Ammonia exposure induces oxidative stress, endoplasmic reticulum stress and apoptosis in hepatopancreas of pacific white shrimp (Litopenaeus vannamei)

The shrimp NF-κB pathway is activated to mediate the antioxidant defense and apoptosis under ammonia-N stress

Ammonia-N stress from aquaculture system can interfere physiological function in shrimp leading to constant oxidative stress and apoptosis, but little is known concerning the upstream regulators. In this study, survival analysis and Western blot was perform to determine the optimal concentration and inhibitory effect on NF-κB pathway inhibitor (PDTC). Then the influence of 30 mg/kg PDTC on the ammonia-N tolerance, antioxidation, and apoptosis in L. vannamei exposed to 20 mg/L NH4Cl were evaluated. The results showed that PDTC promoted the gills tissue damage, hemolymph ammonia-N accumulation, and total hemocyte count (THC) decrease, thus resulting in a decreased survival rate in ammonia-exposed shrimp. Furthermore, PDTC exacerbated the oxidative damage by downregulating the expression of antioxidant-related genes. In addition, PDTC could enhance the Caspase-3 activity and apoptosis rate in gills by modulating the expression of genes associated with the mitochondrial apoptosis pathway. In primary cultured hemocytes of L. vannamei treated with 10 mM NH4Cl, PDTC treatment resulted in elevated ROS level and Caspase-3 activity, but also a decrease in mitochondrial membrane potential (MMP) and cell viability. These findings indicate that NF-κB activation acts as a critical upstream regulator of antioxidant defense and apoptosis in shrimp under ammonia-N stress.

Ammonia-induced testicular tissue damage: Apoptosis and autophagy pathways mediated by regulating Cyt C/Bcl-2 and p62/LC3B pathways

Ammonia gas (NH3) is a major hazard in animal husbandry that negatively affects animal growth and reproductive activities. Although the adverse effects of ammonia on livestock health and performance have been studied, its specific effects on the male reproductive system and its underlying biological mechanisms remain unclear. The aim of this study was to investigate the effects of ammonia exposure on male reproduction and its potential mechanisms of action. Immunohistochemistry revealed a significant increase in IL-10 expression in mouse testicular tissues under ammonia-induced stress. Ammonia exposure significantly decreased anti-apoptotic factor Bcl-2 and anti-autophagy factor p62 expression, coupled with increased expression of pro-apoptotic factors, including p53, Caspase-8, Bax, and Apaf, as well as the pro-autophagy factors Beclin1, ATG5, LC3B, the ratio of Bax/Bcl-2 and the ratio of P53/Bcl-2. The fluorescence intensity of the Cyt C apoptotic gene and pro-autophagy factor LC3B in immune tissues was significantly higher than that in the normal control group. In summary, ammonia exposure significantly affects the reproductive ability of male mice by inducing inflammation, apoptosis, and autophagic damage in the testes. Our findings provide insights into ammonia-induced reproductive disorders, which will contribute to the management and control of ammonia in animal husbandry, thereby reducing the negative effects of ammonia on the reproductive health of livestock and poultry and improving the quality and yield of livestock products.

Dietary Melatonin Supplementation Improved Intestinal Health and Immune Function of Pacific White Shrimp (Litopenaeus vannamei) Under High Alkali Stress

The intestinal tract serves as a critical immune regulator in aquatic species, maintaining homeostasis and environmental stress resistance. This study evaluates the protective effects of melatonin (MT) on Litopenaeus vannamei (L. vannamei) under acute alkaline stress through a comprehensive analysis of intestinal morphology, antioxidant responses, apoptosis regulation, and microbial community dynamics. A total of six groups of melatonin treatment groups were designed. After another 2 months of breeding, a 96 h acute alkalinity stress experiment was conducted. Experimental supplementation revealed dose-dependent outcomes: 82.7 mg/kg MT significantly improved survival rates without affecting growth parameters, while higher concentrations (329.2 mg/kg) induced elevated apoptosis (p < 0.05). Histological examination demonstrated mitigated intestinal structural damage in MT-treated groups compared to non-supplemented controls under alkaline stress. Antioxidant capacity initially increased and then stabilized at optimal MT doses (82.7-165.1 mg/kg), accompanied by enhanced immune marker expression (p < 0.05). Microbial profiling indicated MT-mediated enrichment of commensal bacteria associated with polysaccharide metabolism, energy utilization, and intestinal immunity. This study establishes that melatonin exerts dose-dependent protection in L. vannamei under alkaline stress, balancing antioxidant enhancement, apoptosis modulation, and microbiome regulation to fortify intestinal health, with 82.7-165.1 mg/kg identified as the optimal therapeutic range for mitigating environmental stress without compromising physiological homeostasis. The results of this study establish an empirical framework for optimizing MT application in crustacean aquaculture, particularly highlighting its role in maintaining intestinal barrier integrity and microbial homeostasis under alkaline environmental challenges.

Metabolic Response of Black Tiger Shrimp (Penaeus monodon) to Acute Ammonia Nitrogen Stress

High concentrations of ammonia nitrogen could result in the death of aquatic animals and cause a huge economic loss in the aquaculture industry. However, the metabolic responses to acute ammonia nitrogen stress remain largely unknown in Penaeus monodon. In this study, we first investigated the histological change in tissues in Penaeus monodon under 96 h acute ammonia nitrogen stress. The result of the paraffin section showed that acute ammonia nitrogen stress induced severe epithelial detachment and lumen dilatation of the hepatopancreas, swollen and hemocyte infiltration of the gills, and mucosa exfoliation and shortened villi of the intestine in Penaeus monodon, suggesting the impairment of the normal physiological function in these tissues. We next examined the change in the metabolic product in the plasma and the enzyme activity in the hepatopancreas after ammonia nitrogen stress. Upon ammonia stress, both the concentration of ammonia and urea nitrogen significantly increased, while there was no significant increase in the concentration of uric acid, which is consistent with the results that the enzyme activity of glutamine synthetase (GS), glutamate dehydrogenase (GDH), and aspartate transaminase (GOT) became significantly elevated and the enzyme activity of adenosine deaminase (ADA) in the purine metabolism pathway significantly decreased after ammonia stress, suggesting that shrimp could convert excessive ammonia to urea for ammonia detoxification through the ammonia-nitrogen metabolism pathways. Interestingly, we also observed a significant increase in superoxide dismutase (SOD) activity, suggesting a potential role of this antioxidant enzyme in the clearance of reactive oxygen species (ROS) induced via ammonia stress. Moreover, we found that acute ammonia nitrogen stress inhibited the enzyme activity of caspase 3 and caspase 8, suggesting an important role of apoptosis in protecting Penaeus monodon against acute ammonia stress. Overall, our findings revealed that Penaeus monodon may employ metabolic and purine pathways and undergo oxidative stress and apoptosis for ammonia detoxification under ammonia nitrogen stress, thus providing new insight into the metabolic response of shrimp to acute ammonia stress.

An integrated investigation of major environmental stressors on the Pacific white shrimp Litopenaeus vannamei

Ammonia, nitrite and sulfide are major environmental stressors in aquaculture. They can injury tissue structure, interfere with the immune system, impair growth and development, and make aquatic animals more vulnerable to infections. In the present study, four groups were set up as Control group (no treatment), Ammonia group (30 mg/L ammonia-N), Nitrite group (60 mg/L nitrite-N) and Sulfide group (4 mg/L sulfide), so as to examine the effects of different environmental stressors on histopathology, immune indices and transcriptome of Litopenaeus vannamei. After 48 h stimulation, the results showed that all the three environmental stressors caused damage to the hepatopancreas, midgut, muscle and gill tissues of the shrimp, and that the hepatopancreas and midgut were the most seriously damaged and the muscle was the least affected. Superoxide dismutase (SOD) activity increased and total antioxidant capacity (T-AOC) activity decreased in all the three treatment groups. Glutathione peroxidase (GSH-PX) activity decreased significantly in Sulfide group and alkaline phosphatase (AKP) activity increased significantly in Ammonia and Nitrite groups. In the hepatopancreas of the Ammonia, Nitrite, and Sulfide groups, transcriptome analysis revealed 709, 715 and 289 differential expressed gene (DEGs), respectively. GO and KEGG enrichment demonstrated that the three environmental stressors had an impact on the shrimp's immune response, metabolic processes, growth and development. The combination of histopathology, immune indicators, and transcriptome yielded that the Nitrite group had the most serious impact on the shrimp, followed by Ammonia group, while Sulfide group had the least impact.

Upregulation of HDAC3 mediates behavioral impairment in the bile duct ligation model of hepatic encephalopathy

Hepatic encephalopathy (HE), an outcome of chronic liver disease is characterized by behavioral impairments. The present study investigated the role of HDAC-mediated transcriptional regulation causing behavioral impairments in the bile duct ligation (BDL) model of HE. Post-BDL surgery in rats, dynamic alterations in liver function tests, liver morphology were observed. In BDL rats, histological staining in brain demonstrated reduced neuronal viability and warped neuronal architecture. Additionally, BDL animals showed impaired spatial learning, memory, and increased anxiety in the open field, Barnes maze, and Y maze tests. Further, the Golgi cox staining revealed a significantly altered spine density and spine clustering patterns of granular neuron in dentate gyrus of BDL rats. Concordantly, a significant downregulation of memory encoding genes was also observed in BDL rats that may account for aberrant behavior. Molecular analysis of modifiers, such as HDAC, showed significant changes in the expression of HDAC3 and HDAC6 in both the cortex and hippocampus of BDL rats. Upregulation of HDAC3 promoted its localization on the promoter of genes like c-Fos, NPAS4, Arc, and others, likely causing their decreased expression. Our findings suggest that increased HDAC3 activity downregulates key synaptic plasticity and memory-related genes, potentially driving neurobehavioral changes in BDL rats.

