Juvenile Chinese Mitten Crab Eriocheir Research Articles

Seasonal dynamics of intestinal microbiota in juvenile Chinese mitten crab (Eriocheir sinensis) in the Yangtze Estuary

Seasonal dynamics of intestinal microbiota in juvenile Chinese mitten crab (Eriocheir sinensis) in the Yangtze Estuary

Study on the Optimal Phospholipid Addition Levels for Button-Sized Juvenile Chinese Mitten Crab (Eriocheir sinensis): Survival, Growth, Physiological Parameters, and Neverland Expression

A 50-day feeding experiment was performed to investigate the effects of dietary phospholipid (PL) addition on the survival, growth, serum, and hepatopancreas lipid indexes, calcium content, and neverland (Nvd) gene expression in button-sized juvenile Chinese mitten crab (Eriocheir sinensis). Five experimental diets were formulated with increasing addition of PL (0%, 1%, 2%, 3%, and 4%), which were named PL0, PL1, PL2, PL3, and PL4, respectively. Each diet was randomly assigned to four tanks of juvenile E. sinensis (initial weight: 5.00 ± 0.55 g), with eight crabs held in each tank. The results showed that PL addition significantly increased the survival rate (SR) but just slightly increased the weight gain rate (WGR) of juvenile E. sinensis. As the PL addition level increased, SR and WGR first increased and then decreased, with the highest values observed in the PL3 group. As the PL addition level increased, the activities of trypsin and cellulase significantly increased and then decreased, with the highest value observed in the PL2 group and PL3 group, respectively. As PL addition level increased from 1% to 2%, lipase activity increased sharply and then kept constant with a further increase of dietary PL. As PL addition level increased from 0% to 3%, the calcium content in the serum significantly increased from 7.96 to 12.43 mmol/L and then significantly decreased to 11.36 mmol/L with a further increase of PL addition. PL addition just slightly promoted the calcium content in the hepatopancreas compared with the control group. As PL addition level increased from 0% to 3%, the expression of Nvd in the hepatopancreas significantly increased by 1.47-fold and then decreased to basal level with a further increase of PL addition. In conclusion, 2%−3% addition of the optimal PL addition level was estimated to be 2%−3% for juvenile E. sinensis based on their survival, growth performance, and digestive enzyme activities. PL addition at a relatively higher level (3%) increased the calcium content and Nvd expression, the latter possibly facilitating cholesterol metabolism into vitamin D.

The effect of intermittent starvation on growth performance, precocity, digestive enzyme activity, and body chemical composition of juvenile Chinese mitten crab Eriocheir sinensis

The effect of intermittent starvation on growth performance, precocity, digestive enzyme activity, and body chemical composition of juvenile Chinese mitten crab Eriocheir sinensis

Impacts of three feeding modes on the diet composition and contribution ratios for juvenile Chinese mitten crab Eriocheir sinensis

The diet composition and contribution ratios for juvenile Chinese mitten crab Eriocheir sinensis can vary with different feeding modes during pond culturing. To investigate this, the stomach contents of juvenile crabs and the contributions of different food sources to their growth were compared across three feeding modes: alligator weed Alternanthera philoxeroides alone (Diet 1), formulated diet feed alone (Diet 2), and a 1:1 mixture of A. philoxeroides and the formulated diet (Diet 3). The analysis utilized 18 S rDNA high-throughput sequencing and carbon and nitrogen stable isotopes. There were five replicates for each treatment group, and the experimental period was 120 d. The results showed that the diversity of the food composition in the stomach contents of the juvenile crabs was significantly lower (P < 0.05) with Diet 2 than with Diets 1 and 3. The seven phyla with the highest relative abundances in the stomach contents in descending order were Chloroplastida; Stramenopiles, Alveolata, and Rhizaria (SAR); Arthropoda; Cryptomycota; Phragmoplastophyta; Rotifera; and Eukaryota. The highest abundance of Phragmoplastophyta was 12.96 % with Diet 1, 53.66 % with Diet 2 %, and 8.23 % with Diet 3. The stable isotopes analysis showed that Diet 1 resulted in the lowest δ13C‰ values, whereas the δ15N‰ values were not significantly different among the three groups, indicating that there were differences in the food compositions of the juvenile crabs with the different feeding modes. The main food source for juvenile crabs fed Diet 1 was A. philoxeroides, with an average contribution of 28.91 % whereas that for juvenile crabs fed Diets 2 and 3 was the formulated feed, with average contributions of 33.35 % and 33.15 %, respectively. Particulate organic matter was the secondary food for all three diets. Therefore, in the juvenile crab pond culture feeding mode, the addition of a formulated feed when A. philoxeroides has a contribution ratio of 10.39 % can improve feed utilization. This study can provide a scientific reference and theoretical basis for the promotion of the formulated feed feeding mode and the development of A. philoxeroides as a vegetal feed added to the formuated feed of juvenile Chinese mitten crabs.

