Nutritional regulation strategies contribute significantly to optimize the quality of aquatic products. In this study, the potential of dietary soy isoflavones (SIF) at different levels (0, 32.51, 70.83, and 369.03 mg/kg) to improve the nutritional value and edible quality of female Chinese mitten crabs (Eriocheir sinensis) was evaluated through an 11-week feeding trial. The results demonstrated that 32.51–70.83 mg/kg SIF significantly increased the total edible yield and condition factor. It also promoted protein and lipid deposition in the ovary and muscle. Additionally, SIF improved the fatty acid composition, particularly the LC-PUFA profile. Concomitant improvements in tissue coloration and muscle textural properties were also observed. Moreover, flavor-related free amino acids were significantly enriched in muscle, collectively contributing to improved edible quality. In contrast, 369.03 mg/kg dietary supplementation enhanced coloration in certain tissues and muscle hardness. However, it had adverse effects on lipid accumulation in the hepatopancreas and the textural properties of leg muscle. Therefore, dietary supplementation with 32.51–70.83 mg/kg SIF promoted better nutritional value and flavor quality of E. sinensis.

Salinity stress imposes substantial energetic and oxidative challenges on fish, thereby limiting their survival and growth in saline aquaculture systems. This study evaluated the effects of dietary CoQ10 supplementation on growth performance, osmoregulation, intestinal function, and metabolic responses in Nile tilapia (initial body weight: 2.18 ± 0.10 g) under hyperosmotic conditions. A total of 500 fish were randomly distributed into 20 tanks (four replicates per treatment) and fed five diets containing 0, 5, 10, 20, and 40 mg/kg CoQ10 for 8 weeks under 20 psu salinity. The results showed that moderate CoQ10 supplementation significantly improved survival rate and weight gain, with an estimated optimal level of 13.03 mg/kg. CoQ10 also improved osmoregulatory responses under salinity stress, as reflected by improved serum ion homeostasis, altered expression of gill ion transport-related genes (cftr, nka, nhe1, and nkcc), and reduced gill cell apoptosis. In addition, intestinal physiological status was improved, as evidenced by enhanced digestive enzyme activities, reduced intestinal permeability markers, and modulation of intestinal barrier- and inflammation-related genes. Together, these findings suggest that CoQ10 effectively enhances physiological adaptation to salinity stress in Nile tilapia under hyperosmotic conditions. Mechanistically, CoQ10 promoted glucose utilization and tricarboxylic acid (TCA) cycle activity, enhanced fatty acid β-oxidation, increased ATP and acetyl-CoA production, and reduced lactate accumulation, indicating improved metabolic efficiency and energy supply capacity. Meanwhile, hepatic oxidative stress and histological damage were markedly alleviated, as evidenced by reduced MDA and ROS levels together with elevated GSH content, T-AOC, and SOD activity. Overall, these findings demonstrate that dietary CoQ10 improves salinity adaptation of Nile tilapia through coordinated regulation of energy metabolism and redox homeostasis, thereby enhancing intestinal physiological function and osmoregulatory capacity under hyperosmotic conditions.

