Abstract:Mercury (especially methylmercury) is easily accumulated by fish, thus posing a great threat to human health. Fish consumption is the main pathway for human exposure to MeHg, thus the MeHg accumulation in fish is critical for food safety. In the Pearl River Delta, bosh fish farming and wild fishing are well developed, leading to be the highest fishery production in China. MeHg in fish is mainly derived from food consumption. Compared with wild fish, farmed fish have more stable food sources and more simple food composition, resulting in a much higher rate of growth. However, the MeHg accumulation in fish from Pearl River Delta has not been thoroughly understood, and the effects of fish food (composition and MeHg concentration) on MeHg levels in fish have not been reported. This study investigated the bioaccumulation of MeHg in farmed and wild freshwater fish in Pearl River Delta and evaluated the MeHg exposure risk by fish consumption, aiming to figure out the key factors determining MeHg levels in fish. The farmed and wild fish (with fish food for farmed fish) were collected from 15 sites located in the Pearl River Delta and three tissues (muscle, liver and intestine) were sampled. The fish tissues and fish food samples were digested by 25% KOH/methanol solution at 80^oC for 4 h, and MeHg in the digested solution was ethylated by 1% NaBEt₄ solution and then detected by Gas Chromatography-Cold Vapor Atomic Fluorescence Spectrometry (GC-CVAFS). ① MeHg concentrations in fish tissues in this area were generally low and did not exceed the limit in the Food Safety Standard of China (GB 2762—2017) (Carnivore fish: 1 000 ng/g dw, others: 500 ng/g dw). Particularly, MeHg concentrations in muscle tissues of farmed fish (mean value: 61.53 ng/g dw, ranged from 0.26 to 331.27 ng/g dw) were significantly lower (P<0.05) than those of wild fish (mean value: 110.77 ng/g dw, ranged from 0.71 to 1 006.05 ng/g dw). ② Significant positive correlations were observed between MeHg concentrations in fish food and MeHg levels of farmed fish muscle (R²=0.39, P<0.05), and between trophic levels of wild fish and MeHg levels of wild fish muscle (R²=0.23, P<0.05). This suggested that MeHg accumulation in fish was mainly affected by food composition and the MeHg level in fish food. ③ Risk assessment showed that the MeHg exposure to human through fish consumption was low in this region. However, it should be noted that the MeHg intake through fish consumption was higher in wild fish than that of farmed fish. Fish is generally safe for human consumption in Pearl River Delta. However, MeHg levels in wild fish were higher than farmed fish, leading to a potential risk of MeHg exposure by consuming some specific species of wild carnivorous fish (e.g. Siniperca chuatsi). For farmed fish, the MeHg concentration in fish food was the key factor determining MeHg level in fish. Thus, feeding fish with clean fish food can be an effective practice to diminish MeHg contamination in farmed fish.

Abstract:In recent years, with the improvement of production and living needs, surimi products as a product of intensive processing, production and consumption are gradually increasing. Silver carp (Hypophthalmichthys molitrix) is low in price and large in output. But because of the existence of endogenous protease, it will lead to low gel strength and poor texture characteristics, and therefore the utilization rate of fish is not high. Improving production value and promoting its high value utilization has become a research hotspot. Transglutaminase (TG) is involved in the catalytic protein cross-linking reaction that improves the breaking force, hardness and water holding capacity of surimi products. However, with the increase of cross-linking degree of the product, the digestibility showed a downward trend, which was difficult to digest. In order to explore the changes of gel properties of silver carp myofibrillar protein during TG catalysis, further enhance the characteristics and nutritional value of silver carp surimi products, in this paper, myofibrillar protein (MP) of silver carp was catalyzed by TG for different time periods (0, 15, 30 and 60 min). The cross-linking extent, gel strength, whiteness, water-holding capacity, microstructure and digestive characteristic changes were analyzed to investigate the effect of TG on its gel properties and digestibility. The experiment results showed that the cross-linking extent of MP gel significantly increased after TG-induced protein gelling (P<0.05). At 30 min, the crosslinking degree was the highest, reaching 61.21%. The gel strength of protein increased by 186.68% compared with that of non catalyzed group. In the process of TG catalysis, the whiteness and water-holding capacity increased with the prolonged crosslinking time. At 60 min, the L^* and whiteness value increased by 5.37% and 5.30% respectively. Scanning electron microscope (SEM) analysis showed that the pore size of the gel network structure became smaller and denser. Under the catalytic time of 30 min, the cross-linking extent, whiteness and water-holding capacity significantly increased (P<0.05), and the relaxation time T₂₂ significantly decreased (P<0.05). The TG-induced MP gel had a low degree of hydrolysis in the initial stage of digestion, because the cross-linking extent increased and the protein network structure became denser and denser, which reduced the accessibility of pepsin to its hydrolysis site. After the digestion time reached 90 min, the protein network was destroyed and the hydrolysis rate increased significantly. These results suggested that appropriate crosslinking time can help to improve the gel properties of protein gels. This study provides an experimental basis for improving the quality and digestive characteristics of fish products by TG.