Sublethal urea exposure in Nile tilapia: Morphological, behavioural, and histological alteration

The pace of research efforts has been extraordinarily accelerated across the globe to address the contamination issues caused by pesticides, and fertilizers, especially in the aquatic ecosystem. The sole aim of this study was to assess the effect of urea on Nile tilapia (Oreochromis niloticus). For this purpose, the fish fingerlings were exposed to increasing concentrations of urea such as 0, 1, 2.5, 5, 10, 20, and 40 g/l for 72 h. Survival analysis suggested a strong correlation between the increasing doses of urea and the mortality rate among tested fingerlings. This study reported remarkable morphological, and behavioural alternation such as increased operculum movement, bottom-dwelling, lethargy, secretion of mucus, reduction in food intake, and bleeding in the fin and around the mouth in the treated group. Haematological analysis revealed that a significant reduction in RBC count and Hb along with an increase in WBC number is associated with urea toxicity. Our study showed a significant rise in glucose concentration upon urea toxicity in Nile tilapia fingerlings for the first time, emphasizing the adverse effect of fertilizers on carbohydrate metabolism. Significant rises in the enzymatic activity such as alanine aminotransferase (ALT), alkaline phosphatase (ALP), and aspartate aminotransferase (AST) upon urea treatment emphasize the possibilities of liver damage, biliary obstruction, and abnormal glucose metabolism. Histological analysis of urea-treated fish compared to normal fish revealed that urea toxicity drastically altered the tissue architecture of fish's gills, eyes, intestine, and stomach. As the visual systems of mammals and fish resemble in more aspects, our findings may be useful in understanding the impact of pollutants on sensory organs concerning humans. We conclude that our findings highlight the importance of urea toxicity on Nile tilapia fingerlings and invite multidisciplinary research to uncover molecular mechanisms underlying urea toxicity.

Mechanisms of intestinal DNA damage and inflammation induced by ammonia nitrogen exposure in Litopenaeus vannamei

Ammonia nitrogen, a common aquaculture pollutant, harms crustaceans by causing intestinal inflammation, though its exact mechanisms are unclear. Thus, we exposed shrimp to 0, 2, 10 and 20 mg/L NH4Cl exposure for 0, 3, 6, 12, 24, 48, 72 h, and explored the intestinal stress, apoptosis, proliferation, inflammation and its histopathological changes. This research indicated that ammonia nitrogen exposure heightens plasma dopamine (DA), 5-hydroxytryptamine (5-HT), norepinephrine (NE), and acetylcholine (ACh) levels, alters gene expression of neurotransmitter receptors in the intestine, triggering the PLCCa2+ pathway and induces endoplasmic reticulum stress. Additionally, mitochondrial fission-related genes (Drp1, FIS1) significantly increase, the level of reactive oxygen species (ROS) was significantly elevated in the intestine, which induced DNA damage effects and initiated the DNA repair function, mainly through the base excision repair pathway, but with a low repair efficiency. By determining the expression of key genes of caspase-dependent and non-caspase-dependent apoptotic pathways, it was found that ammonia nitrogen exposure induced apoptosis in intestinal cells, proliferation key signaling pathways such as Wnt, EGFR and FOXO signaling showed an overall decrease after ammonia nitrogen exposure, combined with the gene expression of cell cycle proteins and proliferation markers, indicated that the proliferation of intestinal cells was inhibited. Performing pearson correlation analysis of intestinal cell damage, proliferation, and inflammatory factors, we hypothesized that ammonia nitrogen exposure induces intestinal endoplasmic reticulum stress and mitochondrial fission, induces elevated ROS, leads to DNA damage, and causes inflammation and damage in intestinal tissues by the underlying mechanism of promoting apoptosis and inhibiting proliferation.

Immune and physiological responses in Penaeus monodon to ammonia-N stress: a multi-omics approach

Ammonia-N stress is a significant environmental factor that adversely affects the health and productivity of aquaculture species. This study investigates the effects of ammonia-N stress on the shrimp Penaeus monodon through a combination of biochemical, histological, transcriptomic, and metabolomic analyses. Shrimp were exposed to ammonia-N stress for 12 and 96 hours, and key markers of oxidative stress, nitrogen metabolism, immune response, and overall health were assessed. The results showed that prolonged ammonia-N exposure causes significant hepatopancreatic damage, including atrophy and deformation. Transcriptomic analysis revealed significant changes in gene expression related to apoptosis, immune response, and key metabolic pathways, with particular emphasis on the disruption of innate immune signaling and defense mechanisms. Metabolomic analysis identified disruptions in nucleotide turnover, antioxidant defenses, and fundamental metabolic processes. These findings suggest that ammonia-N stress induces a multifaceted stress response in shrimp, involving oxidative stress, immune activation, and metabolic disturbances. Understanding these immune-related and metabolic mechanisms provides valuable insights into the molecular responses of crustaceans to environmental stress, laying the foundation for assessing the ecological risk of ammonia-N and identifying potential immunological biomarkers for monitoring and mitigating its adverse effects in aquaculture systems.

Acute ammonia stress affects the immune response, oxidative stress, ammonia transport and detoxication in the hepatopancreas of freshwater mollusk Solenaia oleivora

Ammonia is a common and major pollutant in aquatic systems. Excessive ammonia has toxic effects on hepatopancreas in aquatic animals. In this study, we investigated the toxic effects of acute ammonia (concentration: 10 mg/L; test duration: 48 h) stress on the hepatopancreas of a freshwater mollusk, Solenaia oleivora. Transcriptome analysis identified 3355 differentially expressed genes (DEGs), including 1432 up-regulated and 1923 down-regulated genes. Many DEGs were associated with immune and stress responses, including heat shock proteins, pattern recognition receptors, and lysozyme. In addition, some DEGs were related to ammonia transport and detoxification, such as aquaporins, K+channel, V-ATPase, cytochrome p450, glutathione transferase, and glutamine synthetase. Physiological analysis showed that ammonia stress increased the activities of antioxidant enzymes (superoxide dismutase and catalase) and non-specific immune enzymes (acid phosphatase) and the levels of liver injury markers (malonaldehyde, aspartate aminotransferase, and alanine transaminase). TdT-mediated dUTP nick-end labeling assay revealed that ammonia stress induced apoptosis in the hepatopancreas. These results indicated the toxic effects of ammonia on hepatopancreas on the immune response, oxidative stress, ammonia transport and detoxification of S. oleivora. Our findings will accumulate data on the toxic effects of ammonia on the hepatopancreas of aquatic animals.

Effects of ammonia exposure and post-exposure recovery in pacific white shrimp, Litopenaeus vannamei: Histological, physiological and molecular responses

The toxic effects of ammonia exposure on Litopenaeus vannamei have been widely reported, including tissue damage, oxidative stress, and metabolic disorders, but the ability of L. vannamei to recover from ammonia damage is still unclear. To further understand the adaptation mechanism of L. vannamei to ammonia, this study explored the effects of ammonia exposure and recovery on histopathology, physiological indicators, and transcriptomic responses. In the ammonia exposure (NH4+-N 25 mg/L) and recovery experiment, shrimp were sampled at 0 h, 24 h, 48 h of exposure, and 24 h, 48 h of recovery. The results showed that histopathological damage to the hepatopancreas and gills caused by short-term ammonia exposure could be alleviated after recovery. Ammonia exposure inhibited superoxide dismutase (SOD) and catalase (CAT) activities, decreased total antioxidant capacity (T-AOC), and increased malondialdehyde (MDA) in shrimp. Restoration of the antioxidant system after exposure mitigated oxidative damage and reduced MDA levels. The inhibition of acid phosphatase (ACP) and alkaline phosphatase (AKP) activities in shrimp caused by ammonia exposure was reversible. Ammonia excretion and metabolism attenuate ammonia toxicity and promote recovery in L. vannamei. Transcriptome analysis identified 1690, 1568, and 1463 differentially expressed genes (DEGs) in the hepatopancreas at 48 h of stress, 24 h, and 48 h of recovery, respectively. KEGG enrichment analysis revealed that ammonia exposure induced oxidative damage, resulting in apoptosis. Furthermore, activation of antioxidant-related pathways, such as glutathione metabolism and peroxisomes, helped reduce oxidative damage during the post-exposure recovery period. The addition of exogenous spermine and spermidine may contribute to post-exposure recovery and enhance ammonia acclimation in L. vannamei. Differential expression of the inflammatory gene STEAP4 in the ammonia stress and recovery phases, as screened by transcriptome analysis, may play a positive role in post-stress recovery. This study demonstrated the reversibility of the toxic effects of ammonia exposure on L. vannamei, complemented the knowledge of the mechanisms of adaptation of shrimp under ammonia exposure, and provided a basis for subsequent ammonia tolerance studies in crustaceans.