Developing low-protein feeds is essential for reducing aquaculture costs and environmental impact. This study examined the effects of alpha-Ketoglutarate (AKG) on growth performance, protein metabolism, intestinal microbiota, and transcriptomic responses in Chinese mitten crab (Eriocheir sinensis) under varying dietary protein levels. A 3 x 3 factorial design was employed in a 56-day feeding trial, with three protein levels (28 %, 33 %, and 38 %) and three AKG supplementation levels (0 %, 0.5 %, and 1 %). Juvenile crabs (1400 ind., 0.58 +/- 0.02 g) were randomly allocated to nine treatments with four replicates each. Results showed that low-protein diets (28 % and 33 %) impaired growth and protein deposition. However, AKG supplementation (0.5 % and 1 %) markedly enhanced weight gain (WG), specific growth rate (SGR), and feed utilization across all protein levels. Notably, crabs fed a 33 % protein diet with 1 % AKG achieved similar WG to those fed the 38 % protein diet. AKG supplementation reduced hemolymph ammonia levels, increased hepatic glutamate content, and enhanced glutamate dehydrogenase activity, optimizing nitrogen metabolism. Additionally, AKG improved digestive enzyme activities, upregulated amino acid transporter genes, and activated the mTOR pathway to promote protein synthesis. AKG also enhanced intestinal morphology and microbial composition, thereby improving intestinal health. Transcriptomic analysis further indicated that AKG might mitigate disruptions in extracellular matrix (ECM) receptor interactions and activate the PI3K-Akt pathway, facilitating protein synthesis. This study suggests that low-protein diets inhibit the growth of juvenile E. sinensis, whereas 1 % AKG supplementation enhances nutrient assimilation, nitrogen metabolism, and cellular signaling, ultimately improving feed efficiency and growth performance.

Saline-alkaline aquaculture is a promising strategy to alleviate freshwater shortages; however, such environments severely impair fish growth and physiological homeostasis. Nutritional regulation has been proposed to improve stress tolerance, yet the benefits of single additives are often limited under the multifactorial challenges imposed by saline-alkaline conditions. Therefore, a compound feed additive (CFA) consisting of glutamate, cholesterol, β-glucan, myo-inositol, zinc methionine, and curcumin was developed and evaluated in Nile tilapia (Oreochromis niloticus). To assess the robustness and practical applicability of this nutritional strategy, three independent feeding trials were conducted using different commercial basal diets as validation systems. Within each dietary system, fish were reared under freshwater (FW), saline-alkaline water (SAW), or saline-alkaline water supplemented with CFA (SAW+CFA). Saline-alkaline stress significantly reduced WG and SR, increased FCR, and elevated VSI and HSI, indicating impaired growth performance and metabolic burden. These changes were accompanied by increased serum glucose and ion concentrations (Na+, K+, Cl-), elevated ammonia levels, and reduced crude protein content. Dietary CFA improved growth and feed utilization under saline-alkaline conditions. It enhanced hepatic glycogen content and reduced serum glucose levels. Meanwhile, it downregulated glycolysis-related genes (hk, pfk1, pk) and upregulated genes involved in gluconeogenesis and the pentose phosphate pathway (g6pase, pc, g6pdh), indicating altered glucose metabolism and improved energy homeostasis. Saline-alkaline stress induced oxidative stress, apoptosis, and histological damage in the liver, whereas CFA alleviated these alterations by reducing MDA levels, enhancing antioxidant enzyme activities (CAT, GSH-Px, T-SOD) and suppressing apoptosis-related genes (caspases, p53, c-myc). In addition, CFA alleviated saline-alkaline stress-induced gill structural damage and reduced serum ion concentrations while modulating ion transport-related gene expression, suggesting improved osmoregulatory capacity. It also enhanced ammonia metabolism and transport, as reflected by reduced serum ammonia levels and altered expression of related genes. Furthermore, Saline-alkaline stress impaired intestinal structure and function, whereas CFA improved intestinal villus structure, increased digestive enzyme activities (amylase, trypsin, lipase), and suppressed pro-inflammatory genes (il-1β, il-8). Importantly, similar beneficial response patterns were observed across the three independently analyzed dietary systems. Overall, CFA improved saline-alkaline adaptability of Nile tilapia and was associated with improvements in energy metabolism, oxidative homeostasis, osmoregulation, ammonia detoxification, and intestinal function, providing a practical nutritional strategy for saline-alkaline aquaculture.

