Histopathological Evaluation of the Curative Effects of EDTA on Lymnaea stagnalis Exposed to Subacute Cadmium.

We investigated the therapeutic effects of EDTA application for 14 and 28 days on cadmium (Cd) induced pond snail Lymnaea stagnalis (Linnaeus, 1758). The sublethal concentration of cadmium (63.4 mg/l Cd) caused tissue damages to the snail after an exposure for 28 days.In the groups treated with EDTA, the concentration of Cd in the foot, mantle and hepatopancreas tissues showed significantly decreased during the recovery period. The curative effects of EDTA on Cd-induced damage were assessed using a scoring system. Cadmium exposure led to histopathological changes including increased mucositis, pigment and protein cells, foot epithelium desquamation, muscle fibril damage, connective tissue cell atrophy, and increased lipid vacuoles in the mantle and hepatopancreas. However, these changes were less severe in snails treated with EDTA (2.00 mL/L for 28 day), indicating that EDTA reduces their susceptibility to heavy metal toxicity.

Pathological and ultrastructural changes of Bellamya bengalensis under chronic carboxylic acid exposure at environmentally relevant levels: Inferences from general unified threshold model for survival (GUTS) predictions and hepatopancreatic integrity assessment.

This study aimed to understand the effects of freshwater acidification, driven by industrial runoff, agricultural activities, and atmospheric deposition, on the freshwater mollusk Bellamya bengalensis. By systematically investigating the impact of two common carboxylic acids, acetic acid (AA) and benzoic acid (BA), this research employed diverse toxicological, pathological, and ecological assessments. We explored survival predictions through the generic unified threshold model of survival (GUTS-SD), examined oxidative stress responses, and investigated hepatopancreatic alterations. In the experimental design, Bellamya bengalensis were subjected to environmentally relevant sublethal concentrations (10%, 20% LC50) of AA (39.77 and 79.54 mg/l) and BA (31.41 and 62.82 mg/l) over 28 days. Acute toxicity tests revealed increased LC50 values, indicating heightened toxicity with prolonged exposure, particularly due to the greater potency of benzoic acid compared to acetic acid. The GUTS-SD model provided accurate predictions of time-specific effects on populations, presenting long-term exposure (100 days) LC50 values for AA (263.7 mg/l) and BA (330.9 mg/l). Sequentially, the integrated biomarker response (IBR) analysis across study intervals highlighted the 28-day interval as the most sensitive, with GST emerging as the most responsive enzyme to oxidative stress induced by AA and BA. Histopathological and ultrastructural assessments of the hepatopancreas showed severe alterations, including necrosis, vacuolation and disrupted micro-villi, which were especially pronounced in higher BA exposure concentrations. These findings highlight the health and survival impacts of carboxylic acid toxicity on Bellamya bengalensis, emphasizing the need for proactive measures to mitigate acidification in aquatic ecosystems. The broader ecological implications underscore the importance of effective management and conservation strategies to address ongoing environmental challenges.

Effects of glyphosate-based herbicide on gut microbes and hepatopancreatic metabolism in Pomacea canaliculata.

Roundup®, a prominent glyphosate-based herbicide (GBH), holds a significant position in the global market. However, studies of its effects on aquatic invertebrates, including molluscs are limited. Pomacea canaliculata, a large freshwater snail naturally thrives in agricultural environments where GBH is extensively employed. Our investigation involved assessing the impact of two concentrations of GBH (at concentrations of 19.98 mg/L and 59.94 mg/L, corresponding to 6 mg/L and 18 mg/L glyphosate) during a 96 h exposure experiment on the intestinal bacterial composition and metabolites of P. canaliculata. Analysis of the 16 S rRNA gene demonstrated a notable reduction in the alpha diversity of intestinal bacteria due to GBH exposure. Higher GBH concentration caused a significant shift in the relative abundance of dominant bacteria, such as Bacteroides and Paludibacter. We employed widely-targeted metabolomics analysis to analyze alterations in the hepatopancreatic metabolic profile as a consequence of GBH exposure. The shifts in metabolites primarily affected lipid, amino acid, and glucose metabolism, resulting in compromised immune and adaptive capacities in P. canaliculata. These results suggested that exposure to varying GBH concentrations perpetuates adverse effects on intestinal and hepatopancreatic health of P. canaliculata. This study provides an understanding of the negative effects of GBH on P. canaliculata and may sheds light on its potential implications for other molluscs.

