Postlarval Shrimp Research Articles

Immunomodulatory effects of PACAP sequence modifications in juvenile white shrimp Litopenaeus vannamei

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a highly conserved multifunctional neuropeptide belonging to the secretin/glucagon/vasoactive intestinal peptide superfamily. In recent years, the role of PACAP in immunoregulation has been partially elucidated in mammals and teleost fishes, demonstrating that PACAP modulates both innate and acquired immunity. However, in invertebrates, little is known about its immunostimulant and antimicrobial properties. In previous research, studies performed in Litopenaeus (Penaeus) vannamei have revealed that Clarias gariepinus PACAP-38 improves immune functions like lectins, superoxide dismutase and nitric oxide synthase derived metabolites in postlarvae shrimp. In this study, the immunomodulatory effects of C. gariepinus PACAP-38 and four PACAP sequence modified peptides in juvenile L. vannamei were evaluated. The effect of several administrations of PACAP and its variants on shrimp immune effectors, as well as the effect of different doses was examined. Results revealed that PACAP can influence hemolymph immune parameters, and immune-related gene mRNA levels in the hemocytes, gill and hepatopancreas with different effects depending on the modification of the peptide sequence, the dose and the tissue assessed. Altogether, these findings provide valuable insights regarding the role of PACAP in crustacean innate immunity and highlight the need for further research into its potential application as an alternative to antibiotics in aquaculture.

Evaluation of dietary yeast derived mannan oligosaccharide for pacific whiteleg shrimp Penaeus vannamei: Effects on growth performance, immune response, hepatopancreas morphology and resilience to infection against Vibrio parahaemolyticus

With trends towards low fishmeal and higher plant ingredient-based diets for shrimp, there is consequently greater demand on feed additives to bolster the protein and nutrient profile quality for achieving more efficiency. Also, there is a need to enhance innate immunity and resilience to infection under intensive shrimp production scenarios. This investigation tested incremental levels 0, 0.2; 0.4; 0.6 and 0.8 % of a commercial yeast cell wall extract mainly comprising β-glucan and mannan oligosaccharides (MOS) (YM, YeaMOS, Angel Yeast, Yichang, Hubei, China) for post-larval shrimp Penaeus vannamei in isonitrogenous and iso-lipidic diets with proteinaceous plant ingredients amounting to 50 % contribution of the diet formulation. After 60 d, growth and feed utilization performance were not significantly affected in shrimp in terms of weight gain or FCR, but due to much higher survival, total biomass in groups of shrimps fed with dietary YM was higher compared to the control treatment. A sequential specific pathogen challenge test with Vibrio parahaemolyticus at final dose of 104 CFU mL−1 resulted in a marked improvement in survival against the control group with much enhancement at the inclusion level of 0.4 % YM (p<0.05). Before challenged, the total haemocyte count (THC) and the relative gene expression of Prophenoloxidase (ProPO) were higher in the group of shrimps fed with YM. Likewise, after infection, the amount of THC and ProPO remained better in the group of shrimps fed with YM. However, the 0.8 % YM treatment did not significantly differ from the control for phagocytic activity and index. The histomorphology condition of the hepatopancreas of shrimp before the infection for all treatments appears normal without significant numbers of hepatopancreatic tubules (T) and epithelial cell vacuoles (V). After pathogen challenge, all shrimp exhibited severe necrotic cell damage and massive sloughing of hepatopancreatic tubule epithelial cells into the lumen. Overall, giving YM as feed additives can improve the shrimp biomass and health, with the use of 0.4 % inclusion levels in practical diets for shrimp P. vannamei become the optimum dose to develop more efficient aquafeed production.

Effects of stocking density and salinity on the flavour performance and muscle microstructure of black tiger shrimp (Penaeus monodon) post larvae

Effects of stocking density and salinity on the flavour performance and muscle microstructure of black tiger shrimp (Penaeus monodon) post larvae

Study on Ferritin Gene Expression to Evaluate the Health of White Leg Shrimp (Litopenaeus vannamei) Postlarvae Due to Changes in Water Temperature, Salinity, and pH

