Acute Toxicity of Ammonia, Nitrite and Nitrate to Shrimp Litopenaeus vannamei Postlarvae in Low-Salinity Water

Metabolomics revealed more deleterious toxicity induced by the combined exposure of ammonia and nitrite on Ruditapes philippinarum compared to single exposure

NH3-N and NO2-N always co-exist in the aquatic environment, but there is not a clear opinion on their joint toxicities to the molluscs. Presently, clams Ruditapes philippinarum were challenged by environmental concentrations of NH3-N and NO2-N, singly or in combination, and analyzed by metabolomics approaches, enzyme assays and transmission electron microscope (TEM) observation. Results showed that some same KEGG pathways with different enriched-metabolites were detected in the three exposed groups within one day, and completely different profiles of metabolites were found in the rest of the exposure period. The combined exposure induced heavier and more lasting toxicities to the clams compared with their single exposure. ACP activity and the number of secondary lysosomes were significantly increased after the combined exposure. The present study shed light on the joint-toxicity mechanism of NH3-N and NO2-N, and provided fundamental data for the toxicity research on inorganic nitrogen.

Dissolved oxygen and ammonia affect ammonia production via GDH/AMPK signaling pathway and alter flesh quality in Chinese perch (Siniperca chuatsi)

The dissolved oxygen (DO) and ammonia are crucial to the growth of Chinese perch (Siniperca chuatsi). Information on the effects of DO and total ammonia nitrogen (TAN) in regulating ammonia nitrogen excretion and flesh quality in Chinese perch is scanty. This study aimed to evaluate the effects of dissolved DO at oxygen levels of 3 mg/L and 9 mg/L, as well as the TAN concentrations of 0.3 mg/L and 0.9 mg/L on ammonia excretion and flesh quality. Results showed that the ammonia contents in plasma, muscle, and liver of the 9 mg/L DO group were significantly higher than those of the 3 mg/L DO group (P < 0.05). However, the expression of AMPK-related signaling pathway genes (gdh, lkb1, and ampd) and flesh quality indicators (gumminess, chewiness, hardness) in the 9 mg/L DO group were significantly lower than those in the 3 mg/L DO group. Under long-term exposure to 0.9 mg/L TAN, the ammonia contents in plasma and gill filaments, as well as muscle flesh quality (resilience, gumminess, chewiness, cohesiveness), were significantly lower than those in the 0.3 mg/L TAN group (P < 0.05). However, the activities of GDH and AMPD enzymes in the 0.9 mg/L TAN group were significantly higher than those in the 0.3 mg/L TAN group. In summary, when fish are exposed to 3 mg/L DO and 0.9 mg/L TAN in the environment for a long time, their amino acids are used for transamination and deamination, resulting in insufficient energy supply for Chinese perch, whereas 9 mg/L DO and 0.9 mg/L TAN caused deterioration of the flesh quality.

First transcriptome profiling in gill and hepatopancrease tissues of Metapenaeus ensis in response to acute ammonia-N stress

The greasyback shrimp, Metapenaeus ensis, suffers from ammonia-N stress during intensive factory aquaculture. Optimizing ammonia-N stress tolerance has become an important issue in M. ensis breeding. The metabolic and adaptive mechanisms of ammonia-N toxicity in M. ensis have not been comprehensively understood yet. In this study, a large number of potential simple sequence repeats (SSRs) in the transcriptome of M. ensis were identified. Differentially expressed genes (DEGs) in the gill and hepatopancreas at 24 h post-challenges under high concentrations of ammonia-N treatment were detected. We obtained 20,108,851-27,681,918 clean reads from the control and high groups, assembled and clustered a total of 103,174 unigenes with an average of 876 bp and an N50 of 1189 bp. Comparative transcriptome analyses identified 2000 different expressed genes in the gill and 2010 different expressed genes in the hepatopancreas, a large number of which were related to immune function, oxidative stress, metabolic regulation, and apoptosis. The results suggest that M. ensis may counteract ammonia-N toxicity at the transcriptome level by increasing the expression of genes related to immune stress and detoxification metabolism, and that selected genes may serve as molecular indicators of ammonia-N. By exploring the genetic basis of M. ensis' ammonia-N stress adaptation, we constructed the genetic networks for ammonia-N adaptation. These findings will accelerate the understanding of M. ensis' ammonia-N adaptation, contribute to the research of future breeding, and promote the level of factory aquaculture of M. ensis.

