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This study examined whether diets with high dietary methionine levels could alleviate chronic heat stress in Chinese mitten crab Eriocheir sinensis. Crabs were fed three dietary methionine levels of 0.49%, 1.29% and 2.09% for six weeks. The analyzed methionine concentration of diets was 0.48%, 1.05% and 1.72%, respectively. Crabs were fed three different supplemental concentrations of dietary methionine at 24 °C and 30 °C, respectively. The trial was divided into six groups with five replicates in each group, and 40 juvenile crabs (initial average weight 0.71 ± 0.01 g) in each replicate. During the trial, crabs were fed twice daily (the diet of 4% of the body weight was delivered daily). The effects of dietary methionine level on nutrient metabolism, antioxidant capacity, apoptosis factors and immunity were evaluated at a normal water temperature of 24 °C and high temperature of 30 °C. Feed conversion ratio decreased under chronic heat stress. Chronic heat stress increased weight gain, specific growth rate, molting frequency, and protein efficiency ratio. The survival of crabs decreased under chronic heat stress, whereas a high level of dietary methionine significantly improved survival. Chronic heat stress induced lipid accumulation and protein content reduction. The high-methionine diet decreased lipid in the body and hepatopancreas, but increased protein in the body, muscle and hepatopancreas under chronic heat stress. Simultaneously, the high dietary methionine levels mitigated oxidative stress by reducing lipid peroxidation, restoring the antioxidant enzyme system, decreasing apoptosis and activating immune function under chronic heat stress. This study suggests that supplementing 1.72% dietary methionine could alleviate the adverse effects of a high water temperature in E. sinensis farming. [ABSTRACT FROM AUTHOR]

Zinc (Zn) is an essential trace mineral element in organisms and is involved in physiological processes. This study investigates the effects of dietary Zn on the growth, antioxidant capacity, non‐specific immunity and disease resistance of juvenile Chinese mitten crab. Zn was supplemented, respectively, at 0 (control), 25, 50, 100, 200 and 400 mg/kg to the basal diet to form six diets as Zn0, Zn25, Zn50, Zn100, Zn200 and Zn400. Each diet was separately used to feed the crabs (0.40 ± 0.01 g) for 56 days. Diet without Zn supplementation led to a higher feed intake rate, a lower Zn content in the hepatopancreas and a lower non‐specific immune enzyme activity than other groups with Zn supplement. The results also showed that compared with the control group: (1) The final weight, weight gain rate, specific growth rate, Zn in the hepatopancreas, body crude protein and the activities of serum alkaline phosphatase (AKP), acid phosphatase (ACP) and copper‐zinc superoxidase (CuZnSOD) were significantly increased in the Zn100 group. (2) Moreover, Zn accumulation in the hepatopancreas and body ash were significantly increased in the Zn200 group, and the antioxidant enzyme activities such as CuZnSOD and glutathione peroxidase (GSH‐Px) in the hepatopancreas were significantly increased. (3) In addition, the addition of Zn can activate the TLRs/NF‐κB pathway after the lipopolysaccharide (LPS) injection, resulting in upregulation of the relative mRNA expression of antimicrobial peptide (ALFs). This study demonstrates that dietary Zn supplements can significantly improve growth performance, antioxidant capacity, non‐specific immunity and disease resistance of juvenile crabs. The regression analysis showed that the optimal dietary Zn level was 94.87 mg/kg for weight gain and 96.96 mg/kg for specific growth. [ABSTRACT FROM AUTHOR]

Effects of dietary Polychlorinated biphenyl (PCB) exposure and dietary vitamin A supplementation on Chinese mitten crab Eriocheir sinensis were studied with the aim to explain dietary PCB toxicity and toxic alleviation by vitamin A intake in crab. Four diets were used including three experimental diets containing 0, 80000 or 240000 IU/kg vitamin A with each experimental diet containing 10 mg PCB/kg diet, and a control diet (without vitamin A and PCB supplementation) in 56 days feeding trial. Crabs fed the PCB-only diet had significantly lower weight gain than those fed the control diet. No significant difference was observed in crab survival among all groups. Crabs fed the PCB-only diet had a significantly higher malondialdehyde content and antioxidase superoxide dismutase activity in the serum and hepatopancreas, and higher erythromycin N-demethylase and glutathione S-transferase activities in the hepatopancreas than those fed the control diet. However, supplementation of dietary vitamin A decreased the levels of all these parameters. The hepatopancreatic cytochrome P450 2 and 4 (CYP2, CYP4), fatty acid binding proteins 3 and 10 (FABP3, FABP10) and intracellular lipolytic enzyme (IL) Messenger Ribonucleic Acid (mRNA) levels in the PCB-only group were significantly higher than those in the control group, and dietary 240000 IU/kg vitamin A supplementation decreased hepatopancreatic CYP4, FABP3, FABP10 and IL enzyme mRNA level. The crabs fed 80000 IU/kg vitamin A supplementation diet had the highest level of retinoid X receptor mRNA in the hepatopancreas. The structure of the hepatopancreas was damaged and the deposit of lipid droplets decreased with dietary PCB exposure. Both levels of vitamin A supplementation alleviated the damage and increased lipid droplets in the hepatopancreas. Dietary PCB exposure significantly reduced total hemocyte count (THC), and phenoloxidase, acid phosphatase activities in the serum. Post-challenge survival of crab in the experimental PCB-only diet group was low compared with that in the control. Supplementation of 240000 IU/kg vitamin A significantly increased the THC and phenoloxidase activity in the serum and post-challenge survival compared with those in the PCB-only group. This study indicates that dietary vitamin A can improve the antioxidant capacity, immune response, detoxification enzymes activities, energy metabolism and hepatopancreas tissue structure of Chinese mitten crab fed PCB contaminated diets. [ABSTRACT FROM AUTHOR]

Abstract: An 8-week feeding trial was conducted to determine the dietary copper (Cu) on growth performance and immune responses of juvenile Chinese mitten crab Eriocheir sinensis. Six semi-purified diets with six copper levels (1.88, 11.85, 20.78, 40.34, 79.56 and 381.2 mg kg−1 diet) of CuSO4·5H2O were fed to E. sinensis (0.45 ± 0.01 g). Each diet was fed to the crab in five replicates. The crab fed diets with 20.78 and 40.34 mg Cu kg−1 diet had significantly greater weight gain and hemolymph oxyhemocyanin content than those fed diets with 1.88 and 381.2 mg Cu kg−1 diet. Survival rates of crab were not significantly different between all treatment groups. The activities of copper–zinc superoxide dismutase (Cu–Zn SOD), phenoloxidase (PO), and total hemocyte count (THC) significantly increased when the supplementation of dietary copper reached 20.78–40.34 mg Cu kg−1 diets. In the bacteria challenge experiment with Aeromonas hydrophila, survival rates significantly increased and reached a plateau when the dietary copper increased from 1.88 to 40.34 mg kg−1, whereas significantly decreased when the dietary copper increased from 40.34 to 381.2 mg kg−1. This study indicates that the level of dietary copper is important in regulating growth and immune response in crab. [Copyright &y& Elsevier]