The growth and survival of marine organisms are influenced by environmental factors such as water temperature, salinity, and pH. Unsuitable environmental conditions may negatively impact marine organisms. The white leg shrimp (Litopenaeus vannamei), a euryhaline organism highly adapted to salinity, is a valuable species for aquaculture. This study examined the effects of water temperature, salinity, and pH on the health of postlarvae L. vannamei. Stress levels within the organisms were analyzed through the expression of a biomarker gene. Ferritin was selected as the biomarker gene for analysis. The experimental animal samples used were the hepatopancreas of L. vannamei postlarvae. The analysis was performed by qRT-PCR. The results showed that the adaptation of L. vannamei postlarvae to temperature was dependent on salinity. Under low-salinity conditions (5 psu), ferritin expression increased at 25 °C and 30 °C after 48 h of exposure; however, it decreased after 72 h of exposure. Under normal salinity conditions (27 psu), ferritin expression increased from 24 h to 72 h at water temperatures of 25 °C and 30 °C. These results indicate that low-salinity conditions may enable L. vannamei postlarvae to rapidly adapt to high temperatures. In conclusion, L. vannamei postlarvae adapt more efficiently to high temperatures under low-salinity conditions than that under high-salinity conditions. The results of this study could beneficially impact L. vannamei farming.

Influence of stocking density on the growth, immune and physiological responses, and cultivation environment of white-leg shrimp (Litopenaeus vannamei) in biofloc systems

Biofloc (BF) stands out as a promising system for sustainable shrimp farming. Optimizing various culture conditions, such as stocking density, carbohydrate source, and feeding management, is crucial for the widespread adoption of the BF system. This study compares the growth performance of white-leg shrimp (Litopenaeus vannamei) in culture ponds at low density (LD) with 50 organisms/m2 and high density (HD) with 200 organisms/m2. Post-larvae of white-leg shrimp were stocked for 16 weeks in both LD and HD groups. The LD group exhibited a superior survival rate, growth rate, and feed consumption compared to the HD group. The BF from the LD system recorded a significantly higher protein content (16.63 ± 0.21%) than the HD group (15.21 ± 0.34%). Heterotrophic bacterial counts in water did not significantly differ with stocking density. However, Vibrio count in water samples was higher in the HD group (3.59 ± 0.35 log CFU/mL) compared to the LD group (2.45 ± 0.43 log CFU/mL). The whole shrimp body analysis revealed significantly higher protein and lipid content in the LD group. In contrast, the total aerobic bacterial count in shrimp from the HD group was high, with the identification of Salmonella enterica ssp. arizonae. Additionally, Vibrio counts in shrimp samples were significantly higher in the HD group (4.63 ± 0.32 log CFU/g) compared to the LD group (3.57 ± 0.22 log CFU/g). The expression levels of immune-associated genes, including prophenoloxidase, transglutaminase, penaiedin 3, superoxide dismutase, lysozyme, serine proteinase, and the growth-related gene ras-related protein (rap-2a), were significantly enhanced in the LD group. Conversely, stress-related gene expression increased significantly in the HD group. Hepatopancreases amylase, lipase, and protease were higher in the LD group, while trypsin activity did not differ significantly. Antioxidant enzyme activity (catalase, glutathione, glutathione peroxidase, and superoxide dismutase) significantly increased in the LD group. The histological structure of hepatopancreas, musculature, and female gonads remained similar in both densities. However, negative effects were observed in the gills' histology of the HD group. These results suggest that increasing stocking density is associated with significantly negative biological, microbial, and physiological effects on white-leg shrimp under the BF system.

Alterations in the gut microbiome of whiteleg shrimp (Penaeus vannamei) postlarvae following exposure to an AHPND-causing strain of Vibrio parahaemolyticus

Acute hepatopancreatic necrosis disease (AHPND), attributed to the production of PirA/PirB toxins by certain Vibrio sp. strains, poses a significant threat to global shrimp aquaculture, causing substantial mortality and economic losses. To enhance our understanding of this disease within a closed culture system on the northern coast of Peru, we conducted a comparative analysis of the gut microbiomes between healthy and diseased postlarvae. Diseased postlarvae were obtained through exposure to an AHPND-causing strain of Vibrio parahaemolyticus. Five healthy and five diseased postlarvae were randomly sampled from experimental rearing tanks, and their medial guts were extracted. High-throughput sequencing targeting the V4 region of the 16S rRNA gene was employed for amplicon library construction, and assessments of alpha and beta diversities and taxonomic composition were conducted. Our results revealed reduced diversity and distinct compositional profiles in the gut microbiomes of diseased postlarvae. The order Rhodobacteriales was dominant in the gut microbiomes of healthy postlarvae. In contrast, the order Vibrionales (including an unassigned genus within Vibrionales, Vibrio, and Pseudoalteromonas) exhibited the highest abundance in diseased postlarvae. In conclusion, exposure to an AHPND-causing strain of V. parahaemolyticus induces significant dysbiosis in the gut microbiome of whiteleg shrimp postlarvae.