The role of probiotics in vannamei shrimp aquaculture performance – A review

Vannamei shrimp (Litopenaeus vannamei) is an important food commodity of economic benefit due to its high price, low susceptibility to disease, and popularity for consumption. These advantages have led many farmers to cultivate vannamei shrimp. Efforts are underway to improve the aquaculture performance of this species, including the use of probiotics, which are non-pathogenic bacteria that aid in digestion and help fight disease. Probiotics are usually obtained from the intestines of vannamei shrimp or the culture environment. They are low-cost, non-pathogenic, and largely non-toxic source of antibiotics and are able to synthesize various metabolites that have antibacterial functions and applications. Research on probiotic use has primarily been focused on increasing vannamei shrimp aquaculture production. Bacterial species, such as Lactobacillus or Nitrobacter, can be administered orally, by injection, or as a supplement in aquaculture water. Probiotics help to improve survival rate, water quality, immunity, and disease resistance through space competition with disease-causing bacteria, such as Vibrio spp. An increased number of probiotic bacteria suppresses the growth and presence of pathogenic bacteria, which lowers disease susceptibility. In addition, probiotic bacteria also aid digestion by breaking down complex compounds into simpler substances that the body can absorb more easily. This mechanism improves growth performance in terms of weight, length, and feed conversion ratio. This review aimed to provide information regarding contribution of probiotic to improve vannamei shrimp production in aquaculture. Keywords: application, bacteria, farm, microbiome, shrimp.

Non-Invasive Methods for Assessing the Welfare of Farmed White-Leg Shrimp (Penaeus vannamei)

Gradually, concern for the welfare of aquatic invertebrates produced on a commercial/industrial scale is crossing the boundaries of science and becoming a demand of other societal actors. The objective of this paper is to propose protocols for assessing the Penaeus vannamei welfare during the stages of reproduction, larval rearing, transport, and growing-out in earthen ponds and to discuss, based on a literature review, the processes and perspectives associated with the development and application of on-farm shrimp welfare protocols. Protocols were developed based on four of the five domains of animal welfare: nutrition, environment, health, and behaviour. The indicators related to the psychology domain were not considered a separate category, and the other proposed indicators indirectly assessed this domain. For each indicator, the corresponding reference values were defined based on literature and field experience, apart from the three possible scores related to animal experience on a continuum from positive (score 1) to very negative (score 3). It is very likely that non-invasive methods for measuring the farmed shrimp welfare, such as those proposed here, will become a standard tool for farms and laboratories and that it will become increasingly challenging to produce shrimp without considering their welfare throughout the production cycle.

The combined effects of salinity and ammonia on the growth behavior, stress-related markers, and hepato-renal function of common carp (Cyprinus carpio)

One of the most critical factors affecting aquaculture efficiency is the capability of releasing ammonia from the water. By applying a high salinity strategy, this study provides a prompt approach for removing high ammonia levels and relieving its adverse impacts on common carp. The study investigated five groups with triplicates where the control was kept with fresh water, and the remaining four groups stressed with different salinity levels (5, 10, 15, and 20 ppt) for 8 weeks. Then fish were exposed to unionized ammonia (NH₃ ) stress (0.5 ppm) for 6 h. The final weight (FBW) and weight gain (WG) showed lower values in fish stressed with 15 and 20 ppt salinity levels than fish reared in 0 and 5 ppt salinity levels (p < 0.05). The lowest FBW and WG and the highest feed conversion ratio were shown in fish grown in 20 ppt (p < 0.05). The survival rate was markedly lowered by 15 and 20 ppt salinity levels (p < 0.05), while no significant differences were observed among 0, 5, and 10 ppt salinity levels (p > 0.05). Liver condition-related indices (alanine aminotransferase, aspartate aminotransferase, and alanine aminotransferase) were markedly increased in fish grown in 15 and 20 ppt before or after ammonia stress (p < 0.05). The results showed higher creatinine levels in fish raised in 15 and 20 ppt than the remaining salinity levels, with the highest value in fish of 20 ppt salinity before and after ammonia stress (p < 0.05). Markedly the blood glucose and cortisol levels were upraised in fish reared in 10, 15, and 20 ppt before and after ammonia stress (p < 0.05). The glucose level was not significantly different in fish reared in 5 ppt than 0 and 10 ppt salinity levels (p < 0.05). Generally, the blood glucose and cortisol levels were decreased markedly after ammonia stress than before ammonia stress (p < 0.05). Interestingly, total protein, albumin, and globulin levels were increased in common carp reared in different salinity levels after ammonia stress (p < 0.05). In conclusion, ammonia toxicity combined with high salinity resulted in a regulatory effect on the hepato-renal function and stress-related markers in common carp.

Water parameters correlated with the zootechnical performance of shrimp Litopenaeus vannamei grown in oligohaline waters

The present study aimed to correlate the influence of water quality, cultivation time, area, and density of ponds on the zootechnical performance of shrimp Litopenaeus vannamei in oligohaline waters. It was demonstrated that, under the conditions of this research, better control of temperature, pH and water alkalinity can be employed. Ammonia levels were within the normal range and correlated positively with the growth rate (ρ = 0.69859) and production (ρ = 0.66362) of the ponds. There was also a positive correlation between cultivation time and pond density with shrimp weight (ρ = 0.75305 and 0.68933) and pond productivity (ρ = 0.74763 and 0.79367, respectively). Negative correlations were observed between: I) pH with shrimp survival (ρ = -0.73238) and pond production (ρ = -0.68696); II) alkalinity and pond production (ρ = -0.66162). The results show that the cultivation of shrimp L. vannamei in oligohaline waters is viable and there is potential for increased productivity associated with better hydrological monitoring and use of higher density and cultivation time by some producers.

