Shrimp Aquaculture Research Articles

The Hippo-Yki Signaling Pathway Positively Regulates Immune Response against Vibrio Infection in Shrimp.

In the Hippo pathway, activation of Hippo and Warts (Wts) kinases results in the phosphorylation of Yorkie (Yki), to prevent its nuclear translocation. Shrimp aquaculture is threatened by Vibrio genus bacteria. In this study, we examine the role of the Hippo pathway in immune defense against Vibrio parahaemolyticus in Pacific white shrimp Penaeus vannamei. We show that V. parahaemolyticus infection promotes the expression of Yki and facilitates the dephosphorylation and nuclear translocation of Yki, indicating the inhibition of Hippo signaling upon bacterial infection. There is a complex regulatory relationship between the Hippo pathway components Hippo, Wts, and Yki and the immune-related transcription factors Dorsal, Relish, and STAT. Silencing of Hippo and Wts weakened hemocyte phagocytosis, while the silencing of Yki enhanced it, suggesting a positive regulation of shrimp cellular immunity by Hippo signaling activation. In vivo silencing of Hippo and Wts decreased the survival rates of V. parahaemolyticus-infected shrimp and elevated the bacterial content in tissues, while the silencing of Yki showed the opposite results. This suggests that the activation of Hippo signaling and the inhibition of Yki enhance antibacterial immunity in shrimp.

The loud crowd: Interactions between stocking density and acoustic feeding activity of different size classes of Litopenaeus vannamei

Passive acoustic monitoring (PAM) has been used to evaluate Litopenaeus vannamei feeding activity, as shrimp mandibles emit click sounds during food ingestion. PAM has also been used as a tool to estimate the population density of several aquatic species. Although stocking density is an important factor in shrimp farming, there is no information about its effect on shrimp acoustics during feeding activity. The present study aimed to explore the interactions between stocking density and acoustic activity of L. vannamei of different size classes under laboratory conditions. The trials were conducted in three circular fiberglass tanks using three shrimp stocking densities (50, 100 and 150 shrimp m−2) and four size classes (1, 3, 9 and 12 g). Recordings of feeding activity were carried out using omnidirectional hydrophones (sampling rate: 96 kHz; 16 bits) installed in each trial tank and lasted 30 min. Shrimp were fed with commercial pelleted diet and the uneaten food was collected to calculate the food consumption at the end of each recording. The clicks emitted by shrimp during acoustic recordings were automatically detect using Raven® acoustic software. The shrimp acoustic activity started immediately upon feed was offered, reaching the maximum click emission rate during the first minute and lasting up to about 10 min. The clicking emission rate shown a significant progressive increase from the lowest to the highest shrimp size class and stocking density, suggesting that a calibration approach can be applied to predict the population density when feeding sound signals are detectable. Significantly linear relationships between food consumption and number of clicks emitted by all size classes and stocking densities confirms that PAM is a feasible tool to estimate shrimp feed intake. Taken together, the present findings provide novel information about interactions between stocking density and acoustic activity that can contribute to research and development of feeding management in shrimp aquaculture.

Coordinated pattern of multiple element variability in Aegiceras corniculatum propagule in shrimp aquaculture effluent habitats

Human activities and environment changes have changed river estuary ecosystems, which impacts element changes in coastal sediments and mangroves. Mangrove propagule chemical traits showed a systematic shift along environmental gradients. But knowledge about how the pattern of multi-element variability is coordinated in propagule remains limited, and the conservation of macro and trace elements in propagules is also unknown. In this study, the concentrations, variability and coordinated pattern variation of 13 elements in Aegiceras corniculatum propagule across shrimp aquaculture effluent habitats, as well as the relationship between propagule element and environment factors were explored. We used CV to quantify the variability of each element, and then explore the pattern of multi-element variability. The results showed that: (1) in the habitats affected by shrimp aquaculture, the elements content shows: C > K > Cl > N > Na > P > S > Mg > Ca > Fe > Mn > Zn > Cu, and the coefficient variation shows: Mn > Cu > Fe > Zn > S > N > P > Cl > Na > K > Mg > Ca > C, which means that the element concentration are negatively correlated with the element variability and the variability of macro-elements was more conservative than micro-elements in these habitats; (2) pH, OM, C:P, and SiO32− were the four important environmental factors explaining the A. corniculatum propagule variation. In conclusion, effluent from shrimp aquaculture does affect the coordinated pattern of multiple element variability in A. corniculatum propagules. These results provide a strong evidence for assessing the impact of shrimp aquaculture effluent discharges on mangrove and provide an important theoretical basis for mangrove conservation and restoration.