Protective effects of butyric acid during heat stress on the survival, immune response, histopathology, and gene expression in the hepatopancreas of juvenile pacific shrimp (L. Vannamei).

This study looked at the effects of adding butyric acid (BA) to the diets of juvenile Pacific shrimp and how it affected their response to survival, immunity, histopathological, and gene expression profiles under heat stress. The shrimp were divided into groups: a control group with no BA supplementation and groups with BA inclusion levels of 0.5 %, 1 %, 1.5 %, 2 %, and 2.5 %. Following the 8-week feeding trial period, the shrimp endured a heat stress test lasting 1 h at a temperature of 38 °C. The results showed that the control group had a lower survival rate than those given BA. Interestingly, no mortality was observed in the group receiving 1.5 % BA supplementation. Heat stress had a negative impact on the activities of alkaline phosphatase (AKP) and acid phosphatase (ACP) in the control group. Still, these activities were increased in shrimp fed the BA diet. Similar variations were observed in AST and ALT fluctuations among the different groups. The levels of triglycerides (TG) and cholesterol (CHO) increased with high temperatures but were reduced in shrimp-supplemented BA. The activity of an antioxidant enzyme superoxide dismutase (SOD) increased with higher BA levels (P < 0.05). Moreover, the groups supplemented with 1.5 % BA exhibited a significant reduction in malondialdehyde (MDA) content (P < 0.05), suggesting the potential antioxidant properties of BA. The histology of the shrimp's hepatopancreas showed improvements in the groups given BA. Conversely, the BA significantly down-regulated the HSPs and up-regulated MnSOD transcript level in response to heat stress. The measured parameters determine the essential dietary requirement of BA for shrimp. Based on the results, the optimal level of BA for survival, antioxidant function, and immunity for shrimp under heat stress is 1.5 %.

Exploring the impact of nonylphenol exposure on Litopenaeus vannamei at the histological and molecular levels.

Nonylphenol (NP) is one of the common pollutants in the environment that have toxic effects on aquatic animals. Nevertheless, little is known about the possible toxicity mechanism of NP on the hepatopancreas of Litopenaeus vannamei. In the present study, the detrimental effects of NP on the hepatopancreas of the L. vannamei were explored at the histological and transcriptomic levels. The findings indicated that after NP exposed for 3, 12, and 48 h, the hepatopancreas histology was changed significantly. Transcriptomic analysis showed that a total of 4302, 3651, and 4830 differentially expressed genes (DEGs) were identified at 3, 12, and 48 h following NP exposure. All these DEGs were classified into 12 clusters according to the expression patterns at different time points. GO and KEGG enrichment analyses of DEGs were also performed, immunological, metabolic, and inflammatory related pathways, including arachidonic acid metabolism (ko00590), the PPAR signaling pathway (ko03320), and the regulation of TRP channels by inflammatory mediators (ko04750) were significantly enriched. Six DEGs were selected for validation by quantitative real-time PCR (qRT-PCR) and the results confirmed the reliability of transcriptome data. All results indicated that NP is toxic to L. vannamei by damaging the histopathological structure and disrupting the biological function. The findings would provide a theoretical framework for lowering or limiting the detrimental impacts of NP on aquaculture and help us to further study the molecular toxicity of NP in crustaceans.

Bisphenol S exposed changes in intestinal microflora and metabolomics of freshwater crayfish, Procambarus clarkii.

