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This study investigated the effect of different dietary selenium (Se) sources on the growth performance, antioxidant capacity, gut microbiota, and molecular responses of the Pacific white shrimp Litopenaeus vannamei. Four Se sources (sodium selenite, L-selenomethionine, selenium yeast, or Se nanoparticles) were added to purified diets to 0.4 mg Se/kg diet for shrimp ( 1.60 ± 0.14 g ). Each treatment was randomly assigned to 3 replicated tanks and 30 shrimp in each tank (500 L). After 8 weeks of breeding, L-selenomethionine and selenium yeast significantly increased weight gain compared with sodium selenite treatment, while sodium selenite significantly decreased the shrimp hepatosomatic index compared with the other groups. The L-selenomethionine significantly increased the superoxide dismutase and glutathione peroxidase activities in the hepatopancreas compared with the shrimp fed sodium selenite and decreased catalase activity and malondialdehyde content compared with other groups. The composition and β-diversity of gut microbiota were markedly changed in each group. The abundances of Rubrobacter and Rubritalea, Winogradskyella and Motilimonas, and Photobacterium in the gut microbiota were specially altered by L-selenomethionine, Se yeast, and Se nanoparticles, respectively. The sodium selenite group showed lower complexity of gut interspecies interactions. RNA-seq analysis showed that “arachidonic acid metabolism”-related genes were significantly enriched in the L-selenomethionine and Se yeast groups; “peroxisome” and “drug metabolism–other enzymes”-related genes were enriched in the Se nanoparticle group. Vibrio, Motilimonas, and Photobacterium were associated with amino acid and lipid metabolism. Pseudoalteromonas, Silicimonas, Roseovarius, and Halomonas inhibited the expression of glutathione peroxidase genes. These results suggested that organic Se, especially selenomethionine, is an effective feed supplement to promote growth and antioxidant capacity, maintain the health of gut microbiota, and promote the utilization of fatty acid and glutathione peroxidase genes in shrimp fed a 0.4 mg Se/kg diet.

To understand the physiological response of estuarine fish to acidification, barramundi (Lates calcarifer) juveniles were exposed to acidified seawater in experimental conditions. The molecular response of barramundi to acidification stress was assessed by RNA-seq analysis. A total of 2188 genes were identified as differential expression genes. The gene ontology classification system and Kyoto Encyclopedia of Genes and Genomes database analysis showed that acidification caused differential expressions of genes and pathways in the gills of barramundi. Acidification had a great influence on the signal transduction pathway in cell process. Furthermore, we detected that numerous unigenes involved in the pathways associated with lipid metabolism, carbohydrate metabolism, amino acid metabolism, glycan biosynthesis and metabolism specific and non-specific immunity were changed. This study indicates that the physiological responses in barramundi especially the immune system and energy allocation correspond to the variation of environmental pH. This study reveals the necessity for assessment of the potential of estuarine fishes to cope with acidification of the environment and the need to develop strategies for fish conservation in coastal areas.

Copper can be accumulated in water through excessive sewage discharge or residual algaecide to generate toxic effect to aquatic animals. In this study, the juvenile of Pacific white shrimp, Litopenaeus vannamei was exposed to 0 (control), 0.05, 0.1, 0.2, 0.5 or 1 mg Cu2+ L−1 for 30 days. Growth, immune function, anti-oxidative status and gut microbiota were evaluated. Weight gain and specific growth rate of L. vannamei were significantly decreased with the increase of ambient Cu2+. Enlarged lumen and ruptured cells were found in the hepatopancreas of shrimp in the 0.5 or 1 mg Cu2+ L−1 treatment. Total hemocyte counts of shrimp in 0.5 or 1 mg Cu2+ L−1 were significantly lower than in the control. The hemocyanin concentration was also significantly increased in 0.2 or 0.5 mg Cu2+ L−1. Lysozyme contents were reduced in shrimp when Cu2+ exceeded 0.2 mg L−1. Meanwhile, activities of superoxide dismutase and glutathione peroxidase were increased in the hepatopancreas and the activity of Na+-K+ ATPase was decreased in the gills with increasing Cu2+. The mRNA expressions of immune deficiency, toll-like receptor and caspase-3 were all significantly higher in the hepatopancreas in 0.05 mg Cu2+ L−1 than in the control. For the diversity of intestinal microbes, Bacteroidetes significantly decreased in 1 mg Cu2+ L−1 at the phylum level. KEGG pathway analysis demonstrates that 1 mg L−1 Cu2+ can significantly alter metabolism, cellular processes and environmental information processing. This study indicates that the concentration of 1 mg L−1 Cu can negatively impact growth, hemolymph immunity, anti-oxidative capacity and gut microbiota composition of L. vannamei.

Cobalt (Co) is an important component of vitamin B12, but is toxic to aquatic animals at a high level. In this study, the Pacific white shrimp, Litopenaeus vannamei were exposed to three Co concentrations (0, 100, and 1000 μg/L) for 4 weeks. The survival and condition factor in shrimp exposed to the Co treatments were not different from the control, but the shrimp exposed to 100 μg Co/L gained more weight than in other two groups, and the shrimp exposed to 1000 μg Co/L gained less weight than in other groups. The SOD and GSH-PX activities were higher in shrimp exposed to 100 μg Co/L, but lower in the shrimp exposed to 100 μg Co/L compared with the control, respectively. The MDA contents in the hepatopancreas decreased in the 100 μg Co/L, but increased in the 1000 μg Co/L. The serum lysozyme decreased with ambient cobalt, was lower in the shrimp exposed to 1000 μg Co/L than in other two groups. The expression of C-type lectin 3 was down-regulated by Co concentrations. The Toll and immune deficiency in shrimp exposed to 100 μg Co/L was higher than in other two groups. The mucin-1 was lower in the 1000 μg Co/L group than in other two groups, but mucin-2 and mucin-5AC were higher in the 1000 μg Co/L group than in the control. With increasing Co concentration, Shannon and Simpson indexes of the intestinal microbial communities were decreased. The abundance of pathogenic bacteria (Ruegeria and Vibrio) increased in both Co groups. This study indicates that chronic exposure to waterborne cobalt could affect growth, cause oxidative stress, stimulate the immune response, damage intestinal histology, and reshape intestinal microbiota community L. vannamei.