A Broad-Host-Range Phage Cocktail Selectively and Effectively Eliminates Vibrio Species from Shrimp Aquaculture Environment.

The protective effects of a phage cocktail composed of vB_Vc_SrVc2 and vB_Vc_SrVc9 were tested in Pacific white shrimp (Litopenaeus vannamei) postlarvae, which were originally isolated from diseased shrimps and selected due to their broad-host-range properties against several pathogenic Vibsrio species. We used culture-dependent and culture-independent approaches to explore its effect on bacterial communities associated with shrimp postlarvae. Both methods revealed that the levels of Vibrio species were significantly reduced after phage cocktail administration. Phage-treated shrimp also exhibisuppted lesser damage and higher lipid accumulation in B cells of the hepatopancreas, as revealed by histopathological examination. Taken together, this study provides clear evidence that phage therapy can selectively and effectively reduce Vibrio species, thereby providing an environmentally safe alternative to the prophylactic use of antibiotics in shrimp aquaculture.

A simple culture technique of Rhodobacter azotoformans EBN-7 for public use: application to NH4+-N removal in shrimp aquaculture water

Photosynthetic bacteria (PSB) attract considerable interest as useful microorganisms; nevertheless, a generalized culture technique has not been previously reported owing to difficulty in their cultivation. Therefore, a simple culture technique suitable for public use was investigated. Among the PSB tested, the strain Rhodobacter azotoformans EBN-7 was the most suitable for scaleup production because it showed the highest specific growth rate (0.20 h−1) on basal medium. In scale-up cultivation (500 L), R. azotoformans EBN-7 showed 4.50 × 1010 colony-forming units mL−1 (number of viable cells), dry cell weight of 26.8 g/L, and a specific growth rate of 0.15 h−1. Cultivation using this final culture broth (as seed culture) in a 15 L simple reactor was successful, with maintenance of cell activity evident. For use as seed culture, the maximum allowable preservation period of R. azotoformans EBN-7 at 4°C was 3 months. When R. azotoformans EBN-7 cultivated in a simple technique was applied to shrimp aquaculture water, NH4+-N was reduced from 0.61 mg/L to 0.24 mg/L (by 60.7%) in 4 days in comparison with the control. Thus, this simple culture technique using R. azotoformans EBN-7 has the potential for a good removal efficiency of NH4+-N, making seed culture easier and suitable for public use.

Farmed shrimp aquaculture in coastal wetlands of Latin America - A review of environmental issues.

The world production of farmed Whiteleg shrimp was 5,812,180t in 2020. Ecuador, Mexico, and Brazil produced 1,012,830 in that year according to data FishStatJ. Environmental impact studies were scarce given the rapid growth of this activity, mainly on cummulative impacts, loss of ecosystems services or resilience of wetlands and mangroves. Aspects of the management of environmental impacts published on American studies during 1986-2020 are analyzed. The main impacts included the loss of mangroves and their transformation of these ecosystems and their water bodies by receiving enriched effluents from shrimp farms. Different management measures are discussed between Ecuador, which contributes 63.76% of American production of white leg shrimp; Brazil which published 46.2% of the environmental studies of the analyzed period, and Mexico, in an intermediate situation. Finally, alternatives are discussed to improve the management of shrimp aquaculture with emphasis on the Ecuadorian context.