Characterization of Isolated Aerobic Denitrifying Bacteria and Their Potential Use in the Treatment of Nitrogen-Polluted Aquaculture Water

Ammonia and nitrite treatments are the critical steps that must be done to ensure the healthy growth of aquatic animals. The nitrification process is often used for nitrogen removal purposes due to its efficiency and environmentally friendly properties. However, the varied growth rate between ammonia and nitrite-oxidizing bacteria can cause nitrite accumulation, leading to the massive mortality of aquatic animals at high concentrations. Therefore, this study aimed to integrate the fast-growing heterotrophic nitrite-reducing bacteria with nitrifying bacteria to achieve a quicker nitrite removal activity. The two denitrifying Bacillus sp. ST20 and Bacillus sp. ST26 were screened from shrimp ponds in Bac Lieu province, Vietnam. Obtained results showed that under anoxic conditions, the nitrite removal efficiency of these two strains reached 68.5-82% at nitrite initial concentration of 20 mgN-NO₂/L after 72 h. Higher efficiency of over 95% was gained under oxic conditions. Hence, it enabled the use of denitrifying and nitrifying bacteria-co-immobilized carriers for ammonia oxidation and nitrite reduction simultaneously in a single-aerated bioreactor. A total of over 96% nitrogen content was removed during the bioreactor operation, despite the increase of inputting nitrogen concentration from 40 to 200 mgN/L. Moreover, the suitable conditions for bacterial growth and nitrite conversion activity of the ST20 and ST26 were detected as 15‰ salinity and 35 °C. The isolates also utilized various C-sources for growth, hence widening their applicability. The present study suggested that the isolated aerobic denitrifying bacteria are potentially used for the complete removal of nitrogen compounds from aquaculture wastewater.

A multi-step nitrifying microbial enrichment to remove ammonia and nitrite in brackish aquaculture systems

One of the most important advancements in harnessing the biological nitrification in the field is enrichment solution of nitrifying microbial consortia. In the current study, we developed an improved multi-step enrichment to amplify a targeted microbial consortium from a sediment sample collected in tropical mangrove, Vietnam. The results showed that it took 122 culturing days with five unique continuous enrichment steps, the microbial consortium consumed total 5665 mgN L^-1. Relative substrate removal rate increased rapidly from 0.114 mgN L^-1 h^-1 at the end of the first-step enrichment up to 3.58 mgN L^-1 h^-1 at the end of the fifth-step enrichment. High-throughput sequencing revealed that Nitrospirae, Proteobacteria and Bacteroidetes were the dominant taxa at the phylum level while Nitrospira, Marinobacter, Denitromonas and Nitrosomonas were the dominant taxa at the genus level in the enriched consortia. A pilot-scale experiment for shrimp cultivation of L. vannamei in 84 day-period proved the efficiency of Total ammonium nitrogen and nitrite removal in the consortium-activated treatment was much higher than the control.

Effects of ammonia on gill (Na+, K+)-ATPase kinetics in a hololimnetic population of the Amazon River shrimp Macrobrachium amazonicum

Water quality is essential for successful aquaculture. For freshwater shrimp farming, ammonia concentrations can increase considerably, even when culture water is renewed frequently, consequently increasing the risk of ammonia intoxication. We investigated ammonia lethality (LC₅₀-96 h) in a hololimnetic population of the Amazon River shrimp Macrobrachium amazonicum from the Paraná/Paraguay River basin, including the effects of exposure to 4.93 mg L^-1 total ammonia concentration on gill (Na⁺, K⁺)-ATPase activity. The mean LC₅₀-96 h was 49.27 mg L^-1 total ammonia, corresponding to 1.8 mg L^-1 un-ionized ammonia. Except for NH₄⁺ affinity that increased 2.5-fold, that of the gill (Na⁺, K⁺)-ATPase for ATP, Mg²⁺, Na⁺, K⁺ and ouabain was unchanged after ammonia exposure. Western blotting of gill microsomal preparations from fresh caught shrimps showed a single immunoreactive band of ≈110 kDa, corresponding to the gill (Na⁺, K⁺)-ATPase α-subunit. Ammonia exposure increased (Na⁺, K⁺)-ATPase activity by ≈25%, coincident with an additional 130 kDa α-subunit immunoreactive band, and increased K⁺-stimulated and V(H⁺)-ATPase activities by ≈2.5-fold. Macrobrachium amazonicum from the Paraná/Paraguay River basin is as tolerant to ammonia as are other Amazon River basins populations, showing toxicity comparable to that of marine crustaceans.