The T-2 toxin is a trichothecene mycotoxin and is highly toxic to aquatic animals, but little is known on its toxic effect in crustaceans. In the present study, the crab juveniles were fed with diets containing four levels of T-2 toxin: 0 (control), 0.6 (T1), 2.5 (T2) and 5.0 (T3) mg/kg diet for 56 days to evaluate its impact on the juvenile of Chinese mitten crab (Eriocheir sinensis). The crabs fed the T-2 toxin diets had significantly lower weight gain and specific growth rate than those fed the control diet. Moreover, crab survival in T3 group was obviously lower than that in the control. Oxidative stress occurred in all the treatment groups as indicated by higher activities of total superoxide dismutase, glutathione peroxidase, and total antioxidant capacity than those in the control. The total hemocyte count, respiratory burst, phenoloxidase in the hemolymph, and phenoloxidase, acid phosphatase and alkaline phosphatase in the hepatopancreas of crabs fed T-2 toxin were significantly lower than those in the control. The transcriptional expressions of lipopolysaccharide-induced TNF-alpha factor, relish, and the apoptosis genes in the hepatopancreas were induced by dietary T-2 toxin. The genes related to detoxication including cytochrome P450 gene superfamily and glutathione S transferase were induced in low concentration, then decreased in high concentration. Dietary T-2 toxin damaged the hepatopancreas structure, especially as seen in the detached basal membrane of hepatopancreatic tubules. This study indicates that dietary T-2 toxin can reduce growth performance, deteriorate health status and cause hepatopancreas dysfunction in crabs.

Reproductive and sexual health issues, including infertility and sexual dysfunctions (SD), are common concerns affecting millions of reproductive age worldwide. Scattered literature reports that marine animals such as oysters, sea cucumbers, seahorses and spoon worms have unique bioactive compounds like saponins, steroids, seahorse-derived hydrolysates, polypeptide, oligopeptides and essential trace elements that significantly improve infertility, hormonal imbalance, SD, and impotence. In addition, these compounds have exhibited pharmacological properties against reproductive problems due to diabetes and exposure to electromagnetic fields, cyclophosphamide, or a high exercise load. This review presents the first critical assessment of the advances in understanding and applying bioactives from marine organisms to support human reproductive health. Key knowledge and technical gaps have been identified for future research to improve the lack of in-depth understanding of the mechanism and action of these bioactives in human clinical studies. There is a need to develop simple, selective, low-cost, and scalable processes to isolate and purify individual bioactive compounds for industrial applications. The optimizing culturing and farming conditions for specific bioactive compounds from targeted species are suggested for sustainable production. The review indicates a promising future of extracts and marine-derived bioactives as functional foods in preventing and managing human reproductive health issues, but mechanistic studies and further clinical trials are urgently required to evaluate their efficacy and safety.

Recruiting King George whiting Sillaginodes punctatus were studied to assess the potential for food competition with permanent resident fish species in a nursery habitat. Marine migrant pos...

Mannan oligosaccharide (MOS) is a common prebiotics to improve health and immunity of animals in aquaculture. However, its optimum level and effects on the immune response in crab are currently unknown. The present study investigated the optimum level of dietary MOS supplementation and its effects on growth performance, antioxidant capacity, non-specific immunity and intestinal morphology of juvenile Chinese mitten crab (Eriocheir sinensis). Crab juveniles (2.95 ± 0.05 g) were fed either a control diet or one of the six diets supplemented with MOS (0.1%, 0.2%, 0.3%, 0.4%, 0.5% and 0.6%) for eight weeks. The crabs fed 0.3% MOS showed greater weight gain, specific growth rate and lower feed conversion ratio than those fed the control diet. The acid phosphatase activity was significantly higher in the gut of crab fed 0.2% MOS than those fed the other diets except the 0.3% MOS diet. The lysozyme and alkaline phosphatase activities in the gut were higher in crabs fed the 0.1% and 0.3% MOS diets compared to those fed other diets. The antioxidant capacity was higher in crab fed the 0.2% and 0.3% MOS diets than those fed other diets. In addition, the mRNA expression of genes related to immunity (E. sinensis (Es)-Crustin, Es-Toll2, Es-Lech and Es-prophenoloxidase (proPO)) in the hepatopancreas of crabs fed the 0.2 and 0.3% MOS diets were significantly up-regulated compared with those fed other diets. Duplicature length and width increased significantly in the crab fed 0.3% MOS than other diets. The optimum inclusion levels of MOS were 0.32%, 0.20% to 0.30% and 0.27% to 0.29% based on growth performance, antioxidant capacity and immunity, respectively. This study indicates that supplementing diets with MOS at 0.2% to 0.3% can improve growth performance and enhance antioxidant capacity and immunity in E. sinensis.

An 8-week trial was conducted to evaluate the effect of dietary β-glucan supplement (0, 0.01%, 0.02%, or 0.04%) on growth and health of Pacific white shrimp Litopenaeus vannamei at low salinity of 3 practical salinity unit (psu). The L. vannamei fed 0.02% and 0.04% β-glucan gained more weight and showed higher activities of protease, amylase, superoxide dismutase, and glutathione peroxidase in the intestine than in the control (0% β-glucan). The L. vannamei fed 0.04% β-glucan had a higher condition factor than those fed the control diet. Amylase activity in the hepatopancreas of L. vannamei fed 0.02% β-glucan was higher than those fed the control diet. Dietary β-glucan supplement increased the mRNA expressions of Toll-like receptor, myostatin, immune deficiency or heat shock protein 70, but decreased the mRNA expressions of tumor necrosis factor-α and C-type lectin 3 in both hepatopancreas and intestine. The response of intestine microbiota in L. vannamei fed 0.04% β-glucan was further compared to the control. The 0.04% β-glucan supplement reduced richness and diversity of the intestinal microbial community as indicated by the low values of Chao1 estimator, ACE estimator, Simpson index and Shannon diversity index. Abundances of Bacillus, Chitinibacter, Geobacillus and Vibrio in the intestine increased, while Flavobacterium, Microbacterium and Mycobacterium decreased significantly in L. vannamei fed 0.04% β-glucan compared to the control. This study indicates that dietary β-glucan supplement at 0.02%-0.04% can significantly improve digestibility, antioxidant capacity and immunity in L. vannamei, and thus improve growth performance and survival at low salinity. These beneficial effects of β-glucan probably are related to the dominance of probiotics over potential pathogens in the intestine.

The effects of system partition on the water quality were studied using three shrimp ponds (Ts), and each one of the shrimp pond was connected individually with a fish pond by piping and pump. Three other isolated shrimp ponds were designated as the Cs treatment. The results showed that the implementation of the system can improve the water quality in the shrimp ponds. Particulate organic matter (POM), chemical oxygen demand (COD), nitrite nitrogen (NO₂–N) and nitrate nitrogen (NO₃–N) in the Ts were lower than those in the Cs during the experiment, and in some cases, they were significantly lower (p

The Major State Basic Research Development Program of China (973 Program) (No. 2014CB138600) and China Agriculture Research System‐46 (CARS‐46).