Effects of Ammonia Stress on Liver Tissue Structure, Enzyme Activities, and Metabolome of Juvenile Largemouth Bass Micropterus salmoides

Background: Ammonia, a ubiquitous contaminant in aquatic ecosystems, poses multifaceted threats to fish species at elevated concentrations. Methods: In order to investigate the toxic effects of chronic ammonia stress on the liver of juvenile Micropterus salmoides, the present experiment was conducted to investigate the differences in changes in liver tissue structure, enzyme activities, and metabolomes after 28 days of ammonia exposure (0, 4, 8, and 16 mg/L). Results: The findings revealed that ammonia exposure induced significant oxidative stress in the liver, manifesting in decreased activities of antioxidant enzymes SOD and GSH-Px, elevated levels of GSH, GST, and MDA, and heightened activities of immune enzymes LZM, ALP, and ACP. An increase in ammonia concentration exacerbated liver tissue damage. Metabolome analysis further unveiled perturbations in liver metabolites of Micropterus salmoides exposed to ammonia, with Ala-His emerging as a potentially pivotal functional substance under chronic stress. Specifically, the 4 mg/L group responded to ammonia toxicity by augmenting GSH and L-Carnosine levels, the 8 mg/L group detoxified via upregulation of L-Glutamine, and the 16 mg/L group mitigated toxicity through the urea synthesis pathway. Conclusions: This research offers preliminary insights into the toxicological responses of Micropterus salmoides under chronic ammonia stress. It is suggested that the duration of ammonia concentration exceeding 4 mg/L in high-density aquaculture should not exceed 7 days.

Temporal and tissue-specific regulation of energy metabolism in the swimming crab Portunus trituberculatus during nitrite stress and recovery

Nitrite is a common pollutant in aquaculture systems that poses a significant threat to aquatic animals. Energy metabolism is critical in ensuring survival of animals under environmental stressors. However, regulation of energy metabolism in crustaceans under nitrite stress has not been well understood. Here we investigated energy metabolism regulation during nitrite stress and recovery in different tissues of the swimming crab Portunus trituberculatus, an important aquaculture species in China. Our results revealed that nitrite can cause tissue hypoxia and impair energy homeostasis, and energy balance cannot be restored even after a 96-hour recovery. Following exposure, mobilization of glycogen and lipids exhibited different temporal patterns. In response to energy imbalance, AMPK signaling was activated to counter energy imbalance. However, prolonged nitrite stress impaired AMPK signaling, leading to a further decline in energy supply. The findings improve our understanding for nitrite toxicity in P. trituberculatus, and provide valuable information for aquaculture management.

Transcriptome Analysis Reveals Immune and Antioxidant Defense Mechanisms in the Eriocheir japonica sinensis after Exposure to Ammonia

As a key species in freshwater aquaculture, Eriocheir japonica sinensis was subjected to ammonia stress to assess its impact on the hepatopancreas. A total of 4007 differentially expressed genes (DEGs) were identified between control and treatment groups, comprising 1838 upregulated and 2169 downregulated genes. Following exposure to 300 mg/L of ammonia, the oxidative phosphorylation pathway was activated, while the lysosomal pathway was suppressed, thereby influencing immune functions. Thirteen DEGs from these pathways were further validated via qRT-PCR, revealing gene expression changes of one- to two-fold. Both acid phosphatase (ACP) and alkaline phosphatase (AKP) levels in the hepatopancreas and hemolymph initially increased and then decreased, indicating a disruption in immune functionality. Additionally, alanine transaminase (ALT) and triglyceride (TG) levels were measured, alongside catalase (CAT) activity, total antioxidant capacity (T-AOC), and malondialdehyde (MDA) content, all of which showed an upward trend, signifying oxidative stress and tissue damage. These results offer critical insights into the antioxidant and immune mechanisms of E. j. sinensis in ammonia-enriched environments.

Effects of Vibrio harveyi infection on the biochemistry, histology and transcriptome in the hepatopancreas of ivory shell (Babylonia areolata)

The ivory shell (Babylonia areolata) is one of the most promising high quality marine products. However, ivory shell is susceptible to Vibrio harveyi infection during the culture period. In this study, we investigated the biochemical indicators, histological changes and transcriptomic response in the hepatopancreas of ivory shells from the PBS control group (PC) and infection group (A3) with 1 × 109 CFU/mL V. harveyi after 24 h. Results showed that compared to the PC group, biochemical indicators, including malondialdehyde (MDA), reactive oxygen species (ROS), acid phosphatase (ACP), and Caspase 3 (Casp-3) were significantly increased (p < 0.05) in A3 group after V. harveyi infection for 24 h. Compared with the PC group, the hepatopancreas of A3 group were seriously damaged, the columnar epithelial cells of the tissue were enlarged, the space of digestive cells was increased, and vacuolar cavities appeared. A total of 95,581 unigenes were obtained and 2949 (1787 up-regulated and 1162 down-regulated) differential expressed genes (DEGs) were identified in the A3 group. GO and KEGG enrichment analysis showed that DEGs were mainly enriched in immune system process (GO:0002376), antioxidant activity (GO:0016209), lysosome (ko04142), toll and IMD signaling pathway (ko04624), and etc. These biological functions and pathways are associated with immune and inflammatory responses and apoptosis. 12 DEGs were randomly selected for real-time quantitative PCR (RT-qPCR) validation, and the expression profiles of these DEGs were consistent with the transcriptome data, confirming the accuracy and reliability of the transcriptome results. In summary, V. harveyi infection of ivory shells inducing oxidative stress, leading to severe hepatopancreatic damage, stimulating glutathione production to neutralize excessive ROS, and stimulating antimicrobial peptides production to counteract the deleterious effects of bacterial infection, which in turn modifying the immune and inflammatory response, ultimately resulting in apoptosis. This study provided valuable information to explore the immune regulation mechanism after V. harveyi infection and established molecular basis to support the prevention of V. harveyi infection.

Physiological and Transcriptomic Analyses Provide Insights into Nitrite Stress Responses of the Swimming Crab Portunus trituberculatus

Nitrite is a common environmental pollutant in intensive aquaculture systems. In this study, physiological and transcriptomic analyses were performed to investigate nitrite stress responses in the swimming crab Portunus trituberculatus, an important aquaculture species in China. The results revealed that nitrite can affect neurotransmitter signaling via the expression of neurotransmitter receptors such as octopamine receptor (OAR) and 5-hydroxytryptamine receptor (5-HTR), and depress ecdysteroid signaling by downregulating ecdysteroid receptor (EcR) as well as its downstream transcription factors in hepatopancreas. In addition, nitrite suppressed the expression of hemocyanins, the oxygen-transporting protein, which at least partly contributed to tissue hypoxia, resulting in a switchover of energy metabolism from aerobic to anaerobic pathway. To meet the energy demand, glycogens and lipids were mobilized and transported to the hemolymph, and the catabolism of amino acids and fatty acids was enhanced to provide energy for hepatopancreas. β-oxidation of fatty acids, the major process by which fatty acids are oxidized to generate energy, seems to occur mainly not in mitochondria but in peroxisomes. Although the cellular protective mechanisms, including antioxidant defense, heat shock response (HSR), unfolded protein response (UPR), and autophagy, were activated, nitrite-induced cellular stress overwhelmed the repairing capacity and caused significant increase in the levels of apoptosis. These results indicated that nitrite stress influences neurotransmitter and endocrine signaling, disturbs energy metabolism, damages cellular components, and induces apoptosis in P. trituberculatus. The findings of this study provide new insights into nitrite stress response in the swimming crab and provide valuable information for aquaculture management of this species.

The tricarboxylic acid cycle is inhibited under acute stress from carbonate alkalinity in the gills of Eriocheir sinensis

Owing to population growth and environmental pollution, freshwater aquaculture has been rapidly shrinking in recent years. Aquaculture in saline-alkaline waters is a crucial strategy to meet the increasing demand for aquatic products. The Chinese mitten crab is an important economic food in China, but the molecular mechanism by which it tolerates carbonate alkalinity (CA) in water remains unclear. Here, we found that enzyme activities of the tricarboxylic acid (TCA) cycle in the gills, such as citrate synthase, isocitrate dehydrogenase, α-ketoglutarate dehydrogenase, and malate dehydrogenase, were markedly reduced under CA stress induced by 40 mM NaHCO3. Secondly, the TCA cycle in the gills is inhibited under acute CA stress, according to proteomic and metabolomic analyses. The expressions of six enzymes, namely aconitate hydratase, isocitrate dehydrogenase, 2-oxoglutarate dehydrogenase, dihydrolipoyl dehydrogenase, succinate-CoA ligase, and malate dehydrogenase, were downregulated, resulting in the accumulation of phosphoenolpyruvic acid, citric acid, cis-aconitate, and α-ketoglutaric acid. Finally, we testified that if the TCA cycle is disturbed by malonate, the survival rate increases in CA water. To our knowledge, this is the first study to show that the TCA cycle in the gills is inhibited under CA stress. Overall, the results provide new insights into the molecular mechanism of tolerance to saline-alkaline water in crabs, which helped us expand the area for freshwater aquaculture and comprehensively understand the physiological characteristics of crab migration.