Bisphenol S (BPS), a typical endocrine-disrupting chemical (EDC), can cause hepatopancreas damage and intestinal flora disturbance. Comprehensive studies on the mechanisms of acute toxicity in crustaceans are lacking. In this study, 16S rRNA and liquid chromatography were used to investigate intestinal microbiota and metabolites of freshwater crayfish (Procambarus clarkii). In this study, freshwater crayfish were exposed to BPS (10 µg/L and 100 µg/L). The results showed a significant decrease in catalase (CAT) and superoxide dismutase (SOD) activities after exposure to BPS, which inhibited the Nrf2-Keap1 signaling pathway and induced oxidative stress toxicity in freshwater crayfish. In addition, BPS exposure induced the structural changes of intestinal microbial in the freshwater crayfish, showing different patterns of effects. The number of potentially pathogenic bacteria increased, such as Citrobacter, Hafnia-Obesumbacterium, and RsaHf231. A total of 128 different metabolites were analyzed by LC-MS/MS. The inositol and leukotriene (LT) contents in the hepatopancreas of freshwater crayfish were significantly decreased after 10 µg/L BPS exposure, which in turn led to the accumulation of lipids causing hepatopancreas damage. In conclusion, when the concentration of BPS in the water environment exceeded 10 µg/L, the freshwater crayfish intestinal microbiota was dysbiosis and the hepatopancreas metabolism was disturbed.

Efficacy of Annona glabra extract against acute hepatopancreatic necrosis disease in white-leg shrimp (Penaeus vannamei).

This study aims to investigate the use of pond apple (Annona glabra) compounds as a novel strategy to prevent and treat acute hepatopancreatic necrosis disease (AHPND) as well as to better understand the mechanism of health improvement in shrimp. The A. glabra leaf extracts were extracted using various solvents and examined for in vitro and in vivo activity against Vibrio parahaemolyticus strains. In comparison with ethanol and water extracts, methanol extract showed the strongest bactericidal effect (MBC/MIC ratio of 2.50 ± 1.00), with minimal inhibitory concentration (MIC) of 0.023 ± 0.012 mg ml-1 and minimum bactericidal concentration (MBC) of 0.065 ± 0.062 mg ml-1. White leg shrimp (P. vannamei, body weight 10.37 ± 0.27 g) fed A. glabra methanol extracts-containing diets (AMEDs) at 1 %, 1.5 %, and 2.0 % demonstrated no deleterious effects on survival and were significantly increased in length and weight after 30 days of feeding. The level of total haemocyte, hyaline haemocyte on day 15 and granulocyte on day 30 remarkably increased (p < 0.05) in shrimps fed AMEDs groups compared to those in the control group. The finding demonstrates that granulocyte was induced time dependently. In particular, the survival rate of V. parahaemolyticus challenged shrimps under medication with AMEDs at 1.5 % and 2.0 % was significantly higher (p < 0.05) than that of the control group. The decrease in bacterial load of Vibrio spp. and V. parahaemolyticus was obviously recorded in hepatopancreas shrimp given AMEDs 1.5 % and 2.0 % and may be linked to herb characteristics such as antibacterial activity, enhancing innate immunity, and its potential to maintain the integrity of hepatopancreatic tissue. Our findings suggest that A. glabra extract might be used as a health enhancer in commercial farmed shrimp.

Dietary lipid supplementation alleviated the impacts of polystyrene nanoplastic exposure in Litopenaeus vannamei.

The widespread occurrence of nanoplastic (NP) pollution in the environment is a growing concern, and its presence poses a potential threat to cultured aquatic animals. Previously, we found that NPs can significantly affect the lipid metabolism of shrimp. However, relevant reports about the effects of increasing dietary lipid levels on NP toxicity are lacking. Therefore, we explored the effects of dietary supplementation with different lipid levels on the growth and lipid metabolism of Pacific white shrimp (Litopenaeus vannamei). We cultured L. vannamei at three dietary lipid levels (3 %, 6 %, and 9 %) and three NP concentrations (0, 1, and 3 mg/L) for 2 months. We evaluated the effects of lipid levels on growth indexes, hepatopancreas morphological structure, lipid metabolism-related enzyme activity, and gene expression of the shrimp. The results showed that as lipid intake increased, the survival rate, body weight growth rate, and hepatosomatic ratio of the shrimp increased while the feed conversion rate decreased. Additionally, the crude protein and crude lipid contents increased, whereas the moisture and ash contents did not change much. We found that the morphological structure of the hepatopancreas was seriously damaged in the 3 mg/L NPs and 3 % dietary lipid group. Finally, lipid metabolism-related enzyme activities and gene expression levels increased with increased dietary lipid levels. Together, these results suggest that increasing dietary lipid content can improve shrimp growth and alleviate lipid metabolism disorders caused by NPs. This study is the first to show that nutrition regulation can alleviate the toxicity of NPs, and it provides a theoretical basis for the green and healthy culture of L. vannamei.