Asynchronous contributions of decapod life history stages to the zooplankton of tropical estuarine, coastal and shelf ecosystems - new insights from semi-automatic image analysis

Decapod crustaceans include many species of socioeconomic importance and are key components of pelagic ecosystems, both as adults and as larval forms. Knowledge on seasonal and spatial synchronicity of planktonic larvae in coastal tropical ecosystems is fundamental to understand the dynamics of these complex ecosystems. The objective of the present study was to quantify the contributions of decapods to the zooplankton in adjacent tropical estuarine, coastal and shelf ecosystems, while considering their seasonal life cycles and probable dispersal strategies. We evaluated the contributions of decapod biomass and biovolume in three distinct ecosystems: Rio Formoso estuary, Tamandaré bay, and Pernambuco continental shelf off Tamandaré, northeastern Brazil. Zooplankton samples were taken bimonthly from June 2013 to May 2015, with a 300 μm mesh net, and analyzed using a ZooScan equipment. Decapods were the second most important organisms (after copepods), in abundance, biomass and biovolume, in all sampling areas. Total decapods contributed on average with 33.6%, 4.4% and 7.1% relative abundance and 30.9%, 30.9%, and 15.2% relative biovolume in estuary, bay, and shelf areas, respectively. Overall, the most relevant decapod taxa and stages found in the three sampling areas were brachyuran crab zoeae and megalopae, penaeid shrimp postlarvae (mostly Penaeus spp.), holoplanktonic luciferids (adults, protozoeae and mysis), anomuran zoeae (mostly Paguridae and Diogenidae hermit crabs), pistol shrimp zoeae (Alpheidae), and porcelain crab zoeae (Porcellanidae). Brachyuran zoeae contributed with up to 81.3% abundance and up to 69% biovolume, in the estuary. Penaeid postlarvae comprised up to 28.1% of total abundance and up to 94.7% of total biovolume, on the shelf. These postlarvae were transported shorewards from the offshore shelf. Decapod contributions were especially relevant during massive larval release events of crab zoeae and during shoreward migration of pre-settlement stages. Seasonal peaks were clearly asynchronous between taxa and areas. Possible functional relationships between copepods and key decapod groups are discussed, as well as the processes triggering and regulating the input of larvae. Our results show the importance of quantitative, semi-automatic approaches and the relevance of decapod larvae for pelagic food webs in tropical coastal areas.

Terminalia catappa L. leaf extract interferes with biofilm formation of Vibrio parahaemolyticus and enhances immune response of Penaeus vannamei against acute hepatopancreatic necrosis disease (AHPND)

Crude ethanolic extract from Terminalia catappa L. leaves was investigated for its ability to interfere with biofilm formation of acute hepatopancreatic necrosis disease (AHPND)-causing and a reference Vibrio parahaemolyticus strains and modulate the immune response of Penaeus vannamei shrimp postlarvae. Results showed that biofilms formed by both AHPND-causing and reference strains of V. parahaemolyticus were rendered susceptible to dispersal upon treatment with the sublethal concentration of the extract. Furthermore, results of the qPCR analyses showed upregulation of six immune-related genes after 7 and 14 d of feeding. Pre-infection survival rates equivalent to the shrimp fed with un-supplemented feed suggest that T. catappa extract is safe for shrimp consumption. Upon infection with the AHPND strain, V. parahaemolyticus R1, the survival rate of the treatment group was 77% - significantly greater than those fed with un-supplemented feed. Similarly, those fed with T. catappa-supplemented feed and subsequently infected with V. parahaemolyticus ATCC17802 had a 93% survival rate, which is as high as the uninfected control group. These results ultimately indicate that feed supplementation with T. catappa increases the survival rate of the shrimp, possibly via attenuation of V. parahaemolyticus pathogenesis and stimulation of the shrimp's immune response against infections.