Abstract:Pseudocaranx dentex belongs to Actinopterygii, Perciformes, Carangidae, Caranginae, Pseudocaranx, and it is widely distributed in the warm waters of Indo-Pacific and Atlantic Ocean. It is mainly distributed in the South China Sea and East China Sea. The research on the breeding of P. dentex in China is still in the initial stage, and there are few reports about the genetic background of this species. As a species with high nutritional and economic values, it was studied from the perspective of molecular biology. The complete mitochondrial genome of P. dentex was obtained by second-generation sequencing and analyzed through the related software. The results showed that the mitochondrial genome was a typical circular DNA structure, with the total length of the sequence 16 570 bp, and the base composition was A (27.2%), G (17.18%), C (30.24%) and T (25.38%). It contained 13 protein-coding genes, 22 tRNA genes and 2 rRNA genes. Except for ND6, tRNA^Gln, tRNA^Ala, tRNA^Asn, tRNA^Cys, tRNA^Tyr, tRNA^Ser, tRNA^Glu, tRNA^Pro, all the other genes were encoded on the H-strand. Except for ATC and ATA, the starting codon of CO Ⅰ and ND5 were ATG; the A + T contents of mitochondrial genome and protein encoding genes were 52.58% and 51.55% respectively, and the noncoding control region (D-loop) is rich in 61.69%, which had an obvious A+T bias. Among the 22 tRNA genes, except for tRNA^ser-GCT, the other 21 tRNA genes contained typical secondary structure of clover. The phylogenetic tree was constructed with the complete sequence of mitochondrial genome of 18 species belonging to 13 genera of Carangidae fishes. Each species has an independent branch, and P. dentex and Carangoides equula belong to the same branch in the evolutionary tree, which indicated that these two species are closely related to each other. Our findings could help to explore the genetic relationship between P. dentex and other Carangidae fish, and provide a basis for germplasm identification, phylogenetic evolution analysis, genetic diversity evaluation and utilization of P. dentex.

Abstract:Polyketone (POK) material is an engineering plastic copolymerized by carbon monoxide and olefins (ethylene, propylene). It has good tensile properties and excellent impact resistance, and is expected to become a new fishery material. In order to explore the suitability of POK monofilament materials for fishing, the thermal properties, dynamic mechanical properties, creep properties, mechanical properties and wear resistance of POK monofilament were comprehensively tested and analyzed by differential scanning calorimeter, dynamic mechanical properties analyzer, universal tensile testing machine, abrasion tester and other equipment. The results showed that: the crystallinity of POK monofilament is 38. 44%,the melting temperature is 200. 8 ℃, and the use environment temperature can reach 150 ℃. Compared with the UHMWPE monofilament and polyamide (PA) monofilament of the same diameter,the modulus of POK monofilament is the largest (118. 04 MPa) at the same temperature, and it also has a better mechanical modulus at low temperature (0-20 ℃). The creep test shows that the tensile strain of POK monofilament is about 9%. The advantage of POK monofilament in the long effect of rope net is obviously higher than that of UHMWPE monofilament and PA monofilament. In the knotting state, the knot breaking load of POK monofilament is higher than UHMWPE monofilament and PA monofilament of the same diameter in both dry (3. 96 daN) and wet (4. 02 daN) conditions. In addition, the wear resistance of POK monofilament is excellent. Under the same friction conditions, the rate of retention strength of POK monofilament in the dry (wet) state is 58. 38% (60. 90%), which is also higher than that of UHMWPE monofilament and PA monofilament with the same diameter. Research shows that compared with UHMWPE monofilament and PA monofilament of the same diameter, POK monofilament has abrasion resistance, high temperature resistance, high modulus, low creep, high nodular strength, and its comprehensive performance and adaptability are good,which provides theoretical and technical support for the development and industrial application of POK monofilament rope netting for fishing. With the far-reaching sea cage aquaculture, large fence aquaculture, Antarctic krill fishery and tuna seine fishery development of modern fishery, fishing fiber should possess wear resistance, anti-pollution function, degradation performance, creep resistance. In order to meet the high-quality development needs of modern fisheries, through further technical research and development, it is expected to develop new modified POK monofilament materials with antifouling function,degradation function and high strength performance in the future. Therefore, POK monofilament has a broad application prospect in fisheries, and can be used as fiber materials in fields such as deep sea cage, breeding fence, and ocean fishing gear. However, there is a long way to go and further research is needed.

Abstract:The traditional rice-crayfish coculture systems may develop a novel sustainable agriculture by clarifying whether crayfish is serving as a stimulus for rice growth. In order to investigate this mechanism, the experiment selected Cherax quadricarinatus as the cultured species and compared rice root exudates (organic acids, amino acids and phenolic acids) and microbial community structure in integrated rice-crayfish farming (RSC)and rice monoculture (RMC). Gas chromatography/mass spectrometry (GC–MS) and Illumina MiSeq sequencers were adopted as the research method. The results showed that the secretions of malic acid, tartaric acid, maleic acid, isoleucine, serine, total organic acids and total amino acids in rice roots were increased significantly in coculture system during the grain filling stage, with the gap reaching 29.07% ,61.84%,10.8%, 136.11%, 218.54%, 21.50% and 12.69% respectively compared to the control group; The total amount of p-hydroxybenzoic acid, coumaric acid and phenolic acid decreased by 20.38%, 25.5% and 9.48%. In the hard dough stage, the abundance of Methylomirabilota and Latescibacterota were increased in integrated farming system by 101.11% and 48.86%, respectively; At the genus level, the rice-crayfish integrated model significantly increased the abundance of Vicinamibacteria-norank and Latescibacterota-norank by 22.96% and 48.23%. Correlation analysis showed that the total amount of organic acids and phenolic acids secreted by roots were negatively correlated with Chloroflexi and Actinobacteriota. Similarly，tartaric acid, isoleucine, serine and total organic acids were negatively correlated with Actinobacteriota. In contrast, tartaric acid and serine were positively correlated with Vicinabacteria-norank. In conclusion integrated rice-crayfish farming could significantly enhance the secretion of organic acids and amino acids in rice roots and tap sufficient carbon source for the microorganisms of Methylomirabilota, Latescibacterota, Latescibacterota-norank and Vicinamibacteria-norank, thus to stimulate their accumulation in rice rhizosphere and accelerate the release of soil nutrients. These findings provide unique insights into how positive interactions between crayfish and rice root properties in terms of efficient nutrient absorption and how modern agricultural systems might be improved by boosting grain yield and quality.