Yeast culture (YC), a microecological product derived from yeast fermentation, can enhance animal growth, health, and resistance to heat stress. However, its impact on the economically significant crustacean Eriocheir sinensis has not been demonstrated. This study investigated the effects of low-fishmeal YC on the growth, intestinal health, and heat stress resistance of juvenile Chinese mitten crabs. Crabs (0.72 ± 0.01 g) were distributed across 42 tanks, and 40 crabs were randomly maintained per tank in six replicates. The crabs were fed a control diet (35% fish meal) or six YC concentrations (15% fish meal; 0, 0.8, 1.6, 2.4, 3.2, or 4.0 g/kg) for 56 days. After sample collection, the remaining crabs were subjected to a 72-h heat stress challenge at 32 °C. A moderate-yield YC diet significantly improved weight gain, specific growth rate, and digestive enzyme activities (α-amylase, trypsin, and lipase) compared to those of crabs fed a 15% fishmeal diet without YC. Notably, the diet with 3.2 g/kg YC supplementation was performed as well as crabs fed a 35% fishmeal diet. YC also enhanced intestinal morphology in the low-fishmeal diet group and reduced oxidative damage by increasing the expression of genes related to the peritrophic membrane and tight junction proteins. Furthermore, YC supplementation diversified the intestinal microbiota, significantly increased the abundance of Firmicutes and the genus Shewanella , increased acetate and butyrate levels and decreased the abundance of Proteobacteria. Correlation analysis revealed that weight gain and specific growth rate were associated with most digestive activity and intestinal health indicators. Following heat stress challenge, YC protected against oxidative stress and enhanced serum immunity at elevated temperatures. This study indicated that incorporating YC in low-fishmeal diets significantly increases juvenile crab growth, improves intestinal health, and mitigates oxidative stress induced by temperature elevation. The optimal YC concentration was determined to be 2.71 g/kg through regression analysis. [Display omitted] • Dietary 2.71 g/kg yeast culture was optimal for E. sinensis fed low-fishmeal diets. • Yeast culture boosted the growth of E. sinensis fed low-fishmeal diets. • Yeast culture enhanced the intestinal health of E. sinensis. • Yeast culture increased the resistance of E. sinensis to heat stress. [ABSTRACT FROM AUTHOR]

Inhibitory neurotransmitter gamma-aminobutyric acid (GABA) is an immunomodulator to inhibit immune-mediated pro-inflammatory response and has been used to treat various immune-related diseases in mammals. However, the immunoregulatory effect of GABA in crustaceans has not been reported. This study evaluates the regulatory effect of dietary GABA supplementation on the innate immune status and immunoregulatory potential in lipopolysaccharide (LPS)-induced immune response in juvenile Eriocheir sinensis. Juvenile crabs were fed with six diets supplemented with graded GABA levels (0, 40, 80, 160, 320 and 640 mg/kg dry matter) for 8 weeks and then 24 h LPS challenge test was carried out. The results showed that dietary GABA supplementation significantly decreased mortality at 4 and 8 weeks. Moreover, the hemocyanin content, acid phosphatase, and alkaline phosphatase activities significantly increased in the crabs fed GABA supplementation compared with the control. On the contrary, the alanine aminotransferase and alanine aminotransferase activities in serum decreased significantly in the GABA supplementation groups compared with the control. Similarly, superoxide dismutase activity, glutathione content, and the transcriptional expression of the antioxidant-related genes and immune-related genes were significantly higher in the GABA supplementation groups than in the control. In addition, the mRNA expressions of anti-lipopolysaccharide factors (ALF 1 , ALF 2 , ALF 3) and inflammatory signaling pathways related genes (TLR , Myd88 , Relish , LITAF , P38-MAPK , ADAM17) were significantly up-regulated in LPS stimulation groups compared with PBS treatment. Meanwhile, pro-apoptosis-related genes' mRNA expressions were significantly up-regulated, and anti-apoptosis-related genes were significantly down-regulated under LPS stimulation compared with PBS treatment. However, GABA pretreatment effectively alleviated LPS-induced immune overresponse and apoptosis. Therefore, this study demonstrates that dietary GABA supplementation could be used as an immunomodulator to improve the non-specific immunity and antioxidant capacity and alleviate the immune-mediated immune overresponse of juvenile E. sinensis. • GABA supplementation significantly decreased mortality at 4 and 8 weeks of E. sinensis. • GABA could enhance the non-specific immunity and antioxidant capacity of E. sinensis. • GABA could enhance the antibacterial ability of E. sinensis. • LPS induced inflammatory response and triggered apoptosis in E. sinensis. • GABA pretreatment effectively alleviated LPS-induced pro-inflammatory response and apoptosis. [ABSTRACT FROM AUTHOR]

Abstract: Hemocyanin is a copper-binding protein and plays a crucial role in the physiological processes in crustacean. In this study, the cDNA encoding hemocyanin subunit from Chinese mitten crab Eriocheir sinensis (EsHc) was cloned by using EST analysis and rapid amplification of cDNA ends (RACE) approach. The full-length cDNA of EsHc was 2573 bp, consisting of a 5′ untranslated region of 51 bp, a 3′ untranslated region of 458 bp, and an open reading frame of 2064 bp. The deduced protein had 688 amino acid residues with molecular mass of 77,997.31 Da. Quantitative real-time RT-PCR analysis showed that the EsHc gene was expressed in haemocytes, hepatopancreas, muscles, gills, and intestines with the highest level of expression in the hepatopancreas and the lowest in the muscles. After Aeromonas hydrophila challenge, the relative expression level of EsHc in hemolymph was up-regulated at 3 h post-injection of bacteria followed by a gradual recovery from 12 to 24 h. In the second set of transcriptional studies, the mRNA expression patterns of EsHc in haemocytes and hepatopancreas were measured by quantitative real-time RT-PCR after the Chinese mitten crab were fed six diets containing different levels of copper (0, 10, 20, 40, 80 and 400 mg kg−1) for 8 weeks, respectively. The feeding trial showed that the expression levels of EsHc mRNA significantly increased at the copper levels of 20–40 mg kg−1. This study implies that the expression levels of EsHc could be affected by dietary copper in the hepatopancreas and haemocytes, and hemocyanin may be potentially involved in the immune responses of the Chinese mitten crab. [Copyright &y& Elsevier]