Gut bacterial consortium enriched in a biofloc system protects shrimp against Vibrio parahaemolyticus infection

BackgroundShrimp cultured in a biofloc system (BFS) have a lower disease incidence than those farmed in a water exchange system (WES). Although a number of studies have reported that the gut bacterial community induced by BFS is highly associated with shrimp disease resistance, the causal relationship remains unknown. Here, the promotive roles of gut bacterial community induced by BFS in pathogenic Vibrio infection resistance and its potential micro-ecological and physiological mechanisms were investigated by gut bacterial consortium transplantation and synthetic community (SynCom) construction.ResultsThe BFS induced a more stable and resistant gut bacterial community, and significantly enriched some beneficial bacterial taxa, such as Paracoccus, Ruegeria, Microbacterium, Demequina, and Tenacibaculum. Transplantation of a gut bacterial consortium from BFS shrimp (EnrichBFS) greatly enhanced the stability of the bacterial community and resistance against pathogenic V. parahaemolyticus infection in WES shrimp, while transplantation of a gut bacterial consortium from WES shrimp significantly disrupted the bacterial community and increased pathogen susceptibility in both WES and BFS shrimp. The addition of EnrichBFS in shrimp postlarvae also improved the pathogen resistance through increasing the relative abundances of beneficial bacterial taxa and stability of bacterial community. The corresponding strains of five beneficial bacterial taxa enriched in BFS shrimp were isolated to construct a SynComBFS. The addition of SynComBFS could not only suppress disease development, but also improve shrimp growth, boost the digestive and immune activities, and restore health in diseased shrimp. Furthermore, the strains of SynComBFS well colonized shrimp gut to maintain a high stability of bacterial community.ConclusionsOur study reveals an important role for native microbiota in protecting shrimp from bacterial pathogens and provides a micro-ecological regulation strategy towards the development of probiotics to ameliorate aquatic animal diseases.1NpdyYjfCEzGqNeY6CWHQHVideo

Vibrio parahaemolyticus becomes lethal to post-larvae shrimp via acquiring novel virulence factors.

Translucent post-larvae disease (TPD), caused by Vibrio parahaemolyticus (Vp TPD), has become an emerging shrimp disease, affecting more than 70%-80% of coastal shrimp nurseries in China in spring 2020. Here, we investigated the key virulence factors of Vp TPD by analyzing protein fragments, related genomic information, as well as experimental challenge tests. After investigating the toxic effects of purified protein fragments with different molecular weights (MWs) from Vp TPD, we found that only the protein fragments with MW >100 kDa showed similar lethality to live Vp TPD in the experimental challenge test using post-larvae shrimp. Meanwhile, similar histopathological changes exhibiting in the hepatopancreas and midgut of the diseased individuals were observed in the post-larvae shrimp challenged with either bacterial protein fragments (MW >100 kDa) or live Vp TPD. Based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and mass spectrometry analyses, two novel proteins, Vibrio high virulent protein (VHVP)-1 and VHVP-2, were identified as the candidates of key virulence factors to cause TPD. Moreover, VHVP-1 and VHVP-2 were found to be encoded by two genes (vhvp-1 and vhvp-2) tandemly located on a 187,791-bp plasmid and were predicted to depend on the same promoter following a comparative genomic analysis. Further epidemiological investigation and challenge test indicated that the V. parahaemolyticus isolate carrying only the vhvp-1 gene and lacking vhvp-2 gene could not cause mortality of experimental Penaeus vannamei post-larvae. The mutant (Δvhvp-2) by deleting vhvp-2 gene could only cause 4.92% of accumulative mortality of post-larvae that is similar to the non-Vp TPD Vibrio strain. Additionally, the complemented strains, Δvhvp-2/pBT3-vhvp-2 and Δvhvp-2/pwtCas9-vhvp-2, showed similar virulence to the wild-type Vp TPD. The results demonstrated that V. parahaemolyticus becomes lethal to post-larval shrimp by acquiring the VHVP-2 virulence factor. This study sheds light on further investigations of the pathogenic mechanism of Vp TPD and the development of strategies for early diagnosis of TPD in shrimp hatcheries. As a severe emerging shrimp disease, TPD has heavily impacted the shrimp aquaculture industry and resulted in serious economic losses in China since spring 2020. This study aimed to identify the key virulent factors and related genes of the Vp TPD, for a better understanding of its pathogenicity of the novel highly lethal infectious pathogen, as well as its molecular epidemiological characteristics in China. The present study revealed that a novel protein, Vibrio high virulent protein-2 (MW >100 kDa), is responsible to the lethal virulence of V. parahaemolyticus to shrimp post-larvae. The results are essential for effectively diagnosing and monitoring novel pathogenic bacteria, like Vp TPD, in aquaculture shrimps and would be beneficial to the fisheries department in early warning of Vp TPD emergence and developing prevention strategies to reduce economic losses due to severe outbreaks of TPD. Elucidation of the key virulence genes and genomics of Vp TPD could also provide valuable information on the evolution and ecology of this emerging pathogen in aquaculture environments.

