Abstract:From the point of view of the link between animal welfare and human welfare, the potential upgrading driving force of domestic aquaculture industry was discussed, tracing from the products quality-enhancement back to the practical feasibility of the industry-upgrading from quantity to quality. This paper focuses on fish aquaculture, explores the space for improving the quality reputation of domestic fish products from the perspective of animal welfare, and systematically reviews relevant literature from the following aspects. Firstly, the 'Five Freedoms' principle and the definition scope of animal welfare were reviewed, and the development process and current situation of fish welfare were discussed by comparison with the research and development process of animal welfare in livestock and poultry industries. Secondly, focusing on the quantitative assessment of fish welfare, the literatures related to the fish welfare evaluation system were reviewed, the evaluation indicators and evaluation methods were summarized from stress mechanisms of physiological response, behavioral response and psychological/pain response. Thirdly, in view of the fish aquaculture industry, the profiles and practice status of fish welfare were analyzed and discussed, with emphasis on aquaculture production, catching and post-harvest handling. Finally, an ignored fish welfare link from catching to death was pointed out，which is the critical transform phase from live animal to food raw material. Also, a package solution of fish welfare at the quality determination period was prospected: ① to maintain the natural properties of fish to the maximum and break through the dilemma of "fresh but not tasty enough"; ② to change the current situation of sales of primary aquatic products and reduce both quantity and quality losses post-harvest by implement post-fishery industrialization; ③ to reduce carbon emissions in the supply chain by substituting freshness-locked products for live fish. In conclusion, the implementation of animal welfare at the critical transform phase is necessary to provide targeted guidance for the practicing of harvest and post-harvest handling/slaughtering, and at the same time enrich cultural value to domestic seafood products through high-quality products induced by improved animal welfare.

Abstract:Tumor necrosis factor receptor (TNFR) is an important cytokine receptor, mainly involved in biological processes such as apoptosis, host immune defense, and inflammation. In order to reveal the role of TNFR gene in the immune process of Pinctada fucata martensii, a full length of PmTNFR27 was obtained using rapid amplification of cDNA ends technology, and the expression levels of different tissues, LPS and Poly (I:C) immune stimulation and cadmium stress were analyzed by quantitative real-time PCR (qRT-PCR). Results showed that the total length of cDNA was 1,524 bp, including a 5′UTR of 186 bp, a 3′UTR of 248 bp and an open reading frame (ORF) of 1,062 bp encoding 353 amino acids. Domain prediction showed that PmTNFR27 contained a transmembrane domain and a CRD domain which is typical of the TNFR superfamily. Multiple sequence alignment indicated that PmTNFR27 has low similarity compared with other bivalve species, but its domain regions were highly conservative. Phylogenetic analysis showed that it clustered with other bivalves. In addition, qRT-PCR data indicated that PmTNFR27 was expressed in all tested tissues, with the highest expression in gill. After LPS stimulation, the relative expression of PmTNFR27 in gills reached the maximum at 3 h and decreased to the minimum at 72 h, and the maximum was 9.67 times of the minimum. After Poly (I:C) stimulation, the relative expressin of PmTNFR27 in gills was significantly up-regulated, reached the maximum at 6 h and 12 h, and decreased to the minimum at 96 h, the maximum being13.16 times of the minimum. After cadmium stress, the relative expression of PmTNFR27 reached the maximum at 3 h, and was significantly down-regulated at 24 h and 48 h. This study suggested that PmTNFR27 may be involved in the immune defense response of P. fucata martensii and could provide basis for the further study of the biological functions of TNFR in the shellfish.