Effect of bovine lactoferricin on the growth performance, digestive capacity, immune responses and disease resistance in Pacific white shrimp, Penaeus vannamei

The present study evaluated the growth performance, digestive enzyme activity, non-specific immunity, immunity and growth genes in Penaeus vannamei fed diets supplemented with Bovine lactoferricin (the basal diet without Bovine lactoferricin, the control; 1.0‰ Bovine lactoferricin，LCB1; 1.5‰ Bovine lactoferricin，LCB1.5; 2.0‰ Bovine lactoferricin, LCB2; 2.5‰ Bovine lactoferricin, LCB2.5) for 56 days. The feeding trial showed that the final weight, weight gain rate, and specific growth rate of the shrimp were improved significantly, while the feed conversion ratio was reduced significantly in the LCB1.5 group compared to the control (P < 0.05). The challenge test of Vibrio parahaemolyticus showed that the cumulative mortalities of shrimp in the LCB1.5, LCB2 and LCB2.5 groups were significantly lower than that in the control (P < 0.05). Compared with the control, Lipase and Trypsin activities in the hepatopancreas of LCB1.5 and LCB2 groups were significantly enhanced (P < 0.05). Compared with the control, alkaline phosphatase, acid phosphatase activities in the hepatopancreas and the relative expression levels of Relish, Toll, JAK, STAT, TOR, Raptor, 4E-BP, eIF4E1α, eIF4E2 genes in the hepatopancreas of LCB1.5, LCB2 and LCB2.5 groups were all significantly enhanced (P < 0.05). These results suggested that dietary Bovine lactoferricin could improve the growth performance, digestive capacity and immune responses of shrimp. When resistance against Vibrio parahaemolyticus in shrimp is considered, high dosage of Bovine lactoferricin showed a better effect than low dosage of Bovine lactoferricin. However, high dosage of Bovine lactoferricin can have a negative impact on the growth performance of shrimp. Considering collectively the above, Bovine lactoferricin could improve the growth performance, digestive enzymes activities, immune responses and disease resistance of P. vannamei.

Sedimentary Nitrogen and Sulfur Reduction Functional-Couplings Interplay With the Microbial Community of Anthropogenic Shrimp Culture Pond Ecosystem

Sediment nitrogen and sulfur cycles are essential biogeochemical processes that regulate the microbial communities of environmental ecosystems, which have closely linked to environment ecological health. However, their functional couplings in anthropogenic aquaculture sedimentary ecosystems remain poorly understood. Here, we explored the sediment functional genes in shrimp culture pond ecosystems (SCPEs) at different culture stages using the GeoChip gene array approach with 16S amplicon sequencing. Dissimilarity analysis showed that the compositions of both functional genes and bacterial communities differed at different phases of shrimp culture with the appearance of temporal distance decay (p < 0.05). During shrimp culture, the abundances of nitrite and sulfite reduction functional genes decreased (p < 0.05), while those of nitrate and sulfate reduction genes were enriched (p < 0.05) in sediments, implying the enrichment of nitrites and sulfites from microbial metabolism. Meanwhile, nitrogen and sulfur reduction genes were found to be linked with carbon degradation and phosphorous metabolism (p < 0.05). The influence pathways of nutrients were demonstrated by structural equation modeling through environmental factors and the bacterial community on the nitrogen and sulfur reduction functions, indicating that the bacterial community response to environmental factors was facilitated by nutrients, and led to the shifts of functional genes (p < 0.05). These results indicate that sediment nitrogen and sulfur reduction functions in SCPEs were coupled, which are interconnected with the SCPEs bacterial community. Our findings will be helpful for understanding biogeochemical cycles in anthropogenic aquaculture ecosystems and promoting sustainable management of sediment environments through the framework of an ecological perspective.

A state-of-the-art review on producing engineered biochar from shellfish waste and its application in aquaculture wastewater treatment

Global production of shellfish aquaculture is steadily increasing owing to the growing market demands for shellfish. The intensification of shellfish aquaculture to maximize production rate has led to increased generation of aquaculture waste streams, particularly the effluents and shellfish wastes. If not effectively managed, these wastes could pose serious threats to human health and the ecosystem while compromising the overall sustainability of the industry. The present work comprehensively reviews the source, composition, and environmental implications of shellfish wastes and aquaculture wastewater. Moreover, recent advancements in the valorization of shellfish wastes into value-added biochar via emerging thermochemical and modification techniques are scrutinized. The utilization of the produced biochar in removing emerging pollutants from aquaculture wastewater is also discussed. It was revealed that shellfish waste-derived biochar exhibits relatively higher adsorption capacities (300-1500 mg/g) compared to lignocellulose biochar (<200 mg/g). The shellfish waste-derived biochar can be effectively employed for the removal of various contaminants such as antibiotics, heavy metals, and excessive nutrients from aquaculture wastewater. Finally, future research priorities and challenges faced to improve the sustainability of the shellfish aquaculture industry to effectively support global food security are elaborated. This review envisages that future studies should focus on the biorefinery concept to extract more useful compounds (e.g., carotenoid, chitin) from shellfish wastes for promoting environmental-friendly aquaculture.

