 × 105 cells/mL), semigranular (59 × 105 cells/mL), and granular (18.67 × 105 cells/mL) hemocytes and without atypical hemocytes. Furthermore, a higher number of hemocytes positive for prophenoloxidase (98%), a shorter hemolymph clotting time (42.87 s), a higher activity of acid phosphatase (12.50 U/mL) and glutathione-S-transferase (GST) (0.186 U/mL) were also observed in dietary yeast group. On the contrary, there were no differences in the activity of superoxide dismutase (SOD) enzyme in prawns from any dietary treatment. Results from this research demonstrate for the first time that the diet containing activated yeast increases the growth and immune response of the freshwater prawn through a significant increase in hemocyte and acid phosphatase levels, a decrease in hemolymph clotting time, and a greater number of proPO-positive hemocytes. However, activated yeast is not effective in increasing the activity of antioxidant enzymes SOD and GST. Therefore, the activated yeast diet can be useful to improve the aquaculture production of C. (C.) caementarius and possibly of other commercially important crustaceans.

Genomic Characterization of Bacillus pumilus Sonora, a Strain with Inhibitory Activity against Vibrio parahaemolyticus-AHPND and Probiotic Candidate for Shrimp Aquaculture

Acute hepatopancreatic necrosis disease, caused by Vibrio parahaemolyticus strains carrying the pirA and pirB toxin genes (VpAHPND), has been causing great economic losses in Asia and America in the shrimp farming industry. Numerous strains are resistant to antibiotics. However, supplementation with probiotic antagonists has become a more desirable treatment alternative. Fourteen strains of microorganisms were assessed for their potential to inhibit VpAHPND in vitro activity. The bacteria with the highest activity were challenged with VpAHPND-infected Pacific white shrimp Litopenaeus vannamei. Furthermore, the genomic characteristics of probiotic bacteria were explored by whole-genome sequencing. We identified the Sonora strain as Bacillus pumilus, which possesses positive proteolytic and cellulolytic activities that may improve shrimp nutrient uptake and digestion. Challenge trials showed a low cumulative mortality (11.1%). B. pumilus Son has a genome of 3,512,470 bp and 3734 coding sequences contained in 327 subsystems. Some of these genes are related to the biosynthesis of antimicrobial peptides (surfactins, fengycin, schizokinen, bacilibactin, and bacilysin), nitrogen and phosphorus metabolism, and stress response. Our in vitro and in vivo findings suggest that B. pumilus Sonora has potential as a functional probiotic.

Effects of dietary glycerol monolaurate on growth and digestive performance, lipid metabolism, immune defense and gut microbiota of shrimp (Penaeus vannamei)

The advancement of the Penaeus vannamei industry in a sustainable manner necessitates the creation of eco-friendly and exceptionally effective feed additives. To achieve this, 720 similarly-sized juvenile shrimp (0.88 ± 0.02 g) were randomly divided into four groups in this study, with each group consisting of three replicates, each tank (400 L) containing 60 shrimp. Four experimental diets were formulated by adding 0, 500, 1000, and 1500 mg kg-1 glycerol monolaurate (GML) to the basal diet, and the feeding trial lasted for 42 days. Subsequently, a 72-h White Spot Syndrome Virus (WSSV) challenge test was conducted. Polynomial orthogonal contrasts analysis revealed that with the increase in the concentration of GML, those indicators related to growth, metabolism and immunity, exhibit linear or quadratic correlations (P < 0.05). The results indicate that the GML groups exhibited a significant improvement in the shrimp weight gain rate, specific growth rate, and a reduction in the feed conversion ratio (P < 0.05). Furthermore, the GML groups promoted the lipase activity and reduced lipid content of the shrimp, augmented the expression of triglyceride and fatty acid decomposition-related genes and lowered the levels of plasma triglycerides (P < 0.05). GML can also enhanced the humoral immunity of the shrimp by activating the Toll-like receptor and Immune deficiency immune pathways, improved the phagocytic capacity and antibacterial ability of shrimp hemocytes. The challenge test revealed that GML significantly reduced the mortality of the shrimp compared to control group. The 16S rRNA sequencing indicates that the GML group can increases the abundance of beneficial bacteria. However, 1500 mg kg-1 GML adversely affected the stability of the intestinal microbiota, significantly upregulating intestinal antimicrobial peptide-related genes and tumor necrosis factor-alpha levels (P < 0.05). In summary, 1000 mg kg-1 GML was proven to enhance the growth performance, lipid absorption and metabolism, humoral immune response, and gut microbiota condition of P. vannamei, with no negative physiological effects.