Due to the global shortage and high price of fish meal, replacing fish meal with plant protein sources is essential for the sustainable development of aquaculture. However, plant protein substitution can exert a series of negative effects on cultured animals, including reduced feed intake and growth performance, and impaired intestinal health. Thus, it is necessary to actively explore nutritional strategies to alleviate these negative impacts. In this study, six experimental diets were formulated: a fish meal control diet containing 35

Saline-alkali cultivation is a crucial approach to alleviate the fresh water crisis. However, prolonged saline-alkali stresses might bring adverse effects on fish growth, health, and even death. This study evaluated the effects of different carbohydrate supplementation on growth performance, carbohydrate metabolism, antioxidant capacity, and tissue morphology of mandarin fish (Siniperca chuatsi) under saline-alkali stress. Fish with an initial weight of 31.03 ± 0.12 g, were fed with three carbohydrate levels (8%, 13%, and 18%) in either a freshwater or a saline-alkali water environment (salinity = 6, alkalinity = 0.7 g/L). Results indicated that fish cultured in saline-alkali water performed a higher specific growth rate (SGR) and weight gain (WG). In addition, the activities of the glycolysis pathway, pentose phosphate pathway, and gluconeogenesis pathway were enhanced prominently under this stress. The growth performances were also improved significantly by the increased carbohydrate diets. However, the activities of amylase were inhibited with the increased carbohydrate intake, which impeded the process of glycometabolism. In contrast, the pentose phosphate pathway and gluconeogenesis pathway responded positively to dietary carbohydrate levels, especially under saline-alkali stresses. Moreover, improving the carbohydrate level appropriately could significantly reduce the accumulation of malondialdehyde, promote the activities of superoxide dismutase, and total antioxidant capacity under saline-alkali stress. Furthermore, the expression of insulin receptors showed an ascending tendency in freshwater, while opposite in saline-alkali water with increased carbohydrate intake. In summary, an appropriate saline-alkali environment was more conducive to the growth of mandarin fish. Moreover, 13% carbohydrate diets could enhance its growth performance in saline-alkali environments. It was noteworthy that the effects of insulin on the regulation of carbohydrate metabolism might not be the same as normal conditions during the adaptation process in mandarin fish. The pentose phosphate pathway played a critical part in osmoregulation under saline-alkali stress.

Cholesterol serves as a precursor for bile acids and molting hormones, while taurine is involved in bile acid conjugation and lipid regulation in vertebrates. However, their synergetic roles in crustacean nutrition remain poorly understood. This study investigated the interactions between dietary cholesterol (0%, 0.64%, and 1.00%) and taurine (0% and 0.65%) in juvenile Chinese mitten crabs (Eriocheir sinensis). A total of 960 juvenile crabs (3.08 ± 0.02 g) were randomly assigned to six dietary treatments (four replicates per treatment, 40 crabs per replicate) in a 3 × 2 factorial design for 8 weeks. Growth performance, body proximate composition, serum and hepatopancreas biochemical indices, bile acid profiles, and expression of genes related to lipid metabolism and the nutrient-sensitive mammalian target of rapamycin (mTOR) signaling pathway were evaluated. Significant improvements in final body weight, weight gain, specific growth rate, and feed conversion ratio were observed in crabs fed the diet containing 0.64% cholesterol and 0.65% taurine (P < 0.05). Dietary cholesterol significantly increased hepatopancreas total cholesterol and bile acid contents (P < 0.05), particularly taurohyodeoxycholic acid and epi-allolithocholic acid, while taurine supplementation further elevated cholic acid content. Taurine effectively reduced serum total cholesterol and low-density lipoprotein cholesterol concentrations (P < 0.05), especially at higher dietary cholesterol levels. The combination of cholesterol and taurine significantly alleviated antioxidant impairment by increasing superoxide dismutase activity (P < 0.001), and upregulated key genes in lipid metabolism (fas and cpt1a), cholesterol transport (abcg8), and mTOR pathway components (mtorc1, s6k1, and 4ebp1) (P < 0.05). Dietary 0.64% cholesterol in combination with 0.65% taurine optimized growth performance and improved the health of E. sinensis. Taurine enhanced cholesterol utilization by facilitating its conversion into bile acids and activating key nutrient-sensing pathways such as the mTOR pathway, thereby improving lipid metabolism and antioxidant capacity. These findings reveal a synergistic metabolic interaction in which taurine enhances the nutritional value of cholesterol by facilitating its conversion into signaling-active bile acids and directly modulating lipid metabolism pathways.