Identification of new Vibrio campbellii strains harboring the pVA1 plasmid isolated from Penaeus vannamei postlarvae affected by outbreaks of acute hepatopancreatic necrosis disease (AHPND) in Mexico

At present, AHPND continues to produce large losses in Mexican shrimp farms, but no scientific report on mortality in commercial hatcheries has been published. Here, we present the clinical signs, histopathological lesions, bacteriological analyses and identification through whole-genome sequencing of the isolates obtained in three natural outbreaks of AHPND in Penaeus vannamei postlarvae obtained from three local hatcheries. After three to four days of acclimation, mortality was recorded and clinical signs such as an empty digestive tract, whitish hepatopancreas, anorexia and lethargy were observed in shrimp postlarvae. Histopathological analysis and detection of pirAB genes using the PCR AP4 method after sample enrichment were used as presumptive diagnoses of AHPND. Significantly more Vibrio-like density (p = 0.045) and green colonies (p = 0.021) were found in the hepatopancreas of postlarvae affected by AHPND compared to apparently healthy organisms in outbreak 1 and 2, respectively. Finally, 29 isolates from the hepatopancreas and stomachs of shrimps with or without AHPND clinical signs were sequenced, and two new Vibrio species were obtained, one closely related to the Harveyi clade and one to the Orientalis clade. Vibrio campbellii were the most abundant species followed by V. parahaemolyticus. The six genomes identified as V. campbellii harbour the pVA1-like plasmid carrying the pirAB genes, responsible for producing the delta-endotoxin that causes AHPND. The pVA1-like plasmids were similar to V. parahaemolyticus strains from the Americas. pVA1 plasmid hosts the Tn3 transposon like the V. campbellii strain from Ecuador, but absent in the China strain, suggesting a horizontal plasmid transfer between coexisting V. parahaemolyticus and V. campbellii within a geographic region. These findings provided the first report of V. campbellii strains carrying a pVA1-like plasmid that causes AHPND in postlarvae from commercial hatcheries in Mexico and may help in the adoption of active genomic surveillance of this disease.

Critical temperatures and aerobic metabolism in post-larvae of Pacific white shrimp Litopenaeus vannamei (Boone, 1931).

Increasing water temperature because of climate change decreases the oxygen concentration while increasing the oxygen requirement of species in aquatic environments. Temperature is one of the most important environmental factors affecting the physiological functions of organisms, especially poikilothermic animals, such as shrimp at all levels. In intensive shrimp culture, it is of great importance to know the tolerable temperature range of cultured species and their metabolism since this affects the physiological condition. In this study, critical temperatures (CTM: CTmin and CTmax) of Pacific white shrimp, Litopenaeus vannamei, post-larvae (PL), were determined at different acclimation temperatures of 15, 20, 25, and 30°C. Lower and upper incipient lethal temperatures (ILT: LILT and UILT) were also calculated for the PL. The thermal windows of the PL were developed using the CTM and ILT values. The standard metabolic rate (SMR) of the PL was determined based on the oxygen consumption rate (OCR) at the different acclimation temperatures mentioned above. The acclimation temperature had a subsequent effect on the thermal tolerance and SMR of the PL (P < 0.01). The PLs of Pacific white shrimp have high thermal tolerance and can survive at extreme temperatures (CTmin and CTmax: 8.2-43.8°C) with their large dynamic and static thermal window areas of 1128 and 931°C2, respectively. The optimal temperature range for Pacific white shrimp PLs is the 25-30°C range, where a decrease in SMR is determined with increasing temperature. The result of this study reveals that a range of 25-30°C is optimal for effective PL culture of Pacific white shrimp.