Abstract:Wind power, as one of the important clean energy sources, has been highly valued by all countries in the world to reduce carbon emissions in the power industry and achieve the goal of carbon neutralization. With the continuous development and utilization of onshore wind power, space resources of onshore wind farms are becoming increasingly scarce. Human beings are beginning to bring the wind power industry into the broader ocean. The coastline of China is long and close to the power load area. In recent years, offshore wind farm construction has achieved rapid development. Offshore wind power will become one of the main directions of renewable energy development in China in the future. During the construction and operation of offshore wind power projects, noise and electromagnetic pollution may occur, which may have a certain negative impact on marine life. Research and evaluation of wind farms is the prerequisite to ensuring the sustainable development of wind farms. In this paper, the literature on the Influence Factors of fishes in offshore wind farms is sorted out and analyzed. It is summarized as follows: at present, there are fewer types of research on acoustic effects of offshore wind farms at home and abroad in field investigation, construction period, operation period, and outage period, and fewer studies on marine invertebrates, marine mammals, and benthos. Piling is the main construction stage, which produces high-intensity short-term impact noise to fish. Fish will startle and swim within a certain range, produce stress response, increase breathing frequency, and reduce the ability of bio-acoustic detection, thus increasing the risk of predation, but it has no significant impact on the natural mortality rate. Noise generated during the operation of offshore wind farms can disguise fish communication and direction signals and lead to stress response, but will not cause physiological damage or sustained avoidance response. As far as the influence of electromagnetic fields generated by offshore wind farms is concerned, excessive magnetic field intensity will delay the development of fish embryos, significantly affect their biochemical indicators, and even kill them. Some fishes, such as eels, are positioned by magnetic fields, which reduce the speed of fish swimming in offshore wind farms but do not significantly affect the overall migration behavior. Pile foundations of fixed offshore turbines have similar aggregation effects on fish as artificial reefs, so they will increase fish habitats and thus have a positive impact on species diversity. Long-term effects of noise and electromagnetic fields on fish health during offshore wind farm operations have not been determined. We suggest that in the future, we need to study the effects of sector noise on different species, different life cycle stages, and different perceptions of the sound structure of fish, as well as on the physiology and genetics of fish. Systematic research, combined with laboratory and field experiments, has proved the mechanism of its effects on fish and established relevant research standards and preventive measures.

Abstract:Interleukin-12 (IL-12) is an important cytokine that connects the innate and adaptive immune systems and has been shown to play an increasingly important role in immune and inflammatory responses. The study of IL-12 in fish is mainly focused on cloning and expression, but the study of IL-12 in Megalobrama amblycephala, one of the economically important freshwater fish, has not been reported yet. Therefore, in this study, four IL-12 subunits in M. amblycephala were cloned, sequenced and phylogenetically analyzed; the expressions of IL-12 in healthy tissues and after infection by Aeromonas hydrophila in vivo and stimulated by LPS in vitro were detected; and the function of the recombinant proteins of IL-12Bb and IL-12BC was verified. The results showed that the open reading frame (ORF) sequences of IL-12A、IL-12Ba、IL-12Bb and IL-12Bc were 588, 993, 939 and 837 bp, respectively. Quantitative real-time PCR (RT-qPCR) results showed that the four IL-12 subunits were expressed in all the 10 different healthy tissues tested, but their expression patterns were different. After intraperitoneal injection of A. hydrophila, the M. amblycephala IL-12 subunits were significantly induced in the immune-related tissues. After LPS stimulation, the four IL-12 subunits were rapidly induced in the head-kidney lymphocytes (HKL) of M. amblycephala. Furthermore, the recombinant IL-12Bb and IL-12Bc proteins were obtained by Escherichia coli prokaryotic expression system, and then were used to stimulate HKL. The results showed that the expressions of TNF-α, IL-1β and IFN-γ in the stimulated HKL were significantly up-regulated, indicating that the obtained recombinant proteins had biological activity. Finally, the antimicrobial activity of the obtained protein was tested, and the results showed that the recombinant IL-12Bb and IL-12Bc monomers had obvious inhibitory effects on A. hydrophila, E. coli and Staphylococcus aureus. The above results of this study indicate that IL-12 plays an important role in the process of regulating immune response in M. amblycephala, which will provide theoretical basis for further study of IL-12 in fish.