Aquaculture in saline environments is expanding worldwide, but elevated salinity can alter growth performance and physiological homeostasis in cultured fish. Nile tilapia (Oreochromis niloticus) is a euryhaline freshwater species widely used in salinity tolerance research and aquaculture production. Here, this study evaluated whether dietary mannitol improves salinity adaptation in tilapia. Fish (1.86 ± 0.04 g) were fed isonitrogenous and isoenergetic diets containing 0, 1, 2, 5 or 10

High plant protein diets can induce oxidative stress and tissue damage, disrupt glucose and lipid metabolism, and ultimately impair the growth of aquatic animals. This study examined the effects of ferulic acid on growth performance, health status, digestive function and glycolipid metabolism in juvenile Eriocheir sinensis fed a high plant protein diet. A total of 960 juvenile crabs (mean weight: 0.50 +/- 0.02 g) were randomly allocated to six experimental groups and fed either a control diet (35 % fishmeal) or low fishmeal diets (15 % fishmeal, with concentrations of 0, 40, 80, 160, and 320 mg/kg ferulic acid) for 56 days. Compared with juvenile crabs fed highfishmeal diets, those fed low-fishmeal diets exhibited reduced weight gain rates and impaired antioxidant capacity, digestive function, and glucose-lipid metabolism. But compared to the low-fishmeal control group, the inclusion of 80-160 mg/kg ferulic acid showed the higher weight gain rate and higher specific growth rate of juvenile crabs, and lowered the feed conversion ratio. Ferulic acid supplementation at levels of 40-160 mg/kg enhanced total antioxidant capacity (T-AOC) in the hepatopancreas, reduced aspartate aminotransferase (AST) levels in hemolymph, and decreased malondialdehyde (MDA) levels in the hepatopancreas. Additionally, a 160 mg/kg ferulic acid supplementation improved the histology of intestinal tissues. Ferulic acid also promoted lipid biosynthesis, causing a substantial rise in the crude lipid content of the whole crab, as well as elevated hemolymph triglyceride (TG), cholesterol (TCHO), and high-density lipoprotein (HDL) levels. Furthermore, ferulic acid upregulated the expression and activity of key genes and enzymes involved in glycolysis, gluconeogenesis, and the pentose phosphate pathway. Conversely, the expression of glycogen synthase (gs) and glycogen phosphorylase (gp) was downregulated. In conclusion, supplementation with ferulic acid in a high plant protein diet significantly enhanced the growth, health, and lipid accumulation in juvenile crabs, while also promoting the utilization of carbohydrates for energy production. According to the regression analysis of weight gain rate and crude lipid content, the optimal supplementation range of ferulic acid was determined to be 123.90-126.09 mg/ kg.

Soy isoflavones are phytoestrogens that exhibit both estrogenic and/or antiestrogenic effects. This research investigated the potential of soy isoflavones as functional feed additives to promote ovarian development in female Chinese mitten crabs (Eriocheir sinensis). One hundred ninety-two crabs (101.52 ± 4.57 g) were randomly assigned to four groups (six replicates per group and eight crabs per replicate), and fed diets supplemented with 0.00, 32.51, 70.83, or 369.03 mg/kg soy isoflavones for 11 weeks. Compared to the control group, supplementation with 32.51 mg/kg soy isoflavones significantly increased the gonadosomatic index, hemolymph vitellogenin content, and the vtg mRNA levels in the hepatopancreas and ovary (P < 0.05). Moreover, supplementation with 32.51 and 70.83 mg/kg soy isoflavones significantly promoted yolk granule formation (P < 0.05). At the molecular level, soy isoflavones modulated estradiol levels and activated the estrogen-related receptor signaling. They also upregulated the expression levels of esrrb, hsd3b2, and hsd17b6 genes (P < 0.05), compared to the control group. Additionally, they increased estradiol synthesis through activating the cyclic adenosine monophosphate/PKA/CREB protein signaling pathway. High dose supplementation (369.03 mg/kg) did not significantly affect ovarian development (P > 0.05). Therefore, soy isoflavones exhibit a U-shaped effect on ovarian development of E. sinensis, with 32.51 mg/kg being an effective dose for promoting ovarian maturation.