Integrated histological, physiological, and transcriptome analysis reveals the post-exposure recovery mechanism of nitrite in Litopenaeus vannamei

Nitrite is one of the most common toxic pollutants in intensive aquaculture and is harmful to aquatic animals. Recovery mechanisms post exposure to nitrite in shrimp have rarely been investigated. This study focuses on the effect of nitrite exposure and post-exposure recovery on the histological and physiological aspects of Litopenaeus vannamei and utilizes transcriptome sequencing to analyze the molecular mechanisms of adaptation to nitrite exposure. The results showed that histopathological damage to the hepatopancreas and gills caused by short-term nitrite exposure resolved with recovery. The total antioxidant capacity (T-AOC), superoxide dismutase (SOD), and catalase (CAT) of shrimp were significantly reduced during nitrite exposure and returned to the control level after recovery, malondialdehyde (MDA) levels were opposite to them. Restoration of the antioxidant system after exposure mitigated oxidative damage. Nitrite exposure results in reduced activity of the immuno-enzymes acid phosphatase (ACP) and alkaline phosphatase (AKP), which can be recovered to the control level. L. vannamei can adapt to nitrite exposure by regulating Na+/K+-ATPase (NKA) activity. Transcriptome analysis revealed that activation of glutathione metabolism and peroxisomal pathways facilitated the mitigation of oxidative damage in L. vannamei during the recovery period. Excessive oxidative damage activates the apoptosis and p53 pathways. Additionally, Sestrin2 and STEAP4 may have a positive effect on recovery in shrimp. These results provide evidence for the damage caused by nitrite exposure and the recovery ability of L. vannamei. This study can complement the knowledge of the mechanisms of adaptation and recovery of shrimp under nitrite exposure.

miR-8-3p regulates the antioxidant response and apoptosis in white shrimp, Litopenaeus vannamei under ammonia-N stress

Exposure to excess ammonia-N (NH3/NH4+) in aquaculture can disrupt physiological function in shrimp leading to enhanced oxidative stress and apoptosis, but little is known concerning the post-transcriptional regulation mechanism. In this study, the first miR-200 family member in crustacean was identified and characterized from Litopenaeus vannamei (designed as Lva-miR-8-3p). Lva-miR-8-3p was highly expressed in eyestalks, brainganglion, and gills. The expression of Lva-miR-8-3p in gills significantly decreased after ammonia-N stress, and Lva-miR-8-3p was confirmed to target IKKβ 3'UTR for negatively regulating IKKβ/NF-κB pathway. Overexpression of miR-8-3p promoted the hemolymph ammonia-N accumulation, total hemocyte count (THC) decrease, and gills tissue damage, thus resulting in a decreased survival rate of ammonia-exposed shrimp. Besides, Lva-miR-8-3p silencing could enhance the antioxidant enzymes activities and reduce the oxidative damage, whereas overexpression of Lva-miR-8-3p exerted the opposite effects. Furthermore, Lva-miR-8-3p overexpression was found to aggravate ammonia-N induced apoptosis in gills. In primarily cultured hemocytes, the cell viability decreased, the ROS content and caspase-3 activity increased after agomiR-8-3p transfection, while antagomiR-8-3p transfection caused the opposite change except the cell viability. These findings indicate that Lva-miR-8-3p acts as a post-transcriptional regulator in ammonia-N induced antioxidant response and apoptosis by negatively regulating IKKβ/NF-κB pathway.

The mechanism of reactive oxygen species generation, DNA damage and apoptosis in hemocytes of Litopenaeus vannamei under ammonia nitrogen exposure

Ammonia-N poses a significant threat to aquatic animals. However, the mechanism of ROS production leading to DNA damage in hemocytes of crustaceans is still unclear. Additionally, the mechanism that cells respond to DNA damage by activating complex signaling networks has not been well studied. Therefore, we exposed shrimp to 0, 2, 10, and 20 mg/L NH4Cl for 0, 3, 6, 12, 24, 48, and 72 h, and explored the alterations in endoplasmic reticulum stress and mitochondrial fission, DNA damage, repair, autophagy and apoptosis. The findings revealed that ammonia exposure led to an increase in plasma ammonia content and neurotransmitter content (DA, 5-HT, ACh), and significant changes in gene expression of PLC and Ca2+ levels. The expression of disulfide bond formation-related genes (PDI, ERO1) and mitochondrial fission-related genes (Drp1, FIS1) were significantly increased, and the unfolded protein response was initiated. Simultaneously, ammonia-N exposure leads to an increase in ROS levels in hemocytes, resulting in DNA damage. DNA repair and autophagy were considerably influenced by ammonia-N exposure, as evidenced by changes in DNA repair and autophagy-related genes in hemocytes. Subsequently, apoptosis was induced by ammonia-N exposure, and this activation was associated with a caspase-dependent pathway and caspase-independent pathway, ultimately leading to a decrease in total hemocytes count. Overall, we hypothesized that neurotransmitters in the plasma of shrimp after ammonia-N exposure bind to receptors on hemocytes membrane, causing endoplasmic reticulum stress through the PLC-IP3R-Ca2+ signaling pathway and leading to mitochondrial fission. Consequently, this process resulted in increased ROS levels, hindered DNA repair, suppressed autophagy, and activated apoptosis. These cascading effects ultimately led to a reduction in total hemocytes count. The present study provides a molecular support for the understanding of the detrimental toxicity of ammonia-N exposure to crustaceans.

Investigation of the Alternations in the Muscle Quality of Swimming Crab (Ovalipes punctatus) during Cold-Chain Transportation Using Physicochemical and TMT-Based Quantitative Proteomic Analysis

Physicochemical properties and protein alterations in Ovalipes punctatus during cold-chain transportation were examined via sensory scores, water-holding capacity (WHC), glucose (GLU) content, catalase (CAT) activity, urea nitrogen (UN) content, and tandem mass tag (TMT)-based proteomic analysis. The results revealed that sensory characteristics and texture of crab muscle deteriorated during transportation. Proteomic analysis revealed 442 and 470 different expressed proteins (DEPs) in crabs after 18 h (FC) and 36 h (DC) of transportation compared with live crabs (LC). Proteins related to muscle structure and amino acid metabolism significantly changed, as evidenced by the decreased WHC and sensory scores of crab muscle. Glycolysis, calcium signaling, and peroxisome pathways were upregulated in the FC/LC comparison, aligning with the changes in GLU content and CAT activity, revealing the stress response of energy metabolism and immune response in crabs during 0-18 h of transportation. The downregulated tricarboxylic acid (TCA) cycle and carcinogenesis-reactive oxygen species pathways were correlated with the decreasing trend in CAT activity, suggesting a gradual retardation in both energy and antioxidant metabolism in crabs during 18-36 h of transportation. Furthermore, the regulated purine nucleoside metabolic and nucleoside diphosphate-related processes, with the increasing changes in UN content, revealed the accumulation of metabolites in crabs.

Toxicity of Ammonia Stress on the Physiological Homeostasis in the Gills of Litopenaeus vannamei under Seawater and Low-Salinity Conditions

Ammonia is a major water quality factor influencing the survival and health of shrimp, among which the gill is the main effector organ for ammonia toxicity. In this study, we chose two types of Litopenaeus vannamei that were cultured in 30‱ seawater and domesticated in 3‱ low salinity, respectively, and then separately subjected to ammonia stress for 14 days under seawater and low-salinity conditions, of which the 3‱ low salinity-cultured shrimp were domesticated from the shrimp cultured in 30‱ seawater after 27 days of gradual salinity desalination. In detail, this study included four groups, namely the SC group (ammonia-N 0 mg/L, salinity 30‱), SAN group (ammonia-N 10 mg/L, salinity 30‱), LC group (ammonia-N 0 mg/L, salinity 3‱), and LAN group (ammonia-N 10 mg/L, salinity 3‱). The ammonia stress lasted for 14 days, and then the changes in the morphological structure and physiological function of the gills were explored. The results show that ammonia stress caused the severe contraction of gill filaments and the deformation or even rupture of gill vessels. Biochemical indicators of oxidative stress, including LPO and MDA contents, as well as T-AOC and GST activities, were increased in the SAN and LAN groups, while the activities of CAT and POD and the mRNA expression levels of antioxidant-related genes (nrf2, cat, gpx, hsp70, and trx) were decreased. In addition, the mRNA expression levels of the genes involved in ER stress (ire1 and xbp1), apoptosis (casp-3, casp-9, and jnk), detoxification (gst, ugt, and sult), glucose metabolism (pdh, hk, pk, and ldh), and the tricarboxylic acid cycle (mdh, cs, idh, and odh) were decreased in the SAN and LAN groups; the levels of electron-transport chain-related genes (ndh, cco, and coi), and the bip and sdh genes were decreased in the SAN group but increased in the LAN group; and the level of the ATPase gene was decreased but the cytc gene was increased in the SAN and LAN groups. The mRNA expression levels of osmotic regulation-related genes (nka-β, ca, aqp and clc) were decreased in the SAN group, while the level of the ca gene was increased in the LAN group; the nka-α gene was decreased in both two groups. The results demonstrate that ammonia stress could influence the physiological homeostasis of the shrimp gills, possibly by damaging the tissue morphology, and affecting the redox, ER function, apoptosis, detoxification, energy metabolism, and osmoregulation.

Comparative toxic effect of ammonia exposure on Mauremys sinensis and invasive species Trachemys scripta elegans

As one of main pollutants, ammonia could cause adverse effects to aquatic animals. To explore the toxic effects of ammonia on Chinese striped-necked turtles (Mauremys sinensis) and invasive species red-eared slider (Trachemys scripta elegans), we compared the activities of antioxidant enzymes, the mRNA levels of genes involved in immune status, endoplasmic reticulum stress and apoptosis between T. s. elegans and M. sinensis under ammonia exposure for 30 days. The results showed that ammonia obviously increased the activities of SOD, CAT, GPX and T-AOC in both T. s. elegans and M. sinensis, especially CAT and GPX in T. s. elegans were higher than that in M. sinensis. The expression levels of JAK, RELA and Mcl-1 in T. s. elegans obviously increased, while IL-6 mRNA levels significantly increased in M. sinensis. In addition, Bip and IRE1 levels in M. sinensis showed a marked increase, and were significantly higher than that in T. s. elegans. Bcl-2 and Bcl-xL transcriptional levels in T. s. elegans showed an increase, especially Bcl-xL were significantly higher than that in M. sinensis. These results indicated that T. s. elegans exhibited more stronger antioxidant defense and immune function than M. sinensis under ammonia exposure. M. sinensis was more likely to occur endoplasmic reticulum stress and inflammation in ammonia environment. This research reveals the physiological response of turtles to ammonia, helps to understand adverse effects of environmental pressure on aquatic turtles, and further explains the tolerance of invasive species T. s. elegans to environmental pollution.