Abstract:Mytilus coruscus is an important marine cultured shellfish in China, and it is also a fouling organism. Once the larvae of M. coruscus have the ability of the settlement and metamorphosis, they need to undergo behavior changes and body structure remodeling, complete the settlement and metamorphosis, and start benthic life. If the larvae cannot complete the settlement and metamorphosis, they eventually die. Therefore, the settlement and metamorphosis is very important for the normal development and population maintenance of M. coruscus. Previous studies have shown that biofilm can significantly improve the settlement and metamorphosis rate of larvae. In addition, lipopolysaccharide (LPS) plays an important role in the process of biofilm formation. To explore the effects of LPS on the formation of marine bacterial biofilm and the settlement and metamorphosis of mussel larvae, this study used firstly different concentrations of LPS to directly stimulate the larva of M. coruscus to observe the direct effect of LPS on larval metamorphosis. In addition, the biofilm was formed by adding different concentrations of LPS and Pseudoalteromonas marina, to analyze the changes in biological characteristics of the biofilm and the influence of the changed biofilm on the metamorphosis of the mussel larvae. The results showed that LPS at three concentrations could directly induce metamorphosis of M. coruscus larvae. The bacterial density and thickness of biofilm treated with 10.0 mg/L LPS were significantly decreased, especially the thickness of biofilm decreased by 12.1%. After being treated with 10.0 mg/L LPS, the polysaccharides and lipids in extracellular products were significantly increased, the content of colanic acid increased by 35.4%, and the induction of larval metamorphosis was also increased by 53.3%. Thus, LPS has a direct effect on the settlement and metamorphosis of M. coruscus larvae, and LPS might indirectly affect the settlement and metamorphosis of M. coruscus larvae by regulating the production of extracellular substances in the biofilm, especially colanic acid. The finding of this study is helpful for underpinng the mechanism of biofilm regulating the settlement and metamorphosis of M. coruscus, improving seedling production technology, and providing a theoretical basis for marine antifouling.

Abstract:Interleukin 21 (IL-21) is a kind of pleiotropic cytokine, mainly through its specific receptor (IL-21R) to exercise immunomodulatory function, including promoting T cells proliferation, regulating B cells differentiation and enhance the cytotoxicity of natural killer cells (NK), and play an important role in the immune response to pathogen infection. In order to study the role of IL-21 and its receptor IL-21R in the immune response of fish against pathogenic bacteria, homologs of IL-21 and IL-21R in Oreochromis niloticus were identified, and their roles in bacterial infection and the regulation of inflammatory response were investigated. The open reading frame of OnIL-21 and OnIL-21R are 420 bp and 1548 bp, encoding 139 and 515 amino acids, respectively. The deduced OnIL-21 is a secreted protein containing an Ig-like domain. OnIL-21R is a transmembrane protein, contains two conserved cysteine residues, a FNIII domain and a highly conserved WSXWS motif of the type I cytokine receptor family. Both OnIL-21 and OnIL-21R contained multiple conserved phosphorylation sites and glycosylation sites. Expression analysis indicate that the OnIL-21 exhibited constitutive expression in the examined tissues, with the highest expression in skin. OnIL-21R was also widely expressed in multiple tissues, with the highest expression in gill and spleen. In addition, the OnIL-21 and OnIL-21R expressions are significantly up-regulated in spleen and anterior kidney following challenges of Streptococcus agalactiae and Aeromonas hydrophila in vivo and in vitro, and maintained high expression level within 72 h, which suggested that OnIL-21 and OnIL-21R may get involved in host defense against bacterial infection. Further, after being stimulated with recombinant protein (r)OnIL-21 in vitro, the expressions of OnIL-21R and inflammation-related cytokines such as interleukin-1β (IL-1β), tumor necrosis factor α (TNF-α), interferon γ (IFN-γ), interleukin 6 (IL-6) and interleukin 10 (IL-10) were up-regulated significantly in spleen lymphocytes, which indicated that OnIL-21 and OnIL-21R may play an important role in immune response. Taken together, the molecular biological characteristics of OnIL-21 and its receptor OnIL-21R were described systematically. It also preliminarily clarified that OnIL-21 and OnIL-21R were likely involved in host defense against bacterial infection and may have an important effect on the inflammation response of O. niloticus, which may provide an important reference for further exploring the mechanism and signaling pathway of IL-21 regulating the immune response of the inflammatory responses through its specific receptor IL-21R.

Abstract:Gelatins are natural polypeptide polymers obtained by partial hydrolysis of collagens. Due to their unique functional properties such as emulsifying, film-forming, foaming, gelling and excellent biocompatibility and biodegradability, gelatins have been widely explored and applied in food processing industry. Mammalian gelatins take up the main gelatin market share, but considering religious factors and health concerns, the application of mammalian gelatins in food processing industry has been restricted and questioned. Fish skin gelatins have similar functional properties to mammalian gelatins, and they can meet the requirements of people with special cultures and needs such as Islam due to the special sources, gradually becoming a key research object in food processing industry. In order to comprehensively introduce the application of fish skin gelatins in food, this paper summarizes in detail the use of fish skin gelatins as emulsifier, foaming agent, clarifier, thickener and gelling agent, as well as edible packaging, edible coating, emulsion and microcapsule, nanofiber and hydrogel preparation materials in food processing industry. Due to their unique functional properties, fish skin gelatins have shown better biological safety and processing characteristics than mammalian gelatins. Therefore, fish skin gelatins can be used as food additives, food packaging materials and active substance encapsulation materials in food processing industry. Thus, fish skin gelatins have good application prospects in food processing industry and are expected to become good substitutes for mammalian gelatins. This review paper can provide a basis for the future studies on improving the functional properties of fish skin gelatins and expanding their applications in food processing industry.