Abstract: C-type lectins are pattern-recognition proteins which are functionally important for pathogen recognition and immune regulation in vertebrates and invertebrates. In this study, a lectin cDNA named as Es-Lectin was cloned and characterized from the Chinese mitten crab, Eriocheir sinensis. The full-length sequence of this Es-Lectin cDNA was 651 bp, including an open reading frame of 483 bp encoding 160 amino acids. The predicted molecular weight of the Es-Lectin was 11.8 kDa. A typical signal peptide of 21 amino acids was deduced at the N-terminus of the predicted protein. This Es-Lectin belongs to a C-type lectin and contains six cysteines, a conserved EPN motif (Glu-Pro-Asn) and an imperfect WND (Trp-Asn-Asp) motif (FND, Phe-Asn-Asp). This Es-Lectin had 55% and 32% identity with other two C-type lectins in E. sinensis, and 29–36% homology with decapods. Although the Es-Lectin was also expressed in gill, hepatopancreas, intestine, muscle and stomach, its expression in haemocytes was the greatest. The expression of Es-Lectins in haemocytes increased at 1.5 h after the Aeromonas hydrophila challenge. After a slight decrease, the Es-Lectin expression in haemocytes significantly increased at 48 h post-challenge. The diverse distribution of Es-Lectin and its enhancement by bacterial challenge indicate that C-type lectins are important in the innate immune response to bacterial infection, and can be activated for innate immune response in crab at the initial stage after pathogen infection. [Copyright &y& Elsevier]

As a fat-soluble vitamin, vitamin D 3 relies on fat to perform its biological function, affecting lipid metabolism and innate immunity. This study used different percentages of lipid and vitamin D 3 diets to evaluate the synergistic effects on the growth, lipid metabolism and immunity of juvenile Eriocheir sinensis (5.83 ± 0.01 g) for 56 days, including low lipid (LL, 1.5%) and normal lipid (NL, 7.5%) and three levels of vitamin D 3 : low (LVD, 0 IU/kg), medium (MVD, 9000 IU/kg) and high (HVD, 27,000, IU/kg). The synergistic effect of lipid and vitamin D 3 was not significant on growth but significant on ash content, total protein, hepatopancreas lipid content, hemolymph 1α,25-hydroxy vitamin D 3 [1α,25(OH) 2 D 3 ] content, hepatopancreas lipolysis and synthesis genes. Crabs fed normal lipid (7.5%) and medium vitamin D 3 (9000 IU/kg) had the highest hepatopancreas index, hemolymph 1α,25(OH) 2 D 3 content, antibacterial ability, immune-related genes and hepatopancreatic lipid synthesis genes expression, but down-regulated the lipolysis genes expression. In contrast, crabs fed diets with low lipid percentage (1.5%) had low growth performance, hemolymph 1α,25(OH) 2 D 3 , mRNA levels of lipid synthesis genes, antibacterial ability and immune-related gene expression. At the 1.5% lipid level, excessive or insufficient vitamin D 3 supplementation led to the obstruction of ash and protein deposition, reduced growth and molting, aggravated the reduction in antioxidant capacity, hindered antimicrobial peptide gene expression and reduced innate immunity, and resulted in abnormal lipid accumulation and the risk of oxidative stress. This study suggests that diets' lipid and vitamin D 3 percentage can enhance antioxidant capacity, lipid metabolism and innate immunity in E. sinensis. A low lipid diet can cause growth retardation, reduce antioxidant capacity and innate immunity, and enhance lipid metabolism disorder. • The recommended optimal combination dosage is 7.5% lipid and 9000 IU/kg vitamin D 3. • If lack of lipids, vitamin D 3 is a key factor leading to abnormal lipid accumulation. • Deficiency or excess of vitamin D 3 inhibits antimicrobial peptide and innate immunity. • Synergistic effect of vitamin D 3 and lipids is important to the TLR–NF–κB pathway. [ABSTRACT FROM AUTHOR]

Soy isoflavones are phytoestrogens that provide protection against some hormonal disorders and regulate several physiological functions in animals. This study investigates the effects of soy isoflavones on body composition, antioxidant activity, non-specific immunity, and lipid metabolism in juvenile Chinese mitten crabs, Eriocheir sinensis. A total of 960 juvenile crabs (1.09 ± 0.01 g) were randomly assigned to 24 tanks (300L), with 40 crabs in each tank in four replicates. The crabs were fed diets (43.5% protein and 7% lipid) with six levels of soy isoflavones (0, 8.8, 15.8, 33.8, 66.8, and 137.0 mg/kg) at 4% BW/day for 56 days. The final biomass and biomass gain of crabs supplemented with 15.8 and 33.8 mg/kg soy isoflavones were significantly higher than those in the control group. The total lipid content in the whole-body and hepatopancreas of the crabs fed 15.8 and 33.8 mg/kg soy isoflavones was significantly lower than in the control group. Compared with the control group, soy isoflavones significantly enhanced the activities of superoxide dismutase, glutathione peroxidase and total antioxidant capacity in the hepatopancreas by 40%, 57% and 79%, respectively, and significantly decreased malondialdehyde content by 24%. The high dietary soy isoflavones levels increased total protein and hemocyanin contents in hemolymph, and alkaline phosphatase activity was also significantly enhanced. The triglyceride contents in the hepatopancreas and hemolymph were significantly lower in the soy isoflavones-supplemented group. Dietary soy isoflavones may reduce lipid accumulation in the hepatopancreas by repressing genes related to lipid synthesis and promoting the expression of lipid oxidation and transport genes. The broken-line model analysis of biomass gain against dietary soy isoflavones levels shows that the optimal supplemental level of soy isoflavones for juvenile crabs is approximately 26.66 mg/kg. Thus, this study suggests that dietary soy isoflavones supplementation can improve growth performance and health and reduce lipid accumulation in the hepatopancreas of juvenile crabs. • Feeds with six concentrations of soy isoflavones (0, 8.8, 15.8, 33.8, 66.8, and 137.0 mg/kg) were fed to E. sinensis. • Soy isoflavones gave improved growth, increased antioxidant enzyme activity and capacity, and promoted non-specific immunity. • Soy isoflavones repressed the expression of genes for lipid synthesis and promoted those related to lipid oxidation. • Based on analysis of biomass gain, the optimal level of feed soy isoflavones is ca 27 mg/kg. [ABSTRACT FROM AUTHOR]