Abstract:To investigate the effects of warm waste water from nuclear power plants on the long-term stress of aquatic animals, the influence of free residual chlorine on the oxidative pressure of Tegillarca granosa under different temperature conditions were studied through laboratory simulation. Water temperatures were set as 19 and 29 °C, and two different gradients of free residual chlorine concentration were set as 0.33 mg/L and 6.66 mg/L. The results showed that: ① water temperature can significantly affect the ROS level. The higher the temperature, the higher the ROS level. ② the ROS level and DNA damage of T. granosa in 0.33 mg/L group were increased significantly on day 20, which were 2.2, 2.9 times and 1.8, 2.2 times higher than those in the control group at 19 and 29 °C, respectively; the cell activity, ATPase activity and SOD enzyme activity decreased significantly; the ROS level in the 6.66 mg/L group increased significantly on day 20, which was 6.2 and 3.6 times higher than that in the control group at 19 °C and 29 °C, respectively; the DNA damage increased; the cell activity, hemocyte phagocytosis rate and ATPase activity decreased; SOD enzyme activity decreased to the minimum value of (36.4±8.4) U/(mg prot) at 29 °C on day 20. ③ two-factor analysis of variance showed that water temperature and free residual chlorine had significant interaction on the parameters of ROS level, DNA damage, hemocyte phagocytosis rate and ATPase activity. The results indicate that free residual chlorine can significantly increase the ROS level and the DNA damage of T. granosa. The combined exposure of water temperature and residual chlorine, which caused greater stress pressure on T. granosa, affected the physiological processes related to oxidative stress. In the residual chlorine discharge area, greater oxidative stress would be faced by T. granosa in summer than in winter. This study can give a reference for studying oxidative stress toxicity of marine organisms exposed to warm water combined with residual chlorine, and provide scientific basis for ecological risk assessment.

Abstract:In order to explore the mechanism of innate immunity in Onchidium reevesii under hypoxia stress, the cDNA sequence of Toll-like receptor 4 (TLR4) gene was cloned by RACE-PCR, and bioinformatics analysis was conducted. In addtion, the expression changes of TLR4, the activity changes of hemocyte, lysozyme (LSZ), superoxide dismutase (SOD) and alkaline phosphatase (AKP) under hypoxia stress were determined. The results showed that the full length of TLR4 cDNA was 3,605 bp, the length of open reading frame was 2,817 bp, and it encoded a total of 956 amino acids. The phylogenetic tree results suggest that the TLR4 gene was the closest to the TLR4 gene of Biomphalaria glabrata. The results of qRT-PCR indicated that the TLR4 gene was expressed in all tissues, and the relative expression in the hepatopancreas was the highest. The expression of each tissue increased significantly under hypoxia stress and the expression of ganglion reached its peak earlier than the other tissues at 4 h. In addition, hemocyte viability, LSZ activity and AKP activity decreased at first and then increased, while SOD activity increased at first, then decreased and finally increased, which was more sensitive to hypoxia stress than the others. The results provide a data base for illustrating TLR4 biological functions and a theoretical foundation for investigation the mechanism of the immune system in intertidal macrobenthos under hypoxia stress.

Abstract:Gracilariopsis lemaneiformis is a kind of cultivated seaweed with the second highest production in China, which is mainly used to feed abalone and extract agar, but its yield and cultivated period are limited due to the high temperature of the summer in the southern coast. As a signaling molecule, non-reducing disaccharide trehalose plays an important role in enduring high temperature, drought and other adverse stresses. To explore the role and mechanism of trehalose in the stress resistance of G. lemaneiformis, this paper investigated the effects of exogenous trehalose on the growth, stress resistance-related substances, metabolic enzymes, endogenous salicylic acid and related genes under high temperature stress using physiological and biochemical test, HPLC-MS/MS and real-time fluorescent quantitative PCR (qRT-PCR). The results showed that application of 10 mmol/L trehalose promoted the algal growth and proline content of G. lemaneiformis with 0.34-fold (3 d) and 0.30-fold increases(24 h) compared to the control, respectively. Meanwhile, trehalose significantly activated the chlorophyll fluorescence parameters and the activities of superoxide dismutase and trehalose-6-phosphate synthase, but malonaldehyde content and lipoxidase (LOX) activity were reduced. Moreover, trehalose significantly stimulated the activity and gene expression of isochorismate synthase, the key enzyme in salicylic acid biosynthesis, and the accumulation of salicylic acid (2.05-fold). Finally, supplementation with trehalose could maintain the stable increase of the gene expression level of heat shock protein 70, while the lox2 gene expression was downregulated at 12 h. All of these results revealed that trehalose could promote algal growth through scavenging the reactive oxygen species, alleviating the lipid peroxidation of the cell membrane, enhancing the accumulation of osmolytes and phytohormones and so on. This study verifies that exogenous trehalose plays a vital role in resisting high temperature, which will provide a reference for future breeding efforts to improve the stress resistance of G. lemaneiformis.