Abstract:To explore the differences of growth and nutrient composition for Scylla paramamosain under different water conditions, Aleken classification method was used to classify the aquaculture water of the Yellow River Delta group (DY), saline-alkali group (ZD) and Sanmen group based on the ion composition; The t-test method was used to compare the growth of S. paramamosain in 3 groups by measuring the morphological indicators and calculating the condition factor. The amino and fatty acid content of hepatopancreas and muscle were measured, and principal component analysis and cluster analysis were used to analyze the amino acid and fatty acid composition of each group of S. paramamosain. The results showed that the fatness of the 90-day-old crabs in 3 groups was between 0.54 and 0.89, ZD and DY groups were significantly higher than the SM group, while the 140-day-old crabs had no significant difference in the fatness between 3 groups. 20 kinds of amino acids and 26 kinds of fatty acids were detected. The total amino acid contents (TAA) of the hepatopancreas and muscle of 3 groups of crabs were 3.94-6.87 and 9.73-12.42 g/100 g, respectively, and the SM group was the highest. The ratio of total unsaturated fatty acid content of hepatopancreas and muscle of S. paramamosain to total fatty acid content (TUFA/TFA) was 59.68%-68.80% and 70.08%-73.79%, respectively. Among others, the content of C20:5n-3 (EPA) in hepatopancreas of the ZD group was the highest in each group; the results of principal component analysis and cluster analysis respectively showed that the ZD group is distinct from other groups in amino and fatty acids content, but not significantly, while the cluster analysis results of the amino and fatty acid contents were similar in each group. This study showed that compared with normal seawater, the growth rate, plumpness, amino and fatty acids contents of S. paramamosain in saline-alkali aquaculture were not much different, and some indicators were dominant. To ensure the growth rate and aquaculture production, appropriate supplementation of Mg²⁺ and K⁺ in the breeding process can be used in saline-alkali water aquaculture of S. paramamosain. This study provides a reference for the breeding and the cultivation of S. paramamosain in saline-alkali water aquaculture.

Abstract:To understand the synthesis, secretion and immune functions of type I interferons (IFN) in Ctenopharyngodon idella, CiIFNa and CiIFNd were expressed in Escherichia coli (E. coli) cells and purified. The mature peptides of CiIFNa and CiIFNd were cloned into pET-21d and pEHISTEVb expression vectors, respectively, and transformed in E. coli Rosetta cells. The recombinant proteins were expressed as inclusion bodies after IPTG induction. Following denaturation with guanidine hydrochloride, renaturation and concentration, the recombinant proteins were purified by size exclusion chromatography and used for immunization of mice. Hybridoma cells were obtained using the PEG method and injected into the abdominal cavity of mice to generate ascites. Four monoclonal antibodies of CiIFNa and CiIFNd (2 antibodies each) were purified, and characterized by SDS-PAGE, ELISA, Western blot and immunofluorescence assay. It has been shown that the monoclonal antibodies produced had good specificity and high titers against the antigens and could specifically recognize recombinant proteins expressed in E. coli and eukaryotic cells. The CiIFNa antibodies did not react with CiIFNd and vice versa. Taken together, the CiIFNa and CiIFNd monoclonal antibodies prepared in this study may provide the basis for further in-depth study of the cellular sources and protein expression profiles of IFNs in grass carp.

Abstract:In order to explore the effects of different carbohydrates levels on gill tissue structure, antioxidant capacity and immunity of the gill tissue of Micropterus salmoides, three kinds of isonitrogen and lipid feeds with different carbohydrate levels were designed: 7% (L group), 12% (M group), 17% (H group). 360 fish were selected and fed for 8 weeks with an initial weight of (4.0±0.2) g. Through the study of tissue sections, anti-oxidation enzyme and immunoenzyme activity determination, and related mRNA expression, the effect of dietary carbohydrate on gills were analyzed, the results showed that diet in 17% carbohydrate feed can cause the proliferation and fusion of the base cells of the gill lamella, and the shedding of epithelial cells; the content of malondialdehyde (MDA) in the 17% carbohydrate feed and 12% carbohydrate feed was significantly higher than that of 7% carbohydrate feed; the superoxide dismutase (SOD) and peroxidase (CAT) of gill tissue in 17% carbohydrate feed and 12% carbohydrate feed were significantly lower than 7% carbohydrate feed; Antioxidant enzymes (CAT, GPX, SOD1, SOD2, SOD3a and SOD3b) mRNA levels in 17% carbohydrate feed and 12% carbohydrate feed were also significantly lower than 7% carbohydrate feed; in 17% carbohydrate feed and 12% carbohydrate feed acid phosphatase (AKP), alkaline phosphatase (ACP) and lysozyme (LZM) were also significantly lower than the 7% carbohydrate feed; the mRNA levels of immune-related genes (IL-1β, IL-10, IL-15, TNF-α and TGF-1β) and antimicrobial peptides (hepcidin-1 and hepcidin-2) in the 17% carbohydrate feed and 12% carbohydrate feed were significantly lower than those in 7% carbohydrate feed; the apoptosis-related genes(caspase-3, caspase-8, caspase-9) mRNA level in 17% carbohydrate feed were significantly higher than that of the 7% carbohydrate feed and 12% carbohydrate feed; the occluding and claudin-7 mRNA levels of the 17% carbohydrate feed were significantly lower than those of the 7% carbohydrate feed and 12% carbohydrate feed.The study showed that: under the experimental conditions, 17% carbhydrate feed will damage the gill tissue structure , reduce the antioxidant capacity and immune capacity of Micropterus salmoides.