Frequent detection of thiamethoxam in global surface waters has provoked great concern in environmental safety, as thiamethoxam exhibits high toxicity to aquatic arthropods. However, little systematic investigation has been conducted on the chronic toxicity of thiamethoxam to crustaceans. This study exposed Eriocheir sinensis to thiamethoxam (0, 0.5, 5 and 50 μg/L) in water for 28 days. No significant difference in mortality was observed among all groups. A high concentration of thiamethoxam (50 μg/L) impaired the righting ability of E. sinensis. Thiamethoxam significantly increased antioxidant enzyme activities (superoxide dismutase, total antioxidant capacity and glutathione peroxidase) and malondialdehyde levels. Simultaneously, detoxification enzyme activities (aminopyrine N-demethylase, erythromycin N-demethylase and glutathione-S-transferase) increased under chronic thiamethoxam stress. In addition, thiamethoxam caused immune and hepatopancreas damage. Moreover, thiamethoxam induced intestinal flora dysbiosis by altering the microbiome structure. The reduced complexity of the gut microbiota further illustrated that thiamethoxam could disrupt the stability of the microbiota ecological network. The transcriptomic results revealed that the number of downregulated DEGs increased in a dose-dependent manner, and most downregulated DEGs were enriched in energy metabolism-related pathways. These results indicate that thiamethoxam can adversely affect the crab behavior, biochemistry, intestinal microflora and transcriptomic responses. [Display omitted] • Chronic thiamethoxam exposure impaired the motor functioning of E. sinensis. • Antioxidant and detoxification systems were activated in response to thiamethoxam exposure. • Thiamethoxam caused immune and hepatopancreas damage. • Thiamethoxam induced intestinal flora dysbiosis. [ABSTRACT FROM AUTHOR]

The present study investigated the effect of vitamin A on growth performance, lipid metabolism, fatty acid composition, antioxidant ability and inflammatory response of crabs fed different vegetable oils. The dose of 6000 IU/kg of dietary vitamin A was supplemented into three basal diets with different lipid sources: coconut oil (CO), olive oil (OO) and perilla oil (PO), respectively, to make six diets to feed crabs (0.71 ± 0.01 g) for 8-week. The interaction between vitamin A and lipid source did not influence the survival rate, final body weight, weight gain and specific growth rate of crabs. Crabs fed CO showed the worst growth performance and aggravating inflammation. In contrast, crabs fed PO tended to have optimal growth performance with the lowest body lipid content and hemolymph triglyceride. Besides, there were high contents of polyunsaturated fatty acids and malonaldehyde in the hepatopancreas of crabs fed PO. However, dietary vitamin A improved growth performance and relieved inflammation of crabs fed different lipid sources. Vitamin A enhanced the antioxidant activity in crabs fed OO and PO and mitigated lipid peroxidation in crabs fed PO. Moreover, vitamin A tended to hinder lipid synthesis, increase fatty acid catabolism and decrease triglyceride in the hepatopancreas and hepatopancreas index. The relative proportion of n-3 highly polyunsaturated fatty acids was improved in the hepatopancreas of crabs fed three sources of vegetable oil after supplementing vitamin A. This study indicates that dietary vitamin A supplements can improve vegetable oil utilization and relieve the adverse effect caused by vegetable oil. • The interaction between vitamin A and lipid source did not affect the growth of E. sinensis. • Coconut oil caused the worst growth in crabs compared to olive oil and perilla oil. • Vitamin A supplement improved the health and growth of crabs fed vegetable oil. • The proportion of n-3HUFA was improved in the hepatopancreas by dietary vitamin A. [ABSTRACT FROM AUTHOR]

Hypoxia is one of the serious stress challenges that aquatic animals face throughout their life. Our previous study found that hypoxia stress could induce neural excitotoxicity and neuronal apoptosis in Eriocheir sinensis , and observed that gamma-aminobutyric acid (GABA) has a positive neuroprotective effect on juvenile crabs under hypoxia. To reveal the neuroprotective pathway and metabolic regulatory mechanism of GABA in E. sinensis exposed to hypoxia stress, an 8-week feeding trial and acute hypoxia challenge were performed. Subsequently, we performed a comprehensive transcriptomic and metabolomic analysis of the thoracic ganglia of juvenile crabs. Differential genes and differential metabolites were co-annotated to 11 KEGG pathways, and further significant analysis showed that only the sphingolipid signaling pathway and the arachidonic acid metabolism pathway were significantly enriched. In the sphingolipid signaling pathway, GABA treatment significantly increased long-chain ceramide content in thoracic ganglia, which exerted neuroprotective effects by activating downstream signals to inhibit hypoxia-induced apoptosis. Moreover, in the arachidonic acid metabolism pathway, GABA could increase the content of neuroprotective active substances and reduce the content of harmful metabolites by regulating the metabolism of arachidonic acid for inflammatory regulation and neuroprotection. Furthermore, the decrease of glucose and lactate levels in the hemolymph suggests the positive role of GABA in metabolic regulation. This study reveals the neuroprotective pathways and possible mechanisms of GABA in juvenile E. sinensis exposed to hypoxia stress and inspires the discovery of new targets for improving hypoxia tolerance in aquatic animals. [Display omitted] • Transcriptomic and metabolomic analysis revealed key neuroprotective mechanisms. • Two key neuroprotective pathways for GABA in response to hypoxia were revealed. • Cer acts as a key messenger to protect neuronal apoptosis in response to hypoxia. • Neuroprotection of GABA under hypoxia is closely related to inflammation regulation. [ABSTRACT FROM AUTHOR]