Experimental Infection Models and Their Usefulness for White Spot Syndrome Virus (WSSV) Research in Shrimp

White spot syndrome virus (WSSV) is marked as one of the most economically devastating pathogens in shrimp aquaculture worldwide. Infection of cultured shrimp can lead to mass mortality (up to 100%). Although progress has been made, our understanding of WSSV's infection process and the virus-host-environment interaction is far from complete. This in turn hinders the development of effective mitigation strategies against WSSV. Infection models occupy a crucial first step in the research flow that tries to elucidate the infectious disease process to develop new antiviral treatments. Moreover, since the establishment of continuous shrimp cell lines is a work in progress, the development and use of standardized in vivo infection models that reflect the host-pathogen interaction in shrimp is a necessity. This review critically examines key aspects of in vivo WSSV infection model development that are often overlooked, such as standardization, (post)larval quality, inoculum type and choice of inoculation procedure, housing conditions, and shrimp welfare considerations. Furthermore, the usefulness of experimental infection models for different lines of WSSV research will be discussed with the aim to aid researchers when choosing a suitable model for their research needs.

Surface defects due to bacterial residue on shrimp shell

The changes in the surface chemistry and morphological structure of chitin forms obtained from shrimp shells (ShpS) with and without microorganisms were evaluated. Total mesophilic aerobic bacteria (TMAB), estimated Pseudomonas spp. and Enterococcus spp. were counted in Shp-S by classical cultural counting on agar medium, where the counts were 6.56 ± 0.09, 6.30 ± 0.12, and 3.15 ± 0.03 CFU/g, respectively. Fourier Transform Infrared (FTIR) Spectroscopy and Scanning Electron Microscopy (SEM)/Energy dispersed X-ray (EDX) were used to assess the surface chemistry/functional groups and morphological structure for ChTfree (non-microorganism), and ChTmo (with microorganisms). ChTfree FTIR spectra presented a detailed chitin structure by OH, NH, and CO stretching vibrations, whereas specific peaks of chitin could not be detected in ChTmo. Major differences were also found in SEM analysis for ChTfree and ChTmo. ChTfree had a flat, prominent micropore, partially homogeneous structure, while ChTmo had a layered, heterogeneous, complex dense fibrous, and lost pores form. The degree of deacetylation was calculated for ChTfree and ChTmo according to FTIR and EDX data. The results suggest that the degree of deacetylation decreases in the presence of microorganisms, affecting the production of beneficial components negatively. The findings were also supported by the molecular docking model.

A comprehensive review on the utilization of probiotics in aquaculture towards sustainable shrimp farming

Probiotics in shrimp aquaculture have gained considerable attention as a potential solution to enhance production efficiency, disease management, and overall sustainability. Probiotics, beneficial microorganisms, have shown promising effects when administered to shrimp as dietary supplements or water additives. Their inclusion has been linked to improved gut health, nutrient absorption, and disease resistance in shrimp. Probiotics also play a crucial role in maintaining a balanced microbial community within the shrimp pond environment, enhancing water quality and reducing pathogen prevalence. This article briefly summarizes the many ways that probiotics are used in shrimp farming and the advantages that come with them. Despite the promising results, challenges such as strain selection, dosage optimization, and environmental conditions are carefully addressed for successful probiotic integration in shrimp aquaculture. The potential of probiotics as a sustainable and ecologically friendly method of promoting shrimp development and health while advancing environmentally friendly shrimp farming techniques is highlighted in this analysis. Further research is required to fully exploit probiotics' benefits and develop practical guidelines for their effective implementation in shrimp aquaculture.