This study investigated the physiological and metabolic responses of juvenile Chinese mitten crab (Eriocheir sinensis) to dietary inclusion of coenzymatically hydrolyzed anchovy-cottonseed protein (HACP) with or without arginine and methionine supplementation. A 56-day feeding trial was conducted. Juvenile crabs were fed a control diet containing 15% fishmeal and experimental diets in which fishmeal was partially replaced by HACP at graded levels (5%, 10%, and 15%). Increasing dietary HACP levels significantly affected growth performance, feed intake, digestive enzyme activities, hepatopancreatic condition, and intestinal microbial composition. The 5% HACP inclusion maintained growth performance and protein utilization comparable to the control, whereas higher inclusion levels reduced feed intake and digestive enzyme activity, suggesting potential alterations in digestive enzyme activity and metabolic status. Arginine and methionine supplementation partially alleviated these effects by enhancing trypsin and lipase activities, reducing hepatopancreatic stress indicators, and improving antioxidant status, suggesting potential improvements in nutrient utilization and metabolic responses. Microbiota and metabolomic analyses further revealed coordinated shifts in intestinal microbial composition and metabolic pathways associated with amino acid, lipid, and energy metabolism. Overall, these findings indicate that dietary HACP influences physiological function through integrated effects on digestion, metabolism, and microbiome-metabolome interactions, and highlight the role of amino acid balance in mediating metabolic response under altered dietary protein composition.

The aim of this experiment was to investigate the effects of dietary niacin supplementation on the growth, osmoregulatory capacity, and energy metabolism of Nile tilapia (Oreochromis niloticus) under salinity stress. this study, five diets with varying niacin concentrations were prepared, with practical niacin levels of 3.33, 12.18, 33.98, 94.28, and 275.23 mg/kg. Fish with an initial weight of 1.80 +/- 0.22 g were selected for an 8-week feeding trial under 20 psu salinity. The results indicated that the dietary niacin significantly increased the weight gain, specific growth rate, and condition factor of tilapia. Furthermore, niacin supplementation also increased the crude protein and crude fat contents of tilapia. 12.18-94.28 mg/kg dietary niacin significantly improved the ion transport capacity of the gills which is a main tissue of the osmoregulation. Histological analysis of gill revealed that dietary niacin at concentrations ranging from 12.18 to 275.33 mg/kg relieved structural damage from salinity stress. After ingestion, niacin primarily accumulated in the liver and gills, activating the niacin metabolic pathway. As a result, compare to the control group, fish fed with dietary niacin got higher level NAD+, NAD+/NADH. The addition of 94.28 mg/kg niacin affected the glycolysis, TCA cycle and gluconeogenesis processes through SIRT1/GLUT1/HK signaling pathway. In addition, content of liver glucose was decreased, while pyruvate and ATP contents were increased. Optimal dietary niacin could improve the growth performance of Nile tilapia under salinity stress by activating the carbohydrate metabolism by SIRT1/GLUT1/HK signaling pathway. It can also enhance the salinity tolerance by activating ion transportation. Based on the second-order polynomial regression analysis with weight gain rate and specific growth rate, the optimal dietary niacin for Nile tilapia under salinity stress is 151.67-171.73 mg/kg.