Biochemical, histological and transcriptional response of intestines in Litopenaeus vannamei under chronic zinc exposure

Zinc (Zn) is an essential trace element for the normal physiological function of aquatic organisms, but it could become toxic to organisms when the concentration increased in water. As the first line of defense, the shrimp intestines are the most susceptible organ to environmental stress. In this study, the chronic toxicity of 0 (control, IC), 0.01(IL), 0.1(IM) and 1 mg/L (IH) Zn in intestines of Litopenaeus vannamei was investigated from the perspectives of biochemical, histological and transcriptional changes after exposure for 30 days. The results showed that the intestinal tissue basement membrane is swollen in the IM and IH groups and detached in the IH group. The total antioxidant capacities (T-AOC) were reduced while the content of malondialdehyde (MDA) were increased significantly in IM and IH groups. The production of reactive oxygen species (ROS) was increased significantly in IH group. Many differentially expressed genes (DEGs) were identified in IL, IM and IH groups, respectively. GO and KEGG enrichment analyses were conducted on the DEGs to obtain the underlying biological processes and pathways. The gene modules related to the sample were identified by weighted gene co-expression network analysis (WGCNA), and genes in modules highly corelated with IH group were mainly enriched in immune related pathways. Nine DEGs were selected for validation by quantitative real time PCR (qRT-PCR) and the expression profiles of these DEGs kept a well consistent with the high-throughput data, which confirmed reliability of transcriptome results. Additionally, 10 DEGs were screened to detect the changes of expression level in different groups. All these results indicated that Zn exposure could damage the intestinal barrier, provoke oxidative stress, reduce the immune function, increase the susceptibility to bacterial infections of L. vannamei and cause inflammation, ultimately result in cell apoptosis. Our study provides more perspective on the stress response of crustacean under Zn exposure.

Impacts of acute ammonia-N exposure on the muscle quality of whiteleg shrimp (Penaeus vannamei): Novel insights into lipid and protein oxidation

This study explored the effect of ammonia-N exposure on the muscle quality of Penaeus vannamei and the underlying mechanisms based on the oxidation of lipids and proteins. Acute ammonia-N exposure reduced the hardness but increased the centrifugal loss and drip loss of the shrimp muscle. Meanwhile, reactive oxygen species and reactive nitrogen species were overproduced, thereby increasing the free fatty acid (FFA) content, fluorescent compound content, peroxide value (PV), and thiobarbituric acid reactive substance (TBAR) value. In addition, lipid peroxidation byproducts and free radicals could reduce sulfhydryl (SH) content and intrinsic fluorescence intensity. They may also increase carbonyl concentration, disulfide bond (SS) content, and surface hydrophobicity, and degrade myofibrillar protein, leading to the unfolding and conformational alterations in proteins in shrimp muscle. This study provided significant insights into the mechanisms underlying the impacts of ammonia toxicity on the quality of shrimp muscle.

The effect of astaxanthin on the alkalinity stress resistance of Exopalaemon carinicauda

Astaxanthin (Axn), a feed additive, can improve growth performance and enhance the environmental stress tolerance of shrimp at all growth stages. High carbonate alkalinity is considered a major stressor that affects the survival, growth, and reproduction of aquatic animals in saline-alkaline waters. In this study, a combined analysis of physiology, transcriptomics, and metabolomics was performed to explore the effected mechanism of Axn on Exopalaemon carinicauda (E. carinicauda) under alkalinity stress. The results revealed that dietary Axn can inhibit oxidative stress damage caused by alkalinity stress and maintain the normal cell structure and mitochondrial membrane potential. Transcriptomic data indicated that differentially expressed genes (DEGs) under alkalinity stress and those under alkalinity stress after Axn feeding were associated with apoptosis. The metabolic data suggested that alkalinity stress has adverse effects on ammonia metabolism, unsaturated fatty acid metabolism, and TCA cycle, and dietary Axn can improve the metabolic processes in E. carinicauda. In addition, transcriptomics and metabolomics analyses showed that Axn could help maintain the cytoskeletal structure and inhibit apoptosis under alkalinity stress; a TUNEL assay further confirmed these effects. Lastly, metabolic responses to alkalinity stress included changes in multiple amino acids and unsaturated fatty acids, and pathways related to energy metabolism were downregulated in the hepatopancreas of E. carinicauda under alkalinity stress. Collectively, all these results provide new insights into the molecular mechanisms underlying alkalinity stress tolerance in E. carinicauda after Axn feeding.

Harnessing probiotics and prebiotics as eco-friendly solution for cleaner shrimp aquaculture production: A state of the art scientific consensus

In recent years, the advancement and greater magnitude of products, which led to the intensification in shrimp aquaculture is the result of utilization of modern tools and synchronization with other fields of science like microbiology and biotechnology. This intensification led to the elevation of disorders such as the development of several diseases and complications associated with biofouling. The use of antibiotics in aquaculture is discouraged due to their certain hazardous paraphernalia. Consequently, there has been a growing interest in exploring alternative strategies, with probiotics and prebiotics emerging as environmentally friendly substitutes for antibiotic treatments in shrimp aquaculture. This review highlighted the results of probiotics and prebiotics administration in the improvement of water quality, enhancement of growth and survival rates, stress resistance, health status and disease resistance, modulation of enteric microbiota and immunomodulation of different shrimp species. Additionally, the study sheds light on the comprehensive role of prebiotics and probiotics in elucidating the mechanistic framework, contributing to a deeper understanding of shrimp physiology and immunology. Besides their role in growth and development of shrimp aquaculture, the eco-friendly behavior of prebiotics and probiotics have made them ideal to control pollution in aquaculture systems. This comprehensive exploration of prebiotics and probiotics aims to address gaps in our understanding, including the economic aspects of shrimp aquaculture in terms of benefit-cost ratio, and areas worthy of further investigation by drawing insights from previous studies on different shrimp species. Ultimately, this commentary seeks to contribute to the evolving body of knowledge surrounding prebiotics and probiotics, offering valuable perspectives that extend beyond the ecological dimensions of shrimp aquaculture.

Ammonia-induced oxidative stress triggered apoptosis in the razor clam (Sinonovacula constricta)

As one of the most significant contaminants and stressors in aquaculture systems, ammonia adversely jeopardizes the health of aquatic animals. Ammonia exposure affects the development, metabolism, and survival of shellfish. However, the responses of the innate immune and antioxidant systems and apoptosis in shellfish under ammonia stress have rarely been reported. In this study, razor clams (Sinonovacula constricta) were exposed to different concentrations of non-ion ammonia (0.25 mg/L, 2.5 mg/L) for 72 h and then placed in ammonia-free seawater for 72 h for recovery. The immune responses induced by ammonia stress on razor clams were investigated by antioxidant enzyme activities and degree of apoptosis in digestive gland and gill tissues at different time points. The results showed that exposure to a high concentration of ammonia greatly disrupted the antioxidant system of the razor clam by exacerbating the accumulation of reactive oxygen species ( O 2 - , H2O2) and disordering the activities of antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase), and the level of activity remained at a significantly high level after recovering for 72 h (P < 0.05). In addition, there were significant differences (P < 0.05) in the expression of key genes (Caspase 7, Cyt-c, Bcl-2, and Bax) in the mitochondrial apoptotic pathway in the digestive glands and gills of razor clams as a result of ammonia stress and were unable to return to normal levels after 72 h of recovery. TUNEL staining indicated that apoptosis was more pronounced in gills, showing a dose and time-dependent pattern. As to the results, ammonia exposure leads to the activation of innate immunity in razor clams, disrupts the antioxidant system, and activates the mitochondrial pathway of apoptosis. This is important for comprehending the mechanism underlying the aquatic toxicity resulting from ammonia in shellfish.

Acute Ammonia Causes Pathogenic Dysbiosis of Shrimp Gut Biofilms

Acute ammonia exposure has detrimental effects on shrimp, but the underlying mechanisms remain to be fully explored. In the present study, we investigated the impact of acute ammonia exposure on the gut microbiota of the white shrimp Litopenaeus vannamei and its association with shrimp mortality. Exposure to a lethal concentration of ammonia for 48 h resulted in increased mortality in L. vannamei, with severe damage to the hepatopancreas. Ammonia exposure led to a significant decrease in gut microbial diversity, along with the loss of beneficial bacterial taxa and the proliferation of pathogenic Vibrio strains. A phenotypic analysis revealed a transition from the dominance of aerobic to facultative anaerobic strains due to ammonia exposure. A functional analysis revealed that ammonia exposure led to an enrichment of genes related to biofilm formation, host colonization, and virulence pathogenicity. A species-level analysis and experiments suggest the key role of a Vibrio harveyi strain in causing shrimp disease and specificity under distinct environments. These findings provide new information on the mechanism of shrimp disease under environmental changes.

miR-2765 involved in ammonia nitrogen stress via negative regulation of autophagy in shrimp

MicroRNA (miRNA) is a highly conserved non-coding tiny endogenous RNA molecule that regulates various cellular functions by inhibiting mRNA translation or promoting the degradation of proteins. In this study, we identified a specific miRNA (designed as Pva-miR-2765) from Penaeus vannamei, which widely distributed in different tissues of shrimp, with the highest concentration found in the intestine. Through fluorescence in situ hybridization (FISH), we observed that Pva-miR-2765 is primarily located in the cytoplasm. Interestingly, we found that the expression of Pva-miR-2765 significantly decreased in hemocytes, hepatopancreas and gill under ammonia nitrogen stress. Furthermore, when Pva-miR-2765 was silenced, the autophagy level in shrimp significantly increased. Additionally, Pva-miR-2765 was found to promote pathological damage in the hepatopancreas of shrimp. Subsequently, correlation analysis revealed a negative relationship between the expression of Pva-miR-2765 and PvTBC1D7. To confirm this interaction, we conducted a dual luciferase reporter gene assay, which demonstrated that Pva-miR-2765 inhibit the expression of PvTBC1D7 by interacting with its 3'UTR. And the expression level of PvTBC1D7 in shrimp decreased significantly under ammonia nitrogen stress in Pva-miR-2765 overexpressed. Our findings suggest that Pva-miR-2765 can reduce autophagy in P. vannamei by inhibiting the regulation of PvTBC1D7, thereby participating in the oxidative stress of shrimp caused by ammonia nitrogen stress.