Abstract:Understanding the reproductive biology of bigeye tuna (Thunnus obesus) and quantifying size-specific parameters provides the means for accurately predicting the effects of fishing on the reproductive potential of stock and the basis for improving the assessment and management of bigeye tuna stocks. In this paper, a total number of 886 T. obesus were sampled by pelagic longline fishing in the tropical western and central Pacific Ocean (WCPO, 2°3'-11°17'S, 163°14'-173°35'E) from May 2018 to March 2019 and then their reproductive biology was investigated. The effect of biological factors, such as individual fork length, and temporal and spatial factors, such as fishing depth and month, on the reproductive traits of T. obesus was assessed by a generalized linear model (GLM) and polytomous logistic regression for the ordinal response model, combined with the circular statistics method. The results showed that the mean fork lengths of male and female T. obesus were (132.2±19.1) cm and (125.4±16.8) cm, respectively. The sex ratio (female: male) of sampled T. obesus was (0.54±0.74), and a significant negative correlation between fork length and sex ratio was detected (r=?0.263 P=0.016). Males would dominate the sample group when the fork length is greater than 140cm. The output of the GLM fit showed that there was a significant quadratic relationship between gonadosomatic index (GSI) and fork length (P<0.001), which means GSIs of T. obesus increased with fork length, peaked at a certain fork length (130-140 cm for males and 140-150 cm for females, respectively) and then decreased with fork length. Based on circular statistics, a significant effect of fishing months on GSIs was also detected. It is found that the GSIs of males in the first half of the year are higher than those in the second half (sine significant, P<0.001), while GSIs of females at the end and beginning of the year are higher than those at the middle of the year (cosine significant, P=0.021). The output of the ordered multivariate logistic model fit indicated that gonad maturity stages increased significantly with fork length (P<0.001) and gonad maturity stages of male T. obesus were relatively higher during May and July (cosine significant, P=0.004). In addition, fishing depth has a significant effect on the maturity stage of males (positive correlation, P<0.001). Fork lengths at 50% sexual maturity were (96.13±1.24) cm and (104.93±2.60) cm for males and females, respectively. The findings in this paper reduce uncertainty in current stock assessment models, which will ultimately assist the fishery in becoming sustainable for future generations and will contribute to scientific conservation and sustainable yield of this species.

Abstract:Antarctic krill (Euphausia superba) is a key species in the Antarctic ecosystem. Investigating its habitat suitability can help the sustainable use of this resource and enhance our understanding of the Southern Ocean ecosystem. Such work is also useful for assessing krill population and exploring main fishing ground. However, different model algorithms may result in large deviations in calculating habitat suitability index (HSI) for krill resource. Therefore, this study aimed to explore appropriate methods for constructing HSI models for E. superba by using environmental factors such as sea surface temperature (SST), sea surface height (SSH), sea surface chlorophyll (SSC), and sea ice concentration (SIC). Two fitting methods, Neural Network (NN) model and Univariate Nonlinear (UN) model, were used to fit the environmental factors. Six algorithms, including minimum value, maximum value, product, arithmetic mean, geometric mean, and weighted arithmetic mean, were combined to construct HSI models. The results showed that the neural network model better predicted the actual distribution of habitats, while the univariate nonlinear regression method yielded more consistent results. The maximum and minimum value methods showed greater differences in their calculated results, introducing larger errors compared to other approaches. The continued multiplication method produced good predictive performance, while the arithmetic, geometric, and weighted arithmetic mean methods had similar results and were more stable. The proposed methods and conclusions in this study are of guiding significance for the assessment of similar species and the prediction of their habitats in the future.