Phytochemical and Antibacterial Effects of Leaf Extract from Mangrove Plant (Avicennia Marina) on Vibrio Parahaemolyticus in Shrimps

Recently, there has been a tremendous increase in the studies addressing the application of bioactive compounds from the natural ecosystem, particularly for medical purposes. Hence, the present study investigated the antibacterial properties of the secondary metabolites possibly contained in the leaves of Avicennia marina (A. marina) for possible prevention of Vibrio parahaemolyticus (V. parahaemolyticus), a devastating bacterial pathogen in shrimp aquaculture. In the current study, secondary metabolites were extracted from the leaves of mangrove plant using ethanol extraction method. The ethanolic extracts were then subjected to phytochemical and antibacterial activity tests. The results from the phytochemical analysis demonstrated that the ethanolic extract from the mangrove plant contained varying amounts of flavonoids, tannins, saponins, polyphenols, alkaloids, steroids, and triterpenoids. However, the number of flavonoids and alkaloids seemed to be higher than the other metabolites. The antibacterial activity analysis through the agar diffusion method has shown that different concentrations (50 ppm, 100 ppm, 200 ppm, and 300 ppm) of the ethanolic extract of A. marina inhibited the V. parahaemolyticus. At 300 ppm, the plant extract exhibited 17.3% antibacterial effectiveness, compared to the antibacterial activity of chloramphenicol. The findings indicated that the secondary metabolites of A. marina have the potential that can be developed as an alternative treatment for aquatic animal diseases in the future.

A modification of nested PCR method for detection of Enterocytozoon hepatopenaei (EHP) in giant freshwater prawn Macrobrachium rosenbergii.

The microsporidian Enterocytozoon hepatopenaei (EHP) has become a critical threat to the global shrimp aquaculture industry, thus necessitating early detection by screening. Development of a rapid and accurate assay is crucial both for the active surveillance and for the assessment of shrimp with EHP infection. In the present study, a distinct strain of E. hepatopenaei (EHP Mr ) was found in Macrobrachium rosenbergii. The SWP1 gene analysis revealed it was a new genotype that differed with the common strain isolated from the Litopenaeus vannamei (EHP Lv ). A nested SWP-PCR method was modified to fix the bug that the original inner primers could not recognize the EHP Mr strain. The redesigned inner primers successfully amplified a product of 182 bp for both the EHP Mr strain and the EHP Lv strain. The new primers also had good specificity and high sensitivity, which may serve as an alternative for EHP genotyping. This study provided a method for detection of EHP in the biosecurity of Macrobrachium rosenbergii farming, and the developed protocol was proposed for the routine investigation and potential carrier screening, especially for molecular epidemiology.

How a holobiome perspective could promote intensification, biosecurity and eco-efficiency in the shrimp aquaculture industry

The aquaculture industry faces many challenges regarding the intensification of shrimp rearing systems. One of these challenges is the release of excessive amounts of nitrogen and phosphorus into coastal areas, causing disruption in nutrient cycling and microbial equilibrium, which are important for coastal productivity. Biosecurity within the shrimp rearing systems can also be compromised by disruption to the nutrient fluxes, and as consequence the microbiome of the system. In certain conditions, these changes could lead to the blooming of potentially pathogenic bacteria. These changes in the external microbiome of the system and the constant fluctuations of nutrients can affect the intestinal microbiome of shrimp, which is involved in the growth and development of the host, affecting nutrient absorption, regulating metabolic processes, synthesising vitamins, modulating the immune response and preventing growth of pathogenic bacteria. It has been suggested that specific changes in the intestinal microbiome of Litopenaeus vannamei may be an avenue through which to overcome some of the problems that this industry faces, in terms of health, growth and waste. Recent research, however, has focussed mainly on changes in the intestinal microbiome. Researchers have overlooked the relevance of other aspects of the system, such as the microbiome from the benthic biofilms; zooplankton, plankton and bacterioplankton; and other sources of microorganisms that can directly affect the microbial status of the intestinal and epiphytic communities, especially in rearing systems that are based on intensification and microbial maturation processes, such as a biofloc system. It is therefore necessary to place holobiome studies into context, including the ‘holobiome of the aquaculture system’ (microbiomes that make up the culture system and their interactions) and not only the intestinal microbiome. Thus, we describe factors that affect the shrimp microbiome, the methodology of study, from sampling to bioinformatic workflows, and introduce the concept of the ‘holobiome of the aquaculture system’ and how this enables us to promote the intensification, biosafety and eco-efficiency of shrimp farming. The holobiome perspective implies a greater investment of resources and time for research, but it will accelerate the development of technology that will benefit the development and sustainability of the aquaculture industry.