This study investigated the protective mechanisms of postbiotics from the Saccharomyces cerevisiae fermentation product (SCFP) against combined hypoxia-thermal stress in Chinese mitten crabs. Juvenile crabs were randomly allocated into four treatment groups (n = 4 tanks/group, 40 crabs/tank) and fed diets with 0 g/kg SCFP (control and nonsupplemented stress groups), 3.2, or 6.4 g/kg SCFP for 56 days. SCFP supplementation significantly increased weight gain compared with the control group (p < 0.05). Following the feeding trial, the control group remained under optimal conditions (24 °C, 7.0 mg/L dissolved oxygen), whereas the three stress groups (0, 3.2, and 6.4 g/kg SCFP) were exposed to acute hypoxia-thermal stress (30 °C, 1.0 mg/L dissolved oxygen, 24 h). Under stress conditions, oxygen consumption rates were significantly elevated in nonsupplemented crabs, whereas SCFP supplementation maintained rates comparable to those of the control (p < 0.05). Integrated transcriptomic and WGCNA analyses revealed that hypoxia-thermal stress significantly upregulated stress response pathways while suppressing energy metabolism pathways. SCFP supplementation modulated key metabolic pathways, particularly oxidative phosphorylation and amino acid metabolism. Biochemical and cellular analyses confirmed that 6.4 g/kg SCFP restored the NADPH-dependent redox balance and maintained integrity of the mitochondrial membrane potential, effectively counteracting stress-related metabolic imbalances. This improved metabolic state was supported by enhanced antioxidant capacity. Specifically, SCFP supplementation reduced cellular reactive oxygen species levels, decreased malondialdehyde content (p < 0.05), and improved glutathione/oxidized glutathione ratio. These findings demonstrate that SCFP supplementation protects crabs against hypoxia-thermal stress through integrated metabolic and antioxidant mechanisms, offering a promising nutritional strategy for intensive aquaculture.

This study investigates the effects of salidroside and astragalus polysaccharides on growth performance and hypoxia tolerance of juvenile Chinese mitten crabs (Eriocheir sinensis). A total of 1200 crabs (0.23 +/- 0.01 g) were randomly allocated to 5 groups, each with 6 replicates of 40 crabs. Crabs were fed isonitrogenous and isolipidic diets containing 0 (control), 300 or 600 mg/kg salidroside (S300 or S600), 300 or 600 mg/kg astragalus polysaccharides (A300 or A600) for 8 weeks. After feeding trial, each group underwent a 24-h hypoxia stress with dissolved oxygen maintained at 2.0 +/- 0.2 mg/L. The weight gain of A600 group has significantly increased. Hypoxia significantly reduced the oxygen consumption rate and hemocyanin content. In contrast, S300 group exhibited a significant increase in hemocyanin content, whereas A600 group showed a significant decrease in oxygen consumption rate. S300 group showed significant increases in glycogen content and cpt1 expression, whereas lactic acid and triglyceride contents significantly decreased. Supplementation with 600 mg/kg astragalus polysaccharides reduced glycogen and triglyceride contents at different oxygen levels. Salidroside significantly reduced malondialdehyde content, it also increased glutathione peroxidase and superoxide dismutase activities. Under hypoxia, only A600 group increased alkaline and acid phosphatase activities compared to the control group. Thus, salidroside and astragalus polysaccharides effectively increased hypoxia tolerance by reducing the oxygen consumption rate, improving energy metabolism, strengthening antioxidant capacity and regulating immune responses. Based on these findings, dietary supplementation with 300 mg/kg salidroside or 600 mg/kg astragalus polysaccharides is recommended to improve crab growth performance and hypoxia tolerance.