Intestinal bacterial community composition of juvenile Chinese mitten crab Eriocheir sinensis under different feeding times in lab conditions

Feeding time is an important factor affecting the physiological activity and feeding rhythm of crustaceans. However, little is known about the factors and mechanisms contributing to variations in feeding time in aquatic species or their impacts. Moreover, the gut microbiome largely affects host physiology and is associated with diet. To investigate the effects of different feeding times on the composition of intestinal bacterial communities, high-throughput 16S rRNA sequencing was used to monitor the gut bacteria of the Chinese mitten crab Eriocheir sinensis over a 10-day period under different feeding times: 06:00 h, 12:00 h, 18:00 h, and 24:00 h. Weight gain of the day-fed groups was significantly higher than that of the night-fed groups. Two probiotics, Akkermansia muciniphila and Faecalibacterium prausnitzii, were detected in the intestines of crabs in the 12:00 group. In addition, the diversity and richness of the flora in the 12:00 group were slightly higher than those in the other treatment groups. These results collectively indicate that different feeding times change the intestinal flora composition of Chinese mitten crabs, and further identified specific feeding times associated with a more significant weight gain effect. Our findings provide important insights into improving farming strategies for Chinese mitten crabs.

Gamma-aminobutyric acid enhances hypoxia tolerance of juvenile Chinese mitten crab (Eriocheir sinensis) by regulating respiratory metabolism and alleviating neural excitotoxicity

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.

Effects of Protein Level on the Production and Growth Performance of Juvenile Chinese Mitten Crab (Eriocheir sinensis) and Environmental Parameters in Paddy Fields

Rice–crab co-culture systems represent integrated agriculture–aquaculture systems developed in China over the last 30 years. The rice–crab co-culture area comprised approximately 1.386 × 105 hm2 in 2019. However, there is no specific feed designed for Chinese mitten crab (Eriocheir sinensis) cultured in this system until now. In this study, we investigated feed formulae for the nutritional requirements of Chinese mitten crab in this mode. The control group was not fed with any artificial feed (Co), and the experimental groups were fed with three different feeds of 15% (T15), 30% (T30), or 45% (T45) protein content, respectively. Growth performance variations in E. sinensis were investigated along with water quality, phytoplankton, zooplankton, aquatic vascular plants, and benthic animals in the paddy fields to determine the effect of crabs and their diet on the paddy ecosystem. Dietary protein levels had no significant effect on water quality. The biomass and species of phytoplankton, zooplankton, aquatic vascular plants, and zoobenthos in the paddy field were affected by crabs and their diet. Morphological parameters of crabs were significantly more pronounced in the high-protein group than in the other groups. However, the T45 diet negatively affected production by increasing feed costs, causing precocious puberty and inducing water eutrophication. In conclusion, adding a 15% protein compound feed can meet the nutritional needs of crabs, reduce culture costs, and improve water quality. The discharged water had low ammonia nitrogen and nitrite content and no eutrophication occurred, so the water could be recycled. These findings provide a scientific reference for supporting rice and fish co-cultivation.