Integration of transcriptome, gut microbiota, and physiology reveals toxic responses of the red claw crayfish (Cherax quadricarinatus) to imidacloprid.

Imidacloprid enters the water environment through rainfall and causes harm to aquatic crustaceans. However, the potential chronic toxicity mechanism of imidacloprid in crayfish has not been comprehensively studied. In this study, red claw crayfish (Cherax quadricarinatus) were exposed to 11.76, 35.27, or 88.17 µg/L imidacloprid for 30 days, and changes in the physiology and biochemistry, gut microbiota, and transcriptome of C. quadricarinatus and the interaction between imidacloprid, gut microbiota, and genes were studied. Imidacloprid induced oxidative stress and decreased growth performance in crayfish. Imidacloprid exposure caused hepatopancreas damage and decreased serum immune enzyme activity. Hepatopancreatic and plasma acetylcholine decreased significantly in the 88.17 µg/L group. Imidacloprid reduced the diversity of the intestinal flora, increased the abundance of harmful flora, and disrupted the microbiota function. Transcriptomic analysis showed that the number of up-and-down-regulated differentially expressed genes (DEGs) increased significantly with increasing concentrations of imidacloprid. DEG enrichment analyses indicated that imidacloprid inhibits neurotransmitter transduction and immune responses and disrupts energy metabolic processes. Crayfish could alleviate imidacloprid stress by regulating antioxidant and detoxification-related genes. A high correlation was revealed between GST, HSPA1s, and HSP90 and the composition of gut microorganisms in crayfish under imidacloprid stress. This study highlights the negative effects and provides detailed sequencing data from transcriptome and gut microbiota to enhance our understanding of the molecular toxicity of imidacloprid in crustaceans.

Differential effects of oxytetracycline on detoxification and antioxidant defense in the hepatopancreas and intestine of Chinese mitten crab under cadmium stress.

This study aims to evaluate the effects of oxytetracycline (OTC) on detoxification and oxidative defense in the hepatopancreas and intestine of Chinese mitten crab (Eriocheir sinensis) under cadmium (Cd) stress. The crab was exposed to 0.6 µM Cd, 0.6 µM OTC, and 0.6 µM Cd plus 0.6 µM OTC for 42 days. Our results showed that in the intestine, OTC alone enhanced protein carboxylation (PC) and malondialdehyde (MDA) contents, which was associated with the increased OTC accumulation. Compared to Cd alone, Cd plus OTC increased Cd and OTC contents, and reduced detoxification (i.e., glutathione (GSH) content, gene expressions of cytochrome P450 (CYP) isoforms, 7-ethoxyresorufin O-deethylase (EROD) activity, mRNA levels and activities of glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione-S-transferase (GST)), and antioxidant defense (i.e., gene expressions and activities of catalase (CAT) and superoxide dismutase (SOD)) in the intestine, leading to the increased in PC and MDA contents, suggesting that OTC had a synergistic effect on Cd-induced oxidative damage. In the hepatopancreas, although OTC alone increased OTC accumulation, it did not affect PC and MDA contents. Compared to Cd alone, Cd plus OTC reduced MDA content, which was closely related to the improvement of detoxification (i.e., GSH content, mRNA levels of CYP isoforms, EROD activity, gene expressions and activities of GPx, GR and GST), and antioxidant defense (gene expressions and activities of CAT and SOD, metallothionein content). Aryl hydrocarbon receptor (AhR) and nuclear factor E2-related factor 2 (Nrf2) transcriptional expressions were positively correlated with most detoxification- and antioxidant-related gene expressions, respectively, indicating that AhR and Nrf2 were involved in the regulation of these gene expressions. Our results unambiguously demonstrated that OTC had tissue-specific effects on Cd-induced toxicological effect in E. sinensis, which contributed to accurately evaluating Cd toxicity modulated by TCs in crab.

Next-generation neonicotinoid: The impact of cycloxaprid on the crustacean decapod Penaeus vannamei.