To explore the effect of carbonate alkalinity stress on Nile tilapia (Oreochromis niloticus), fish were cultured at 3 alkalinity levels (0, 2 and 3 g/L NaHCO3) for six weeks. Survival, weight gain, and specific growth rate were measured. Liver samples were collected for measuring superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), total antioxidant capacity (T-AOC), and malondialdehyde (MDA) content. Intestinal microbiota was analyzed using 16S rRNA gene sequencing, and metabolomic profiling identified differentially abundant metabolites. The results showed that the survival rate decreased in the fish exposed to 3 g/L NaHCO3, while weight gain and specific growth rate were not affected by the increased carbonate alkalinity. In the group exposed to 3 g/L NaHCO3, activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), total antioxidant capacity (T-AOC), and malondialdehyde (MDA) content in liver increased, while in 2 g/L NaHCO3, only SOD and TAOC activities rose compared to the control. Long-term carbonate alkalinity stress increased the abundance of Luteolibacter in intestine but decreased the abundance of Cetobacterium, Bacteroides, and Lactiplantibacillus. Metabolomics results showed that differentially abundant metabolites were highly enriched in pathways such as purine metabolism, vitamin B6 metabolism, lysine degradation, glycerophospholipid metabolism, and biosynthesis of cofactors in fish cultured at 3 g/L NaHCO3. These results suggested that carbonate alkalinity stress affects intestinal health by increasing the proportion of pathogenic bacteria and reducing beneficial bacteria. The correlation between N6,N6,N6-trimethyllysine, Ne,Ne-dimethyllysine, and Luteolibacter may represent an effective physiological adaptation and tissue repair pathway for Nile tilapia under carbonate alkalinity stress.

Salinity elevation induces hyperosmotic stress in fish, consistently triggering apoptosis. Apoptosis is recognized as the most sensitive indicator for assessing acute or severe salinity stress. Reducing the apoptosis under salinity stress may improve salinity tolerance of fish. Cells showed a significant decrease of hyaluronic acid content under hyperosmotic stress, suggesting that hyaluronic acid may play an important role in salinity adaptation. To investigate the functions and mechanisms by hyaluronic acid participating in osmoregulation, we explored in vitro and in vivo experiments separately. In vitro screening experiments, 100 μg/ml high molecular weight hyaluronic acid (HMW-HA, molecular weight = 1600 kDa) significantly improved cell survival rate under salinity stress. The HMW-HA scavenged ROS, enhanced cellular antioxidant capacity and inhibited apoptosis via the BCL2/caspase3 pathway. In the in vivo experiment, intraperitoneal injection of 90 mg/kg HMW-HA reduced the mortality rate of Nile tilapia (Oreochromis niloticus) under acute salinity stress. In addition to inhibiting apoptosis and improving antioxidant capacity, HMW-HA also enhanced glycolysis to produce more glucose, pyruvate and ATP for osmoregulation energy supplement Further, HMW-HA affected serum ion levels, while it had no significant effect on ion content in gills. HMW-HA alleviated gill damage such as gill filament disorder and inflammatory cell infiltration caused by high salinity. In summary, HMW-HA can enhance salinity tolerance of tilapia by inhibiting apoptosis, alleviating oxidative stress, and enhancing carbohydrate metabolism.

Perfluorooctanesulfonic acid (PFOS) and sodium nitrite may have complex adverse effects on aquatic animals. This study assessed the interactive effects of PFOS and sodium nitrite on Chinese mitten crab (Eriocheir sinensis). A 2 x 3 factorial experiment with 0, 0.1, and 5 mg/L PFOS and 0, 3.50 mg/L sodium nitrite evaluated impacts on growth, behavior, oxygen consumption, health, energy metabolism, and hepatopancreas transcriptome. PFOS <0.1 mg/L with 3.50 mg/L nitrite significantly decreased PFOS accumulation in the hepatopancreas and improved feeding rates and hepatopancreas structure (P < 0.05). Under 5 mg/L PFOS and nitrite, survival, weight gain, hepatosomatic index, and feeding rate significantly decreased (P < 0.05). PFOS (0.1 mg/L) with nitrite significantly prolonged righting response time and increased locomotion speed (P < 0.05). PFOS (5 mg/L) significantly decreased serum triglyceride and lactate levels, while PFOS and nitrite decreased glucose, triglyceride, and glycogen levels and increased lactate in hepatopancreas (P < 0.05). Transcriptomic analysis indicated that PFOS affects p53 signaling, cell cycle and neurotransmission pathways, with notable changes in cell proliferation genes (pcna, ccna, cdk1, cdk2, rbx1) primarily downregulated by PFOS. Overall, PFOS disrupts neurotransmitter regulation and causes hepatopancreatic damage, while nitrite can reduce the toxicity of PFOS by decreasing its hepatopancreas accumulation. However, high levels of PFOS combined with sodium nitrite exacerbate toxicity, emphasizing the need for comprehensive assessment of environmental pollutant interactions.