Effect of Vitamin A Supplementation on Growth Performance, Lipid Deposition, Antioxidant Ability, and Immunity in Juvenile Chinese Mitten Crab Eriocheir sinensis Fed Diet with Fish Oil Totally Replaced by Palm Oil

This research evaluated the protective effect of vitamin A (VA) on the adverse effect of fish oil (FO) substitution with palm oil (PO) in an economical crab Eriocheir sinensis. Three diets of FO, PO, and PO + 8000 IU / kg VA as the main lipid sources were fed to crabs, respectively, for 8 weeks. Compared to crabs fed FO diet, crabs fed PO diet showed reduced hemolymph VA concentration, feed utilization efficiency, and growth performance. Besides, crabs fed PO diet showed elevated lipid content in hepatopancreas and body and triglyceride content in hepatopancreas, leading to decreased antioxidant enzyme and immune parameters activities from biochemical analysis, enzymatic determination, and quantitative polymerase chain reaction. In contrast, compared to crabs fed PO only, VA supplementation in PO improved the growth performance and utilization of fatty acids and reduced lipid deposition in the hepatopancreas. In addition, VA supplementation suppressed gene expression related to triglyceride synthesis (dgat1) and positively affected gene expression related to lipid catabolism (cpt1a, cpt1b, cpt2, and caat). Furthermore, VA supplementation upregulated antioxidant genes (CuZnSOD and CAT) through downregulating gene expression of upstream regulator Keap1. Furthermore, VA supplementation upregulated immune genes (Lzm and proPO) expression and reduced proinflammatory genes (LITAF, ADAM17, and IL-16) expression related to Toll2/MyD88/Relish signaling pathway. This study shows the necessity of VA addition in the feed with FO totally replaced by PO because it can relieve PO’s adverse effects and improve the growth of crabs.

Shift and interaction of intestinal bacterial community in juvenile Chinese mitten crab Eriocheir sinensis upon astaxanthin feeding

Intestinal bacterial communities of juvenile Chinese mitten crab Eriocheir sinensis are investigated for the effects of dietary supplementation with different amounts of micro-algal astaxanthin (0, 30, 60, 90, and 120 mg/kg dry diet) and for the correlation to crab hemolymph antioxidant capacity and immunity. Comprehensively analyzing of bacterial 16S rRNA gene amplicons showed that astaxanthin supplement, particularly of 90 mg/kg, appeared to enrich especially the number of Bacteroidetes members, albeit not significantly, increased the relative abundance of Dysgonomonas sp. (OTU1156), and significantly decreased the relative abundance of Jinshanibacter sp. (OTU1324) (P < 0.05). Both Dysgonomonas sp. (OTU1156) and Jinshanibacter sp. (OTU1324) are dominant and native bacterial lineages, present in neither the farming water nor feed. The Dysgonomonas sp. (OTU1156) are probably probiotics involving the digesting of food rich in plant matter, while the Jinshanibacter sp. (OTU1324) are potential parasitic/pathogenic bacteria. Intestinal bacterial communities were improved for the metabolic capacity by astaxanthin, such as the ability to digest xenobiotics, which significantly correlates with the total antioxidant capacity (P < 0.05) of crab hemolymph. These findings contribute to better understanding of the mutual-interaction among astaxanthin, gut bacterial community structure, and hemolymph antioxidant capability and immunity, and shed light on the health and disease-resistance aquaculture of crabs.

Polystyrene microplastics increase Pb bioaccumulation and health damage in the Chinese mitten crab Eriocheir sinensis

Microplastics may be potential vectors for environmental contaminants such as heavy metals in the aquatic ecosystem due to their highly hydrophobic surfaces and fugacity property. To investigate the combined effects of microplastics with Pb, we exposed juvenile Chinese mitten crabs Eriocheir sinensis to different Pb concentrations (0, 5 and 50 μg/L) combined with microplastics (0 and 400 μg/L) for 21 days to determine the Pb bioaccumulation, oxidative stress, lipid anabolism, and histopathology of hepatopancreas. In general, the results showed that compared to single Pb exposure, the combination of MPs and Pb significantly increased the bioaccumulation of Pb, activities/content of antioxidant biomarkers and lipid metabolism enzymes, and liver injury parameters in crabs, indicating MPs are potential vector of heavy metals and co-exposure exerts more severe effects on crabs. This study provides the insights into the oxidative defense and preliminary lipid anabolism of economic crustaceans in response to combined stress of Pb and MPs.