Cycloxaprid, a new neonicotinoid pesticide, poses ecological risks, particularly in aquatic environments, due to its unique action and environmental dispersal. This study investigated the ecotoxicological effects of various concentrations of cycloxaprid on Penaeus vannamei over 28 days. High cycloxaprid levels significantly altered shrimp physiology, as shown by changes in the hepatosomatic index and fattening. Indicators of oxidative stress, such as increased serum hemocyanin, respiratory burst, and nitric oxide, as well as decreased phenol oxidase activity, were observed. Additionally, elevated activities of lactate dehydrogenase, succinate dehydrogenase, and isocitrate dehydrogenase indicated disrupted energy metabolism in the hepatopancreas. Notably, analyses of the nervous system revealed marked disturbances in neural signaling, as evidenced by elevated acetylcholine, octopamine, and acetylcholinesterase levels. Transcriptomic analysis highlighted significant effects on gene expression and metabolic processes in the hepatopancreas and nervous system. This study demonstrated that cycloxaprid disrupts neural signaling and oxidative balance in P. vannamei, potentially affecting its growth, and provides key insights into its biochemical and transcriptomic toxicity in aquatic systems.

Effects of myo-inositol on growth and biomarkers of environmental stress and metabolic regulation in Pacific white shrimp (Litopenaeus vannamei) reared at low salinity.

This study explored the role of myo-inositol in alleviating the low salinity stress of White Shrimp (Litopenaeus vannamei). Juvenile shrimp (0.4 ± 0.02 g) in low salinity (salinity 3) water were fed diets with myo-inositol levels of 0, 272, 518, 1020 and 1950 mg/kg (crude protein is 36.82 %, crude lipid is 7.58 %), fed shrimp in seawater at a salinity of 25 were fed a 0 mg/kg myo-inositol diet as a control (Ctrl). The experiment was carried out in tanks (50 L) with satiety feeding, and the experiment lasted for 6 weeks. After sampling, the serum was used to measure immune function, the hepatopancreas homogenate was used to measure the antioxidant capacity and hepatopancreas damage state, the hepatopancreas was used for transcriptomics analysis, and the gills were used for qPCR to measure osmotic pressure regulation. The results showed that the final weight and survival of the shrimp in the 1020 mg/kg group increased significantly compared with those in the other low salinity groups, but the final weight and biomass increase were significantly lower than those in the Ctrl group. Dietary myo-inositol improved the antioxidant capacity of shrimp under low salinity. B-cell hyperplasia and hepatic duct damage were observed in the hepatopancreas in the 0 mg/kg group. The results of transcriptome analysis showed that myo-inositol could participate in the osmotic pressure regulation of shrimp by regulating carbohydrate metabolism, amino acid metabolism, lipid metabolism and other related genes. Myo-inositol significantly affected the expression of related genes in ion transporter and G protein-coupled receptor-mediated pathways. This study demonstrated that myo-inositol can not only act as an osmotic pressure effector and participate in the osmolar regulation of shrimp through the phosphatidylinositol signaling pathway mediated by G protein-coupled receptors but also relieve low salinity stress by mediating physiological pathways such as immunity, antioxidation, and metabolism in shrimp. The binomial regression analysis of biomass increases and survival showed that the appropriate amount of myo-inositol in the L. vannamei diet was 862.50-1275.00 mg/kg under low salinity.

Protective effects of dietary icariin on lipopolysaccharide-induced acute oxidative stress and hepatopancreas injury in Chinese mitten crab, Eriocheir sinensis.

To investigate the effects of dietary icariin (ICA) supplementation on acute oxidative stress and hepatopancreatic injury induced by lipopolysaccharide (LPS) injection in Eriocheir sinensis, an 8-week feeding trial of crabs was conducted using 4 diets with different supplementation levels of ICA (0, 50, 100, and 200 mg/kg diet weight, respectively), and then challenged with LPS of 400 µg/kg body weight for 6 h. Results showed that 100 mg/kg ICA supplementation increased the antioxidant capacity, reduced the stress-related indicators in haemolymph, strengthen the mitochondrial membrane potential, and reduce apoptosis compared to the single LPS-treated crabs. The expressions of apoptosis-related genes and proteins were also evaluated to further understand the effects of dietary ICA pretreatment on LPS-induced cell apoptosis. As a result, dietary 100 mg/kg diet weight ICA pre-addition significantly down-regulated the expression of HSP60, HSP70, Caspase 3c, Caspase 8, Caspase 3, Caspase 9, P38, and Bax (P < 0.05), and alleviated the suppressed expression of PI3K, AKT, MEK, and Bcl-2 (P < 0.05) in crabs challenged with LPS. Overall, this research reveals that ICA supplementation of 100 mg/kg diet weight could enhance the resistance to oxidative damage and apoptosis in E. sinensis facing LPS challenge.