With climate change and intensive aquaculture development, environmental hypoxia in aquaculture water has become a common challenge for many aquatic species. Therefore, it is crucial to improve the hypoxic tolerance of animals through nutritional strategies. This study explored the positive role of dietary gamma-aminobutyric acid (GABA) supplementation in enhancing hypoxia tolerance of juvenile Eriocheir sinensis through respiratory regulation and alleviation of hypoxia-induced neural excitotoxicity. Acute hypoxia stress significantly up-regulated the mRNA expression level of hypoxia-inducible factor 1α, oxygen consumption rate and anaerobic respiratory metabolism-related enzyme activities. On the other hand, aerobic respiratory metabolism-related enzyme activities were significantly decreased. However, dietary GABA supplementation remodeled the respiratory metabolism pattern of juvenile crabs exposed to hypoxia stress. In addition, acute hypoxic stress significantly increased the contents of free glutamate and GABA in the nervous tissue. The expression levels of N-Methyl- d -aspartate-related receptor genes and calcium-dependent degradation enzyme-related genes were significantly up-regulated. Similarly, neuronal apoptosis rates, expression levels of apoptosis-related genes, and vesicular glutamate transporter genes were also significantly increased. The high-affinity neuronal glutamate transporter decreased significantly in the crabs exposed to hypoxia stress. However, dietary GABA supplementation could effectively prevent acute hypoxia stress-induced neural excitotoxicity. Furthermore, dietary GABA could significantly improve the redox status in vivo exposed to hypoxia stress. In conclusion, acute hypoxia stress can affect respiratory metabolism and redox state and induce neural excitotoxicity in juvenile E. sinensis. GABA supplementation could improve hypoxia tolerance through multiple physiological regulation pathways. [Display omitted] • Hypoxia stress could affect the respiratory metabolism and induce neural excitotoxicity. • GABA could remodel the respiratory metabolism patterns exposed to hypoxia stress. • GABA could improve the redox state in vivo exposed to hypoxia stress. • GABA could alleviate hypoxia-induced neural excitotoxicity. • GABA improves the hypoxia tolerance through multiple physiological regulation pathways. [ABSTRACT FROM AUTHOR]

Perfluorooctane sulfonate (PFOS) has been widely studied due to its global distribution, slow degradation, high bioaccumulation and toxicological effects on vertebrates. However, the potential toxicity of PFOS to crustaceans is little known. The present study investigated the effects of PFOS on the immune responses and expression of immune-related genes in the Chinese mitten-handed crab Eriocheir sinensis . Crabs were exposed to 0, 0.01, 0.1, 1.0 and 10 mg/L of PFOS, and sampled on 1, 4, 7, 14 and 21 days respectively. The total hemocyte count and lysozyme activity in PFOS-treated crab were significantly lower than in the control. The exposure to 10 mg/L of PFOS led to a marked inhibition in phenoloxidase and superoxide dismutase activities. At other PFOS levels, phenoloxidase and superoxide dismutase showed an initial increase and a subsequent decrease over time. The alkaline and acid phosphatase activities were stimulated in 10 mg/L PFOS until 21 days. The mRNA expression of immune related genes including hepatopancreas-specific C-type lectin and prophenoloxidase activating factors were up-regulated after the exposure to the concentrations of 1 and 10 mg/L of PFOS, while the expression of lysozyme gene was up-regulated only in the crab exposed to 0.1 mg/L PFOS. The results demonstrate that the high dose of PFOS leads to immune toxicity and the hepatopancreas is a major target organ for PFOS accumulation and immunotoxicity. Hemocyte counts, phenoloxidase and acid phosphatase are useful biomarkers for the risk assessment of PFOS toxicity to crustaceans. [ABSTRACT FROM AUTHOR]

This study was to determine the effects of different iron sources on the growth performance, iron utilization, antioxidant capacity and non-specific immunity in Eriocheir sinensis. Juvenile crabs (3.29 ± 0.06 g) were fed with six basic diets supplemented with 100 mg/kg iron in the form of ferrous sulfate (S-100), ferrous fumarate (F-100), ferrous glycine (G-100), ferrous sulfate + ferrous fumarate (S-50 + F-50), ferrous sulfate + ferrous glycine (S-50 + G-50) and ferrous fumarate + ferrous glycine (F-50 + G-50) for 10 weeks. The crab in the G-100 group and the S-50 + G-50 group had higher weight gain, specific growth rate and lower whole-body total lipid than those in the S-100 group. The expression levels of divalent metal ion transporter 1 and ferroportin in the intestine and hepatopancreas were significantly enhanced in the G-100 group and the S-50 + G-50 group compared with the S-100 group. Crabs fed the G-100 diet possessed higher hemolymph iron, transferrin concentration and iron contents in the whole body, hepatopancreas and muscle than in other treatments. In addition, the total antioxidant capacity in the G-100 group and the activities of acid phosphatase and phenoloxidase in the G-100 group and the S-50 + G-50 group significantly improved compared to the S-100 group. This study demonstrates that ferrous glycine might be the proper iron source for improving growth performance, iron utilization, antioxidant capacity and non-specific immunity of E. sinensis , and can be a source of effective iron supplementation in aquafeed. • There is lack of relevant studies on different dietary iron sources in Eriocheir sinensis. • Dietary ferrous glycine could facilitate iron uptake, transport and utilization of E. sinensis compared with ferrous sulfate. • Ferrous glycine is an effective iron supplementation source in aquafeed of E. sinensis. [ABSTRACT FROM AUTHOR]

An 8-week feeding trial was conducted to investigate the optimum dietary vitamin B 12 requirement of juvenile Chinese mitten crab, Eriocheir sinensis , and its effect on non-specific immunity responses and resistance against Aeromonas hydrophila . Vitamin B 12 was supplemented to the basal diet at 0, 0.05, 0.1, 0.2, 0.4, 0.8 and 1.6 mg/kg to formulate seven semi-purified diets. A diet free of vitamin B 12 and folic acid was also included as a control. Each diet was fed to E. sinensis (0.051 ± 0.001 g) in four replicates, followed by a challenge study for 2 weeks. Relative growth rate and specific growth rate were best in crabs fed 0.2 and 0.4 mg vitamin B 12 /kg diets, followed by the 0.1, 0.8, 0, 0.05 and 1.6 mg/kg groups and lowest in the control group (vitamin B 12 and folic acid free). Feed efficiency and survival rate peaked at the supplementation of 0.2 mg/kg. The whole body crude protein of juvenile crabs was significantly higher when crabs fed 0.2–0.8 mg vitamin B 12 /kg than those fed the diets without vitamin B 12 supplementation. Total hemocyte count was significantly higher in crabs fed 0.2 and 0.4 mg vitamin B 12 /kg than those in the other feeding groups, and crabs fed the 0.2 mg/kg diet had the highest phenoloxidase, lysozyme, acid phosphatase and alkaline phosphatase activities but the lowest cumulative mortality. Hepatopancreatic vitamin B 12 concentration increased as the level of vitamin B 12 supplementation increased. The optimum dietary vitamin B 12 requirement by E. sinensis is recommended at 0.20–0.22 mg/kg diet. [ABSTRACT FROM AUTHOR]