As global warming intensifies, aquatic species are increasingly threatened by heat stress, urging the aquaculture industry to explore innovative strategies to mitigate the adverse impact of thermal stress on animals. Supplementing diets with yeast culture (YC) has shown promising results in coping with heat stress. This study evaluated the effects of YC on the survival, biochemical responses, transcriptome, and intestinal microbiota of the Chinese mitten crab (Eriocheir sinensis) under chronic heat stress. Juvenile crabs were subjected to four conditions over 42 days: a control temperature of 24 degrees C and a high temperature of 30 degrees C supplemented with three YC doses: 0, 3.2, and 6.4 g/kg. Each group had six replicates of 30 crabs each. Chronic heat stress substantially reduced survival rates and increased molting frequency. However, YC supplementation significantly improved survival and antioxidant enzyme activities (SOD and GSH-Px) while reducing MDA levels, indicating a reduction in oxidative stress. The immune response metrics (PO and AKP activities) were comparable to those of the control group when YC was included in the diet. A significant correlation existed between the crab survival rate, antioxidant performance and gut health. Histological assessment revealed that YC maintained the integrity of the intestinal lining under heat stress. 16S rRNA sequencing revealed that YC ameliorated disruptions in the diversity and structure of the intestinal microbiota caused by high temperature. Transcriptomic analysis identified DEGs linked to serine-type peptidases and ascorbate and aldarate metabolism pathways. Significant correlations were detected between Candidatus_Hepatoplasma, Rhodobacter, Aeromonas, and genes related to antioxidant and immune responses. In conclusion, dietary YC at 3.2 g/kg effectively enhanced the resilience of E. sinensis to chronic heat stress by increasing survival rates and antioxidant capacity, restoring immune function, and maintaining gut health.

Prebiotics are promising alternatives to antibiotics for enhancing disease resistance in aquaculture, yet their immunomodulatory mechanisms remain poorly understood.This study investigated the regulatory effects of prebiotics through in vitro experiments by directly comparing the effects of seven prebiotics, fructooligosaccharides (FOSs), galacto-oligosaccharides (GOSs), Mannan-oligosaccharides (MOSs), inulin, (3-glucan, isomaltodextrin (IMO), and xylo-oligosaccharides (XOSs), on the gut microbiota and metabolites in the Chinese Mitten Crab (Eriocheir sinensis). The pH values and digestive enzyme activities of the fermentation broth were measured. Five prebiotics (GOS, MOS, (3-glucan, IMO, and XOS) exhibited significant effects, and they were subsequently selected for further analysis of short-chain fatty acid (SCFA) production and gut microbiota composition. After 12 h of in vitro fermentation, the MOS-supplemented group presented minimum pH and maximum trypsin and lipase activities. MOS outperformed other prebiotics, particularly butyric acid, in stimulating SCFA production. Compared with the other treatments, MOS significantly increased the growth of Clostridium and Lactococcus. Notably, MOS-driven butyrate accumulation was linked to the upregulation of antiinflammatory pathways (e.g., NF-kappa B inhibition) and enhanced intestinal barrier integrity. Furthermore, MOS suppressed branched-chain fatty acids (BCFAs), potential markers of proteolytic dysbiosis, suggesting its role in mitigating gut inflammation. These findings highlight MOS as a potent immunomodulatory prebiotic for E. sinensis, providing a mechanistic basis for its application in antibiotic-free aquaculture strategies.