Molting, tissue calcium‑phosphorus deposition and immunity of juvenile Chinese mitten crab (Eriocheir sinensis) fed different levels of calcium and vitamin D3

Molting activity and innate immunity play a pivotal role in the development and growth of crustaceans and are related to mortality and body abnormality. To evaluate the synergistic effect of vitamin D3 (vit-D3) and Ca in molting and immunity in Chinese mitten crab (Eriocheir sinensis), the crabs (3.20 ± 0.01 g) were fed six diets formulated with two Ca levels (0% and 1.5%, abbreviated D and N) and three vit-D3 levels (0, 9,000 and 27,000 IU/kg, abbreviated LVD, MVD and HVD) level for 56 days. Crabs fed 1.5% Ca and 9,000 IU/kg vit-D3 (N + MVD) had the highest growth performance, hematic-1,25-dihydroxy vit-D3, hematic‑calcium, hepatic‑phosphorus and antioxidant capacity among all groups. On the contrary, crabs fed diets without Ca reduced growth performance, tissue calcium‑phosphorus deposition, antioxidant capacity, and the expression of molting-related and immune-related genes. Compared to crab fed N + HVD (1.5% Ca + 27,000 IU/kg vit-D3), those fed D + HVD (0% Ca +27,000 IU/kg vit-D3) had significantly low growth performance and the gene expressions of molting and antibacterial immunity. This study demonstrates that adequate dietary calcium and vit-D3 can enhance growth, molting activity, antioxidant capacity and innate immunity in E. sinensis. Moreover, it provides an in-depth understanding of the molecular mechanism of molting activity and antibacterial immunity in Chinese mitten crab

Moderate acidification mitigates the toxic effects of phenanthrene on the mitten crab Eriocheir sinensis

Freshwater acidification and phenanthrene may result in complex adverse effects on aquatic animals. Juvenile Chinese mitten crabs (Eriocheir sinensis) were exposed to different pH levels (7.8, 6.5, and 5.5) under phenanthrene (PHE) (0 (control) and 50 μg/L) conditions for 14 days. Antioxidant and transcriptomic responses were determined under stress conditions to evaluate the physiological adaptation of crabs. Under the control pH 7.8, PHE led to significantly reduced activities of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) and glutathione S-transferase (GST), but increased glutathione peroxidase (GSH-Px), 7-ethoxyresorufin-o-deethylase (EROD) activities, and malondialdehyde (MDA) levels. However, moderate acidification (pH 6.5) changed PHE effects by increasing antioxidant enzymes. Acidification generally reduced SOD, GPx, GST and EROD activities, but increased CAT, GR, MDA. Compared with pH7.8 group, pH7.8 × PHE and pH6.5 × PHE groups had 1148 and 1498 differentially expressed genes, respectively, with “Biological process” being the main category in the two experimental groups. pH7.8 × PHE treatment caused significant enrichment of disease and immune-related pathways, while under pH6.5 × PHE, more pathways related to metabolism, detoxification, environmental information processing, and energy supply were significantly enriched. Thus, PHE had a significant inhibitory effect on antioxidant performance in crabs, while moderate acidification (pH6.5) mitigated the toxic effects of PHE. Overall, moderate acidification has a positive effect on the defense against the negative effects of PHE in Chinese mitten crabs, and this study provides insights into the defense mechanism of crustaceans in response to combined stress of acidification and PHE.

Impact of Dietary Vitamin D3 Supplementation on Growth, Molting, Antioxidant Capability, and Immunity of Juvenile Chinese Mitten Crabs (Eriocheir sinensis) by Metabolites and Vitamin D Receptor.