Responses and correlation among ER stress, Ca2+ homeostasis, and fatty acid metabolism in Penaeus vannamei under ammonia stress

The role of endoplasmic reticulum (ER) stress, Ca2+ homeostasis, and fatty acid metabolism in the environmental adaptation of aquatic animals is significant, but further confirmation of the relationship between these factors is needed. This study aimed to investigate the responses and correlations among ER stress, Ca2+ homeostasis, and fatty acid metabolism in Penaeus vannamei under ammonia stress. A total of 640 P. vannamei weighing 3.0 ± 0.4 g were selected and exposed to different total ammonia concentrations (0 mg/L for the control group and 3.80, 7.60, and 11.40 mg/L for the stress groups). The experiment involved a 96 h ammonia stress period to assess indicators related to ER stress, Ca2+ homeostasis, and fatty acid metabolism. The experimental results revealed that after 12 h, exposure to ammonia induced the ER stress response in the hepatopancreas of the shrimp. The groups exposed to concentrations of 3.8 mg/L and 7.6 mg/L exhibited an increase in ER Ca2+ efflux, a decrease in influx, an elevation in mitochondrial Ca2+ influx, an enhanced energy demand within the organism, and substantial consumption of triglycerides. The 11.3 mg/L group exhibited a significant enhancement in fatty acid metabolism. At 24 h, the ER stress response induced by ammonia in the shrimp exhibited a gradual recovery. In the 7.6 mg/L and 11.3 mg/L groups, the ER Ca2+ influx and efflux exhibited significant enhancements, while the mitochondrial Ca2+ influx decreased and the organism's energy demand increased. Moreover, there was a substantial enhancement in fatty acid metabolism. At 48 h, the ER stress response disappeared in each stress group, ER Ca2+ efflux was reduced, triglycerides were consumed, and the body's energy homeostasis was basically restored. At 96 h, a stress response reoccurred in the ER in each stress group, resulting in increased influx of Ca2+ into the ER, augmented energy demand within the organism, and notable enhancement in fatty acid metabolism. Pearson correlation analysis revealed a significant positive correlation between the NH3-N content in the hepatopancreas and the expression of ER stress-related genes, as well as between ER Ca2+ influx/efflux and energy homeostasis/fatty acid metabolism. The findings indicate that the stress induced by ammonia triggers an ER stress response in P. vannamei, resulting in ER Ca2+ efflux and mitochondrial Ca2+ influx, which, in turn, enhances fatty acid metabolism to generate additional energy for adaptation in stressful environments. This study contributes to a deeper understanding of the environmental adaptability of P. vannamei in the context of Ca2+ homeostasis.

A mixed animal and plant protein source replacing fishmeal affects bile acid metabolism and apoptosis in largemouth bass (Micropterus salmoides)

Chicken meal, shrimp meal, blood meal, and soybean protein concentrate are common alternatives to fishmeal. This study used them to prepare three diets with different levels of fishmeal (FM48, FM40, and FM32) for largemouth bass (Micropterus salmoides). The results found no significant difference in the growth performance of largemouth bass fed different diets. Mixed protein increased the total cholesterol (T-CHO) content in plasma, and reduced the total superoxide dismutase (T-SOD) activity in plasma and liver. Targeted metabolomics analysis found that the low fishmeal diets affected the cholesterol and bile acid metabolism of largemouth bass. Mixed protein inhibited cyp7a1 and enhanced hmgcr and pparγ mRNA levels, as well as enhanced the expression levels of FXR in the liver. The fish-fed FM32 diet showed inhibited fxr, rxrα, and cyp7a1 mRNA levels in the intestine. The results of TUNEL fluorescence staining showed that mixed protein induced apoptosis in largemouth bass. The caspase 3 and caspase 9 mRNA levels in the fish-fed FM40 and FM32 diet significantly increased, as well as the expression levels of CASPASE 3. The experiment also found that it could induce oxidative stress and endoplasmic reticulum stress. In conclusion, the replacement of fishmeal with mixed animal and plant protein diets did not affect the growth performance, but the health and bile acid metabolism of largemouth bass was affected when the fishmeal level was reduced to 32%.

The adverse impacts of ammonia stress on the homeostasis of intestinal health in Pacific white shrimp (Litopenaeus vannamei)

Ammonia is a prevalent pollutant in aquaculture systems that poses a risk to shrimp health. The shrimp's intestine plays a crucial role in immunity and metabolism. Therefore, we exposed Litopenaeus vannamei to 2 mg/L ammonia-N stress for a duration of 7 days, and explored the alterations in intestinal tissue morphology, physiological status, microbial community, and metabolic function. The findings revealed that ammonia stress led to a decrease in shrimp survival rates and inflicted damage to the intestinal mucosa, resulting in epithelial exfoliation. The mRNA relative expression levels of oxidative stress genes (Nrf2 and SOD) were elevated, while the level of GPx was decreased. Additionally, there was an increase in the levels of endoplasmic reticulum stress genes (Bip, IRE1 and XBP1), inflammatory cytokines (NF-κB and JNK), and apoptosis mediators (CytC and Casp-3) were increased. Ammonia stress also caused a decline in intestinal microbial diversity and significant variations in the bacterial community composition, including Bacteroides, Enterococcus, Faecalibacterium, Nautella, Pseudoalteromonas, Tenacibaculum, and Weissella. Furthermore, ammonia stress disrupted the intestinal metabolic function, particularly affecting pyrimidine, purine, amino acid, and alkaloid metabolism. These results revealed that 2 mg/L ammonia-N stress damaged the intestinal health of the shrimp by damaging mucosal integrity, affecting physiological homeostasis, causing microbial community and metabolic variation, which are related to the decreased survival of the shrimp and should be paid attention to in shrimp farming.

Differential Toxicity Responses between Hepatopancreas and Gills in Litopenaeus vannamei under Chronic Ammonia-N Exposure

Ammonia nitrogen is one of the main toxic substances in aquatic cultivation environments. Chronic exposure to excessive amounts of ammonia-N creates toxic consequences, retarding the growth of aquatic organisms. This study investigated the growth performance, morphological and physiological alterations, and transcriptome changes in the hepatopancreas and gills of white shrimp Litopenaeus vannamei. The results showed that there was no significant difference in the survival rate (p > 0.05), whereas growth performance was reduced significantly in the treated groups compared to the control groups (p < 0.05). Significant structural damage and vacuolation occurred in hepatopancreas and gill tissues in the treated groups. Superoxide dismutase (SOD) activity and Na+/K+-ATPase content were significantly increased by chronic ammonia-N exposure in the two tissue groups. In addition, catalase (CAT) activity and malondialdehyde (MDA) levels were significantly altered in the hepatopancreas groups (p < 0.05), whereas no differences were observed in the gill groups (p > 0.05). There were 890 and 1572 differentially expressed genes identified in the hepatopancreas (treated versus control groups) and gills (treated versus control groups), respectively, of L. vannamei under chronic ammonia-N exposure. Functional enrichment analysis revealed associations with oxidative stress, protein synthesis, lipid metabolism, and different serine proteases. The gills maintained cellular homeostasis mainly through high expression of cytoskeleton and transcription genes, whereas the hepatopancreas down-regulated related genes in the ribosome, proteasome, and spliceosome pathways. These genes and pathways are important in the biosynthesis and transformation of living organisms. In addition, both tissues maintained organismal growth primarily through lipid metabolism, which may serve as an effective strategy for ammonia-N resistance in L. vannamei. These results provided a new perspective in understanding the mechanisms of ammonia-N resistance in crustaceans.

Transcriptomic analysis revealed the dynamic response mechanism to acute ammonia exposure in the ivory shell, Babylonia areolata

The ivory shell (Babylonia areolata) is an economically important shellfish in tropical and subtropical regions, but its intensive culture and biological characteristic of hiding in the sandy substrate make it highly susceptible to ammonia stress. In this study, we investigated the dynamic changes in histopathology, oxidative stress, and transcriptome of the ivory shell at different time points under high concentration (60 mg/L) ammonia exposure. With prolonged exposure to stress, vacuoles appeared in the hepatopancreas while cell volume and intercellular space increased. The activities of superoxide dismutase (SOD) and catalase (CAT) decreased significantly under high concentrations of ammonia-induced stress while malondialdehyde (MDA) levels increased significantly. Integrated analysis of differentially expressed genes (DEGs), weighted gene co-expression network analysis (WGCNA), and quantitative real-time polymerase chain reaction (qRT-PCR) revealed that lipid transport primarily contributed to maintaining cellular homeostasis during the early stage of stress (6 and 12 h). Subsequently, a significant upregulation of oxidation-reduction reactions occurred at the middle stage (24 h), leading to oxidative stress. Finally, during the later stage (48 h), metabolic decomposition provided energy for survival maintenance. Additionally, lysosome and apoptosis were identified as potential key pathways in response to acute ammonia toxicity. Overall, our findings suggest that ivory shells can respond to acute ammonia toxicity via immune and antioxidant defense mechanisms but sustained high concentrations may cause irreversible damage. This study provides valuable insights into the response mechanism of mollusks towards ammonia and serves as a data reference for breeding ammonia-tolerant varieties of ivory shells.