This study investigates the effects of two soybean antigens (glycinin and β-conglycinin) as an antinutritional substance in the diet on the growth, digestive ability, intestinal health and microbiota of juvenile Chinese mitten crabs (Eriocheir sinensis). The isonitrogenous and isolipidic diets contained two soybean antigens at two levels each (70 and 140 g/kg β-conglycinin, 80 and 160 g/kg glycinin) and a control diet without β-conglycinin or glycinin supplementation, and were used respectively to feed juvenile E. sinensis for seven weeks. Dietary inclusion of either glycinin or β-conglycinin significantly reduced crab survival and weight gain. The crabs fed diets containing soybean antigens had higher malondialdehyde concentrations and lower catalase activities in the intestine than those in the control. The activities of trypsin and amylase in the intestine were suppressed by dietary β-conglycinin and glycinin. Dietary glycinin or β-conglycinin impaired the immunity and morphological structure of intestine, especially the peritrophic membrane. The mRNA expression of constitutive and inducible immune responsive genes (lipopolysaccharide-induced TNF-α factor and interleukin-2 enhancer-binding factor 2) increased while the mRNA expression of the main genes related to the structural integrity peritrophic membrane (peritrophin-like gene and peritrophic 2) significantly decreased in the groups with soybean antigen addition. Soybean antigen could also change the intestinal microbial community. The abundance of pathogenic bacteria (Ochrobactrum, Burkholderia and Pseudomonas) increased significantly in both soybean antigen groups. Although pathogenic bacteria Vibrio were up-regulated in the glycinin group, the abundance of Dysgonomonas that degraded lignocellulose and ameliorated the gut environment decreased in the glycinin group. This study indicates that existence of soybean antigens (glycinin or β-conglycinin) could induce gut inflammation, reshape the community of gut microbiota, and cause digestive dysfunction, ultimately leading to impaired growth in crabs.

To elucidate the possible molecular reaction of vertebral fusion in juvenile golden pompano at high temperature, we examined the changes in growth, vertebral fusion incidence, histological differences and transcription levels of genes related to bone development in juvenile golden pompano at 27 and 33°C for 30 days, respectively. The growth rate of juvenile fish was faster when the water temperature was 33°C, but the incidence of vertebral fusion was higher. Prolonged high water temperature reduced the osteogenic layer in the growth zone of the vertebral endplate and the elastic externa. The endplate growth areas of the fused vertebrae were transformed into cartilage tissue, which was then remodeled into bone. The intervertebral notochord tissue was transformed into bone and the intervertebral space disappeared. In normal phenotypes of vertebrae, short-term high temperature could promote the expression of genes related to cartilage differentiation and maturation, as well as genes related to osteoblastic differentiation. With the increase of culture time, the expression of genes related to cartilage and osteogenesis development was inhibited. In fused vertebrae, cartilage proliferation was enhanced, osteogenic differentiation was inhibited, and matrix mineralization may be enhanced. Genes associated with the development of chondrocytes and osteoblasts in the vertebrae of juvenile Trachinotus ovatus were significantly regulated by temperature and time. The results may contribute to further understanding of the occurrence of vertebral fusion at high temperature.

This study investigated the impact of water temperature on survival, skeletal development and the molecular mechanism of temperature-induced spinal deformity in golden pompano Trachinotus ovatus. Fish larvae were subjected to three temperatures (26, 29 and 32 °C) from 0 to 32 days post-hatch (DPH). On 32 DPH, significant higher growth rate was observed in fish cultured at 32 °C, but the survival rate and RNA/DNA ratio were significantly lower than fish culture at 26 and 29 °C. At the end of this study, the highest spinal deformity rate was observed in fish cultured at 32 °C. The ambient temperature should be kept at or below 29 °C for the best growth performance. The levels of BMP2, BMP4, BMP5, Sox9, twist and vimentin were significantly regulated by ambient temperature. High temperature may up-regulate the expression of a series of signaling factors during bone formation and down-regulate the expression of sox9, affecting the production of ECM components, thereby affecting the development of bone and cartilage and leading to spinal deformities. The results from the present study provide new evidence to understand the molecular mechanism of spinal deformities and bone development golden pompano.

Environmental pH change is a challenge for growth and health of aquatic animals. In this study, the juveniles of Pacific white shrimp Litopenaeus vannamei were exposed to a higher pH 9.5 or a lower pH 6.5 versus a normal pH (pH 8.0) as the control for four weeks. Growth performance, antioxidant capacity, immune functions, and intestinal histological damage and microbiota were evaluated. The weight gain rate was significantly decreased in shrimp at pH 9.5 compared with the control shrimp at pH 8.0. The antioxidant capacities of shrimp as activities of SOD, GSH-Px, GST and MDA contents shown at pH 9.5 or pH 6.5 were significantly reduced relative to the control shrimp. The expressions of immune-related genes, including anti-lipopolysaccharide factor, lysozyme, protein toll, immune deficiency, and hemocyte protein-glutamine gamma-glutamyltransferase, were down-regulated and the intestine tissues were distorted. Histology analysis showed that shrimp gut epithelial cells at pH 6.5 separated from the basement membrane, while epithelial cell necrosis were found in shrimp at pH 9.5. The diversity of intestine microbiota was disturbed with lower Shannon and higher Simpson indices in shrimp at pH 6.5 than the control shrimp, but no differences were found in shrimp at pH 9.5. The intestine barrier functions were weakened as the KEGG analysis shown, where functions for protein or carbohydrate digestion and absorption at pH 6.5, and for antibiotics biosynthesis, including streptomycin, penicillin, cephalosporin, novobiocin, ansamycins and vancomycin, at pH 9.5 in shrimp were significantly decreased. All finding in this study suggest that long-term lower or higher pH stress could adversely affect gut microbiota functions, thus leading to shrimp reduced growth, immunity and antioxidant capacity, and even intestine histology damage. Keywords: Litopenaeus vannamei, pH stress, Health, Histology, Intestine microbiota

Copper (Cu) is a widespread pollutant in water and has posed a significant threat to aquatic animals' health. It is essential to find a strategy to reduce the adverse effects of copper on aquatic organisms. This study investigated the role of myo-inositol (MI) in the reducing chronic toxicity induced by copper in Chinese mitten crab (Eriocheir sinensis). Two diets, including 0 mg/kg and 1600 mg/kg MI were fed to crabs exposed to 0 μg/L and 40 μg/L Cu2+ for 7 weeks. Dietary MI could improve the decreased weight gain and specific growth rate induced by copper exposure. Copper exposure increased the copper levels in the whole body and hepatopancreas, increased the malondialdehyde content, and suppressed the antioxidant enzymes system of the crabs. Simultaneously, copper exposure induced DNA fragmentation, decreased the gene expression/activities of immune-related genes/enzymes and the expression of the anti-apoptotic genes, and increased the gene expression of heat shock protein 70 and pro-apoptotic genes. The mitochondrial dysfunction, increased the gene expression of inflammation-related genes and caused the higher activity of damage-related enzymes in the crabs under Cu exposure. The administration of dietary MI markedly ameliorated the copper-induced oxidative stress, immune and hepatopancreas damage, mitochondrial dysfunction, apoptosis and inflammatory responses. This study indicates that dietary MI supplementation can effectively alleviate the negative effect of chronic copper exposure on E. sinensis.