Evaluation of Biofloc-Based Probiotic Isolates on Growth Performance and Physiological Responses in Litopenaeus vannamei

A comparison of the growth performance of Penaeus vannamei was ascertained by supplementing the potential probiotics isolated from a biofloc system incorporated through feed. Post-larvae shrimp (0.045 ± 0.005 g) were stocked at a density of 500/m3 in FRP tanks (500 L) in triplicates for a period of 60 days. A total of 40 bacterial strains were isolated from previous biofloc culture trials and tested for their antimicrobial activity against the pathogen Vibrio parahaemolyticus. Among these, Bacillus megaterium, Exiguobacterium profundum, Pseudomonas balearica, and Pseudomonas stutzeri showed higher antimicrobial activity. The treatment groups included clear water with no probiotics (CW), clear water + isolated probiotic (CW + IP), biofloc alone (BFT), and biofloc + isolated probiotic (BFT + IP), in triplicates. Distillery spent wash was used as a carbon source for biofloc development and maintenance. A probiotic concentration of 1 × 109 cfu/g was supplemented throughout the trial. The recorded water quality parameters (pH, alkalinity, calcium, and magnesium) were observed to be significant among the experimental groups (p ≤ 0.05). The highest weight gain (2.43 g), SGR, PER, and lower FCR values were recorded in BFT + IP. The lowest values of total Vibrio were found in BFT. The histology analysis revealed that there was a mild increase in the B and R cell vacuoles in the hepatopancreas of CW and BFT + IP, whereas mild degeneration was found in the intestine of CW and CW + IP. Microbiome analysis of the shrimp gut revealed that Proteobacteria was the most abundant phylum in all experimental groups. P. balearica, K. pneumoniae, P. stutzeri, and E. profundum were present in the gut of C, whereas P. balearica, K. pneumonia, and P. stutzeri were present in the gut of CW + IP and BFT + IP. The results proved that the probiotics isolated from biofloc colonized in shrimp gut could play a promising role in aquaculture.

Dietary protein requirements of whiteleg shrimp (Penaeus vannamei) post-larvae during nursery phase in clear-water recirculating aquaculture systems

Whiteleg shrimp Penaeus vannamei farming in clear water recirculating aquaculture systems (RAS) is relatively recent, and consequently, knowledge on the shrimp dietary demands is still insufficient, particularly in the initial developmental stages. This study aimed at assessing the dietary protein requirement of whiteleg shrimp post-larvae (PL) in a clear-water recirculating aquaculture system (RAS). Six microdiets were formulated to contain 34%, 44%, 49%, 54%, 58%, and 63% crude protein (P34, P44, P49, P54, P58 and P63, respectively) and were evaluated in triplicates. Whiteleg shrimp PL (3.2 mg wet weight) were reared for 21 days in a clear-water RAS at Riasearch Lda. At the end of the feeding period, the optimal protein requirement was estimated at 47.1%, 46.4%, 47.2%, and 44.0% for weight gain, relative growth rate (RGR), feed conversion ratio (FCR), and survival, respectively. PL fed the P54, P58, and P63 diets achieved significantly higher final body weights than those fed P34. PL fed P34 showed significantly lower RGR and survival and significantly higher FCR values than those fed the remaining diets, suggesting that low protein diets may not be adequate to be used in this stage of shrimp development and/or for the clear-water RAS husbandry conditions. Moreover, diet P34 seemingly reduced the overall antioxidant status of the PL when compared to P44, P49, and P54. However, the P34 diet seems to have stimulated the PL immune mechanisms when compared to P44, P49, and P54, possibly due to increased levels of fish and algae oil. Similarly, despite the good growth performances, a diet containing 63% of protein also seemed to have compromised the overall shrimp PL antioxidant status and stimulate their immune system. Shrimp fed diet P54 showed an apparent overall superior antioxidant status when compared to the remaining diets, evidencing that using protein inclusion levels up to 54% in aquafeeds not only potentiates growth performances and survival but also can potentially be beneficial to the health status of P. vannamei PL grown in a clear-water RAS. Hence, results from this study suggest that a minimum of approximately 47% of protein should be considered when tailoring microdiets for whiteleg shrimp PL grown in a clear-water RAS, but inclusion levels up to 54% can be used with benefits to the PL antioxidant status.