Evaluation of dietary Haematococcus pluvialis in pilot-scale farming of Litopenaeus vannamei: Effects on production performance, physiological health, bacterial communities, and eukaryotic plankton

The dried Haematococcus pluvialis (H. pluvialis) powder rich in astaxanthin is widely investigated as a promising feed additive or ingredient for improving growth, health, feed efficiency, and pigmentation of aquatic animals under the controlled laboratory conditions, whereas few studies have reported its practical application efficacy in shrimp aquaculture. Hence, this study aimed to evaluate the practical effects of supplementation of 3.0 g H. pluvialis kg−1 diet (47.6 mg astaxanthin kg−1 diet) on water quality, production performance, health status, amino acids profile, bacterial communities, and eukaryotic plankton in the pilot-scale farming of Litopenaeus vannamei. After 45-day feeding, supplemental dietary H. pluvialis significantly enhanced the harvested biomass, survival rate, feed conversion ratio, and yield of shrimp farming, with no significant impacts on water quality parameters. The hepatopancreas antioxidant capacity and muscle essential amino acids of shrimp were also improved with dietary H. pluvialis supplementation, especially the decreased malondialdehyde and the increased arginine with statistical significance. The addition of dietary H. pluvialis changed bacterial communities with the dramatical variations of dominant phyla including Proteobacteria, Bacteroidetes, Cyanobacteria, and Actinobacteria in rearing water, shrimp intestine, and faeces. Likewise, dietary H. pluvialis significantly affected eukaryotic plankton with the decreased microalgae Picochlorum (class Trebouxiophyceae) and the increased protozoon Euplotes (family Euplotidae) in rearing water. Moreover, the correlation analysis suggested that the enhanced production performance was closely associated with the significant improvements in shrimp antioxidant status, muscle amino acid profile, and intestinal microflora composition with dietary H. pluvialis addition. This study may provide valuable information for further practical application of H. pluvialis in larger commercial-scale production of L. vannamei farming.

Exploring bacterioplankton communities and their temporal dynamics in the rearing water of a biofloc-based shrimp (Litopenaeus vannamei) aquaculture system.

Biofloc technology (BFT) has recently gained considerable attention as a sustainable method in shrimp aquaculture. In a successful BFT system, microbial communities are considered a crucial component in their ability to both improve water quality and control microbial pathogens. Yet, bacterioplankton diversity in rearing water and how bacterioplankton community composition changes with shrimp growth are rarely documented. In this study, the Pacific white shrimp, Litopenaeus vannamei was cultivated in a greenhouse-enclosed BFT system. Rearing water samples were collected on a weekly basis for 5 months (152 days) and water quality variables such as physicochemical parameters and inorganic nutrients were monitored. In parallel, 16S rRNA gene pyrosequencing was employed to investigate the temporal patterns of rearing-water microbiota. The productivity, survival rate, and feed conversion ratio were 3.2–4.4 kg/m3, 74%–89%, and 1.2–1.3, respectively, representing successful super-intensive cultures. The metataxonomic results indicated a highly dynamic bacterioplankton community, with two major shifts over the culture. Members of the phylum Planctomycetes dominated in rearing water during the early stages, while Actinobacteria dominated during the middle stages, and Chloroflexi and TM7 dominated during the late stages of culture. The bacterioplankton community fluctuated more in the beginning but stabilized as the culture progressed. Intriguingly, we observed that certain bacterioplankton groups dominated in a culture-stage-specific manner; these groups include Rhodobacteraceae, Flavobacteriaceae, Actinobacteria, and Chloroflexi, which either contribute to water quality regulation or possess probiotic potential. Altogether, our results indicate that an operationally successful BFT-based aquaculture system favors the growth and dynamics of specific microbial communities in rearing water. Our study expands the scientific understanding of the practical utilization of microbes in sustainable aquaculture. A thorough understanding of rearing-water microbiota and factors influencing their dynamics will help to establish effective management strategies.