This study evaluates the influence of dietary vitamin A on growth performance, antioxidant capacity, and lipid metabolism of Eriocheir sinensis juveniles (3.95 ± 0.12 g) fed different lipid levels. Crabs were fed with four diets, including normal lipid (7%) with vitamin A devoid (0 IU/kg, NL-VAD), normal lipid (7%) with vitamin A supplement (6000 IU/kg, NL-VAS), high lipid (13%) with vitamin A devoid (0 IU/kg, HL-VAD), and high lipid (13%) with A supplement (6000 IU/kg, HL-VAS) for 8 weeks. The significant interaction between dietary vitamin A and lipid level was found in weight gain, specific growth rate, and the mRNA of lipid synthesis related genes and retinoid X receptor. Under high lipid diets, vitamin A supplementation did not affect final body weight, weight gain, specific growth rate. Regardless of dietary lipid levels, vitamin A enhanced the activities of relevant antioxidant indices (total antioxidant capacity, superoxide dismutase, and glutathione peroxidase). Vitamin A supplementation also reduced the excessive malondialdehyde in the hepatopancreas caused by high-fat diets. In the high lipid group, dietary vitamin A reduced hepatosomatic index, total lipid in the whole body and hepatopancreas, and triglyceride and free fatty acids in the hepatopancreas. Vitamin A supplementation reduced lipid accumulation in the crab fed high lipid diets by promoting genes expression about lipid oxidation and transport. Under high lipid diets, restrained lipid synthesis was found in the vitamin A supplementation group compared with the vitamin A-free group. This research suggests that dietary vitamin A can ameliorate lipid peroxidation and promote lipid utilization by optimizing lipid metabolism in E. sinensis fed a high-fat diet. • The interaction between dietary vitamin A and lipid level affected growth performance and lipid synthesis. • Dietary vitamin A improved the antioxidant capacity in E. sinensis. • Dietary vitamin A reduced the lipid deposition in E. sinensis. • Dietary vitamin A upregulated lipid oxidation and transport genes and downregulated lipid synthesis. [ABSTRACT FROM AUTHOR]

• Acute hypoxia induced neural excitotoxicity and neuronal apoptosis in E. sinensis. • Acute hypoxia caused glutamate reuptake pump dysfunction. • The essential reason was insufficient ATP level due to energy metabolism disorder. • The immediate reason was the massive glutamate accumulation in synaptic cleft. • NMDA receptor served as the bridge of glutamate-induced neural neurotoxicity. Hypoxia can induce neural excitotoxicity in mammals, but this adverse effect has not been investigated in aquatic animals to date, especially in crustaceans. This study explored the induction effect and toxic mechanism of acute hypoxia stress (1.0 ± 0.1 mg dissolved oxygen /L) for 24 h on neural excitotoxicity in juvenile Chinese mitten crab, Eriocheir sinensis. The results showed that hemolymph glucose and serum lactic acid content were significantly increased, and the mRNA expression of crustacean hyperglycemic hormone and hypoxia-inducible factor 1α were significantly up-regulated in the hypoxia group compared with control. RNA-Seq results confirmed that acute hypoxia stress had a more significant impact on carbohydrate metabolism than lipid and protein metabolism. In addition, the TUNEL assay showed that the apoptosis rate of nerve cells was significantly higher in the hypoxia group than in the control, and similar trends were observed in the expression of apoptosis-related genes. RNA-Seq results also showed that acute hypoxia stress-induced neuronal apoptosis by regulating multiple apoptosis-related pathways. Moreover, free glutamate and GABA contents in the nerve tissue of thoracic ganglia were significantly higher in the hypoxia group than in the control group. Furthermore, the mRNA expression of NMDA related receptors was significantly up-regulated in the hypoxia group compared with the control. Similar trends were observed in the expression of calcium-dependent degrading enzymes and endogenous antioxidant-related proteins or enzymes. Meanwhile, the mRNA expression level of high-affinity neuronal glutamate transporter in the hypoxia group was significantly up-regulated compared with the control, whereas the vesicular glutamate transporter was significantly down-regulated. Furthermore, NMDA-R antagonists (MK-801 and Ro25–6981) injection showed that NMDA-R served as the bridge and core position of glutamate-induced neural neurotoxicity. This study provides a new perspective and theoretical guidance for exploring the regulation of hypoxic tolerance in E. sinensis. [ABSTRACT FROM AUTHOR]

Abstract: The lipopolysaccharide and β-1, 3-glucan binding protein (LGBP) is a pattern recognition protein which is fundamental for the innate immune response of crustaceans. A partial cDNA produced by the random sequencing of cDNA clones from a haemocyte cDNA library of Eriocheir sinensis showed similarity to the LGBP gene of the Chinese shrimp (Fenneropenaeus chinensis). The full-length cDNA was subsequently cloned and sequenced by the technique of rapid amplification of cDNA ends (RACE). The E. sinensis LGBP gene (designated as Es-LGBP) was 1236 bases long and was capable of encoding a polypeptide of 362 amino acids showing significant similarity to homologous genes in shrimp. The crab LGBP deduced amino acid sequence carrying conserved features of this gene family including a potential recognition motif for β-1, 3 linkages of polysaccharides and putative RGD (Arg–Gly–Asp)cell adhesion sites. Real-time quantitative reverse transcription-PCR (RT-PCR) analysis showed that LGBP gene expresses in haemocytes, hepatopancreas, muscles, gills, stomachs, and intestines with the highest level in haemocytes and the lowest in the stomach. The LGBP gene expression is up-regulated upon bacterial infection and the binding of lipopolysaccharide and β-1, 3-glucan to LGBP could induce a series of immune reactions. The temporal expression of the LGBP gene after bacterial challenge was measured by real-time quantitative RT-PCR. The result demonstrated that the LGBP gene expression in crab was up-regulated at 1.5 h post-injection of bacteria followed by a step by step recovery at 12 and 24 h. Our data suggest that the crab LGBP is an inducible acute-phase protein that could be critical in crab immunity. [Copyright &y& Elsevier]