Water quality and climate variability of urban and tourism areas in Thailand and northern Vietnam: correlations and possible influences on nearby coastal shrimp farms

This research explored the long-term relationships of climate parameters and coastal water quality nearby shrimp farms in two countries. In Thailand, two sampling points in canals located in Bangkok and Trang provinces were selected as the urban and tourism areas, respectively. In northern Vietnam, the canals located in Thai Binh and Quang Ninh provinces were used as the urban and tourism areas, respectively. The diurnal monitoring of water quality and weather was performed at each site to evaluate the relationships between climate and water quality, pollution load, and risk analysis. A questionnaire was also used to assess the climate and water exposure, vulnerability, and adaptability of each site. All data were ranked on a scale of 1 to 5 to integrate each factor. It was determined that the main water quality problem was fecal pollution. Notably, aquaculture farming in northern Vietnam is more vulnerable than in Thailand; however, Vietnam farmers were adaptable for climate variability.

Effects of Different Densities of Sea Grape Caulerpa lentillifera on Water Quality, Growth and Survival of the Whiteleg Shrimp Litopenaeus vannamei in Polyculture System

The integrated aquaculture-seaweed system has been identified as a bio-mitigation strategy to overcome environmental damage, improve the efficiency of nutrient use, maintain good water quality, and ensure the system’s sustainability. This study was conducted to determine the appropriate density of sea grape (Caulerpa lentillifera) in polyculture with whiteleg shrimp (Litopenaeus vannamei) in the same culture tank. Five treatments were randomly designed in triplicate tanks where shrimp was monocultured (without sea grape) as a control treatment and four polyculture treatments with different seaweed density levels (0.5, 1, 1.5, and 2 kg m−3) for 56 days. The results showed that polyculture of shrimp and sea grape significantly reduced the concentrations of total ammonia nitrogen (TAN), nitrite (NO2−), nitrate (NO3−), and phosphate (PO43−) in the rearing tanks and significantly improved (p < 0.05) the growth rate (6.67–6.76% day−1), survival (73.3–78.5%), and production of shrimp (3.44–3.87 kg m−3) compared to monoculture (6.24% day−1, 54.8%, and 2.02 kg m−3, respectively). Applying shrimp and sea grape polyculture at a density of 1 kg m−3 provided a relatively better shrimp performance and feed conversion ratio than other seaweed densities, although not significantly different among polyculture treatments. The findings suggested that sea grape could be used at densities of 0.5–2 kg m−3 in polyculture with whiteleg shrimp, of which 1 kg m−3 resulted in higher production and feed efficiency.

Abundance, community structure and diversity of nitrifying bacterial enrichments from low and high saline brackishwater environments

The study reports diversity in nitrifying microbial enrichments from low (0·5-5‰) and high (18-35‰) saline ecosystems. Microbial community profiling of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) enrichments was analysed by sequencing 16S rRNA and was processed using Mothur pipeline. The α-diversity indices showed the richness of nitrifying bacterial consortia from the high saline environment and were clustering based on the source of the sample. AOB and NOB enrichments from both the environments showed diverse lineages of phyla distributed in both groups with 38 and 34 phyla from low saline and 53 and 40 phyla in high saline sources, respectively. At class level, α- and γ-proteobacteria were found to be more dominant in both the enrichments. AOBs and NOBs in enrichments from low saline environments were dominated by Nitrosomonadaceae, Gallionellaceae (Nitrotoga sp.) and Ectothiorhodospiraceae and Nitrospira, respectively. Though Chromatiaceae were present in both AOB and NOB enrichments, Nitrosoglobus and Nitrosococcus dominated the AOBs while NOBs were dominated by uncultured genera, whereas Rhizobiales were found in both the enrichments. AOBs and NOBs in enrichments from high saline environments were dominated by Nitrospira-like AOBs, Nitrosomonas and Nitrosococcus genera, whereas ammonia-oxidizing archaea (AOA) group included Nitrosopumilus and Nitrososphaera genera comprising and Nitrospirae, respectively. The majority of the genera obtained in both the salinities were found to be either uncultured or unclassified groups. Results of the study suggest that the AOB and NOB consortia have unique and diverse microbes in each of the enrichments, capable of functioning in aquaculture systems practised at different salinities (0-60 ppt).

Dietary supplementation with probiotic Rhodobacter sphaeroides SS15 extract to control acute hepatopancreatic necrosis disease (AHPND)-causing Vibrio parahaemolyticus in cultivated white shrimp