Abstract:Pyropia haitanensis lives in the mid-high tide area, and will suffer from periodic strong light stress after the ebb tide. However, the thallus can quickly return to normal growth after high tide rehydration, which indicates P. haitanensis has a strong ability to resist high light. To explore the mechanism of high-light resistance, two new strains of P.haitanensis with significant differences in high light resistance were selected for the experiment (green strain: 9-Ⅳ; orange strain: WO141-3). The physiological indexes such as photosynthetic rate and antioxidant enzyme activity of the two strains under high light stress were measured, the differential transcriptional expression profiles of the two strains were constructed and the key pathways and genes regulating the high light resistance of P. haitanensis were obtained by combining with fluorescence quantitative analysis technology. Result showed that under high light stress, the content of MDA in the thallus of the two P. haitanensis strains increased significantly, the expression of some genes in the photosystem was appreciably decreased, and the photosynthetic capacity of the algae was decreased noticeably. Further analysis showed that the WO141-3 strain had stronger high light resistance after 1 h of high light treatment, while the 9-Ⅳ strain had stronger high light resistance after 4 h of treatment. The main reasons for this difference were: Under high light stress for 1 h, the WO141-3 strain had higher reactive oxygen species scavenging ability and stronger non-photochemical quenching ability, lower pigment content and light-harvesting protein gene expression.Under high light stress for 4 h, 9-Ⅳ strain had stronger ability of scavenging reactive oxygen species and stronger non photochemical quenching, lower pigment content and light harvesting protein gene expression. Studies have shown, P. haitanensis can respond to high light stress by activating non-photochemical quenching mechanism and antioxidant system, reducing pigment content and light harvesting protein gene expression, so as to avoid excessive light damage and oxidative damage. The results of this study laid a theoretical foundation for elucidating the mechanism of high light tolerance of P. haitanensis.

Abstract:In order to explore effects of dietary Haematococcus pluvialis on growth, antioxidant enzyme activity, immune response and ammonia tolerance in yellow catfish. Yellow catfish (5.00±0.85) g was selected as the study object. The four diets were formulated to contain four graded dietary H. pluvialis levels: 0.00% (control), 0.30%, 0.50% and 1.00%. Each diet was randomly assigned to triplicate groups of 30 fish twice daily to apparent satiation. The experiment lasted for 10weeks. The results indicated that fish fed the diet containing H. pluvialis more than 0.30% showed the highest weight gain rate and hemoglobin content, and the lowest feed conversion ratio and white blood cell count. Serum superoxide dismutase and glutathione peroxidase activities and malondialdehyde content of fish fed 0.50% H. pluvialis diet were lower than those of fish fed other diets, but serum lysozyme activity was higher. Cumulative mortality and blood ammonia level in fish fed 0.50%~1.00% H. pluvialis were lower than those of fish in control group after being exposed to ammonia for 96 hours. Dietary supplementation of H. pluvialis significantly increased the contents of ammonia metabolism enzymes in liver of fish exposed to ammonia, and the contents of carbamyl phosphate synthase and argininase were significantly increased with the increase of the H. pluvialis levels. The results showed that dietary supplementation of more than 0.30% H. pluvialis could significantly improve the growth, blood health status, oxidative damage and immune response of yellow catfish. The survival rate of yellow catfish exposed to ammonia can be significantly improved by adding more than 0.50% of H. pluvialis in the diet.

Abstract:Gladius is an information carrier of Cephalopoda growth, which is of great significance for the study of the age and the growth of Cephalopoda. Based on the samples collected in Eastern Indian Ocean in autumn, the relationships between gladius length and mantle length and body weight were studied. The growth differences among different mantle length groups, different populations, different maturation stages and different genders of Sthenoteuthis oualaniensis were discussed. The results showed that there was a linear relationship between the gladius length and mantle length (R2=0.980), and a power function relationship between gladius length and body weight (R2=0.950), and the mantle length had a power function relationship with the body weight (R2=0.944), too. The growth rate of S. oualaniensis increased with the increase of mantle length. There was significant difference in the growth rate between the medium and dwarf form of S. oualaniensis (P=0.000<0.05) and the growth rate of medium form (0.051-0.071 cm/d) was greater than that of the dwarf form (0.050-0.058 cm/d). The growth rate of the immature S. oualaniensis was greater than that of the mature S. oualaniensis in the medium form, while the maturity difference of the dwarf form was not obvious(P=0.253>0.05). The growth rate of the female S. oualaniensis was greater than that of the male in the medium form, while there was no difference of growth rate between the female and male of S. oualaniensis in the dwarf form. According to the analysis, the degree of fitting between gladius length and body weight was higher than that between mantle length and body weight, so the gladius length was more suitable as an indicator for growth relationship analysis than body length. The growth rate of the high mantle length group was higher than that of the low mantle length group. The growth rate of medium form was higher, because medium form had an advantage in intraspecific competition. The gonad development resulted in the decrease of growth rate of S. oualaniensis, when the medium form of S. oualaniensis entered the maturation stage. The prematurity phenomenon of the medium form resulted in that the growth rate of the male S. oualaniensis was lower than that of the female. The growth rate range of S. oualaniensis in the dwarf form was low and narrow, which was responsible for the no significant difference of growth rate of S. oualaniensis in different maturation stage and different genders. The study showed that the gladius of S. oualaniensis could be the research materials of S. oualaniensis growth and found that there were differences in the growth of S. oualaniensis in different mantle length groups, different populations, different maturation stages and different genders.