The characterization, expression and activity analysis of three superoxide dismutases in Eriocheir hepuensis under azadirachtin stress.

Superoxide dismutase (SOD) can effectively eliminate of excess ROS, which causes oxidative damage to lipids, proteins, and DNA. In this study, we cloned the CuZn-SOD, cMn-SOD1, and cMn-SOD2 genes in Eriocheir hepuensis, and found that the coding sequence (CDS) lengths were 627 bp, 861 bp and 1062 bp, which encoded 208, 286, and 353 amino acids, respectively. Phylogenetic analysis indicated that all SOD genes were evolutionarily conserved, while cMn-SOD2 had an extra gap (67 amino acids) in the conserved domain compared with cMn-SOD1 without huge changes in the tertiary structure of the conserved domain, suggesting that cMn-SOD2 may be a duplicate of cMn-SOD1. qRT-PCR showed that the three SOD genes were widely expressed in all the tested tissues, CuZn-SOD and cMn-SOD1 were mostly expressed in the hepatopancreas, while cMn-SOD2 was mostly expressed in thoracic ganglia. Under azadirachtin stress, the oxidation index of surviving individuals, including the T-AOC, SOD activity, and MDA contents increased in the early stage and then remained steady except for a decrease in MDA contents in the later stage. qRT-PCR showed that the three SOD genes displayed the same trends as SOD activity in surviving individuals, and the highest expressions of CuZn-SOD in the hepatopancreas, heart, and gill were 14.16, 1.41, and 30.87 times that of the corresponding control group, respectively. The changes were 1.35, 5.77 and 3.33 fold for cMn-SOD1 and 1.62, 1.71 and 1.79 fold for cMn-SOD2, respectively. However, the activity and expression of SOD genes in dead individuals were lower than that observed in surviving individuals. These results reveal that SOD plays a significant role in the defence against azadirachtin-induced oxidative stress.

Comparative transcriptome analysis of the gills and hepatopancreas from Macrobrachium rosenbergii exposed to the heavy metal Cadmium (Cd2+).

Heavy metal Cadmium (Cd2+) pollution has become a severe environmental problem for aquatic organisms. In crustaceans, gills (Gi) and hepatopancreas (Hp) play a vital role in the toxicology. However, in Macrobrachium rosenbergill, there are few researches about gill and hepatopancreases responding to Cd2+ stress at a molecular level. In this study, transcriptomic analysis was applied to characterize gene expression profiles of gills and hepatopancreas of M. rosenbergill after Cd2+ exposure for 0 h, 3 h and 3 d. Six cDNA libraries (Gi 0 h, Gi 3 h, Gi 3 d, Hp 0 h, Hp 3 h, and Hp 3 d) were constructed and a total of 66,676 transcripts and 48,991 unigenes were annotated. Furthermore, differentially expressed genes (DEGs) were isolated by comparing the Cd2+ treated time-point libraries (3 h and 3 d group) with the control library (0 h group). The results showed that most of the DEGs were down-regulated after Cd2+ exposure and the number of DEGs among gill groups were significantly higher than those among hepatopancreas groups. GO functional and KEGG pathway analysis suggested many key DEGs in response to the Cd2+ stress, such as metallothionein and Hemocyanin. Additionally, a total of six DEGs were randomly selected to further identify their expressional profile by qPCR. The results indicated that these DEGs were involved in the response to Cd2+. This comparative transcriptome provides valuable molecular information on the mechanisms of responding to Cd2+ stress in M. rosenbergii, which lays the foundation for further understanding of heavy metal stress.

Combined Effects of Temperature and Toxic Algal Abundance on Paralytic Shellfish Toxic Accumulation, Tissue Distribution and Elimination Dynamics in Mussels Mytilus coruscus.