Understanding fish larval development is of a great interest for aquaculture production efficiency. Identifying possible indicators of fish larvae stress could improve the production and limit the mortality rate that larval stage is subjected to. Heat-shock proteins (HSPs) and heat-shock factors (HSFs) are well known as indicators of response to many kinds of stressor (e.g., environmental, morphological, or pathological changes). In this study, golden pompano larvae were raised at different temperatures (23 °C, 26 °C, and 29 °C), as well as three different diets (Artemia nauplii unenriched, Artemia nauplii enriched with Nannochloropsis sp., and Artemia nauplii enriched with Algamac 3080), and the expression of HSP60, HSP70, HSF1, HSP2, and GRP94 were monitored. While stress genes were widely expressed in the larval tissues, HSP60 and HSP70 were principally from the gills and heart; HSF1 principally from the muscle, brain, and heart; and GRP94 principally from the head kidney and spleen. Golden pompano larvae were found to be more sensitive to thermal changes at later larval stage, and 29 °C was showed to likely be the best condition for golden pompano larval development. Nannochloropsis sp.-enriched Artemia nauplii treatment was found to be the most appropriate feed type with moderate relative expressions of HSP60, HSP70, HSF1, HSF2, and GRP94.

Five isonitrogenous diets were formulated with graded alpha‐linolenic acid (LNA) levels (0, 5, 10, 15 and 20 g/kg) to investigate LNA requirement of juvenile Russian sturgeon Acipenser gueldenstaedtii. Weight gain and specific growth rate of fish fed LNA5 and LNA10 were significantly higher than those in other groups, while the feed conversion ratio of these two groups was lower than others. Dietary LNA increased n‐3 polyunsaturated fatty acid and n‐3/n‐6 ratio, but decreased saturated fatty acid contents in the liver. DHA in the fish tissue also increased with the increased dietary LNA. The superoxide dismutase activity was highest in fish fed LNA5. Fish fed LNA10 showed the highest catalase activity and the highest malondialdehyde content. A 459‐bp fragment of Δ6 fatty acid desaturase and a 474‐bp fragment of elongases of very long chain fatty acids 5 were cloned and analysed. The expressions of these two genes were higher in fish fed LNA15 and LNA20. The highest hepatic lipase activity occurred in fish fed LNA 20, and the malate dehydrogenase activity peaked in the LNA5 group. Based on SGR and FCR, the range of optimum dietary LNA concentration for juvenile Russian sturgeon is recommended at 6.85–10.69 g/kg.

© 2018 Elsevier BV. This manuscript version is made available under the CC-BY-NC-ND 4.0 license: http://creativecommons.org/licenses/by-nc-nd/4.0/ This author accepted manuscript is made available following 24 month embargo from date of publication (May 2018) in accordance with the publisher’s archiving policy., Hypoxia is a critical issue in aquaculture especially in intensive aquaculture systems. Acute hypoxia stress with dissolved oxygen (DO) 0.7±0.1 mg/L for 6 h and chronic hypoxia stress with DO 1.1±0.1 mg/L for 4 weeks were used to investigate the response of nutritional metabolic pathways in Nile tilapia Oreochromis niloticus. Fish in the acute and chronic experiments had different adaptive mechanisms. Upon acute hypoxia stress, the contents of liver glycogen and muscle glycogen were significantly lower, but there was no significant difference in triglycerides (TG). The lactate dehydrogenase (LDH) activities increased after exposure to acute hypoxia stress. The mRNA expression of genes involved in glycolysis and glycogenolysis was significantly up-regulated by acute hypoxia stress. However, the response of fish to long-term hypoxia stress was different from acute hypoxia. Compared with the normoxia treatment, the crude fat in fish decreased in the hypoxia group and TG in the liver and muscle were significantly lower. Beta oxidation of the liver was enhanced in the hypoxia group, while the hepatic glycogen content increased in the hypoxia group. Transcriptomic analysis showed that the expression of genes related to carbohydrate synthesis and lipolysis increased in the hypoxia group, while genes related to carbohydrate catabolism and fat synthesis showed the opposite. This study indicates that fish could utilize carbohydrate as a main energy source during acute hypoxia stress, and metabolize more lipid during long-term hypoxia stress. A high carbohydrate content in the diet may help reduce negative effects from acute hypoxia stress, and an appropriate increase of fat content in the diet may benefit fish growth in a hypoxia environment, e.g., in high-density aquaculture ponds.

Benzo(a)pyrene (BaP) is a highly toxic polycyclic aromatic hydrocarbon and has strong affinity to suspended materials and sediments in the aquatic environment. Most crustaceans are benthic species and are easily affected by the pollution in the sediments, but there is little information on the response mechanism of crustaceans to BaP exposure. This study compared the growth and hepatopancreas transcriptomic responses of the Chinse mitten crab (Eriocheir sinensis) exposed to 0, 0.15 (BaP1) and 0.45 μg /L (BaP2) for 28 days. Crab survival and weight gain were reduced in the water born BaP in a dose-dependent way. The contents of hepatopancreas glycogen, triglyceride, total amino acids and lactic acid were all decreased after BaP exposure, indicating possible more energy consumption during detoxification. In the transcriptome analysis, a total of 106.65 million clean reads were obtained and assembled into 81,714 unigenes with an average length of 594 bp and N50 of 808 bp. Under 0.15 or 0.45 μg /L BaP exposure, 922 and 1129 unigenes in crabs were significantly expressed, annotated to 676 and 802 Gene Ontology (GO) terms respectively. The “cellular process” was the leading category for both concentrations. Thirteen significantly changed pathways were identified in both Control vs BaP1 and Control vs BaP2 groups. These pathways were divided into four different parts according to their reported functions, including metabolism, environmental information processing, organismal systems and cellular processes. Nice out of thirteen pathways in BaP1 were related to metabolism, containing amino acid metabolism, phenylpropanoid biosynthesis, monobactam biosynthesis and styrene degradation. Almost all the pathways related with the biosynthesis processes were down-regulated, while the degradation pathways were up-regulated. Seven out of thirteen pathways were classified into metabolism category in BaP2. These pathways were mostly associated with stress resistance rather than supplying energy. This study indicates that both concentrations of BaP disturbed nutrient metabolism, immune response and defense system in the crabs, while exposure to a higher concentration had a greater impact on immunity system than on metabolism. This study provides a better understanding of the underlying molecular and regulatory mechanisms in crustaceans coping with BaP toxicity.