Characterization of Lactic Acid Bacteria from the Gut of Penaeus vannamei as Potential Probiotic

Background: The present objective of the study was to isolate and characterize the gut associated culturable lactic acid bacteria (beneficial bacteria) from the gut of Penaeus vannamei for their potential application as probiotic. Methods: Penaeus vannamei (host) gut associated bacterial isolates were obtained from ten commercial brackishwater shrimp ponds (n=10) located in Kanchipuram, Chengalpattu, Tiruvallur and Villupuram districts of Tamil Nâdu, during 2021-22 to test their efficiency as indigenous gut probiotic. Twenty-five shrimps from each pond, with salinity ranging from 5 to 25 ppt, were collected for isolation of beneficial bacterial isolates. Result: Thirty lactic acid bacteria were isolated and identified from the gut of 250 Penaeus vannamei, using a 16S ribosomal DNA sequence. Six isolates viz., Pediococcus pentosaceus (ON495586), Lactiplantibacillus plantarum (ON491817), Lactococcus lactis (ON479264), Enterococcus faecium (ON478992), Enterococcus hirae (ON478991) and Enterococcus durans (ON564885) having better enzyme activity were taken and further subjected to in vitro analysis. It was found that these isolates had antibacterial activity against shrimp pathogens V. campbelli, V. harveyi and V. parahaemolyticus with zone of inhibition ranging between 12.33 to 21.00 mm; showed better growth at pH 7.0; tolerated the bile salts up to 1% concentration and endured salt concentrations up to 6.0%. In addition, above isolates demonstrated excellent auto-aggregative activity (74.45 to 91.14%) and hydrophobicity (77 to 99.93%). No antagonist activities were detected among the strains, suggesting its use as the multiple cocktail probiotic. Hence, the investigated isolates could serve as potential probiotics in shrimp aquaculture production systems.

Stimulatory effect of peritrophin on vitellogenesis in female banana shrimp, Fenneropenaeus merguiensis

Glass bottom boat (Gbb) is a member of the transforming growth factor β family that plays several physiological roles in arthropods, including in reproduction. Recently, Fenneropenaeus merguiensis's Gbb (FmGbb) was demonstrated to play a stimulatory role in vitellogenesis of the banana shrimp, but potential partners of FmGbb have not been identified. Therefore, this study aimed to identify proteins that interact with FmGbb and characterize their gonad-regulating function. A yeast two-hybrid assay revealed three potential candidates: peritrophin (FmPT), polehole-like protein (FmPhl), and an uncharacterized protein. Expressions of FmPT and FmPhl were found mainly in the ovaries and significantly increased in the developing stages. However, in a GST-pull down assay, there was no protein–protein interaction between soluble recombinant glutathione-S transferase-fused FmPT (GST-rPT) protein and the recombinant FmGbb protein (His-TF-rgbb). The vitellogenesis stimulatory role of FmPT was then investigated both in vitro and in vivo. Ovarian explants treated with GST-rPT showed no significant change of vitellogenin (Vg) expression, but the injection of GST-rPT in ovaries and hepatopancreas of previtellogenic shrimp did induc Vg expression, suggesting a vitellogenesis stimulating activity of FmPT. Our findings show that FmPT has a novel role in vitellogenesis stimulation and has the potential to be developed as a gonad-stimulating bioproduct for use in shrimp aquaculture.

Pathogenicity and transcriptome analysis of a strain of Vibrio owensii in Fenneropenaeus merguiensis

Vibrio is an important conditional pathogen in shrimp aquaculture. This research reported a dominant bacteria strain E1 isolated from a shrimp tank with the method of biofloc culture, which was further identified as Vibrio owensii. To understand the interaction between V. owensii and the host shrimp, we studied the pathogenicity of the V. owensii and the molecular mechanisms of the Fenneropenaeus merguiensis immunity during the Vibrio invasion. Drug susceptibility tests showed that V. owensii was resistant to antibiotics streptomycin oxacillin, tetracycline, minocycline, and aztreonam, but highly sensitive to cefazolin, cefotaxime, and ciprofloxacin, and moderately sensitive to cefotaxime, ampicillin, and piperacillin. Lethal concentration 50 (LC50) test was performed to evaluate the toxicity of V. owensii to F. merguiensis. The LC50 of V. owensii infected F. merguiensis after 24, 48, 72, 96, 120, 144 and 168 h were 1.21 × 107, 1.68 × 106, 6.36 × 105, 2.15 × 105, 7.58 × 104, 5.55 × 104 and 4.33 × 104 CFU/mL. In order to explore the molecular response mechanism of F. merguiensis infected with V. owensii, the hepatopancreas of F. merguiensis were sequenced at 24 hpi and 48 hpi, and a total 40,181 of unigenes were obtained. Through comparative transcriptomic analysis, 86 differentially expressed genes (DEGs) (including 38 up-regulated DEGs, and 48 down-regulated DEGs) and 305 DEGs (including 150 up-regulated DEGs, and 155 down-regulated DEGs) were identified at 24 hpi and 48 hpi, respectively. Annotation and classification analysis of these 391 DEGs showed that most of the DEGs were annotated to metableolic and immune pathways, which indicated that F. merguiensis responded to the invasion through the regulation of material metableolism and immune system genes during V. owensii infection. In the KEGG enrichment analysis, some pathways related to immune response were significantly influenced by V. owensii infection, including phagosome, MAPK signalling pathway and PI3K-Akt signalling pathway. In addition, some pathways related to the warburg effect were also significantly enriched after V. owensii infection, including pyruvate metableolism, glycolysis/gluconeogenesis, and citrate cycle (TAC cycle). Further analysis showed that C-type lectins and ficolin were also play important roles in the immune response of F. merguiensis against V. owensii infection. The current research preliminarily revealed the immune response of F. merguiensis to V. owensii infection at the molecular level, which provided valuable information to further understand the disease control and the interaction between shrimp and Vibrio.