Cultivation of Penaeus vannamei (Pacific white shrimp) is faced with the serious problem of acute hepatopancreatic necrosis disease (AHPND), caused by Vibrio parahaemolyticus that carries plasmids containing binary toxin genes. The disease is typically moderated by the use of antibiotics. To investigate the control of AHPND and maintenance of water quality without the use of antibiotics, the supplementation of shrimp feed with anti-vibrio compounds from a crude extract of probiotic Rhodobacter sphaeroides SS15 was evaluated. The experimental design comprised four treatments: two that were challenged with AHPND-causing V. parahaemolyticus SR2 at a density of 6.0 x 10⁵ cells mL^-1 and two that were not challenged. The unchallenged groups comprised a control group that received commercial feed only (CF) and a group that received CF supplemented with 0.27% (w/w) of the extract of R. sphaeroides SS15 (modified CF: MCF). The treatments challenged with V. parahaemolyticus SR2 comprised a challenge group that received CF only (challenge CF: CF-SR2) and a challenge group that received modified CF (challenge MCF: MCF-SR2). V. parahaemolyticus SR2 was inoculated at the start of cultivation and at day 48 at the same cell density. No significant difference in growth performance was found among all treatments. All water quality parameters were better in the two treatments that received modified CF but excess nitrite, due to overfeeding in low salinity (5-8 ppt), caused shrimp mortality in all treatments. Vibrio populations were much higher in the CF treatments than in the modified CF treatments. After the first challenge, the survival rate was about 67% in both the CF-SR2 and MCF-SR2 treatments, compared with approximately 83% in the unchallenged treatments. One day after the second challenge, mortality in the CF-SR2 treatment was 100%, whereas 16.67% survived in the MCF-SR2 treatment. The survival rate was roughly 27% higher in the MCF treatment than in the CF treatment. The hepatopancreas and gut of both modified CF treatments showed no sign of AHPND. Via better water quality and trained immunity, the anti-vibrio compounds in the modified CF have great potential to increase the survival of cultivated shrimp infected with AHPND-causing strain SR2.

Sustainability and feasibility assessments of nanobubble aeration technology in economic-socio environment of Penaeus vannamei shrimp farming

Penaeus vannamei shrimp farming in Indonesia is faced with several challenges in the environmental, economic, and social aspects. Therefore, this study aims to assess the benefits of novel nanobubble aeration systems for the ecosystem, businesses, and communities. This is an experimental study conducted by comparing P. vannamei post larva 10 reared at a density of 2000 inds./L in a pond treated with nanobubble and without treatments (control). Furthermore, the Net Present Value (NPV) and payback period were calculated to assess the economic feasibility of nanobubble, while community interviews were used for the social sectors. Based on the results, environmental wastes of shrimp farming in form of total ammonia nitrogen (TAN) were reduced by 9% from 2.58 mg/l (95%CI: 0,91, 4,25) in control compared to 2.35 mg/l (95%CI: 0,86, 3,84) in treatment. Furthermore, the revenues from post larva sales for five years and nanobubble investment costs showed that the estimated NPV was IDR 64,824,374 with a payback period of 1.7 years. The interviews on traditional shrimp farming showed that 61.1% to 72.2% of community members agreed on the use of nanobubble aeration to support livelihoods. Therefore, the use of nanobubbles is feasible to support sustainable P. vannamei farming.

Identification of a quantitative trait loci (QTL) associated with ammonia tolerance in the Pacific white shrimp (Litopenaeus vannamei)

Background

Ammonia is one of the most common toxicological environment factors affecting shrimp health. Although ammonia tolerance in shrimp is closely related to successful industrial production, few genetic studies of this trait are available.

Results

In this study, we constructed a high-density genetic map of the Pacific white shrimp (Litopenaeus vannamei) using specific length amplified fragment sequencing (SLAF-seq). The constructed genetic map contained 17,338 polymorphic markers spanning 44 linkage groups, with a total distance of 6360.12 centimorgans (cM) and an average distance of 0.37 cM. Using this genetic map, we identified a quantitative trait locus (QTL) that explained 7.41–8.46% of the phenotypic variance in L. vannamei survival time under acute ammonia stress. We then sequenced the transcriptomes of the most ammonia-tolerant and the most ammonia-sensitive individuals from each of four genetically distinct L. vannamei families. We found that 7546 genes were differentially expressed between the ammonia-tolerant and ammonia-sensitive individuals. Using QTL analysis and the transcriptomes, we identified one candidate gene (annotated as an ATP synthase g subunit) associated with ammonia tolerance.

Conclusions

In this study, we constructed a high-density genetic map of L. vannamei and identified a QTL for ammonia tolerance. By combining QTL and transcriptome analyses, we identified a candidate gene associated with ammonia tolerance. Our work provides the basis for future genetic studies focused on molecular marker-assisted selective breeding.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-020-07254-x.

Intestine Bacterial Community Composition of Shrimp Varies Under Low- and High-Salinity Culture Conditions

Intestine microbiota is tightly associated with host health status. Increasing studies have focused on assessing how host intestine microbiota is affected by biotic factors but ignored abiotic factors. Here, we aimed to understand the effects of salinity on shrimp intestine microbiota, by comparing the differences of intestine bacterial signatures of shrimp under low-salinity (LS) and high-salinity (HS) culture conditions. Our results found that intestine core bacterial taxa of shrimp under LS and HS culture conditions were different and that under HS contained more opportunistic pathogen species. Notably, compared with LS culture conditions, opportunistic pathogens (e.g., Vibrio species) were enriched in shrimp intestine under HS. Network analysis revealed that shrimp under HS culture conditions exhibited less connected and lower competitive intestine bacterial interspecies interactions compared with LS. In addition, under HS culture conditions, several opportunistic pathogens were identified as keystone species of intestine bacterial network in shrimp. Furthermore, the ecological drift process played a more important role in the intestine bacterial assembly of shrimp under HS culture conditions than that under LS. These above traits regarding the intestine microbiota of shrimp under HS culture conditions might lead to host at a higher risk of disease. Collectively, this work aids our understanding of the effects of salinity on shrimp intestine microbiota and helps for shrimp culture.