The copepod Cyclopina kasignete was supplemented to the Asian seabass Lates calcarifer larvae to evaluate its potential use as a live food supplement during larval rearing. Initial larval feeding began with sole rotifers as a live food from 3 to 7 days post hatch (DPH) followed by the addition of copepod, Artemia, and their combination from 8 to 21 DPH. Fish were sampled every 5 days to measure growth and food selectivity on 11, 15, 19, and 21 DPH. The larvae that were fed the combination diets involving copepods resulted in better growth, survival, and increased the essential fatty acid contents of eicosapentaenoic acid and docosahexaenoic acid. In terms of food selectivity, seabass larvae selected copepods over rotifers and Artemia for feeding. This study indicates that the potential use of copepod as a supplementary live food can improve larval fish performance and thus overcome low survival and slow growth in fish larval aquaculture. The present study demonstrates that the nutritional value of seabass larvae was improved when fed with diets involving copepods. Our finding highlights the importance of incorporating copepods into the feeding regimes for seabass larvae, which may be applicable to the culture of fish larvae for other species.

This study investigates the impact of fishmeal replacement by soybean meal (SM) and improved SM known as EnzoMeal (EZ) on fish growth performance. The SM and EZ were used in five experimental diets: fishmeal (600 g/kg) as the control diet, 50% fishmeal replaced with soybean meal (SM50), 50% fishmeal replaced with EnzoMeal (EZ50), 100% fishmeal replaced with soybean meal (SM100) and 100% fishmeal replaced with EnzoMeal (EZ100). Fish in the control group gained the most weight, followed by those under the SM50 and EZ50 diets, while the least weight gain was observed in fish fed the SM100 and EZ100 diets. The specific growth rate (SGR) was higher in the control, but was not different between fish fed SM50 and EZ50, or between SM100 and EZ100. The highest feed intake occurred in the control but decreased sequentially from fish fed SM50 to fish fed EZ50, EZ100 and SM100. Protein digestibility was best in SM50, poorest in EZ100, but no difference between the control, EZ50 and SM100 diets. This study indicates that EnzoMeal, containing high crude protein (56%), is a potential source of plant meal to replace fishmeal in the barramundi diet, but low feed intake is a challenge when EnzoMeal is >300 g/kg.

This study compared the efficacy of different dietary algae on the growth and reproduction of the cyclopoid copepod Cyclopina kasignete, a potential live food species for fish larvae in aquaculture. The experimental diets for the copepod consisted of three monoalgal diets (Nannochloropsis oculata, Tisochrysis lutea and dry Melosira sp.) and two mixed algae diets (T. lutea + N. oculata, T. lutea + dry Melosira sp.). The experiment was carried out for 30 days, and the population growth, survival and reproductive performance (generation time, hatching rate, life spawning times, daily offspring production, eggs per sac, lifespan and sex ratio) were used to assess the responses of C. kasignete to different food types. Population growth, survival and reproductive capacities of C. kasignete were significantly affected by the mono and binary species of algal diets. The results showed that copepods exhibited superior growth, survival and productivity when fed on fresh T. lutea, dry Melosira sp. and a mixture of both species compared to other dietary treatments. Copepods produced comparable growth, survival and productivity when fed on diatoms (dry Melosira sp.) as a single or in combination with other algae. This study indicates that cyclopoid copepod C. kasignete grow fast and have the potential to serve as a live food for aquaculture. The algae T. lutea, dry Melosira sp. and their combination are appropriate food to sustain the growth and reproduction of this copepods in mass culture as a potential live food in fish hatchery.

Six purified diets were formulated to contain three lipid sources, fish oil (FO), linseed oil (LO) and soybean oil (SO), at 6% diet lipid crossing two levels of vitamin E (100 and 300 mg α‐tocopheryl acetate/kg diet) for each lipid source (FO100, FO300, LO100, LO300, SO100, SO300). The juvenile Chinese mitten crab, Eriocheir sinensis, respectively, fed on these diets with four replicates for 6 weeks. The crab weight gain (WG) and specific growth rate (SGR) were significantly affected by dietary lipid sources. No difference was found between the crabs fed two levels of vitamin E, but the WG and SGR were numerically higher in crab fed 300 mg/kg vitamin E than those fed the other level of vitamin E. The lipid source and vitamin E level could affect fatty acid composition in the hepatopancreas. The contents of saturated fatty acids (SAFA) and n‐3HUFA were significantly higher in the crab‐fed fish oil. The highest contents of n‐6PUFA and n‐3PUFA were found in the crab‐fed soybean oil and linseed oil respectively. The contents of SAFA, n‐3HUFA and n‐3PUFA were higher in the 300 mg/kg vitamin E treatment. A lower malondialdehyde (MDA) content and higher phenoloxidase (PO) activity were observed in the crab fed 300 mg/kg vitamin E. The results of this study indicate that the Chinese mitten crab fed the diet with 6% fish oil and 300 mg/kg vitamin E showed better growth, antioxidant capacity and resistance to Aeromonas hydrophila.

The Pacific white shrimp Litopenaeus vannamei is the most important crustacean species in aquaculture, accounting for 70% of the total shrimp production in the world. In the past decade, development of the shrimp industry has been greatly impeded by disease prevalence, poor growth in low salinity inland water, dietary use of plant ingredients, and antibiotic overuse. The animal gut is a vital organ, and most of the gut functions, such as the functions of immunity, health regulation and nutrient absorption, are achieved by bacterial metabolism in the gut. Therefore, understanding the role of the gut microbiota of L. vannamei is important for improving the performance and production of L. vannamei in aquaculture. This paper summarizes the recent advancements in research on the composition of the gut microbiota of L. vannamei, the factors that influence the microbiota, and nutritional manipulation of the gut microbiota. In addition, based on the review, current problems are raised and future studies ...

Phenotypic plasticity and adaptation are common traits of organisms living in highly dynamic and changing environments. Several copepod species, especially estuarine dwelling species, have demonstrated high phenotypic plasticity and adaptability to variations in environmental conditions. Copepods play a critical role in aquatic foodwebs and their population structure is closely linked to water quality fluctuations, especially salinity and temperature. However, few studies have examined the response of population structure to environmental stress. Here, we examine the population structure, egg production and hatching success of Acartia fancetti in relation to hypersalinity (30, 40, 50 and 60) and temperature (15 °C and 20 °C). A. fancetti is a neritic species occupying a key niche in the hypersaline areas of the Coorong, South Australia. Our results show a significant influence of salinity and temperature on the population size, nauplii production, copepodites production and adults of A. fancetti. The maximum numbers of nauplii, copepodites and adults were at salinity 30 and 40, at both 15 °C and 20 °C. However, substantial population sizes were also observed at salinity 50 and 60 in 15 °C treatments. At 20 °C, no individual was observed at salinity 60. This study indicates that the population of A. fancetti in the Coorong is tolerant to hypersalinity at lower temperatures, but the combined effects of haline and thermal stress significantly reduces the ability of this species to survive at higher temperatures. The distribution of A. fancetti in the Coorong is also affected by the environmental change related to anthropogenic activities .