Abstract:Gymnodiptychus pachycheilus is an endemic schizothoracinae fish in China, which is mainly distributed in the upper reaches of the Yellow River and the middle and upper reaches of Yalong River (tributary of the Jinsha River). In recent years, the wild resources of G. pachycheilus have declined seriously, and it has been listed as a second-class state-protected animal of China since 2021. In order to determine the suitable age identification materials for G. pachycheilus, we studied seven age identification materials of G. pachycheilus (including lapillus, asteriscus, vertebrae, anal scale, operculum, dorsal fin spine, and cleithrum) by using 83 samples from the middle reaches of Yalong River in October-November 2020. Preliminary observations showed that there was no obvious characteristics of annual rings on the dorsal fin spine and cleithrum, and the rings on asteriscus were too dense and complex to be counted. Thus, it was concluded that dorsal fin spine, cleithrum, and asteriscus are not suitable age identification materials for G. pachycheilus. Moreover, the lapillus proved the optimal age identification material for G. pachycheilus, which had the highest clarity, as well as the highest coincidence rate (CR: 84.34%) and the lowest index of average percent error (IAPE: 1.38%) between two age readings by the same observer. However, the weight of lapillus was not suitable for age identification of G. pachycheilus. Due to the similar age readings by the vertebrae and lapillus (CR: 96.39%, IAPE: 0.52%)，the complementary readings of these two materials could make the age identification results of G. pachycheilus more accurate. In addition, the anal scale was only suitable for the age identification of low-aged G. pachycheilus (aged ≤ 5 years), and the operculum was unsuitable for age identification of G. pachycheilus. Our results have filled the research gap concerning age identification of G. pachycheilus, and provided applicable age identification materials for the basic biological studies on growth, feeding, and reproductive characteristics of G. pachycheilus.

Abstract:Environmental DNA (eDNA) technology has emerged as a revolutionary tool for biodiversity monitoring in aquatic ecosystems, offering a non-invasive, cost-effective, and highly sensitive method for detecting species presence and abundance, particularly in complex and dynamic environments like the upper Yangtze River. In order to identify universal primers that are suitable for investigating fish diversity in the upper Yangtze River using eDNA technology, this study selected ten frequently used primers that amplify gene fragments from the 12S rRNA, 16S rRNA, Cytb, and COⅠ genes. The primers investigated were Mifish-U, AcMDB07, Teleo, 12SPv, Fish16S1, Ve16S1, PSI, G, VeCB1, and FishCB. DNA samples extracted from muscle tissues of 32 commonly encountered fish species in the upper Yangtze River and three additional aquatic species not from the upper Yangtze River were subjected to amplification using these primers. The results indicated that six primer pairs could amplify all 35 fish species, with Mifish-U showing the highest amplification efficiency. In addition, the eDNA samples from three sampling sites (Pingshan County, Fuling District, and Wushan County) in the upper Yangtze River were further subjected to high-throughput sequencing using the Mifish-U primer. A total of 80 fish species were detected, including the 32 fish species used in this study, with high discriminatory power. Moreover, through high-throughput sequencing, the Mifish-U primer was utilized to qualitatively and quantitatively analyze eDNA samples from indoor farms for three fish species. The results indicated a significant correlation (P<0.05) between the biomass of Pelteobagrus fulvidraco and Carassius auratus and the number of sequences, highlighting the great potential of the Mifish-U primer for eDNA quantitative analysis. In summary, our findings suggest that Mifish-U is more suitable as a universal primer for investigating fish diversity in the upper Yangtze River using eDNA technology. This study offers important insights into the selection of primers for monitoring fish diversity in the upper Yangtze River using eDNA technology.