Relative Expression of Rab7 Gene in the Penaeid Shrimp Post-Larvae Reared in Different Salinity Conditions

Relative Expression of Rab7 Gene in the Penaeid Shrimp Post-Larvae Reared in Different Salinity Conditions

Effects of high-salinity on the expression of aquaporins and ion transport-related genes in Chinese shrimp (Fenneropenaeus chinensis)

Salinity is one of the most common environmental stress factors, which has a substantial influence on the growth, metabolism, and distribution of crustaceans, while transport of ions and water are considered to play important roles in response to salinity stress. The Chinese shrimp (Fenneropenaeus chinensis) is an important shrimp species cultured in northern China and salinity conditions influence its commercial farming significantly. The study aims to elucidate the potential roles of ion-transport related genes Na+/K+-ATPase α subunit (NKAα), cytoplasmic carbonic anhydrase (CAc), and V-type H+-ATPase subunits (VHA-C, VHA-F, and VHA-G), and water channels of aquaporins (AQP3 and AQP4) in F. chinensis under high-salinity stress. The open reading frames (ORFs) of these genes were cloned, validated, and characterized based on blast against the transcriptomic data. Tissue distribution analysis revealed the predominant expression of these genes in the gills. Then, qPCR was used to examine the expression patterns of genes in the post-larvae shrimp and the gills of adult shrimp in response to hyper-osmotic challenges with two salinities (40 and 45). The results showed that the relative expression levels of these genes were all significantly decreased (p < 0.05) in the post-larvae shrimp after 3 h of high-salinity exposure. With continued stress, the expression levels of these genes varied depending on the intensity, exposure time, and treatment conditions of salinity stress. On the other hand, these genes were also significantly down-regulated (p < 0.05) and continuously decreased up to 12 h in the gills of adult shrimp under high-salinity stress. The results indicated the cooperation of these genes to reduce cellular water efflux and ion uptake or excretion in response to high-salinity environments. Our findings provided insights into the regulatory mechanisms employed during the adaption to high-salinity stress of F. chinensis.

Health-Promoting Additives Supplemented in Inert Microdiets for Whiteleg Shrimp (Penaeus vannamei) Post-Larvae: Effects on Growth, Survival, and Health Status

Dietary additives have the potential to stimulate the whiteleg shrimp immune system, but information is scarce on their use in diets for larval/post-larval stages. The potential beneficial effects of vitamins C and E, β-glucans, taurine, and methionine were evaluated. Four experimental microdiets were tested: a positive control diet (PC); the PC with decreased levels of vitamin C and E as negative control (NC); the PC with increased taurine and methionine levels (T + M); and the PC supplemented with β-glucans (BG). No changes in growth performance and survival were observed. However, post-larvae shrimp fed the NC had lower relative expressions of pen-3 than those fed the PC, suggesting that lower levels of vitamins C and E may impact the shrimp immune status. Lipid peroxidation levels dropped significantly in the BG compared to the PC, indicating that β-glucans improved the post-larvae antioxidant mechanisms. Furthermore, when compared with the NC diet, PL fed with BG showed significant increases in tGSH levels and in the relative expression of crus and pen-3, suggesting a synergistic effect between vitamins C and E and β-glucans. Amongst the additives tested, β-glucans seems to be the most promising even when compared to a high-quality control diet.

How Do Gene Expression Patterns Change in Response to Osmotic Stresses in Kuruma Shrimp (Marsupenaeus japonicus)?