The synthesis of highly unsaturated fatty acids (HUFAs) from C18 fatty acids in the Pacific white shrimp, Litopenaeus vannamei, has long been debated in terms of the limited capacity or even the existence of fatty acid desaturase and elongase. In the present study, a Δ6 fatty acyl desaturase (Fad)-like gene was identified and characterized with a full length of 1,491 bp, including a 39-bp 5′-UTR (untranslated region), a 108-bp 3′-UTR, and a 1,344 bp open reading frame encoding a 448 amino acid protein. The protein contained a cytochrome b5-like heme/steroid binding domain and a Fad domain. The Δ6 Fad-like protein of L. vannamei shared 70%–77% sequence homology with those of Macrobrachium nipponense, Scylla paramamosain, Portunus trituberculatus and Eriocheir sinensis. When salinity was reduced from 30 to 3, Δ6 Fad-like gene expression significantly increased in the gills, muscles, eyestalk, and hepatopancreas (P < 0.05). The highest expression was observed in the hepatopancreas under salinity 3 i...

This study evaluated the effects of supplementing dried macroalgae meal on the shell, foot and lip colour in terms of colour hue, saturation and brightness and pigment concentration in greenlip abalone Haliotis laevigata . Two species of dried macroalgae meal ( Ulva sp. and Gracilaria cliftonii ) at four levels (0% basal diet, 5%, 10% and 20%) of dietary inclusion were fed to the abalone (2.89 ± 0.01 g; shell length 22.41 ± 0.06 mm) for 92 days. The abalone fed G. cliftonii meal developed brown-red colour on the shell and the increased inclusion of algal meal resulted in darker brown shells, whereas abalone fed Ulva sp. meal or the basal diet exhibited light green shells. Although foot hue and foot brightness were not influenced by the type and level of inclusion of dried algal meal, the foot colour saturation of abalone fed ≥ 10% macroalgal meal was significantly higher than those fed the basal diet. Abalone developed a green lip when fed ≥ 10% of G. cliftonii meal, whereas lip colour did not change when fed Ulva sp. meal inclusion, compared to the basal diet, and exhibited milky lip colour. Although diet pigments varied with the species of macroalgae and inclusion level, β-carotene was the major pigment in the tissue of abalone fed all test diets and its content increased significantly with the inclusion level of macroalgae in the diet. Abalone fed the basal diet had significantly lower tissue β-carotene than those fed the diets with macroalgal inclusion. This study suggests that the inclusion of ≥ 5% G. cliftonii can produce a brown-red shell and the inclusion of ≥ 10% G. cliftonii intensifies the green colour of the lip. The brown-red colour mark on the shell by feeding macroalgal meal may be used as a harmless shell-marking method for ranching, stock enhancement or growth study in the wild. Statement of relevance Feed manipulation can change abalone shell, foot and lip colour.

Coastal lagoons are characterised by strong spatial gradient of environmental parameters, especially hypersalinity, and are prone to anthropogenic disturbance. The Coorong (South Australia) is an inverse estuarine coastal lagoon separated from the sea by sand dunes. It is exposed to extreme water quality changes that affect its aquatic communities. Here, we used plankton as indicators of extreme environmental fluctuations to monitor and manage the environmental health of such complex systems. We defined the relationship of different plankton communities with water quality fluctuations and determined plankton species suitable for monitoring the ecosystem health. Two distinct communities of phytoplankton and zooplankton were identified, with salinity and nutrients being the principal factors impacting species distribution. Thus, two sets of indicator species were selected based on the different communities observed. Polychaete and gastropod larvae were positive indicators, showing salinity range restriction of brackish to marine. The distribution Acartia cf. fancetti represented healthy hypersaline conditions (salinity 40–60), while Cyclophora sp. and Scrippsiella sp. were negative indicators, correlating with extreme salinity and ammonia levels. The implementation of planktonic organisms as environmental indicators provided a constructive tool for the management of ecosystem health of the Coorong and will be applicable to similar coastal lagoons.

Butyrate is a fermentation byproduct of gut microbiota and is susceptible to chronic oxidative stress. This study investigates the mitigative effects of sodium butyrate (SBT) on growth inhibition and intestinal damage induced by glycinin in juvenile Chinese mitten crab (Eriocheir sinensis). All four experimental diets containing 80 g/kg glycinin were formulated with 0, 10, 20 and 40 g/kg SBT respectively. There was no glycinin or SBT in the control diet. Juvenile crabs (0.33 ± 0.01g) were respectively fed with these five diets for eight weeks. The diets with 10 and 20 g/kg SBT significantly improved the survival and weight gain of the crabs compared with those in the 0 g/kg SBT group, and showed no difference with the control group. The crabs fed diets containing glycinin without SBT had lower glutathione and glutathione peroxidase activities but higher malondialdehyde in the intestine than those in the control group. Moreover, dietary glycinin decreased the lysozyme and phenoloxidase activities and improved the level of histamine in the intestine compared with the control group, while the supplementation of SBT counteracted these negative effects. The addition of SBT could also restore the impaired immunity and morphological structure of the intestine. Dietary SBT could increase the mRNA expression of antimicrobial peptides genes (anti-lipopolysaccharide factor 1 and 2) and decrease the content of pro-inflammatory factor TNF-α. The SBT could restore the intestinal microbial community disorganized by glycinin. The abundance of pathogenic bacteria (Aeromonas, Vibrio and Pseudomonas) decreased significantly and the potential probiotic bacteria (Bacillus, Lactobacillus, Chitinibacter and Dysgonomonas) increased significantly in the 10 g/kg SBT group. This study suggests that sodium butyrate supplementation can mitigate the negative effects induced by glycinin such as growth inhibition, intestinal inflammation and reduction of beneficial flora in the gut.