This study assessed the impact of increasing seawater surface temperature (SST) and toxic algal abundance (TAA) on the accumulation, tissue distribution and elimination dynamics of paralytic shellfish toxins (PSTs) in mussels. Mytilus coruscus were fed with the PSTs-producing dinoflagellate A. catenella under four simulated environment conditions. The maximum PSTs concentration was determined to be 3548 µg STX eq.kg-1, which was four times higher than the EU regulatory limit. The increasing SST caused a significant decline in PSTs levels in mussels with rapid elimination rates, whereas high TAA increased the PSTs concentration. As a result, the PSTs toxicity levels decreased under the combined condition. Additionally, toxin burdens were assessed within shellfish tissues, with the highest levels quantified in the hepatopancreas. It is noteworthy that the toxin burden shifted towards the mantle from gill, muscle and gonad at the 17th day. Moreover, variability of PSTs was measured, and was associated with changes in each environmental factor. Hence, this study primarily illustrates the combined effects of SST and TAA on PSTs toxicity, showing that increasing environmental temperature is of benefit to lower PSTs toxicity with rapid elimination rates.

The effects of ammonia-N stress on immune parameters, antioxidant capacity, digestive function, and intestinal microflora of Chinese mitten crab, Eriocheir sinensis, and the protective effect of dietary supplement of melatonin.

Ammonia nitrogen pollution seriously affects the economic benefits of Chinese mitten crab (Eriocheir sinensis) farming. In this study, we first evaluated the protective effects of melatonin (MT) on immune parameters, antioxidant capacity, and digestive enzymes of E. sinensis under acute ammonia nitrogen stress. The results showed that ammonia-N stress significantly decreased the antibacterial ability of crabs, nevertheless MT could significantly improve it under ammonia-N stress (P < 0.05). Ammonia-N group hemolymph antioxidant capacity indicators (T-AOC, T-SOD, GSH-Px) were significantly decreased than control (p < 0.05), while the MT ammonia-N group hemolymph T-SOD activity significantly increased than ammonia-N group (p < 0.05). For hepatopancreas, ammonia-N group GSH-PX activity significantly decreased than control group, but MT ammonia-N group was significant increased than ammonia-N (p < 0.05). Ammonia-N stress has significantly increased the content of MDA in hemolymph and hepatopancreas (p < 0.05), but MT ammonia-N treatment significantly decreased than ammonia-N group (p < 0.05). Compared with the control group, ammonia-N significantly reduced the activities of Trypsin in the intestine and hepatopancreas (p < 0.05), while MT ammonia-N group can significantly improve the intestinal trypsin activity than ammonia-N (p < 0.05). The intestinal microbiota of E. sinensis results showed that ammonia-N stress significantly decreased the relative abundance of Bacteroidetes (p < 0.05). Ammonia-N stress significantly decreased the Dysgonomonas and Rubellimicrobium, and the Citrobacter significantly increased. In summary, melatonin has a protective effect on E. sinensis under ammonia-N stress. Acute ammonia-N stress may lead to the decrease of probiotics and the increase of pathogenic bacteria, which may be closely related to the impairment of digestive function and immune function.

Therapeutic effect and immune mechanism of chitosan-gentamicin conjugate on Pacific white shrimp (Litopenaeus vannamei) infected with Vibrio parahaemolyticus.

To explore the disease resistance mechanism of chitosan conjugates, chitosan-gentamicin conjugate (CS-GT) was synthesized and systematically characterized, the immune mechanism of CS-GT on Litopenaeus vannamei infected with Vibrio parahaemolyticus was further explored. The results showed that imine groups in CS-GT were effectively reduced. Dietary supplementation of CS-GT can significantly increase the survival rate, total hemocyte counts, the antioxidant and immune related enzyme activity levels of shrimps (P < 0.05), which are all dose-dependent under the experimental conditions. In addition, CS-GT can protect the hepatopancreas from invading bacteria and alleviate inflammation. Particularly, CS-GT promotes the expressions of legumain (LGMN), lysosomal acid lipase (LIPA) and Niemann-Pick type C2 (NPC2) up-regulated. It is speculated that CS-GT may stimulate the lysosome to phagocytose pathogens more effectively. In conclusions, shrimps fed with CS-GT can produce immune response via lysosome and greatly improve the disease resistance to Vibrio parahaemolyticus.