The effects of dietary vitamin A level on the growth performance, immunity, oxidation resistance and lipid metabolism of juvenile Chinese mitten crab Eriocheir sinensis (0.84 ± 0.00 g) were determined in the present study. Six group of crabs (four replicate tanks per group with 40 crabs per tank) were respectively fed with 0 (control), 2322, 4511, 8478, 14,333 and 30,444 IU/kg dietary vitamin A for 8 weeks. The weight gain (WG) and specific growth rate (SGR) of juvenile crabs significantly increased in dietary vitamin A supplement groups compared with the control. Dietary vitamin A supplementation increased immunity and antioxidant capacity, hepatopancreas health and alleviated lipid peroxidation in the hepatopancreas of crabs. Moreover, total lipid content in the whole body and hepatopancreas, and triglyceride (TG) content in the hepatopancreas and serum of crabs showed a decreasing tendency with increasing inclusion of vitamin A. The hepatosomatic index (HSI) was lowest in crabs fed 30,444 IU/kg dietary vitamin A. Interestingly, the transcriptome sequencing data showed that the expression of genes related to immunity, antioxidant capacity, lipolysis and β-oxidation was up-regulated. In contrast, the expression of genes related to lipid synthesis was down-regulated in crabs fed 30,444 IU/kg dietary vitamin A compared with the control. This study indicates that dietary vitamin A requirement for E. sinensis is 5340 for WG and 5540 IU/kg for SGR based on the broken-line model. • Dietary vitamin A requirement for juvenile Eriocheir sinensis is 5340-5540 IU/kg. • Proper dietary vitamin A improved antioxidant capacity and nonspecific immunity in juvenile E. sinensis. • The RNA-Seq analysis revealed vitamin A regulating the immunity, antioxidant capacity and lipid metabolism. [ABSTRACT FROM AUTHOR]

Animal growth performance is determined by food intake, digestion and nutrient absorption and the complex central and peripheral nerves may regulate the quantity of food intake. This study evaluates the effects of gamma-aminobutyric acid (GABA) supplements in purified diets on the growth performance, food intake and digestive ability of juvenile Chinese mitten crab Eriocheir sinensis , and the possible mechanism of neuromodulation. A total of 1200 juvenile crabs (0.77 ± 0.02 g) were fed with six diets supplemented with graded GABA levels (0, 40, 80, 160, 320 and 640 mg/kg dry matter) for 8 weeks. Each diet group had five replicates, and each replicate had 40 crabs in a tank (100 × 80 × 60 cm). The weight gain, specific growth rate, molting frequency, and the activities of digestion (α-amylase, trypsin and lipase) and absorption (Na+-K+-ATPase and γ- glutamyl transferase) enzymes were significantly increased by moderate dietary GABA supplementation compared with the 0 mg/kg GABA supplementation group. Furthermore, the food intake of juvenile E. sinensis was significantly increased with moderate dietary GABA supplementation compared with the 0 mg/kg GABA supplementation group. The qRT-PCR results showed that the expression of the orexigenic neural signal-related genes was significantly up-regulated, and the anorexigenic neural signal-related genes were significantly down-regulated in the cranial ganglia, thoracic ganglia and intestine tissues. Meanwhile, the expressions of the main genes involved in taste modulation and reward regulation were significantly up-regulated, whereas the expression of genes related to punishment regulation was significantly down-regulated in cranial ganglia and thoracic ganglia. Two-slope broken-line regression analysis of specific growth rate and weight gain against the dietary GABA levels showed that dietary GABA at the optimal dietary level was 84–89 mg/kg, and this level can improve growth performance, food intake, digestion and absorption in juvenile E. sinensis. GABA might act as an orexigenic neural signal or work with other appetite-related nerve signals to promote food intake by participating in regulating the satiety circuit and the reward circuit. • Gamma-aminobutyric acid (GABA) improved the growth of Chinese mitten crab, with an optimum dietary range of 84–89 mg/kg. • Dietary GABA increased food intake and improved digestive capacity of Chinese mitten crab. • GABA might act as an orexigenic neural signal or together with other appetite-related signals to regulate food intake. • GABA is likely to be involved in taste perception and the transmission of taste signals. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of dietary iron levels on growth, antioxidant status and non-specific immunity in juvenile Chinese mitten crab (Eriocheir sinensis). A 56-day feeding trial containing six experimental diets supplemented with six iron levels (0, 30, 60, 120, 240, 480 mg/kg) was conducted. The crabs fed the 177 mg/kg iron diet had significantly higher weight gain and specific growth rate and lower feed conversion ratio compared with those fed the 64 and 508 mg/kg iron diets. A positive correlation was observed between the iron content in the whole body and hepatopancreas with dietary iron supplementation. The catalase activities, total antioxidant capacity, superoxide dismutase and glutathione peroxidase in the hepatopancreas were significantly increased in 89–177 mg/kg iron diets. In addition, the non-specific immunity of the crabs was also improved with the increasing level of dietary iron supplementation (P < 0.05). Broken-line analysis on weight gain, specific growth rate and iron level in the hemolymph against dietary iron levels indicates that the optimal iron requirement for juvenile crabs ranged from 130 to 141 mg/kg. The transcription of iron regulatory protein had a decreasing trend while that of ferritin-1 and ferritin-2 had an increasing trend regardless of the lipopolysaccharide and phosphate buffer saline treatment. The highest transcription of inflammation-related genes in the hepatopancreas was found in the crabs fed diets without iron supplementation under the lipopolysaccharide stimulation. Our results indicate that the optimal iron requirement for juvenile crabs was in the range of 130–141 mg/kg and dietary iron plays an indispensable role in the innate immune system in E. sinensis. • Dietary iron deficiency inhibited growth performance, antioxidant capacity and non-specific immunity of Eriocheir sinensis. • The iron requirement of E. sinensis was estimated to be in the range of 130-141 mg/kg diet. • Lipopolysaccharides induced inflammatory responses in E. sinensis. • Appropriate iron supplementation in diets could alleviate the inflammation induced by lipopolysaccharide in E. sinensis. [ABSTRACT FROM AUTHOR]

This study determined the effects of dietary phosphatidylcholine (PC) levels on growth performance, antioxidant capacity and lipid metabolism of juvenile Eriocheir sinensis. Six isolipidic and isonitrogenous diets were formulated with six graded levels of PC (0%, 1.36%, 2.76%, 4.34%, 5.74% and 7.10%) and fed to juvenile E. sinensis (0.52 ± 0.01 g) for eight weeks. The crabs in the PC-added groups had a better feed conversion ratio and higher final body weight, weight gain and specific growth rate than those in the PC-devoid group. The dietary PC supplement increased antioxidant capacity and reduced lipid peroxidation in the hepatopancreas of E. sinensis. The crabs fed the diet with PC addition showed lower whole-body total lipid contents than those fed the diet without PC addition. The diets supplemented with moderate PC promoted whole-body protein deposition. The total lipid content of the hepatopancreas was also markedly decreased in the PC-added groups, while the total lipid content in muscle showed an opposite trend in the hepatopancreas. In addition, the appropriate dietary PC facilitated the deposition of long-chain polyunsaturated fatty acids (especially C20:5n-3 and C22:6n-3) in muscle and hepatopancreas. The quantitative real-time PCR exhibited that the dietary PC reduced lipid deposition in the hepatopancreas of E. sinensis possibly through inhibiting lipid synthesis as well as facilitating lipid oxidation and transport. Based on the weight gain and specific growth rate, the broken-line regression analysis suggested that the optimum PC requirement of juvenile E. sinensis should be in the range of 2.89% - 2.95% of the diet by weight. • The optimum phosphatidylcholine requirement was in the range of 2.89% - 2.95%. • Dietary phosphatidylcholine could increase antioxidant capacity. • Dietary phosphatidylcholine could inhibit lipid synthesis as well as facilitate lipid oxidation and transport. [ABSTRACT FROM AUTHOR]