Molecular mechanisms underlying mitochondrial damage, endoplasmic reticulum stress, and oxidative stress induced by environmental pollutants

Mitochondria and endoplasmic reticulum (ER) are essential organelles playing pivotal roles in the regulation of cellular metabolism, energy production, and protein synthesis. In addition, these organelles are important targets susceptible to external stimuli, such as environmental pollutants. Exposure to environmental pollutants can cause the mitochondrial damage, endoplasmic reticulum stress (ERS), and oxidative stress, leading to cellular dysfunction and death. Therefore, understanding the toxic effects and molecular mechanisms of environmental pollution underlying these processes is crucial for developing effective strategies to mitigate the adverse effects of environmental pollutants on human health. In the present study, we summarized and reviewed the toxic effects and molecular mechanisms of mitochondrial damage, ERS, and oxidative stress caused by exposure to environmental pollutants as well as interactions inducing the cell apoptosis and the roles in exposure to environmental pollutants.

α-lipoic acid ameliorates hepatotoxicity induced by chronic ammonia toxicity in crucian carp (Carassius auratus gibelio) by alleviating oxidative stress, inflammation and inhibiting ERS pathway

High environment ammonia (HEA) poses a deadly threat to aquatic animals and indirectly impacts human healthy life, while nutritional regulation can alleviate chronic ammonia toxicity. α-lipoic acid exhibits antioxidative effects in both aqueous and lipid environments, mitigating cellular and tissue damage caused by oxidative stress by aiding in the neutralization of free radicals (reactive oxygen species). Hence, investigating its potential as an effective antioxidant and its protective mechanisms against chronic ammonia stress in crucian carp is highly valuable. Experimental fish (initial weight 20.47 ± 1.68 g) were fed diets supplemented with or without 0.1% α-lipoic acid followed by a chronic ammonia exposure (10 mg/L) for 42 days. The results revealed that chronic ammonia stress affected growth (weight gain rate, specific growth rate, and feed conversion rate), leading to oxidative stress (decreased the activities of antioxidant enzymes catalase, superoxide dismutase, glutathione peroxidase; decreased total antioxidant capacity), increased lipid peroxidation (accumulation of malondialdehyde), immune suppression (decreased contents of nonspecific immune enzymes AKP and ACP, 50% hemolytic complement, and decrease of immunoglobulin M), impaired ammonia metabolism (reduced contents of Glu, GS, GSH, and Gln), imbalance of expression of induced antioxidant-related genes (downregulation of Cu/Zu SOD, CAT, Nrf2, and HO-1; upregulation of GST and Keap1), induction of pro-apoptotic molecules (transcription of BAX, Caspase3, and Caspase9), downregulation of anti-apoptotic gene Bcl-2 expression, and induction of endoplasmic reticulum stress (upregulation of IRE1, PERK, and ATF6 expression). The results suggested that the supplementation of α-lipoic acid could effectively induce humoral immunity, alleviate oxidative stress injury and endoplasmic reticulum stress, and ultimately alleviate liver injury induced by ammonia poisoning (50-60% reduction). This provides theoretical basis for revealing the toxicity of long-term ammonia stress and provides new insights into the anti-ammonia toxicity mechanism of α-lipoic acid.

Portable Conductometric Sensing Probe for Real-Time Monitoring Ammonia Profile in Coastal Waters

An ability to real-time and continuously monitor ammonium/ammonia profiles of coastal waters over a prolonged period in a simple and maintenance-free fashion would enable economic conducting large-scale assessments, providing the needed scientific insights to better control and mitigate the impact of eutrophication on coastal ecosystems. However, this is a challenging task due to the lack of capable sensors. Here, we demonstrate the use of a membrane-based conductometric ammonia sensing probe (CASP) for real-time monitoring of ammonia levels in coastal waters. A boric acid/glycerol receiving phase is investigated and innovatively utilized to overcome the high salinity of coastal water-induced analytical errors. A calibration-free approach is used to eliminate the need for ongoing calibration, while the issues concerning practical applications, such as salinity variation, ammonia intake capability, and biofouling, are systematically investigated. The field deployment at an estuary confluence water site over a half-moon cycle period confirms that CASP is capable of continuously monitoring the ammonia profile of coastal waters in real-time with high resolution and accuracy to unveil the dynamic ammonia concentration changes over a prolonged period.

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.

Toxicological mechanism of ammonia-N on haematopoiesis and apoptosis of haemocytes in Litopenaeus vannamei

Ammonia, as an important pollutant, contributed to the reduction of immunity, disruption of physiology in animals. RNA interference (RNAi) was performed to understand the function of astakine (AST) in haematopoiesis and apoptosis in Litopenaeus vannamei under ammonia-N exposure. Shrimps were exposed to 20 mg/L ammonia-N from 0 to 48 h with injection of 20 μg AST dsRNA. Further, shrimps were exposed to 0, 2, 10 and 20 mg/L ammonia-N also from 0 to 48 h. The results showed that the total haemocytes count (THC) decreased under ammonia-N stress and the knockdown of AST resulted in a further decrease of THC, suggesting that 1) the proliferation was decreased through the reduction of AST and Hedgehog, the differentiation was interfered by Wnt4, Wnt5 and Notch, and the migration was inhibited by the decrease of VEGF; 2) oxidative stress was induced under ammonia-N stress, leading to the increase of DNA damage with the up-regulated gene expression of death receptor, mitochondrial and endoplasmic reticulum stress pathways; 3) the changes of THC resulted from the decrease of proliferation, differentiation and migration of haematopoiesis cells and the increase of apoptosis of haemocytes. This study helps to deepen our understanding of risk management in shrimp aquaculture.

Impacts of ammonia stress on different Pacific whiteleg shrimp Litopenaeus vannamei families and the underlying adaptive mechanisms

Ammonia stress in aquaculture systems poses a great threat to the growth and survival of the Pacific whiteleg shrimp Litopenaeus vannamei. Although the ammonia stress tolerance capacity of L. vannamei has been found to vary significantly among different breeding families, the underneath mechanisms are still largely unknown. In this study, the ammonia tolerance capacity of different L. vannamei breeding families was compared. Results confirmed the significant differences in the ammonia adaptability among different families. To ascertain the underlying adaptive strategies, ATP status, ATP synthase activity, expression and activities of ammonia excretion and metabolism-related enzymes, and apoptosis in shrimp gills were analyzed. Furthermore, transcriptomic analyses were also performed to elucidate the molecular mechanisms. Our results indicated that ammonia-tolerant L. vannamei may possess (1) enhanced ability to excrete ammonia, (2) better capacity to convert ammonia into less toxic products, and (3) sufficient energy reserves for ammonia-compensating processes.

Identification of key immune and stress related genes and pathways by comparative analysis of the gene expression profile under multiple environmental stressors in pacific white shrimp (Litopenaeus vannamei)

Water salinity, pH, and nitrite concentration are considered environmental factors affecting the growth rate, survival, health, and physiological conditions of aquatic animals. The identification of key genes that are involved in the response to environmental stressors is essential for controlling stress in aquatic animals and sustainable aquaculture. In this study, RNA sequencing was performed to identify the differentially expressed genes (DEGs) and biological pathways that are involved in the response of the hepatopancreas to environmental stressors, including low salinity stress, nitrite stress, low pH stress, and high pH stress. The DEGs were enriched in biological pathways related to immune response, energy metabolism, oxidative stress response, hemostasis, and enzymatic activity of the hepatopancreas. In addition to the identification of DEGs related to each stressor, some DEGs were found to be expressed among all groups. The most important overlapping DEGs under multiple stressors were juvenile hormone esterase-like protein 2 (JHE-like), myosin light chain, C-type lectin 2, myosin-9-like, anti-lipopolysaccharide factor 1 (ALF-1), peroxisomal acyl-coenzyme An oxidase 1-like (ACX1), hepatic lectin-like, venom phosphodiesterase 2-like, hemolymph clottable protein-like (CP), cathepsin L, and Ras-like protein 2. The results of the present study provide additional information regarding the transcriptional response of the hepatopancreas to low salinity, nitrite, low pH, and high pH stress. Moreover, the discovery of several overlapping DEGs among different stressors provided a better understanding of the molecular function of the hepatopancreas.