Construction of a High-Density Genetic Map and Identification of Quantitative Trait Loci for Nitrite Tolerance in the Pacific White Shrimp (Litopenaeus vannamei)

Nitrite is a major environmental toxin in aquaculture systems that disrupts multiple physiological functions in aquatic animals. Although nitrite tolerance in shrimp is closely related to successful industrial production, few genetic studies of this trait are available. In this study, we constructed a high-density genetic map of Litopenaeus vannamei with 17,242 single nucleotide polymorphism markers spanning 6,828.06 centimorgans (cM), with an average distance of 0.4 cM between adjacent markers on 44 linkage groups (LGs). Using this genetic map, we identified two markers associated with nitrite tolerance. We then sequenced the transcriptomes of the most nitrite-tolerant and nitrite-sensitive individuals from each of four genetically distinct L. vannamei families (LV-I–4). We found 2,002, 1,983, 1,954, and 1,867 differentially expressed genes in families LV-1, LV-2, LV-3, and LV-4, respectively. By integrating QTL and transcriptomics analyses, we identified a candidate gene associated with nitrite tolerance. This gene was annotated as solute carrier family 26 member 6 (SLC26A6). RNA interference (RNAi) analysis demonstrated that SLC26A6 was critical for nitrite tolerance in L. vannamei. The present study increases our understanding of the molecular mechanisms underlying nitrite tolerance in shrimp and provides a basis for molecular-marker-assisted shrimp breeding.

In vitro disinfection efficacy and clinical protective effects of common disinfectants against acute hepatopancreatic necrosis disease (AHPND)-causing Vibrio isolates in Pacific white shrimp Penaeus vannamei

Acute hepatopancreatic necrosis disease (AHPND) is one of the most significant bacterial diseases in global shrimp culture, causing severe economic losses. In the present study, we carried out in vitro antimicrobial tests to investigate the disinfection efficacy of 14 common disinfectants toward different AHPND-causing Vibrio spp., including eight isolates of V. parahaemolyticus, four isolates of V. campbellii, and one isolate of V. owensii. Polyhexamethylene biguanidine hydrochloride (PHMB) was revealed to possess the strongest inhibitory activity. Through analyzing and evaluating the results of antimicrobial tests and acute toxicity test, we selected PHMB and hydrogen peroxide (H₂O₂) for further clinical protection test. Clinical manifestations indicated that both PHMB (2 mg/L and 4 mg/L) and H₂O₂ (12 mg/L) could effectively protect juvenile Penaeus vannamei from the infection of V. parahaemolyticus isolate Vp362 at 10⁶ CFU/ml, and the survival rate was over 80%. When the bacterial concentration was reduced to 10⁵ CFU/ml, 10⁴ CFU/ml, and 10³ CFU/ml, the survival rate after treated by 1 mg/L PHMB was 64.44%, 93.33%, and 100%, respectively. According to the results, PHMB and H₂O₂ showed a lower toxicity while a better protection activity, particularly against a lower concentration of the pathogens. Therefore, these two disinfectants are proved to be promising disinfectants that can be applied to prevent and control AHPND in shrimp culture. Moreover, the methods of this study also provided valuable information for the prevention of other important bacterial diseases and suggested a reliable means for screening potential drugs in aquaculture.

Removal of ammoniacal nitrogen from municipal landfill leachate with floating Typha domingensis (Typhaceae)

 A promising method for the treatment of effluents is the use of floating macrophytes. Ammoniacal nitrogen is a typical compound present in urban landfill leachates and its removal is important due its toxicity to several organisms. Therefore, the study evaluated Typha domingensis survival and nitrification potential artificially floating in domestic solid waste leachate. Plants were exposed for 35 days to leachate (100, 75 and 50 %) and to rainwater with N:P:K (control). Dissolved oxygen (DO) of the treatments was periodically measured, and ammoniacal nitrogen, nitrite and nitrate were analyzed before and after exposure. At the end of the experiment, plant survival rate was calculated. After two weeks, DO increased twice in the control, three times in 50 % leachate, four times in 75 % leachate, and eight times in 100 % leachate. At the end of the experiment, ammoniacal nitrogen was no longer detected, there was a significant reduction of nitrite, and a significant increase of nitrate in the treatments containing leachate. Plant survival was higher in those individuals exposed to 100 % leachate and decreased at lower leachate concentrations: 98 %, 94 %, 92 %, and 86 %. The study demonstrated that the ammoniacal nitrogen concentration of the leachate was not toxic to T. domingensis, and that it was efficient in the removal of this compound from the effluent, indicating that the species may be used artificially floating for the removal of this contaminant from domestic solid waste landfill leachate when in low concentrations.