This study evaluates the effects of different dietary sources of non-protein energy on growth performance, histological structure, antioxidant status and immune response of barramundi Lates calcarifer. Fish were fed with isoenergetic diets (18 kJ/g) with two types of non-protein energy in the experimental groups and a regular diet was used as the control for 56 days. The specific growth rate and survival of fish were not significantly different between experimental diets. Hepatic histology did not reveal significant differences between dietary treatments at cellular level. The activity of most antioxidant enzymes in the lipid group significantly increased, and the antioxidant capacity in the carbohydrate group was significantly higher than that in other treatments. In the TOR pathway, LST8 homolog (mLST8) expression in the high lipid group was downregulated, and the mechanistic target of rapamycin (mTOR) expression in the high carbohydrate group was downregulated and eIF4E expression was upregulated. The C-reactive protein (CRP) expression in the high lipid and high carbohydrate groups was upregulated. The expression levels of heat shock protein genes in the high lipid group and the high carbohydrate group were significantly downregulated. This study indicates that the lipid diet have less effect in fish immunity but is more suitable as a non-protein ingredient for energy supply for barramundi.

This study evaluates the effect of dietary supplementation of immunostimulants on the Chinese mitten crab (Eriocheir sinensis) with a single administration of mannan oligosaccharide (MOS), or its combination with either β-glucan or with inulin for 8 weeks. Four diets included an untreated control diet (C), MOS alone (3 g kg−1, M), MOS with β-glucan (3 g kg −1 MOS + 1.5 g kg −1 β-glucan, MB), and MOS with inulin (3 g kg −1 MOS + 10 g kg −1 inulin, MI). The weight gain and specific growth rate of the crabs fed M, MB, and MI diets were improved by lowing feed conversion ratio. The growth and feed utilization of the crabs fed the MB diet were improved compared with the other three groups. The crabs fed the M, MB and MI diets showed a higher intestinal trypsin activity than that in the M and control groups. The highest trypsin activity in the hepatopancreas was observed in the MB group. Crabs fed M, MB and MI diets increased antioxidant system-related enzyme activities, but reduced malondialdehyde. The highest activities of alkaline phosphatase, acid phosphatase, lysozyme and phenol oxidase in the gut and the respiratory burst of the crabs were found in the MB group. The MB diet promoted the mRNA expression of E. sinensis immune genes (ES-PT, ES-Relish, ES-LITAF, p38MAPK and Crustin) compared with the control. After 3 days of infection with Aeromonas hydrophila, the highest survival of crabs was also found in the MB group. This study indicates that the combination of MOS with β-glucan or with inulin can improve growth, antioxidant capacity, non-specific immunity and disease resistance in E. sinensis.

To investigate the effects of arginine (Arg) on the growth, antioxidant capacity, immunity and disease resistance of juvenile Chinese mitten crab, three diets containing Arg levels at 1.72% (control), 2.73% and 3.72% were formulated and fed to Chinese mitten crab (0.22 ± 0.03 g) for eight weeks. The weight gain, ecdysterone and growth hormone in the serum, relative expression of insulin-like growth factor 2 in the hepatopancreas significantly increased in crabs fed the 2.73% and 3.72% Arg diets. The protein and lipid contents significantly increased in crabs fed the 3.72% Arg diet. The feed conversion ratios in crabs fed the diets with Arg additions were lower than in the control. Arg supplementation also enhanced the antioxidative capacity by increasing the activities of superoxide dismutase, catalase and the relative expression of Kelch-like ECH-associated protein 1 gene in the hepatopancreas, which subsequently decreased malondialdehyde content in the hepatopancreas. Besides, Arg also decreased nitric oxide content in the serum and the activity of nitric oxide synthetase in the hepatopancreas. The relative mRNA levels of crustin, relish, lysozyme and cryptocyanin genes were significantly upregulated by Arg supplementation. The activities of acid phosphatase and alkaline phosphatase in the serum significantly increased in crabs fed the 3.72% Arg diet than those in the control. Similarly, the relative mRNA levels of crustin, cryptocyanin and proPO genes were significantly upregulated in crabs fed the 2.73% Arg diet after lipopolysaccharide challenge, and in crabs fed the 3.72% Arg diet after the Poly (I:C) challenge. The crabs fed the 2.73% and 3.72% Arg diets had higher survival rate after bacterial infection than those fed the control diet. This study indicates that the addition of Arg to the diet at 2.7–3.7% can improve the growth, survival, antioxidant capacity, immunity and disease resistance in juvenile Chinese mitten crab.

Imbalance of intestinal microbiota has been recognized in aquatic animals infected with various diseases. However, the signature of intestinal bacteria of the "cotton shrimp-like" disease in the Pacific white shrimp Litopenaeus vannamei remains unknown. This study investigates the composition, diversity, microbial-mediated function and interspecies interaction of intestinal microbiota on shrimp with different health status using 16S rRNA gene high-throughput sequencing. Meanwhile, the growth performance and the mRNA expression of innate immune gene in hepatopancreas were also investigated. The growth performance and the mRNA expression of innate immune genes (e.g., crustin, toll, and immune deficiency genes) in the hepatopancreas were significantly decreased in diseased shrimp compared with healthy shrimp. Bacteria of the family Rickettsiaceae and genus Tenacibaculum were exclusively enriched and significantly increased in diseased shrimp, respectively, whereas, the Actinobacteria class dramatically deceased. The diseased shrimp exhibited higher ACE and Chao1 indices and lower complexity of intestinal interspecies interaction than healthy shrimp. Microbial-mediated functions predicted by PICRUSt showed that 83% KEGG pathway including nutrient absorption and digestion significantly increased in diseased shrimp. This study provides an overview on the interplay among the "cotton shrimp-like" disease, intestinal microbiota, growth performance and host immune responses from an ecological perspective.

This study characterizes the composition, diversity, function and interspecies interaction of the bacteria community in the gut of shrimp (Penaeus japonicus) and its culture water and sediment by 16S rRNA gene high-throughput sequencing. The relationships of bacterial communities in the gut and the surrounding water and pond sediment were compared and quantified. The sediment bacteria exhibited the highest α-diversity. The bacterial communities were distinctly clustered according to the habitats. Different habitats exhibited a low (8% ~14.12%) similarity of the bacteria community in taxonomic composition, but a surprisingly high (88.77% ~ 92.57%) similarity in functional composition. The proportion of negative links were more abundant in the sediment bacterial networks (51%) than those in the gut and water bacterial networks (8% and 2%, respectively). SIMPER analysis revealed that the bacterial community in the gut was more similar to the sediment than to the water. SourceTracker analysis showed that the sediment is a more important source of the bacterial contributor (64.58%) to the shrimp gut than the pond water (35.32%). Our results have important implications for establishing sustainable microbial management strategies for shrimp farming and also provide information to understand the environmental mechanism of gut bacterial community assembly.