White spot syndrome virus directly activates mTORC1 signaling to facilitate its replication via polymeric immunoglobulin receptor-mediated infection in shrimp.

Previous studies have shown that the mechanistic target of rapamycin complex 1 (mTORC1) signaling pathway has antiviral functions or is beneficial for viral replication, however, the detail mechanisms by which mTORC1 enhances viral infection remain unclear. Here, we found that proliferation of white spot syndrome virus (WSSV) was decreased after knockdown of mTor (mechanistic target of rapamycin) or injection inhibitor of mTORC1, rapamycin, in Marsupenaeus japonicus, which suggests that mTORC1 is utilized by WSSV for its replication in shrimp. Mechanistically, WSSV infects shrimp by binding to its receptor, polymeric immunoglobulin receptor (pIgR), and induces the interaction of its intracellular domain with Calmodulin. Calmodulin then promotes the activation of protein kinase B (AKT) by interaction with the pleckstrin homology (PH) domain of AKT. Activated AKT phosphorylates mTOR and results in the activation of the mTORC1 signaling pathway to promote its downstream effectors, ribosomal protein S6 kinase (S6Ks), for viral protein translation. Moreover, mTORC1 also phosphorylates eukaryotic translation initiation factor 4E-binding protein 1 (4EBP1), which will result in the separation of 4EBP1 from eukaryotic translation initiation factor 4E (eIF4E) for the translation of viral proteins in shrimp. Our data revealed a novel pathway for WSSV proliferation in shrimp and indicated that mTORC1 may represent a potential clinical target for WSSV control in shrimp aquaculture.

Different disease control methods in shrimp aquaculture: A review

Different disease control methods in shrimp aquaculture: A review

Extracts of Moringa oleifera and Croton californicus against infections of Vibrio parahaemolyticus (IPNGS16) in juvenile Pacific white shrimp (Penaeus vannamei)

We evaluated the inhibition activity of extracts from two common plants, moringa (Moringa oleifera) and croton (Croton californicus), against Vibrio parahaemolyticus (IPNGS16), which causes acute hepatopancreatic necrosis disease (AHPND). The experiment was developed in three phases. First, extracts were prepared, and phytochemical screening of plants was performed. Second, microbiological tests were applied to calculate the minimum inhibitory concentration (MIC). Finally, two bioassays were performed on juvenile shrimp by administering the extracts (first) in shrimp feed at 24 and 72 h, pre-infection, and the second in feed and directly to the culture water. Based on preliminary results of antimicrobial activity, an extract concentration of 60 mg mL-1 inhibited V. parahaemolyticus (IPNGS16) at a final concentration of approximately 1×106 CFU mL-1. Bioassays were carried out in order to determine the V. parahaemolyticus (IPNGS16) median lethal dose (LC50) for juvenile Penaeus vannamei (0.20 ± 0.05 g); the LC50 was 85×103 CFU mL-1. As a first test, the extracts were added to commercial feed at doses of 20, 40, and 60 mg mL-1. After feeding, the shrimp were infected with V. parahaemolyticus (IPNGS16), and mortality was recorded. For the first infection time (24 h), survival was 46 and 33% with croton and moringa, respectively; for the second infection time (72 h), survival was 16 and 25% with croton and moringa. Application of antibacterial extracts directly to culture water were effective against V. parahaemolyticus (IPNGS16). The best result (94% survival) was obtained with a high dose (3.6 mg mL-1 or 30%) of moringa extracts added directly to culture water. Moringa methanol extracts produce active compounds capable of inhibiting replication of V. parahaemolyticus (IPNGS16) in shrimp aquaculture and reducing shrimp mortality.