Shrimp Waste Upcycling: Unveiling the Potential of Polysaccharides, Proteins, Carotenoids, and Fatty Acids with Emphasis on Extraction Techniques and Bioactive Properties

Shrimp processing generates substantial waste, which is rich in valuable components such as polysaccharides, proteins, carotenoids, and fatty acids. This review provides a comprehensive overview of the valorization of shrimp waste, mainly shrimp shells, focusing on extraction methods, bioactivities, and potential applications of these bioactive compounds. Various extraction techniques, including chemical extraction, microbial fermentation, enzyme-assisted extraction, microwave-assisted extraction, ultrasound-assisted extraction, and pressurized techniques are discussed, highlighting their efficacy in isolating polysaccharides, proteins, carotenoids, and fatty acids from shrimp waste. Additionally, the bioactivities associated with these compounds, such as antioxidant, antimicrobial, anti-inflammatory, and antitumor properties, among others, are elucidated, underscoring their potential in pharmaceutical, nutraceutical, and cosmeceutical applications. Furthermore, the review explores current and potential utilization avenues for these bioactive compounds, emphasizing the importance of sustainable resource management and circular economy principles in maximizing the value of shrimp waste. Overall, this review paper aims to provide insights into the multifaceted aspects of shrimp waste valorization, offering valuable information for researchers, industries, and policymakers interested in sustainable resource utilization and waste-management strategies.

Bio-reductive synthesis of silver nanoparticles, its antibacterial efficiency, and possible toxicity in common carp fish (Cyprinus carpio)

The biological synthesis of nanoparticles is an emerging field of study that seeks to synthesize nanoparticles using non-chemical mechanisms such as microorganisms, plants, and animal blood serum. Among these, plants have gained particular attention due to their ease of handling, availability, and ability to synthesize a wide range of nanoparticles. Therefore, the current study aimed to fabricate the silver nanoparticles (AgNPs) using Chinese medicinal plants (CMP) for their possible toxicity in common carp fish (Cyprinus carpio). For this purpose, CMP was dried, ground, and used as a bio-reductive agent. The fabricated AgNPs were characterized and a well dispersed AgNPs were obtained. Moreover, the C. carpio was exposed to the AgNPs for bioaccumulation and histological alterations. The obtained findings revealed that the AgNPs were mostly accumulated in the intestines followed by the gills, muscles, liver, and brain. The accumulated AgNPs caused histological alterations in gills and intestines at the highest concentration (0.08 mg/L). However, very less alterations were caused by the lowest concentration, especially in the intestine. In conclusion, further in-depth research is needed to determine the risks associated with the usage of nanoparticles to reveal their harmful impacts on fish and the aquatic environment. HIGHLIGHTS: The biological fabrication of AgNPs is considered eco-friendly. Chinese medicinal plants play a significant role in AgNPs synthesis. AgNPs have excellent antibacterial activity. AgNPs are bioaccumulated in various organs of fish.

Enterocytozoon hepatopenaei Infection in Shrimp: Diagnosis, Interventions, and Food Safety Guidelines

The emergence of disease in shrimp has governed much concern in food safety and security among consumers with the recent reports on hepatopancreatic microsporidiosis (HPM) caused by Enterocytozoon hepatopenaei (EHP). The microsporidians present in shrimp remain a silent pathogen that prevents optimal shrimp growth. However, the biggest threat is in its food safety concerns, which is the primary focus in ensuring food biosecurity and biosafety. Hence, the objective of this review is to summarise the current knowledge of EHP and its infection in shrimp with food safety concerns. This paper provides an analysis of the diagnostic methods for detecting EHP infections in shrimp aquaculture. Interventions with current molecular biology and biotechnology would be the second approach to addressing EHP diseases. Finally, a systematic guideline for shrimp food safety using diagnostic and intervention is proposed. Thus, this review was aimed to shed light on effective methods for the diagnosis and prevention of EHP infection in shrimp. We also include information on molecular and genomics tools as well as innate immune biomolecules as future targets in the intervention strategies on the microsporidsosis life cycle in shrimp and its environment. Overall, this will result in reduced disease outbreaks in shrimp aquaculture, ensuring the shrimp food safety in the future.