Abstract:The Yangtze River estuary is the largest estuary ecosystem in China. It has sufficient nutrients and provides necessary habitat, bait and breeding grounds for different ecological types of fish. With the advancement of the policy “Yangtze River Great Protection”, the key waters of the Yangtze River basin have entered a ten-year fishing ban. From the perspective of scientific research, evaluating the effects of fishing bans is an important research task and carrying out such research has an essential ecological significance for fisheries protection and recovery in the Yangtze River estuary. Based on the fishery and environmental survey data in the four seasons in 2018, the size structure characteristics and community stability were studied using the normalized fish size spectrum and stability assessment model to improve the understanding of fish community in the Yangtze River estuary. Meanwhile，the water quality of the Yangtze River estuary was evaluated using the eutrophication index method. The results showed the following. ① The size classes ranged from ?2 to 6, and all the dome of all fish size spectrum curves located in the size class of 0 and 3, indicating that the fish community was dominated by small fishes and was in a disturbed state. ② There were seasonal changes in fish communities of the North Branch and the South Branch, with the maximum fish size spectral curvature in summer (?0.04) and the minimum in autumn (?0.41) and W values of ?0.11 to 0.12 in the North Branch, and the maximum fish size spectral curvature in summer (?0.04) and the minimum in winter (?0.24) and W values of ?0.03 to 0.37 in the South Branch. ③ The average stability factor of South Branch was 0.57, while it was 0.43 in the Northern Branch, which indicated that the stability of the fish community was different in four seasons. The eutrophic coefficient indicated that the eutrophication levels of the North Branch (18.89) was higher than that of the South Branch (5.43), and there was a significant negative correlation between the eutrophication index and the stability factor, which indicated that eutrophication may have an important influence on the deviation of the community system from the stable state. In general, the size class of the fish community is small, the community stability is weak, and the water quality is eutrophic in the Yangtze River estuary. This study explored the characteristics of fish community size structure and evaluated its community stability in the Yangtze River estuary before the implement of the fishing ban in the Yangtze River basin, thus providing a preliminary research for evaluating the effect of the fishing ban on the Yangtze River estuary ecosystem.

Abstract:Genus Gymnothorax is one of the most diverse, abundant and widely distributed genera of moray eels in the family Muraenidae; there were more than 100 valid species of Gymnothorax all over the world and approximately 20-30 species recorded in China. It was a poorly known group in China, with very few studies focusing on it. To improve the species list information of the Gymnothorax resource, this study reported a newly-recorded species, G. sagmacephalus B?hlke, 1997, which was previously only recorded in Japan and eastern Taiwan, China. Two individuals of the species were collected from the coastal area of Xiamen City, Fujian Province and Shantou City, Guangdong Province. The detailed morphological characteristics of the new species were described, and the molecular identification as well as phylogenetic construction were preformed based on DNA barcoding COⅠgene and 16S rRNA gene. The result showed that, the diagnostic characters of G. sagmacephalus were: body coloration light brown, a dusky saddle-like marking on the top of head just behind eyes, and a large prominent dark triangle marking just before the dorsal-fin origin; black stripes on the abdomen extending from the gill opening to the anus; dorsal and anal fins with a white margin; body was elongate, total lengths were 19.06-19.60 times of body height; teeth were uniserial, and maxillary teeth with 8 on each side without additional inner row teeth; number of dentary teeth were 12-14; total vertebrae were 162-168. Based on the analysis of COⅠand 16S rRNA gene, the genetic distance between G. sagmacephalus and related Gymnothorax species with pure body color were: COⅠ(0.120-0.255); 16S rRNA(0.059-0.132). The genetic value of COⅠ were greater than the 2% minimum diagnostic threshold suggested by Herbert, indicating that G. sagmacephalus was an independent species. The molecular phylogenetic tree showed that G. sagmacephalus and G. albimarginatus were tightly clustered as one group, indicating their close relationship. The results clarified that G. sagmacephalus was a newly recorded species and could be found in the coastal water of mainland China, which also provides a taxonomic basis for the systematic classification and the species list revision of the Gymnothorax fish in China.