The emerging pathogen Enterocytozoon hepatopenaei drives a degenerative cyclic pattern in the hepatopancreas microbiome of the shrimp (Penaeus vannamei)

The microsporidian Enterocytozoon hepatopenaei (EHP) is an emerging pathogen that causes substantial economic losses in shrimp (Penaeus spp.) aquaculture worldwide. To prevent diseases in shrimp, the manipulation of the gut microbiota has been suggested. However, prior knowledge of the host-microbiome is necessary. We assessed the modulation of the microbiome (bacteria/fungi) and its predicted functions over the course of disease progression in shrimp experimentally challenged with EHP for 30 days using high throughput 16S rRNA and ITS amplicon sequencing. Infection grade was assessed for the first time by quantitative digital histopathology. According to the infection intensity, three disease-stages (early/developmental/late) were registered. During the early-stage, EHP was not consistently detected, and a high diversity of potentially beneficial microorganisms related to nutrient assimilation were found. In the development-stage, most of the shrimp start to register a high infection intensity related to a decrease in beneficial microorganisms and an increase in opportunistic/pathogenic fungi. During late-stage, animals displayed different infection intensities, showed a displacement of beneficial microorganisms by opportunistic/pathogenic bacteria and fungi related to pathogen infection processes and depletion of energetic reserves. The degenerative cyclic pattern of EHP infection and its effects on beneficial microorganisms and beneficial functions of the shrimp hepatopancreas microbiome are discussed.

Efficacy of alginate immobilized microalgae in the bioremediation of shrimp aquaculture wastewater

Bioremediation is a promising technology for eliminating pollutants from the atmosphere, replacing harmful substances, and preventing contamination. The current study’s primary objective was to see how effective marine microalgae organisms were at absorbing nutrients when cultured in aquaculture wastewater. Bioremediation trials were run with 18 immobilized microalgae at different RT (Reaction Time) of 75, 150, 225, and 300 min. The laboratory scale study demonstrated that microalgae such as Chlorella marina, Tetraselmis suecica and Picochlorum maculatum have the capabilities to remove maximum inorganic NH3-N and NO2-N. The maximum NO3-N reduction was observed in Chlorella marina (13.75–2.18 µmol/L). Reduction in PO43- was improved in Picochlorum maculatum with increasing RT and minimum concentrations of 10.86–2.39 µmol/L. Navicula sp. (20.17–3.11 µmol/L) and Nitzchia microcephala (20.17–4.46 µmol/L) utilized a higher concentration of silicate than other algal species from aquaculture effluents. Maximum Total Nitrogen (TN) and Total Phosphorus (TP) removal efficiency were observed for immobilized Chlorella marina at RT of 300 min. As a result, immobilized microalgae have been seen to be a viable substitute for nutrient remediation of aquaculture wastewater with RT ranging from 75 to 300 min.

Artificial germination of Enterocytozoon hepatopenaei (EHP) spores induced by ions under the scanning electron microscope

Enterocytozoon hepatopenaei (EHP), is an emerging microsporidian pathogen responsible for hepatopancreatic microsporidiasis (HPM) in shrimps and is associated with severe growth retardation. The disease causes economic losses in shrimp aquaculture. In this study, EHP spore germination was induced and demonstrated with a scanning electron microscope (SEM). The ions (cations and anions) generated by high-energy electrons during frozen water radiolysis in the SEM specimen chamber induce EHP spore germination. This study is the first to demonstrate the induction of a microsporidian spore germination by ions generated under SEM. This study will enhance our understanding of EHP biology, life cycle and lead to the development of prophylactics and therapeutics for EHP control. Also, this method will help standardize the study of germination in other microsporidians.