Gross yield driving the mass fluxes of fishery drugs: Evidence of occurrence from full aquaculture cycle in lower Yangtze River Basin

Expanding aquaculture has generated pollutants like fishery drugs in wastewater, which affects the aquatic environments and hinders sustainable development of aquaculture. To evaluate the occurrence, mass fluxes and production factors of fishery drugs in aquaculture, full-aquaculture-cycle monitoring in finfish and crustacean wastewater was conducted in the lower Yangtze River Basin, and 28 pesticides and 15 antibiotics were detected. The results showed that individual fishery drugs varied from ppt to ppb levels. Among them, sulfonamides were dominant with a mean concentration of 105.95 ± 4.13 ng·L-1 in finfish aquacultural wastewater, and insecticides were prevailing in crustacean aquacultural wastewater with a content of 146.56 ± 0.66 ng·L-1. Since the susceptibility to finfish disease determined the aquaculture practice, there were significant differences between two types of aquacultural wastewater. Finfish aquacultural wastewater contained more drugs and reached peak earlier in rapid-growth period, yet crustacean aquacultural wastewater peaked at the harvest period, to prevent against disease. Meanwhile, higher ecological risk, especially for florfenicol, were found in finfish wastewater. With 6 production factors from Good Aquaculture Practice, the gross yield was the most influential factor of drug mass flux, explaining 98 % variance by stepwise regression. Apart from increasing concentrations of fishery drugs in wastewater, regional high-yield aquaculture also significantly impacted the corresponding mass flux. As estimated by linear regression, 1.63 tons of target drugs would be discharged by 1 Mt. aquatic products, and 7.77 tons were discharged from aquaculture in the lower Yangtze River Basin in 2021. This is the first report to quantify mass fluxes of fishery drugs and to highlight gross yield as the most influential factor, which provides guidance for the supervision and regulation of sustainable aquaculture.

Effects of β-1,3-glucan on growth, immune responses, and intestinal microflora of the river prawn (Macrobrachium nipponense) and its resistance against Vibrio parahaemolyticus

In this study, we investigated the impact of β-1,3-glucan on the immune responses and gut microbiota of the river prawn (Macrobrachium nipponense) in the presence of Vibrio parahaemolyticus stress. Shrimps were fed one of the following diets: control (G1), 0.2% curdlan (G2), 0.1% β-1,3-glucan (G3), 0.2% β-1,3-glucan (G4), or 1.0% β-1,3-glucan (G5) for 6 weeks and then challenged with V. parahaemolyticus for 96 h. Under Vibrio stress, shrimps in G4 exhibited the highest length gain rate, weight gain rate, and survival rate. They also showed increased intestinal muscle thickness and villus thickness compared to the control and 0.2% curdlan groups. The apoptosis rate was lower in G4 than in the control group, and the digestive enzyme activities (pepsin, trypsin, amylase, and lipase), immune enzyme activities (acid phosphatase, alkaline phosphatase, lysozyme, and phenoxidase), and energy metabolism (triglyceride, cholesterol, glycogen, and lactate dehydrogenase) were enhanced. Expression levels of growth-related genes (ecdysone receptor, calmodulin-dependent protein kinase I, chitin synthase, and retinoid X receptor) and immune-related genes (toll-like receptor 3, myeloid differentiation primary response 88, mitogen-activated protein kinase 7, and mitogen-activated protein kinase 14) were higher in G4 than in the control. Microbiota analysis indicated higher bacterial abundance in shrimps fed β-1,3-glucan, as evidenced by Sob, Chao1, and ACE indices. Moreover, 0.2% β-1,3-glucan increased the relative abundances of Bacteroidota and Firmicutes while reducing those of Corynebacteriales and Lactobacillales. In summary, β-1,3-glucan enhances immune enzyme activities, alters immune-related gene expression, and impacts gut microbial diversity in shrimp. These findings provide valuable insights into the mechanisms underlying β-1,3 glucan's immune-enhancing effects.