The present research aimed to investigate the protection of N-acetylcysteine (NAC) on T-2 toxin-induced toxicity in Chinese mitten crab (Eriocheir sinensis). Crabs (0.27 ± 0.00 g) were fed four different diets (Control, T-2, 0.05% NAC + T-2 and 0.1% NAC + T-2) for 8 weeks. The results showed that T-2 toxin decreased growth performance, and induced oxidative stress, immunodepression and apoptosis in juvenile crabs. Crabs with NAC had higher weight gain, specific growth rate and hepatosomatic index than those in the T-2 group. The 0.1% NAC elevated crab survival and oxygen consumption rate and decreased alanine transaminase and aspartate transaminase in the serum of crabs fed T-2 toxin. Reactive oxygen species and malonaldehyde levels of hemolymph and hepatopancreas in crabs fed NAC were significantly lower than those in the T-2 group, while glutathione peroxidase, total antioxidant capacity, γ-glutamylcysteine synthetase activities and glutathione content significantly increased with 0.1% NAC. Total hemocyte count, respiratory burst activity, total protein, acid phosphatase (ACP) in hemolymph and ACP, alkaline phosphatase (AKP) in hepatopancreas were significantly enhanced with 0.1% NAC. Phagocytosis and AKP in hemolymph were significantly enhanced with 0.05% NAC supplementation. Furthermore, the mRNA expressions of antimicrobial peptides (ALF1, ALF2, crustin-1 and crustin-2) and peroxinectin were up-regulated with NAC. Besides NAC down-regulated the mRNA expressions of Relish, lipopolysaccharide-induced TNF-alpha factor, caspase-3, caspase-8 and p53 genes, and the ratio of Bax to Bcl-2 in the hepatopancreas. Our findings indicate that dietary NAC could improve the growth performance and survival of juvenile Chinese mitten crab fed T-2 toxin. The 0.1% NAC could effectively alleviate oxidative stress, immunodepression and apoptosis induced by T-2 toxin.

Understanding the energy budgets of cultured abalone fed graded dietary crude protein levels at different water temperatures gives us the ability to optimise diets for different seasons. In this 91-d study we investigated the effects of feeding four diets containing graded levels of crude protein (CP; 27, 30, 33 and 36%) at three seasonal water temperatures (14, 17 and 20 °C) on the energy budget components for 6-month-old Greenlip Abalone, Haliotis laevigata, (0.91 g; 19.46 mm shell length). The increase of water temperature significantly increased individual energy budget components, rates for somatic growth energy, respiration energy and shell growth energy of abalone. Ammonia excretion energy rate was positively related to increasing dietary CP levels. In contrast, there were significant interactions between water temperature and dietary CP levels for ingested feed energy rate, absorbed energy rate and egested faecal energy rate. For energy budgets, respiration energy accounted for the largest proportion and ranged between 34.1 and 43.9% of the ingested feed energy. Somatic growth energy (16.80–28.10%) also accounted for a large proportion of the energy budget. Although egested faecal energy was lower, it still accounted for 8.2–17.9% of the ingested feed energy. In contrast, pedal mucus production energy (4.12–6.20%), ammonia excretion energy (0.28–1.40%) and shell growth energy (0.22–0.46%) accounted for relatively smaller proportions of ingested feed energy. Water temperature significantly impacted energy budgets more than dietary CP level. To maximise energy transfer to somatic growth, a water temperature of 20 °C is recommended for culturing Greenlip Abalone. Additionally, to minimise energy loss through faecal egestion, a dietary CP level of 36% is recommended for the diet of 6-month-old Greenlip Abalone at optimum water temperatures. However, the increase in ammonia excretion energy at high dietary CP should also be considered when managing water quality and waste production in abalone farms, especially where tank water exchange is limited. These findings provide a better understanding of the energy budgets for Greenlip Abalone, in relation to temperature and dietary protein levels, and will aid in the development of sustainable diets applicable to the three-four years of culture.

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.

Myo-inositol (MI) as a major intracellular osmolyte can be accumulated to protect cells from a variety of stress. The present study was to evaluate the effects of dietary MI on growth, osmotic response and transcriptional response in the liver of euryhaline fish Oreochromis mossambicus under long-term salinity stress. Five isonitrogenous and isolipidic diets were formulated to include 0 (MI0), 200 (MI200), 400 (MI400), 800 (MI800) and 1600 (MI1600) mg/kg MI. In this study, dietary 400 mg/kg MI significantly increased the weight gain and specific growth rate of O. mossambicus compared with the group without dietary MI supplementation under salinity stress. Moreover, dietary MI decreased serum glucose and insulin levels of fish under long-term salinity stress. Fish fed 400 mg/kg MI supplementation had significantly higher serum cortisol, sodium (Na+) and chloride ion (Cl−) than those fed a diet without MI supplementation. A total of 132.17 million and 115.8 million clean reads were obtained from the 0 mg/kg MI (MI0) and 400 mg/kg (MI400) MI group respectively. Compared with the MI0 group, the expression of 704 genes was significantly changed (521-up and 183-down) in the MI400 group under long-term salinity stress. Transcriptome results indicate that myo-inositol can regulate lipid and pyruvic acid metabolism, increase phospholipid synthesis-related mRNA levels and improve antioxidant properties of O. mossambicus under long-term salinity stress. This study suggests that optimum MI supplementation is 400 mg/kg in the diet based on weight gain against dietary MI and this result provides a nutritional solution for tilapia to cope with salinity stress.

This study was to evaluate the relationship between myo-inositol synthesis and carbohydrate metabolism in Mozambique tilapia (Oreochromis mossambicus). Fish were immediately transferred from 0 psu (practical salinity units, the control) to 20 psu for 96 h with 60 fish in each group. Compared with the control group, the volume of the mitochondria-rich cell in the gills of O. mossambicus was significantly increased by acute hypersaline stress. The osmotic pressure and the contents of Na+, K+ and Cl− in the serum were significantly increased in the 20 psu group. Moreover, fish in the 20 psu group had significantly higher activities of glutathione peroxidase and superoxide dismutase and a higher malondialdehyde content than the control in the liver. Salinity stress significantly increased the serum glucose but decreased the liver glycogen. The activities of glucokinase and phosphofructokinase in the liver and gills were significantly higher in the 20 psu group, indicating that glycolysis could be significantly enhanced by salinity stress. The activities of glucose-6-phosphate synthase and phosphoenolpyruvate carboxykinase in the liver were significantly decreased by salinity stress. The expressions of myo-inositol-1-phosphate synthase and myo-inositol monophosphatase were significantly up-regulated in the gills and kidney. However, the expressions of these two genes were significantly down-regulated in the liver. The myo-inositol content in the gills, kidney and liver in the 20 psu group were significantly increased by salinity stress. This study indicates that salinity stress can impair the gill structure and reduce the antioxidant capacity of O. mossambicus. The changes in MI biosynthesis and carbohydrate metabolism could be an effective strategy to alleviate the adverse effect of salinity stress.