Selenium Alleviates Ammonia-Induced Splenic Cell Apoptosis and Inflammation by Regulating the Interleukin Family/Death Receptor Axis and Nrf2 Signaling Pathway

Ammonia (NH₃) is a harmful gas in livestock houses. So far, many researchers have demonstrated that NH₃ is detrimental to animal and human organs. Selenium (Se) is one of the essential trace elements in the body and has a good antioxidant effect. However, there was little conclusive evidence that Se alleviated NH₃ poisoning. To investigate the toxic mechanism of NH₃ on pig spleen and the antagonistic effect of L-selenomethionine, a porcine NH₃-poisoning model and an L-selenomethionine intervention model were established in this study. Our results showed that NH₃ exposure increased the apoptosis rate, while L-selenomethionine supplementation alleviated the process of excessive apoptosis. Immunofluorescence staining, real-time quantitative polymerase chain reaction (qRT-PCR), and western blot results confirmed that exposure to NH₃ changed the expression levels of interleukin family factors, apoptosis, death receptor, and oxidative stress factors. Our study further confirmed that excessive NH₃ induced inflammatory response and mediated necroptosis leading to cell apoptosis by activating the Nrf2 signaling pathway. Excessive NH₃ could mediate spleen injury through oxidative stress-induced mitochondrial dynamics disorder. L-Selenomethionine could alleviate inflammation and abnormal apoptosis by inhibiting the IL-17/TNF-α/FADD axis. Our study would pave the way for comparative medicine and environmental toxicology.

Whole Transcriptome Analysis of Differentially Expressed Genes in Cultured Nile Tilapia (O. niloticus) Subjected to Chronic Stress Reveals Signaling Pathways Associated with Depressed Growth

Chronic stress is a serious threat to aquaculture as it lowers fish growth performance and compromises fish welfare. The exact mechanism by which growth is retarded is, however, not clearly understood. This study sought to elucidate the gene expression profiles associated with chronic stress in cultured Nile tilapia (Oreochromis niloticus) reared for 70 days at different ammonia concentrations and stocking densities. Fish in the treatment groups showed negative growth, while the controls showed positive allometric growth. The specific condition factor (Kn) ranged from 1.17 for the controls to 0.93 for the ammonia and 0.91 for the stocking density treatments. RNA was extracted from muscle tissue using TRIzol followed by library construction and Illumina sequencing. Comparative transcriptome analysis revealed 209 differentially expressed genes (DEGs) (156 up- and 53 down-regulated) in the ammonia and 252 DEGs (175 up- and 77 down-regulated) in the stocking density treatment. In both treatments, 24 and 17 common DEGs were up- and down-regulated, respectively. DEGs were significantly enriched in six pathways associated with muscle activity, energy mobilization and immunity. The heightened muscular activity consumes energy which would otherwise have been utilized for growth. These results bring to fore the molecular mechanisms underlying chronic stress’ suppression of growth in cultured Nile tilapia.

Transcriptomics reveals the effect of ammonia nitrogen concentration on Pseudomonas stutzeri F2 assimilation and the analysis of amtB function

The biological treatment of wastewater with high concentrations of ammonia nitrogen has become a hot research issue, but there are limited reports on the mechanism of ammonia nitrogen utilization by microorganisms. In this paper, a transcriptomic approach was used to investigate the differences in gene expression at 500.0 mg/L (Amo 500) and 100.0 mg/L (Amo 100) ammonium concentrations to reveal the mechanism of ammonia nitrogen removal from water by Pseudomonas stutzeri F2. The transcriptome data showed 1015 (459 up-regulated and 556 down-regulated) differentially expressed genes with functional gene annotation related to nitrogen source metabolism, glycolysis, tricarboxylic acid cycle, extracellular polysaccharide synthesis, energy conversion and transmembrane transport, revealing the metabolic process of ammonium nitrogen conversion to biological nitrogen in P. stutzeri F2 through assimilation. To verify the effect of ammonium transporter protein (AmtB) of cell membrane on assimilation, a P. stutzeri F2-ΔamtB mutant strain was obtained by constructing a knockout plasmid (pK18mobsacB-ΔamtB), and it was found that the growth characteristics and ammonium removal rate of the mutant strain were significantly reduced at high ammonium concentration. The carbon source components and dissolved oxygen conditions were optimized after analyzing the transcriptome data, and the ammonium removal rate was increased from 41.23% to 94.92% with 500.0 mg/L ammonium concentration. The study of P. stutzeri F2 transcript level reveals the mechanism of ammonia nitrogen influence on microbial assimilation process and improvement strategy, which provides a new strategy for the treatment of ammonia nitrogen wastewater.

Adverse effects of chronic ammonia stress on juvenile oriental river prawn (Macrobrachium nipponense) and alteration of glucose and ammonia metabolism

Ammonia is one of the common stress factors in aquaculture. However, the effect of chronic ammonia exposure in juvenile oriental river prawn (Macrobrachium nipponense) is currently unexplored. This study explored the effects of chronic ammonia on juvenile healthy oriental river prawns. Fifty prawns (0.123 ± 0.003 g) were exposed to 0, 5, and 15 mg/L total ammonia nitrogen (TAN) in triplicates for 28 days. The effects of chronic ammonia challenge were evaluated on growth, antioxidant capacity, hepatopancreas and gill morphology, and glucose and ammonia metabolism. The results showed that, the chronic ammonia exposure reduced significantly survival rate and weight gain of prawns. The prawns exposed to 15 mg/L ammonia had induced oxidative stress. However, the prawn exposed to 15 mg/L ammonia had significantly lower aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, and acid phosphatase activities in the serum. Furthermore, exposure of prawns to 15 mg/L ammonia increased the activities of hexokinase, pyruvate kinase, pyruvate and lactic acid content, and glutamine synthase activity. However, the prawns exposed to 15 mg/L ammonia, reduced succinic dehydrogenase, 6-phosphogluconic dehydrogenase, phosphoenolpyruvate carboxykinase, glutamate synthase, and glutamate dehydrogenase activities but increased ammonia content in serum. The exposure of ammonia deformed lumen, damaged basement membrane and decreased secretory cells in the hepatopancreas, disordered gill epithelial and pillar cells, and caused gill filament base vacuolation. Our study indicates that chronic ammonia stress impairs growth performance, tissue morphology, induces oxidative stress, and alters glucose and ammonia metabolism in juvenile oriental river prawns.

Modulation of SREBP Expression and Fatty Acid Levels by Bacteria-Induced ER Stress Is Mediated by Hemocyanin in Penaeid Shrimp

Many environmental and pathogenic insults induce endoplasmic reticulum (ER) stress in animals, especially in aquatic ecosystems, where these factors are crucial for life. In penaeid shrimp, pathogens and environmental stressors induce hemocyanin expression, but the involvement of hemocyanin in ER stress response is unknown. We demonstrate that in response to pathogenic bacteria (Vibrio parahaemolyticus and Streptococcus iniae), hemocyanin, ER stress proteins (Bip, Xbp1s, and Chop), and sterol regulatory element binding protein (SREBP) are induced to alter fatty acid levels in Penaeus vannamei. Interestingly, hemocyanin interacts with ER stress proteins to modulate SREBP expression, while ER stress inhibition with 4-Phenylbutyric acid or hemocyanin knockdown attenuates the expression of ER stress proteins, SREBP, and fatty acid levels. Contrarily, hemocyanin knockdown followed by tunicamycin treatment (ER stress activator) increased their expression. Thus, hemocyanin mediates ER stress during pathogen challenge, which consequently modulates SREBP to regulate the expression of downstream lipogenic genes and fatty acid levels. Our findings reveal a novel mechanism employed by penaeid shrimp to counteract pathogen-induced ER stress.

Effects of environmental factors on the cellular and molecular parameters of the immune system in decapods

Crustaceans and in particular decapods (i.e. shrimp, crabs and lobsters) are a diverse, commercially and ecologically important group of organisms. They are exposed to a range of environmental factors whose abiotic and biotic components are prone to fluctuate beyond their optimum ranges and, in doing so, affect crustaceans' immune system and health. Changes in key environmental factors such as temperature, pH, salinity, dissolved oxygen, ammonia concentrations and pathogens can provoke stress and immune responses due to alterations in immune parameters. The mechanisms through which stressors mediate effects on immune parameters are not fully understood in decapods. Improved knowledge of the environmental factors - above all, their abiotic components - that influence the immune parameters of decapods could help mitigate or constrain their harmful effects that adversely affect the production of decapod crustaceans. The first part of this overview examines current knowledge and information gaps regarding the basic components and functions of the innate immune system of decapods. In the second part, we discuss various mechanisms provoked by environmental factors and categorize cellular and molecular immune responses to each environmental factor with special reference to decapods.

Involvement of Nrf2 in the immune regulation of Litopenaeus vannamei against Vibrio harveyi infection

NF-E2-related factor-like-2 (Nrf2) is a transcription factor that belongs to the Cap'n'Collar transcription factor family and plays a role in regulating inflammation, autophagy, metabolism, proteostasis, and cancer prevention. However, its influence on Vibrio spp infection in L. vannamei remains uncertain. In this study, the effects of Nrf2 on the immune response in Vibrio spp infection was determined by RT-PCR and histopathological analysis. The results showed that RNAi of Nrf2 significantly decreased the expression of antioxidant-related genes (CAT, SOD and GST; p < 0.05), and significantly up-regulated inflammation-related genes (IMD, pro-PO, P38, Toll, Hsp70, NFκB and RAB6A; p < 0.05) and the apoptosis gene (caspase3). Under the infection of V. harveyi, histopathological analysis showed that after RNAi of Nrf2, the hepatopancreas of shrimp has an abnormal arrangement of hepatic tubules and vacuolization of hepatocyte; The basement membrane is peeled off and the epithelial cells are massively necrotic. Compared with the RNAi of Nrf2 group, the tissue damage in the SFN group was much lessened, and there were fewer apoptosis signals in the TUNEL assay. In conclusion, this experiment indicated that Nrf2 is involved in the regulation of inflammatory response, oxidative stress,and apoptosis induced by V. harveyi in L. vannamei.