Application of rhein as an immunostimulant controls spring viremia of carp virus infection

In recent years, the exploration of natural compounds possessing both immunostimulatory and antiviral activities has attracted growing attention in aquaculture research. Consequently, the pursuit of identifying natural products exhibiting anti-SVCV potential as immunostimulants holds significant promise, offering a pathway to mitigate the economic ramifications inflicted by SVCV outbreaks in aquaculture settings. Among them, rhein emerges as a particularly compelling contender. Boasting a widespread distribution, well-established extraction methods, and multiple biological activities, it has exhibited the capacity to enhance the antiviral activity of host cells in vitro by blocking the viral internalization process, with a peak inhibition rate of 44.0%. Based on this intervention, rhein inhibited apoptosis and mitochondrial damage triggered by SVCV infection, ultimately producing a significant antiviral effect. Moving beyond the laboratory setting, rhein's efficacy translates effectively into in vivo scenarios. It has demonstrated substantial antiviral potency by increasing the expression of antiviral-related genes, most notably, retinoic acid-inducible gene I (RIG-I), interferon-φ (IFN-φ) and IFN-stimulated gene product 15 (ISG15). In concert with this genetic modulation, rhein efficiently reduces the viral load, precipitating a consequential enhancement in the survival rate of SVCV-infected fish, elevating it to an encouraging 16%. In conclusion, the outcomes of our investigation offer a compelling testament to rhein's potential as a valuable immunomodulator in the battle against SVCV infections in aquaculture, and the remarkable attributes exhibited by rhein underscore its viability for future commercial deployment.

Exploring the recent developments of alginate silk fibroin material for hydrogel wound dressing: A review

Hydrogels, a type of polymeric material capable of retaining water within a three-dimensional network, have demonstrated their potential in wound healing, surpassing traditional wound dressings. These hydrogels possess remarkable mechanical, chemical, and biological properties, making them suitable scaffolds for tissue regeneration. This article aims to emphasize the advantages of alginate, silk fibroin, and hydrogel-based wound dressings, specifically highlighting their crucial functions that accelerate the healing process of skin wounds. Noteworthy functions include self-healing ability, water solubility, anti-inflammatory properties, adhesion, antimicrobial properties, drug delivery, conductivity, and responsiveness to stimuli. Moreover, recent advancements in hydrogel technology have resulted in the development of wound dressings with enhanced features for monitoring wound progression, further augmenting their effectiveness. This review emphasizes the utilization of hydrogel membranes for treating excisional and incisional wounds, while exploring recent breakthroughs in hydrogel wound dressings, including nanoparticle composite hydrogels, stem cell hydrogel composites, and curcumin-hydrogel composites. Additionally, the review focuses on diverse synthesis procedures, designs, and potential applications of hydrogels in wound healing dressings.

Potential dsRNAs can be delivered to aquatic for defense pathogens

The use of antibiotics to facilitate resistance to pathogens in aquatic animals is a traditional method of pathogen control that is harmful to the environment and human health. RNAi is an emerging technology in which homologous small RNA molecules target specific genes for degradation, and it has already shown success in laboratory experiments. However, further research is needed before it can be applied in aquafarms. Many laboratories inject the dsRNA into aquatic animals for RNAi, which is obviously impractical and very time consuming in aquafarms. Therefore, to enable the use of RNAi on a large scale, the methods used to prepare dsRNA need to be continuously in order to be fast and efficient. At the same time, it is necessary to consider the issue of biological safety. This review summarizes the key harmful genes associated with aquatic pathogens (viruses, bacteria, and parasites) and provides potential targets for the preparation of dsRNA; it also lists some current examples where RNAi technology is used to control aquatic species, as well as how to deliver dsRNA to the target hydrobiont.