• Fasting stress could induce hypoglycemia in juvenile E. sinensis. • GABA treatment could effectively alleviate hypoglycemia and maintain the homeostasis of hemolymph glucose. • GABA can promote the degradation and utilization of hepatopancreas glycogen. • GABA can regulate the levels of glucose metabolism-related hormones and key enzymes. • GABA can improve the hepatopancreas function and immune status under fasting stress. The ability of immune defense and resistance to physiological stress is crucial to animal health and survival. This study investigated the regulation of γ-aminobutyric acid (GABA) on metabolic homeostasis and its enhancement of hepatopancreas health in juvenile Chinese mitten crab (Eriocheir sinensis) under food deprivation. Juvenile crabs of 400 individuals were divided into four treatment groups: a control group without injection, and injections with a phosphate-buffered saline solution, 100 μmol GABA/mL and 1000 μmol GABA/mL, respectively. Hypoglycemia was induced by fasting, whereas the GABA treatment regulated hemolymph glucose homeostasis. The quantitative real-time PCR (qRT-PCR) results showed that the GABA treatment significantly up-regulated the mRNA expression levels of crustacean hyperglycemic hormone (CHH) and pyruvate kinase (PK). In contrast, the expression of E. sinensis insulin-like peptide (EsILP) was significantly down-regulated in the cranial ganglia, thoracic ganglia and hepatopancreas. Moreover, acid phosphatase (ACP), alkaline phosphatase (AKP), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities were significantly increased in the hepatopancreas by the GABA treatment. Furthermore, the hemocyanin content in serum was significantly increased with the GABA injection, and the glutathione (GSH) content, total superoxide dismutase (T-SOD) activity and catalase (CAT) activity in the hepatopancreas showed a similar increasing trend with the dose elevation of GABA. Therefore, these results indicate that GABA can effectively maintain the hemolymph glucose homeostasis by regulating the levels of glucose metabolism-related hormones and key enzymes to promote the degradation and utilization of hepatopancreas glycogen. Meanwhile, GABA can improve the hepatopancreas function and immune status of juvenile E. sinensis under fasting stress. The treatment with GABA may provide a clue to guide health management in crab farming. [ABSTRACT FROM AUTHOR]

This study investigated the effects of dietary phosphorus (P) on growth, body composition, antioxidant activities and lipid metabolism of juvenile Chinese mitten crab (Eriocheir sinensis). Six diets containing available P levels at 0.20%, 0.44%, 0.99%, 1.37%, 1.75% and 2.01% were prepared and fed to juvenile E. sinensis (0.38 ± 0.01 g) for 56 days. The weight gain, specific growth rate and molting frequency were markedly affected by dietary P, and the highest weight gain and specific growth rate were obtained in crabs fed the 0.99% available P diet. With increasing the dietary available P levels, the whole-body ash, Ca, and P contents, as well as the hepatopancreas and serum P contents increased, while the whole-body Mg content decreased. The increase of dietary P levels significantly decreased the lipid contents of whole-body, hepatopancreas and muscle, while increased the crude protein content of hepatopancreas. The hepatopancreas and serum alkaline phosphatase activities increased with an increase in dietary available P levels from 0.20% to 1.37%, and then decreased afterward. The crabs fed 1.37% available P diet had a markedly higher alkaline phosphatase activity than those fed 0.20%, 0.44% and 2.01% available P diets. Moreover, dietary P significantly affected total antioxidant capacity, the activities of total superoxide dismutase and glutathione peroxidase, and the malondialdehyde content in the hepatopancreas. The highest antioxidant activity and lowest malondialdehyde content in the hepatopancreas were found in the crabs fed 1.37% of available P in the diet. The relative mRNA expression showed that dietary P reduced hepatopancreas lipid accumulation might be produced through suppressing the genes related to lipid synthesis and promoting the genes related to lipid transport. This study demonstrates that optimum dietary P could enhance growth, antioxidant capacity and reduce hepatopancreatic lipid accumulation in juvenile E. sinensis and the range of available P in the diet is suggested to be 1.16%–1.51%. • The optimal available P requirement for juvenile E. sinensis is 1.16%–1.51%. • Dietary P addition can improve antioxidant capacity in juvenile E. sinensis. • Dietary P can reduce hepatopancreatic lipid accumulation in juvenile E. sinensis. [ABSTRACT FROM AUTHOR]

This study determines the effects of level and source of dietary phospholipid (PL) on growth performance, body composition, antioxidant capacity and lipid metabolism in juvenile Chinese mitten crab, Eriocheir sinensis. One control diet (PL-devoid) and six test diets containing three PL types (soybean lecithin, egg yolk lecithin, and krill oil) at two levels (1% and 3%) each were formulated to feed E. sinensis juveniles (0.26 ± 0.01 g) for 8 weeks. Final body weight, specific growth rate, weight gain and molting frequency significantly increased in the PL supplementation groups, and the crabs fed 3% krill oil showed the best growth performance. The total lipid of whole body was significantly lower in the PL supplementation groups than that in the control. With PL supplementation, the specific activities of superoxide dismutase and catalase in the hepatopancreas markedly increased, while malondialdehyde decreased. In addition, total lipid and triglyceride contents in the hepatopancreas significantly decreased in the PL supplementation groups. Real-time quantitative PCR revealed that dietary PL reduced hepatic lipid accumulation probably through inhibiting lipid synthesis related genes and promoting lipid export related genes at the transcriptional level. This study indicates that krill oil is an excellent PL source and the diet with 3% PL can improve growth performance, increase antioxidant capacity and promote lipid utilization for juvenile E. sinensis. • The present study suggested that krill oil was an excellent phospholipid (PL) source and 3% PL in the diets could better improve growth performance of juvenile Eriocheir sinensis. • Our results indicate that appropriate supplementation dietary PL could increase the antioxidant capacity in juvenile E.sinensis. • This study was first time to provide an insight on the mechanisms of the lipid-lowering effect of PL in crustaceans. [ABSTRACT FROM AUTHOR]