Euryhaline crustaceans cope with external salinity changes by mechanisms of osmoregulation. In the current study, we first cloned and confirmed the ORF sequences of the ion-transportation-related genes Na+/K+-ATPase α subunit (NKAα), cytoplasmic carbonic anhydrase (CAc), and V-type H+-ATPase G subunit (VHA-G), and water channels of aquaporins (AQP3, AQP4, and AQP11) from kuruma shrimp (Marsupenaeus japonicus). Further tissue expression patterns showed a higher expression of MjAQP4, MjCAc, MjNKAα, and MjVHA-G in the gills, as well as a higher expression of MjAQP3 and MjAQP11 in the intestine and muscle, respectively. Then, qPCR analysis was used to assess the mRNA expression levels of those osmoregulatory genes in both post-larvae and adult shrimp when they were exposed to acute salinity stress or salinity acclimation. The results revealed significantly decreased expression levels of MjAQP3, MjAQP11, MjNKAα, and MjCAc, and higher expression levels of MjAQP4 and MjVHA-G when the post-larvae shrimp were directly subjected to 10‰ or 50‰ salinity. Moreover, similar expression patterns were also observed in the post-larvae shrimp during the accommodation to 10‰ or 50‰ salinity. As to the adult shrimp, significantly higher expression levels of those genes were observed in the gills after exposure to 10‰ salinity, whereas only the expression levels of MjAQP3, MjAQP11, and MjNKAα were up-regulated in the gills at 40‰ salinity. In contrast, the expression of MjVHA-G was significantly decreased at 40‰ salinity. Finally, during the acclimation to 10‰ salinity, the expression levels of MjAQP3, MjAQP11, and MjNKAα were also significantly elevated, while the expression of MjCAc was significantly decreased in the gills. In addition, the expression levels of MjAQP3, MjAQP4, MjCAc, and MjVHA-G were significantly decreased in the gills during the acclimation to 55‰ salinity. The findings of the study suggest that the examined genes are critical for the adaptation of aquatic crustaceans to changing environmental salinity. Our study lays as the foundation for further research on osmoregulation mechanisms in M. japonicus.

Use of Sonneratia alba leaf extract solution for White Spot Syndrome Virus prevention in tiger shrimp postlarvae

White Spot Syndrome Virus (WSSV) is one of the leading causes of mass mortality in tiger shrimp culture. The objective of this study was to determine the impact of different immersion times in 1% Sonneratia alba extract on the ability of WSSV infected tiger shrimp to survive as post-larvae. Eight treatments were used in this study, with three replications for each. The treatments were as follows: A) 12 hours of immersion; B) 24; C) 36; D) 48; E) 60; F) 72; G) Positive control (infected with WSSV but without mangrove extract); and H) Negative control (without WSSV infection and mangrove extract). with three replications in each treatment. Tiger prawn post-larvae were stocked at a density of 20 squares per jar. At a rate of 20% of the daily biomass, they were being fed three times per day. Tiger shrimp post-larvae mortality was examined every day for eight days. At the beginning and conclusion of the study, analyses of water quality such as Total Organic Matter, NH3-N, and NO2-N, were made. The findings revealed that treatment F seemed to have the best survival rate (85.0%) and positive control had the lowest survival rate (0%). (treatment G). The shrimp were more resistant to WSSV due to the longer immersion in the herbal extracts.

Evaluating Artemia biomass and gut weed (Ulva intestinalis) meal as a dietary protein source for black tiger shrimp (Penaeus monodon) postlarvae

A 45-day feeding trial was conducted to assess the influence of Artemia (Artemia franciscana Vinh Chau) biomass and gut weed (Ulva intestinalis) meal as replacement protein sources for fishmeal (FM) and soybean (SB) protein on the performance of black tiger shrimp (Penaeus monodon) postlarvae (PL). The control diet did not include Artemia biomass or gut weed meal, and the experimental feeds were formulated to replace 20%, 40%, 60%, and 80% of the FM protein with Artemia biomass meal, combined with the replacement of 15%, 30%, 45%, and 60% of SB protein with gut weed meal. All the experimental feeds were similar in crude protein (40%) and lipid (7%) content, with three replicates per treatment. Shrimp PL with an average weight of 0.019 ± 0.001 g and length of 1.17 ± 0.02 cm were reared at a salinity of 10 ppt. The results showed that the survival of the shrimp was not significantly influenced by the feeding treatments (P > 0.05) and ranged from 81.1% to 86.7%. Interestingly, the growth rates in terms of the weight, feed efficiency, and resistance to formalin shock of the shrimp that were fed Artemia biomass and gut weed meal were superior to those that received the control feed. The study findings demonstrated that Artemia biomass combined with gut weed meal can replace up to 80% FM protein and 60% SB protein in the P. monodon PL diet. Notably, optimal shrimp performance wasobtained using a 40% Artemia biomass and 30% gut weed protein replacement diet.