Improvement of Moist Heat Resistance of Ascorbic Acid through Encapsulation in Egg Yolk–Chitosan Composite: Application for Production of Highly Nutritious Shrimp Feed Pellets

Simple Summary

Egg yolk (EY) is an excellent supplement for aquatic animals and has good food functionality. According to the high lipid content in EY, it was, for the first time, used in combination with chitosan (CS) to encapsulate the ascorbic acid (AA) to minimize the loss of AA during exposure to feed processing and seawater. The microcapsules’ production yield, EE, and moist heat resistance were evaluated. One selected encapsulated AA was fortified in shrimp feed. The AA retention in feed processing and seawater was evaluated. Both EE and production yields of the microcapsules were relatively high compared to other reports. Moist heat resistance capability of the encapsulated AA was up to 82%. EY was essential in moist heat protection, while CS significantly improved the microcapsules’ production yield, EE, and morphology. The loss of AA in feed processing and seawater was remarkably improved by 16 folds compared to the unencapsulated AA. The microcapsules showed high potential application for foods and aquatic feed to protect heat-labile and hydro-soluble substances.

Abstract

Egg yolk (EY) is an excellent supplement for aquatic animals and has good technofunctionality. Ascorbic acid (AA) is a potent bioactive substance and is essentially added to shrimp feed; however, it is drastically lost in both feed processing and in rearing environments. In this study, AA was microencapsulated in an EY–chitosan (CS) composite. The encapsulated vitamin was then mixed into a shrimp feed mixture to form pelleted feed via twin-screw extrusion. The effects of the EY/AA ratio and the amount of CS on moist heat resistance, production yield, encapsulation efficiency (EE), and morphology of microcapsules were investigated. The molecular interaction of the microcapsule components was analyzed by FTIR. The size and size distribution of the microcapsules were determined using a laser diffraction analyzer. The microstructure was evaluated by SEM. The physical properties of the microcapsule-fortified pelleted feed were determined. The AA retention at each step of feed processing and during exposure to seawater was evaluated. The results showed that the microcapsules had a spherical shape with an average diameter of ~6.0 μm. Decreasing the EY/AA ratio significantly improved the production yield, EE, and morphology of the microcapsules. EY proved to be the key component for moist heat resistance, while CS majorly improved the production yield, EE, and morphology of the microcapsules. The microcapsules showed no adverse impact on feed properties. The loss of AA in food processing and seawater was remarkably improved. The final content of the encapsulated AA remaining in shrimp feed was 16-fold higher than that of the unencapsulated AA.

RNA Nanovaccine Protects against White Spot Syndrome Virus in Shrimp

In the last 15 years, crustacean fisheries have experienced billions of dollars in economic losses, primarily due to viral diseases caused by such pathogens as white spot syndrome virus (WSSV) in the Pacific white shrimp Litopenaeus vannamei and Asian tiger shrimp Penaeus monodon. To date, no effective measures are available to prevent or control disease outbreaks in these animals, despite their economic importance. Recently, double-stranded RNA-based vaccines have been shown to provide specific and robust protection against WSSV infection in cultured shrimp. However, the limited stability of double-stranded RNA is the most significant hurdle for the field application of these vaccines with respect to delivery within an aquatic system. Polyanhydride nanoparticles have been successfully used for the encapsulation and release of vaccine antigens. We have developed a double-stranded RNA-based nanovaccine for use in shrimp disease control with emphasis on the Pacific white shrimp L. vannamei. Nanoparticles based on copolymers of sebacic acid, 1,6-bis(p-carboxyphenoxy)hexane, and 1,8-bis(p-carboxyphenoxy)-3,6-dioxaoctane exhibited excellent safety profiles, as measured by shrimp survival and histological evaluation. Furthermore, the nanoparticles localized to tissue target replication sites for WSSV and persisted through 28 days postadministration. Finally, the nanovaccine provided ~80% protection in a lethal WSSV challenge model. This study demonstrates the exciting potential of a safe, effective, and field-applicable RNA nanovaccine that can be rationally designed against infectious diseases affecting aquaculture.