Vitamin D3 (vit-D3), as an indispensable and fat-soluble nutrient, is associated with skeletal mineralization and health in mammals. However, such associations have not been well studied in economically important crustaceans. Six levels of vit-D3 with isonitrogenous and isolipidic diets were used to feed Eriocheir sinensis. The range of optimal vit-D3 requirements is 5685.43-10,000 IU/kg based on growth. The crabs fed 9000 IU/kg vit-D3 showed the best growth performance. This vit-D3 dose significantly increased antioxidant capacity in the hepatopancreas and intestine and was optimal for molting and innate immunity via quantitative polymerase chain reaction analysis. Transcriptomics analyses indicate that vit-D3 could alter protein processing in the endoplasmic reticulum, steroid biosynthesis, and antigen processing and presentation. As shown by the enzyme-linked immunosorbent assay, vit-D3 could improve vitamin D receptor, retinoic acid receptor, and C-type lectins concentrations. The 1α,25-dihydroxy vit-D3 content in serum was significantly higher in 3000-9000 IU/kg vit-D3. The study suggests that dietary vit-D3 and its metabolites can regulate molting and innate immunity in crabs.

Dietary vitamin A affects growth performance, immunity, antioxidant capacity, and lipid metabolism of juvenile Chinese mitten crab Eriocheir sinensis

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 gamma-aminobutyric acid (GABA) supplementation increases food intake, influences the expression of feeding-related genes and improves digestion and growth of Chinese mitten crab (Eriocheir sinensis)

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.

Evaluation of the optimum dietary iron level and its immunomodulatory effects on juvenile Chinese mitten crab, Eriocheir sinensis

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-1and 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.

Myo-inositol improves growth performance and regulates lipid metabolism of juvenile Chinese mitten crab (Eriocheir sinensis) fed different percentage of lipid.

This study evaluated the effects of dietary myo-inositol (MI) on growth performance, antioxidant status and lipid metabolism of juvenile Chinese mitten crab (Eriocheir sinensis) fed different percentage of lipid. Crabs (4·58 (sem 0·05) g) were fed four diets including a normal lipid diet (N, containing 7 % lipid and 0 mg/kg MI), N with MI supplementation (N + MI, containing 7 % lipid and 1600 mg/kg MI), a high lipid diet (H, containing 13 % lipid and 0 mg/kg MI) and H with MI supplementation (H + MI, containing 13 % lipid and 1600 mg/kg MI) for 8 weeks. The H + MI group showed higher weight gain and specific growth rate than those in the H group. The dietary MI could improve the lipid accumulations in the whole body, hepatopancreas and muscle as a result of feeding on the high dietary lipid (13 %) in crabs. Besides, the crabs fed the H + MI diets increased the activities of antioxidant enzymes but reduced the malondialdehyde content in hepatopancreas compared with those fed the H diets. Moreover, dietary MI enhanced the expression of genes involved in lipid oxidation and exportation, yet reduced lipid absorption and synthesis genes expression in the hepatopancreas of crabs fed the H diet, which might be related to the activation of inositol 1,4,5-trisphosphate receptor (IP3R)/calmodulin-dependent protein kinase kinase-β (CaMKKβ)/adenosine 5'-monophosphate-activated protein kinase (AMPK) signalling pathway. This study demonstrates that MI could increase lipid utilisation and reduce lipid deposition in the hepatopancreas of E. sinensis fed a high lipid diet through IP3R/CaMKKβ/AMPK activation. This work provides new insights into the function of MI in the diet of crustaceans.

Effect of different feeding modes on the growth, biochemical composition, and living environment of the juvenile Chinese mitten crab Eriocheir sinensis

Enhancing the production and quality of juvenile Chinese mitten crab Eriocheir sinensis, while also ensuring environmental sustainability, are becoming increasingly important for both producers and consumers. In this study, the effects of three feeding modes (traditional, formulated, and mixed) on the growth and biochemical composition of juvenile E. sinensis and their living environment were compared. At the end of culture, the terminal mass, weight gain rate and specific growth gain rate of juvenile E. sinensis were the highest in the formulated group (P < 0.05). The crude protein, total lipids, and ash content of the hepatopancreas were not significantly different under the three groups (P > 0.05), and only the ash content of the body in the traditional group was lowest (P < 0.05). The C22:6n3 and ΣHUFA content, and DHA/EPA radio of the hepatopancreas were highest in the formulated group (P < 0.05), but the content of most fatty acids in the body were not significantly different under the three groups (P > 0.05). The ΣEAA, ΣNEAA and TAA content of the body were highest in the mixed group (P < 0.05). Under the three feeding modes, the NH4+, NO3− and TN content in the water negatively accumulated, whereas the NO2− and TP content positively accumulated, with TP of the formulated group having the lowest cumulation (P < 0.05). C accumulated in the sediment were lowest in the formulated group, and N in the mixed group, while P negatively accumulated in the formulated group (P < 0.05). Overall, formulated pellet feed in this study promoted the rapid growth and nutrient accumulation of juvenile crabs. However, the mixed feeding mode enhanced more balanced amino acid ratio in juvenile crabs. Additionally, the formulated feeding mode caused the least pollution to the living environment of juvenile E. sinensis. Collectively, our findings demonstrate that the formulated feeding mode is most conducive for sustainable development of the crab aquaculture industry.