Abstract:The snails of Viviparidae, including Cipangopaludina chinensis, C. cathayensis, Bellamya aeruginosa, B. purificata etc., are commonly known as field snails, and widely distributed in freshwater areas in China. Most of the Viviparidae possess certain economic value, and their meat and shells can be used for edible, medicinal use or as feed for livestock, poultry and aquatic animals. B. aeruginosa and B. purificata are the main raw material of Liuzhou river snails rice noodle. With the rapid development of product and sales of river snails rice noodle, the demand for Bellamya is greatly increased. However, there is limited artificial cultivation of Bellamya. Presently, the freshwater snail species in artificial cultivation mainly include C. chinensis and C. cathayensis. Moreover, the facts are largely unclear that the nutritional differences exist among C. chinensis, C. cathayensis, B. aeruginosa, and B. purificata, and whether C. chinensis and C. cathayensis can be used as the main raw materials for river snails rice noodle replacing B. aeruginosa, and B. purificata. In order to examine the differences of muscle nutritional components and evaluate the nutritional values of four snails of Viviparidae, the national standard methods were adopted to determine the nutrition components in the muscle of C. cahayensis, C. chinensis, B. aeruginosa and B. purificata. The results showed that there were significant differences in moisture, crude protein and crude fat in muscle of four snail species (P<0.05), however, the content of ash was similar among the four snail species (P>0.05). The highest muscle moisture was found in C. chinensis (81.28%), which was significantly higher than those of the other three snail species (P<0.05). C. cathayensis had the highest muscle protein (13.11%), which was significantly higher than those of C. chinensis and B. purificata. The highest muscle fat content was found in B. purificata (1.05%), which was significantly higher than the other three snail species (P<0.05). There were 16 common amino acids in four snail species, including 7 essential amino acids and 2 semi-essential amino acids, of which the first limiting amino acids was methionine. In addition, the contents of umami amino acids of the four snail species were higher than 40%, and the content of glutamate was much higher than the other 15 amino acids. The proportion of essential amino acids to total amino acids (EAA/TAA) in the muscle from all four snail species was more than 33%, of which the EAA/TAA in C. chinensis and B. purificata was more than 35%, which was close to the standard recommended by WHO/FAO model (35.38%). However, the EAAI value of all four snail species was lower, less than 80 points, and the EAAI value of B. purificata was the highest, reaching 74.86. The findings of this study suggested that the muscles of the four snails were rich in nutritional composition and balanced in amino acid proportion, and all of them could provide high quality protein sources. In particular, the content of umami amino acids is rich, which has great value for condiment developing and deep processing. In addition, this study clarified the nutritional composition of four snail species, which can provide a basis for their feed preparation, and can also provide an index for the resident’s daily diet.

Abstract:Larimichthys crocea is one of the four traditional marine economic fishes in China. It is rich in protein, vitamins and unsaturated fatty acids. It is a high-quality marine aquatic product and the main cultured fish species in China. The main aquaculture methods of L. crocea are nearshore net cage, offshore net cage and net enclosure in shallow sea. Among them, the large-scale net-enclosure aquaculture is a newly developed high-end marine aquaculture mode in recent years. Several net-enclosure facilities have been constructed in Shandong province, Fujian Province and other places in China for advantages in providing the right conditions for growth which are closer to the original environment for fishes. However, it is difficult to precisely determine the positions of the fishes and to feed and harvest L. crocea for large aquaculture spaces. Therefore, it is of great significance in application to study the distribution characteristics of L. crocea in large-scale net-enclosure aquaculture. In order to obtain the distribution characteristics of L. crocea in the large-scale net-enclosure aquaculture area, a multi-function Small Unmanned Surface Vehicle equipped with the sensors of sonar fish detector, temperature, salinity, pH, illumination and dissolved oxygen has been successfully developed. The fish detector (DE-FR01 200 kHz) consisted of the single beam energy converter which can integrate transmitting and receiving ultrasonic signals. The working principle is that the acoustic signal transmitted by the energy converter propagates in water, when encountering the medium different from water, part of the signal will be reflected back. According to the time interval between of signal transmission and receiving, it can be used to measure the distance between the target and the energy converter, then analyze and process the echo signal strength (hardness), and through 4G-Network communicates with shore-based system. Finally, the depth and hardness of the target are displayed in the software control terminal. Several field trials have been carried out in Taohua Island, Zhoushan City, Zhejiang Province. By analyzing the detected fish distribution position, water temperature, salinity and illumination of the marine environment in net-enclosure aquaculture area, we obtained the findings that, ① in terms of horizontal distribution, L. crocea is mainly distributed in the areas with rich reefs and slow water flow in the large-scale net-enclosure aquaculture area; ② in the vertical distribution direction, L. crocea is mainly distributed in the middle and lower layers of the aquaculture area with weighted relative depth of 0.6~0.9; ③ the overall changes of temperature, salinity, pH and dissolved oxygen are small in the net-enclosure aquaculture area. L. crocea is often distributed in areas with relatively weak illumination intensity of (5 921±2 702), (50 799±50 988), (5 990±542), (3 494±695), (6 836±4 761) and (15 395±5 531) lx. In this study, the distribution characteristics of L. crocea in net-enclosure aquaculture area and the influence of marine environment on its distribution were studied systematically for the first time. The research results may provide the basis for the site selection of operation platform, feeding management and catching design of L. crocea.

Abstract:To explore the dynamics of microflora on diseased and healthy skin or in water samples of Andrias davidianus in natural environment, and provide microbial basis for rational aquaculture, protection of wild A. davidianus and future development of probiotics to improve the breeding of A. davidianus, in this study, the skin microflora of A. davidianus were profiled by high-throughput sequencing of the V4-V5 region of 16S rDNA gene, and the changes of skin microflora were compared between the healthy and the diseased A. davidianus. There were significant differences in the diversity, structure and function between healthy and diseased A. davidianus skin bacteria.The average number of Tag of each sample was 97 150, and the average length of sequencing was 400 bp. The OTU data showed that the microbial abundance of healthy skin was much higher than that of diseased skin. The dominant bacterium in the living water samples of healthy A. davidianus was Aliihoeflea, and after A. davidianus died, it changed to Chryseobacterium. The abundance of Chryseobacterium, Comamonas and Burkholderiales increased significantly, while that of Aliihoeflea, Exiguobacterium and Planococcus rifietoensis decreased significantly (P<0.05). Meanwhile, the skin surface of the dead Andrias davidianus had a large number of ulcers with pili, with typical symptoms of Burkella infection. Our findings confirmed that there were significant differences in skin microflora of dead and diseased A. davidianus. Burkella zoonotic bacteria might be the main cause of the death of A. davidianus in natural environment contaminated by water vector. This provided a basis for scientific breeding of A. davidianus.