Abstract:Pelteobagrus fulvidraco，Richardson, 1846 is a typical freshwater venomous fish. Poisoning events of P. fulvidraco stings often occur, which brings great harm to human health. In order to study the venomous spines structure of P. fulvidraco, in this study, the methods of macroscopic skelet and microscopic histological section were used. The results indicated that both pectoral fin and dorsal fin of P. fulvidraco had sharp spines. Spines were surrounded by integument, which were associated with venom gland cells. The venom gland cells could secrete venom. P. fulvidraco venomous spines apparatus is composed of spine shaft, venom gland, and surrounding tissues. Macroscopic observation showed that venomous spines in dorsal and pectoral fins of P. fulvidraco had integument surrounding the spine shaft and central canal. Central canal ran through the whole spine shaft. Dorsal venomous spines were elongated, tapered, and slightly arched. Venomous spines of the dorsal fin had a sharp crest and weakly serrated posterior edge. Both anterior and posterior edges of pectoral venomous spines were serrated, but the posterior edge was serrated more obviousely. The shape, size and location of the condyle were completely different in the base structure of dorsal and pectoral venomous spines. Microscopic examination showed that the venom gland cells in the integument gathered in layers and were located between the squamous epithelium and the pigment layer. The catheter was not attached to the venom gland cells. Venom gland cells were not found in the branched bony tubes of venomous spines of the dorsal and pectoralis fin. In addition, the branched bony tubes also connect the central canal and integument. Spines of pectoralis fin are triangular as they extend distally outward, with the central canal narrowing and disappearing completely at the apex. The pectoral and dorsal fin locking apparatus could keep the venomous spines in a lodging or upright locking state, thus reducing the probability of prey breaking free, and this behavioral mechanism may be important for its adaptation to complex environments. In the future, the research on venomous fishes should be strengthened. Overall, this study can help deeply understand the structure and characteristics of venomous spines of P. fulvidraco, enrich the basic knowledge of freshwater venomous fishes, enhance people's understanding of venomous fish and lay a foundation for further research on freshwater venomous fish.

Abstract:In order to explore the effects of dietary acidifiers on the growth, antioxidant indices and intestinal health of Micropterus salmoides, five isonitrogenous and isolipid diets containing different levels of acidifiers (0%, 0.05%, 0.10%, 0.15% and 0.20%) were fed to M. salmoides with an initial body weight of (21.31±0.18) g for 64 days. The results showed that the weight gain rate and specific growth rate of largemouth bass increased first and then decreased with the increase of dietary acidifier level, and reached the maximum value in the 0.15% group. Compared with the control group, supplementing 0.10%-0.15% of dietary acidifiers significantly decreased feed conversion ratio, and significantly increased whole-body crude lipid content and protein deposition rate. The apparent digestibility of dry matter and gross energy of M. salmoides were significantly increased by dietary acidifiers (P<0.05). The intestinal lipase activity of M. salmoides was significantly higher than that of the control group after 0.15% of dietary acidifier (P<0.05). Compared with the control group, the triglyceride content and the total cholesterol content in the 0.15% group were significantly increased, and the high-density lipoprotein cholesterol content in the 0.15% group was significantly increased (P<0.05). Serum total antioxidant capacity, intestinal total antioxidant capacity and superoxide dismutase activity of M. salmoides were significantly increased (P<0.05), and serum aspartate aminotransferase activity and liver malondialdehyde content were significantly decreased by addition of 0.10%-0.15% of dietary acidifier (P<0.05). The villus length, villus width and muscularis thickness in 0.15% group were significantly higher than those in the control group (P<0.05). Compared with the control group, supplementation of 0.15% of dietary acidifiers significantly up-regulated the mRNA expression levels of antioxidant related genes (nrf2, cat and sod1) (P<0.05), and significantly down-regulated the mRNA expression level of anti-inflammatory factor (il-10) gene (P<0.05). Supplementation of 0.20% of dietary acidifier significantly down-regulated the mRNA expression levels of pro-inflammatory factors (tnf-α and il-1β) genes (P<0.05). The results of the broken line model based on the weight gain rate and feed conversion ratio showed that the appropriate supplemental amount of acidifier in the diet of M. salmoides was 0.148%-0.152%. In conclusion, supplementation with 0.15% dietary acidifier could promote the growth and antioxidant capacity of M. salmoides, reduce intestinal inflammation level and maintain intestinal health.