Growth and Lipidomic Responses of Juvenile Pacific White Shrimp Litopenaeus vannamei to Low Salinity

The Pacific white shrimp (Litopenaeus vannamei), a euryhaline penaeid species, can tolerate a wide range of salinities, but little is known on its strategies to cope with low salinity fluctuations from the aspect of lipidomics. Thus, in this study, L. vannamei were grown in two different salinities [3 and 30‰ (control)] for 8 weeks, and then an liquid chromatography (LC)-mass spectrometry (MS)-based lipidomics analysis was performed to reveal the lipid profile differences in gill and muscle. L. vannamei under low salinity had lower weight gain and condition factor than the control shrimp at 30‰, but no differences were found in survival and hepatopancreas index. A higher number of differential lipid metabolites were identified in gill than in muscle in L. vannamei at salinity 3‰ relative to the control shrimp at salinity of 30‰ (159 versus 37), which belonged to 11 and 6 lipids classes, respectively. Of these lipids, phosphatidylcholine (PC), phosphatidylinositol (PI), phosphatidic acid (PA), phosphatidylethanolamine (PE), and triglyceride (TG) were the main lipids in both shrimp gill and muscle, regardless of salinities. Compared with the control shrimp at salinity 30‰, the percentage of PC significantly reduced, but TG and PA significantly increased in gill of shrimp at salinity 3‰. Moreover, the relative fatty acid abundances showed significant changes in L. vannamei between the two salinity groups, but the patterns of the changes were complex and were fatty acid dependent. Neither lipid nor fatty acid composition in muscle was affected by salinity. Further pathway analysis showed that these metabolites were closely related to lipid and fatty acid metabolic pathways. All the findings in this study reveal that the lipid variations are closely related to bio-membrane structure, mitochondrial function, energy supply, or organic osmolyte contents in hemolymph for improving osmoregulatory capacity of L. vannamei under low salinity.

Toxicity of ammonia, nitrite and nitrate to Litopenaeus vannamei juveniles in low-salinity water in single and ternary exposure experiments and their environmental implications

Information on toxicity of nitrogen compounds for Litopenaeus vannamei in coastal ecosystems and culture under low salinity is scarce. Acute toxicity trials were conducted in L. vannamei to determine the single and combined effects of ammonia, nitrite and nitrate at a salinity of 3 g/L. The 96 h-LC₅₀ was 29.0 mg/L for total ammonia nitrogen (TAN); 10.6 mg/L for nitrogen as nitrite (NO₂^--N); and 900 mg/L for nitrogen as nitrate (NO₃^--N). The joint effects of ammonia, nitrite and nitrate exposure were antagonistic at 24-72 h; and additive from 72 to 96 h. The proposed safety levels of single exposure to TAN, NO₂^--N and NO₃^--N for L. vannamei are 1.45, 0.53 and 45.0 mg/L, respectively. When in mixture, the proposed level of TAN/NO₂^--N/NO₃^--N is 0.05 TU (Toxicity Unit) corresponding to 0.48, 0.08 and 14.6 mg/L of TAN, NO₂^--N and NO₃^--N, respectively.

Transcriptome reveals involvement of immune defense, oxidative imbalance, and apoptosis in ammonia-stress response of the black tiger shrimp (Penaeus monodon)

Ammonia is a major aquatic environmental pollutant that negatively impacts shrimp health and commercial productivity. However, we currently do not fully understand the underlying molecular mechanisms of ammonia stress in shrimp. We therefore performed transcriptomic analysis of hepatopancreas from black tiger shrimp (Penaeus monodon) treated with ammonia-stress. We obtained 146,410,174 and 115,241,048 clean reads for the control and treatment groups, respectively. A total of 64,475 unigenes with an average length of 1275 bp and a N50 value of 2158 bp were assembled. A comparative transcriptome analysis identified 3462 differentially expressed genes, 177 of which are highly homologous with known proteins in aquatic species. Most of these genes showing the expression changes were related to immune function. Some significantly down-regulated genes are involved in purine metabolism and other metabolic pathways, which suggests that purineolytic capacity is an ammonia detoxification process in P. monodon, and metabolic depression is a strategy to reduce shrimp exposure to ammonia. Additionally, ammonia stress altered the expression patterns of key apoptosis genes (Bcl-xL, PERK, caspase 7, and caspase 10), confirmed that ammonia-stress induce oxidative stress and eventually even apoptosis. We also found evidence for the involvement of antioxidant defense in response to oxidative imbalance, given the regulation of peroxiredoxin 1, SOD, and CAT under ammonia stress. In conclusion, our study clarifies shrimp defensive response to ammonia toxicity and should benefit efforts to breed more ammonia-tolerant varieties.