Abstract:In order to study the correlation between Larimichthys crocea muscle protein and freshness quality during cold storage, the quality was judged by freshness indicators such as color, TPA, TVB-N and sensory score, water-soluble protein and salt-soluble protein were extracted from L. crocea muscle and biochemical characteristics were analyzed during storage, including protein content, total sulfhydryl content, carbonyl content, protein molecular weight and particle size distribution. The correlation between changes in freshness and biochemical characteristics of L. crocea muscle protein was analyzed. The L^*, a^* and W values of L. crocea fish meat decreased, while the b^* value increased; the chewiness, stickiness and hardness of L. crocea decreased obviously; TVB-N increased from (4.42±0.21) mg/100 g to (38.46±0.87) mg/100 g, and approached the secondary freshness standard on the 8th day, but the sensory evaluation score was not acceptable on the 8th day. During storage, the content of salt-soluble protein, water-soluble protein, total sulfhydryl content, and carbonyl content of L. crocea had similar changes. The content of salt-soluble protein increased slightly in the early stage and decreased in the late stage, from (159.36±6.51) mg/g to (91.99±13.82) mg/g. The quality score decreased by 42.27%. The content of water-soluble protein decreased from (33.68±2.13) mg/g to (17.57±0.70) mg/g, and the quality score decreased by 47.77%. The contents of sulfhydryl group and carbonyl group of salt-soluble protein increased from (3.95±0.04) mol/10⁵ g pro to (1.08±0.13) mol/10⁵g pro and from (1.08±0.04) nmol/mg to (3.94±0.43) nmol/mg, respectively. The sulfhydryl and carbonyl contents of water-soluble protein changed from (4.74±0.17) mol/10⁵ g pro to (2.66±0.15) mol/10⁵ g pro and (0.21±0.14) nmol/mg to (2.67±0.25) nmol/mg, respectively. The particle size of salt-soluble protein increased from (203.32±5.44) nm to (425.40±8.63) nm during 0-8 days of cold storage, and decreased to (317.03±1.20) nm after 2 days. The particle size of water-soluble protein decreased from (190.80±0.30) nm to (144.23±1.32) nm. In the SDS-PAGE electrophoresis, there was a new protein band produced at about 30 ku, and the amount of protein was reduced. The results showed that the biochemical properties of water-soluble protein and salt-soluble protein have a good correlation with freshness, and water-soluble protein has better correlation.

Abstract:Since the industrial revolution, the concentration of CO₂ in the atmosphere has been rising due to the heavy use of fossil fuel and deforestation. As the oceans and atmosphere exchange gases, the pH of seawater decreases. According to the IPCC, if CO₂ emissions are not effectively reduced, the global surface seawater pH will fall to 7.7 by the 21st century and 7.4 by 2300. Acidification is a growing concern because of the damage it can cause to marine life. In addition, ocean acidification often does not occur in isolation, but often acts on marine life in concert with other stressors. Deltamethrin is one of the most widely used pyrethroid insecticides in the world because of its high activity and photostability to pests. Pyrethroid pesticides have little potential to pollute the environment, but they can enter organisms through the food chain and produce toxicity to aquatic organisms. Previously, pyrethroid residues of 6.36μg/L and 16.2μg/L were detected in coastal areas of Fujian and Zhejiang, respectively. At present, studies on deltamethrin toxicity to aquatic organisms mainly focus on acute and subacute toxicity tests of fish and shrimp, but few studies on shellfish. In order to investigate the toxic effects of seawater acidification and deltamethrin (DM) combined exposure on juvenile of Haliotis discus hannai, three pH values (pH 8.1, pH 7.7 and pH 7.4) and three deltamethrin concentrations (0, 0.6 and 6.0 μg/L) were used to stress juvenile of H. discus hannai. The microstructures and hardness of the shlls, the activity of antioxidant enzymes and the expression levels of genes related to stress and apoptosis in the tissues of juvenile of H. discus hannai were detected. The results showed that after the combined exposure of seawater acidification and deltamethrin for 31 days, the CaCO₃ crystal deposition of juvenile abalone shells was difficult, the aragonite became smaller and formed scattered lamellar stacking, the pores between the aragonite increased, and the hardness of the shells decreased significantly. Meanwhile, seawater acidification and deltamethrin could change the activity of antioxidant enzymes in juvenile abalone. When the pH of seawater was 7.7 and 7.4 or the concentration of deltamethrin was 0.6 and 6, the SOD activity of juvenile abalone was lower than that of the control group, and the SOD activity of juvenile abalone under the combined exposure of seawater acidification and deltamethrin was significantly lower than that of single exposure, indicating that there was an obvious interaction between seawater acidification and deltamethrin on the SOD activity of juvenile abalone. However, deltamethrin significantly increased the activities of CAT and GST in juvenile abalone under the same pH exposure. In addition, this study also observed that the expression levels of stress genes and apoptotic genes in the tissues of juvenile abalone were increased with the increase of pCO2 and deltamethrin concentration, and there was a significant synergistic effect between seawater acidification and deltamethrin exposure on the expression levels of HSP70, HSP90, Caspase-3 and FADD. In conclusion, seawater acidification and deltamethrin exposure can produce significant toxic effects on juvenile abalone and play a certain interactive role in the reaction of tissue oxidative stress and cell apoptosis in juvenile abalone.