Abstract:To determine the effects of Clostridium butyricum on growth, body index, nutrient utilization, and intestinal structure and function of discus fish Symphysodon haraldi, C. butyricum was added in basic feed for the fish at concentrations of 0 (control), 1×10⁴, 1×10⁵, 1×10⁶, 1×10⁷ and 1×10⁸ cfu/g, respectively. After 8-week culture, no significant difference was showed on growth and body index of fish in C. butyricum-added groups. However, crude protein content and digestibility in 1×10⁵ cfu/g group increased significantly. Compared to control, height and width of midgut villi in fish fed with C. butyricum was apparently increased and mucopolysaccharide secretion level of fish in 1×10⁵ cfu/g group significantly improved. For intestinal digestive and antioxidant enzymes, the trypsin activity of fish in 1×10⁵ cfu/g group was greatly improved. Furthermore, the malondialdehyde content in 1×10⁶ cfu/g group fish was significantly decreased. Short chain fatty acids (SCFAs) were measured in fish intestinal contents, and it was suggested that acetic acid and propionic acid in 1×10⁵ cfu/g group was significantly higher than that in the control group, and the total acid content reached the maximum in this addition group, which was significantly higher than other groups. Studies have shown that under the conditions of this experiment, adding 1×10⁵ cfu/g C. butyricum to the discus fish bait can improve intestinal structure, intestinal digestion and antioxidant capacity, and increase intestinal SCFAs secretion and nutrition utilization.

Abstract:Chemokines are small molecular secreted proteins with chemoattractive properties. They have bactericidal activity and the ability to recruit leukocytes and activate immune cells. CXCL10 is a kind of CXC chemokine with specificity for CXCR3 receptors, which has been shown to mediate the generation of Th1-type immune responses and have antibactericidal effects similar to defensins. Therefore, CXCL10 might be used as an alternative to antibiotics for bacterial diseases in aquaculture industry. In this study, Pelodiscus sinensis was used to study the expression characteristics of cxcl10 and its response to gram-positive bacteria (Staphylococcus aureus) and gram-negative bacteria (Aeromonas hydrophila). The molecular characteristics and systematic evolution of CXCL10 protein in P. sinensis were analyzed by bioinformatics software. The expression and distribution of cxcl10 mRNA in healthy P. sinensis tissues and that after S.aureus or A. hydrophila challenge were detected by quantitative PCR (qPCR). The results showed that the open reading frame of CXCL10 was 303 bp, encoding a protein of 100 amino acids. The molecular weight was 10.89 ku and the estimated isoelectric point was 9.62. P. sinensis cxcl10 had 8 phosphorylation modification sites and a signal peptide. Each single strand of P. sinensis CXCL10 contains one N-terminal loop region, one α helix and three reverse parallel β-folds. Phylogenetic analysis showed a close relationship between P. sinensis CXCL10 with avian and reptile CXCL10s. P. sinensis cxcl10 basal levels were higher in the liver and heart than that in other organs of health turtles. The stimulation of A. hydrophila and S. aureus led to significant upregulation of P. sinensis cxcl10 and inflammation-related factors tnf-ɑ and il-1β in liver, spleen and blood cells. These results suggested that P. sinensis CXCL10 had a similar protein molecular structure with the cationic antimicrobial peptide. P. sinensis cxcl10 was widely expressed in various tissues of P. sinensis, and up-regulated in response to the stimulation of gram-negative bacteria and positive bacteria in immuno-related tissues. In summary, our study found that P. sinensis cxcl10 might be involved in the pro-inflammatory function of antibacterial immune process. These findings are expected to lay a foundation for further research on the antibacterial function of P. sinensis CXCL10 in vitro and in vivo, and also provide a theoretical basis for disease control in P. sinensis breeding industry.