Transcriptome analysis to elucidate the toxicity mechanisms of fenvalerate, sulfide gatifloxacin, and ridomil on the hepatopancreas of Procambarus clarkii.

Most antibiotics, insecticides, and other chemicals used in agricultural and fishery production tend to persist in the environment. Fenvalerate, sulfide gatifloxacin, and ridomil are widely used in aquaculture as antibacterial, antifungal, and antiparasitic drugs; however, their toxicity mechanism remains unclear. Thus, we herein analyzed the effects of these three drugs on the hepatopancreas of Procambarus clarkii at the transcriptome level. Twelve normalized cDNA libraries were constructed using RNA extracted from P. clarkii after treatment with fenvalerate, sulfide gatifloxacin, or ridomil and from an untreated control group, followed by Kyoto Encyclopedia of Genes and Genomes pathway analysis. In the control vs fenvalerate and control vs sulfide gatifloxacin groups, 14 and seven pathways were significantly enriched, respectively. Further, the effects of fenvalerate and sulfide gatifloxacin were similar on the hepatopancreas of P. clarkii. We also found that the expression level of genes encoding senescence marker protein-30 and arylsulfatase A was downregulated in the sulfide gatifloxacin group, indicating that sulfide gatifloxacin accelerated the apoptosis of hepatopancreatocytes. The expression level of major facilitator superfamily domain containing 10 was downregulated, implying that it interferes with the ability of the hepatopancreas to metabolize drugs. Interestingly, we found that Niemann pick type C1 and glucosylceramidase-ß potentially interact with each other, consequently decreasing the antioxidant capacity of P. clarkii hepatopancreas. In the fenvalerate group, the downregulation of the expression level of xanthine dehydrogenase indicated that fenvalerate affected the immune system of P. clarkii; moreover, the upregulation of the expression level of pancreatitis-associated protein-2 and cathepsin C indicated that fenvalerate caused possible inflammatory pathological injury to P. clarkii hepatopancreas. In the ridomil group, no pathway was significantly enriched. In total, 21 genes showed significant differences in all three groups. To conclude, although there appears to be some overlap in the toxicity mechanisms of fenvalerate, sulfide gatifloxacin, and ridomil, further studies are warranted.

Effects of waterborne cadmium exposure on Spinibarbus sinensis hepatopancreas and kidney: Mitochondrial cadmium accumulation and respiratory metabolism.

To examine the relationship between heavy metal accumulation in mitochondria and their respiration function in fish during in vivo exposure, juvenile Spinibarbus sinensis were exposed to different waterborne cadmium (Cd) concentrations for up to 28 days. We measured the state III respiration rate and cytochrome c oxidase (CCO) activity of mitochondria in hepatopancreas and kidney and the accumulated Cd concentrations in mitochondria and heat-stable protein (HSP) fractions. Dose- and time-dependent Cd accumulation occurred at different levels in both organs, but was lower in hepatopancreas. When hepatopancreas mitochondrial Cd concentrations in Cd-exposed groups were > 5.5 µg/g dwt, their state III respiration rates were significantly lower than the control. CCO activity of hepatopancreas mitochondria exhibited decreasing dose- and time-dependent trends. However, kidney mitochondria respiratory activities were not affected significantly by Cd exposure. Cd concentrations in kidney HSP fraction were 2-5 times higher than in hepatopancreas under all exposure conditions, and were mainly present as non-deleterious metallothionein (MT)-Cd complexes. These results suggest that Cd accumulation occurred in hepatopancreas and kidney mitochondria of S. sinensis following waterborne Cd exposure, which significantly inhibited the respiration function of hepatopancreas mitochondria but did not have a deleterious effect on kidney mitochondria. The inhibitory pattern of hepatopancreas mitochondrial Cd concentrations related to function exhibited threshold and saturation effects, suggesting the capacity of S. sinensis to manage Cd toxicity. The difference in the relative proportion of Cd occurring as MT-Cd complexes in organs likely causes the organ-specific effects of Cd on hepatopancreas and kidney mitochondrial function.