Substitution of fish meal with soybean meal for juvenile Chinese mitten crab ( Eriocheir sinensis ) reared at three salinities: Effects on survival, growth, antioxidant capacity and body composition

A 60-day feeding experiment was conducted to evaluate the survival, growth, antioxidant capacity and body composition of the juvenile Chinese mitten crab (Eriocheir sinensis) reared at three salinities (0.5‰, 2‰ and 6‰) in response to the different substitution levels (0%, 24%, 39%, 57% and 100%) of fish meal (FM) by soybean meal (SBM). The five diets were named as S0, S24, S39, S57 and S100 respectively. Results showed that survival rate (SR) was only significantly affected by the substitution level at the salinity of 0.5‰, with significantly higher SR observed in S39 (p < 0.05). At the salinity of 0.5‰ and 2‰, the significantly higher weight gain rate (WGR) was observed in S39 and S57 respectively (p < 0.05). At the salinity of 6‰, WGR was significantly improved by partial or complete substitution of FM by SBM. At each salinity, the highest GSH-Px activity and lowest MDA content were observed in the treatments of S57, which were comparable to that fed S0. At the salinity of 6‰, the activities of SOD and CAT were significantly decreased in S100 than that in the other treatments (p < 0.05). The proline content significantly increased as the substitution level increased at the salinity of 2‰. At the salinity of 6‰, the contents of proline, glutamine, cysteine, methionine and lysine, first significantly increased and then decreased (p < 0.05), with the highest value observed in the treatment of S39 or S57. These results indicated that the optimal substitution level of FM by SBM was estimated to be 39% and 57% in the diets of E. sinensis at the salinity of 0.5‰ and 2‰ respectively. Although the FM can be completely replaced by SBM without negatively affecting the survival and growth performance at the salinity of 6‰, the antioxidant capacity was reduced to a large extent.

Dietary arginine alleviates the oxidative stress, inflammation and immunosuppression of juvenile Chinese mitten crab Eriocheir sinensis under high pH stress

This study investigates the effect of arginine (Arg) on the growth, antioxidant capacity, inflammation and immunity of juvenile Chinese mitten crab Eriocheir sinensis under high pH stress. Three diets containing 23.7 g/kg (control) 31.4 g/kg and 40.1 g/kg Arg were formulated and fed to crabs (3.37 ± 0.01 g) at high pH (pH = 9.5) for eight weeks. The weight gain and specific growth rate significantly increased in crabs fed the 31.4 g/kg and 40.1 g/kg Arg diets (P < 0.05). Furthermore, Arg improved the antioxidant capacity by increasing the activities of superoxide dismutase, catalase and glutathione production in the hepatopancreas (P < 0.05). In addition, Arg significantly downregulated the inflammatory and apoptotic genes including LPS-induced TNF-α factor, p38 mitogen-activated protein kinase, a disintegrin and metalloprotease 17, Bcl-2-associated X and cysteine-aspartic acid protease 3 (P < 0.05). Arg significantly upregulated the immune genes including crustin, relish and peroxinectin (P < 0.05). The respiratory burst of crabs fed the control diet was significantly lower than those fed the 31.4 g/kg Arg and 40.1 g/kg Arg diets after LPS injection of 0 h, 6 h and 12 h (P < 0.05). This study indicates that dietary Arg can alleviate oxidative stress and inflammation and improve the immunity of juvenile Chinese mitten crab under high pH stress.