Abstract:Cipangopaludina chinensis is an economically important aquatic snail with high medicinal value in China. To improve the technology of preserving C. chinensis and to promote the sustainable development of the snails rice noodle industry, in this study, 1,500 healthy C. chinensis with an initial body mass of (21.71±2.70) g were used to investigate the effects of survival, morphological indices, nutritional composition, fatty acids, digestive enzyme activity and antioxidant indices of storing snails for 0, 14, 28, 42 and 56 d under 4 °C anhydrous conditions. The results showed that the survival rate of snails stored at 4 °C for a short period of time (14-28 d) exceeded 93%, but after 42 days, the value fell below 78%. The liver weight and liver/body ratio of 28 and 42 d of hypothermia were significantly higher than those of the control . Compared with the control, body mass decreased by 7.6% at 56 d of hypothermia, while liver weight was markedly increased. The results of nutritional composition examination showed no difference in crude protein, crude ash and moisture of muscle between the groups, and the crude fat content showed an increasing trend, with 28, 42 and 56 d being considerably higher than the control. The glycogen content showed an overall upward trend, among which the difference between 14 and 56 d was significant. Fatty acid detection revealed that the contents of SFA and MUFA showed an overall downward trend, with 28-56 d dramatically lower than those of the control and 14 d. The PUFA contents at 28 and 42 d were notably higher than the other treatments. All digestive and antioxidant enzyme activities in this study showed an overall decreasing trend. The amylase activity of the control was significantly lower than that in 14 d, but remarkably higher than that in 42 d. Then, except for the 42 d trypsin, the lipase and trypsin content of the other treatments was substantially less than that of the control. The glutathione catalase of the 42 d group was significantly lower than that of the other groups, and the activities of superoxide dismutase, catalase and malondialdehyde at 42 d were dramatically lower than those of the control. In summary, it is shown that anhydrous preservation for more than 42 days at 4 °C will lead to a higher mortality rate of C. chinensis. After 42 d, the digestive enzyme and antioxidant enzyme activities in the body are reduced, and the internal environmental balance is disrupted, which in turn led to high mortality. During the stress period, C. chinensis mainly use protein as an energy source, and then a large amount of saturated fatty acids and monounsaturated fatty acids are consumed as energy materials, while polyunsaturated fatty acids are better retained. This study provides a scientific basis for understanding the physiological and biochemical adaptation countermeasures of snails under different times of low-temperature anhydrous preservation and improving their storage and transportation management.

Abstract:The combination of offshore wind power and aquaculture industry has developed rapidly, which can comprehensively utilize marine space, maximize the benefits of aquaculture and offshore wind power industry, and realize the simultaneous and efficient output of clean energy and high-quality aquatic products. As one of integrated development modes of offshore wind power and cage culture, the integrated system of fish cage and wind turbine using the pile foundation of wind turbines to form the fish cage is exposed to the extreme sea states with severe waves and currents. The hydrodynamic of the fish cage and wind turbine integrated system, as well as the evaluation of the structural safety of the pile foundation, are the basis for the construction of the integrated system. It is of great necessity to conduct a more systematic study on the hydrodynamic characteristics of fish cage and offshore wind turbine pile foundations. In this paper, an integrated system of offshore wind turbine and fish cage was constructed based on the wind turbine jacket of offshore wind power in Liuao, Zhangpu, Fujian Province. The finite element toolbox, Aqua-FE?, was used to investigate the impacts of different deployment depth, wave-current incident angle and percentages of biofouling on mooring rope tension of fish cage in extreme waves and currents. The relationship between the mooring rope tension at the upper end of the upstream side and the deployment depth of fish cage was fitted by nonlinear regression. The effects of waves and currents parameters, as well as mooring line tension of the fish cage, on the stress variations of the wind turbine jacket structure were analyzed by the specialized design software SACS for ocean engineering, and the safety of the wind turbine jacket foundation structure was evaluated. The results show that the increase in the deployment depth of the fish cage could reduce the maximum tension of the mooring rope, significantly improving the stress state of the integrated system. The variation of wave-current incident angles had little effect on the safety of integrated system of offshore wind turbine and fish cage; the rise of the percentage of biofouling significantly increased the maximum tension of mooring ropes, resulting in structural failures of many foundation rods of the wind turbine jacket. In summary, the fish cage can be arranged in an appropriate water depth to reduce stress. At the same time, the fouling organisms shall be cleaned in time, and the thickness of the jacket rod near the mooring point of the fish cage and the pile-soil point rod at the bottom of the jacket shall be appropriately increased to ensure the structural safety of the integrated system. The results can provide data support for further study of the forces in integrated system of offshore wind turbine and fish cage, safety evaluation of the system, and design optimization of the system.