Abstract:The germplasm resources of freshwater fish are relatively abundant in China, and the quantity of their species is enormous, which accounts for a vital part of the high-quality protein supply from aquatic animals. However, the growth, development and reproduction of freshwater fish are seriously affected by the frequent occurrence of fish diseases and culture environment stress, which restricts the healthy sustainable development of the freshwater aquaculture industry. The key constraints of limiting the development of freshwater fish culture are the weak study on genetic basis of disease resistance and anti-stress traits as well as inadequate new breeding materials. It is an effective way to conduct further research on genetic improvement and breeding of resistant traits and cultivate new freshwater fish varieties with better resistance abilities to solve these two main challenges. This article comprehensively reviews the fundamental status of breeding improved varieties of freshwater fish with disease resistance and anti-stress, summarizes the review of new varieties of freshwater fish with disease resistance or anti-stress traits from 1996 to 2023, and introduces the resistant performance indicators, adopted technical routes and actual breeding effectiveness of representative breeding new varieties. Focusing on five types of traits, namely disease resistance, cold resistance, hypoxia tolerance, low-temperature tolerance, and saline-alkali tolerance, this article reviews the main research progress in the accurate evaluation of genetic parameters, excavation of trait linkage markers, and analysis of molecular regulatory mechanism. Combined with the current research status of disease resistance and anti-stress of major freshwater aquaculture fish in China and advanced typical cases at home and abroad, this article summarizes the outstanding problems in current breeding research, such as the slow progress of cultivating new varieties with excellent resistance performance, the lag in research and development of high-throughput measurement technology for phenotypic traits, the insufficient depth of analysis of hereditary basis and regulatory mechanism of traits, and the weakness of breeding and industrial application of varieties that take into account multiple traits. With a focus on the outstanding problems faced by the breeding of resistant traits in cultured freshwater fish at present, this paper proposed to carry out research tasks in four aspects, the high-efficiency conservation and utilization of germplasm resources in cultured freshwater fish, the analysis of genetic mechanism and molecular regulatory of disease resistance and anti-stress traits, the cultivation of new varieties and germplasm creation with excellent resistance abilities, and the parental maintenance and popularization of new resistant varieties. In summary, the information of this review can provide references for researches on breeding of resistant traits of major cultured freshwater fish in China.

Abstract:Edwardsiella piscicida is widely found in the aquatic environment. It infects various economic fish and causes high mortality diseases, seriously threatening the aquaculture industry. The pathogenic mechanism of this pathogen is complex, involving various virulence factors and regulatory systems. The problem of drug resistance of E. piscicida is prominent, and prevention and control are facing particular challenges. Vaccines and antibiotics are the main means of prevention and control, but there are limitations. Probiotics and Chinese herbal medicines, as green prevention and control methods for aquaculture, show the potential to inhibit bacteria and enhance immunity. In the future, it is necessary to study the pathogenic mechanism of the bacteria further and develop new vaccines and prevention and control technologies to deal with the harm of E. piscicida. In this paper, the biological characteristics, pathogenicity and epidemic characteristics, pathogenic mechanism, virulence factors, virulence-related regulatory systems and prevention and control techniques of E. piscicida were comprehensively summarized, which provided reference materials for dealing with the harm of E. piscicida to aquaculture.

Abstract:Specificity Protein 1 (SP1), a member of the Sp/KLF protein family, is one of the earliest identified transcription factors and participates in the transcriptional regulation of many genes. This study aimed to explore the codon usage pattern in evolution process and the phylogenetic relationship among different species of SP1 and also provide references for its high heterologous expression. The software such as Codon W, Clustal X, MEGA 4.0, and SPSS were used to analyze the codon bias and evolutionary of SP1 of 4 cyprinidae fish species and 10 other species. The results showed that the Cyprinidae fish SP1 hithly preferred the codons of CUG and AUC. The mean of an effective number of codons (ENC) of SP1 was 50.57 and the value of the codon adaptation index (CAI) was between 0.184 and 0.379, which was far less than 1. The above two indexes illustrated that SP1 in different species showed codon bias. Moreover, the SP1 of four cyprinid fish showed similar codon preference. The ENC-plot analysis revealed that natural selection was the main reason for the SP1 codon usage bias. In cluster analysis, there was little difference between the phylogenetic analysis based on the CDS sequences of SP1 and the clustering analysis based on RSCU. Escherichia coli was the most suitable heterologous expression system for Ctenopharyngodon idella SP1，and the model animals Danio rerio and Mus musculus could both be used as genetic transformation receptors for C. idella SP1. This study showed that CUG and AUC were the optimal codons of SP1 in 4 cyprinids, there were differences in codon preference between species, and natural selection was the main influencing factor leading to SP1 codon preference in the 14 species. This study provides a theoretical basis for the classification, evolution and expression of Cyprinidae SP1.

Abstract:Standard technologies and models were applied to guarantee the production and supplement of high-quality protein in aquaculture. Recirculating aquaculture systems (RAS) have advantages on the level of intensive use, utilization of water resources, and command of environmental factors, and it was widely used in marine fish aquaculture. However, the higher energy consumption and more serious choices and management in fish. Offshore sea cage systems (OSCS) and offshore aquaculture nets (OANPS) take efficiency advantages of the natural environment to obtain optimal growth performance and flesh quality. Therefore, it is an efficient way to develop offshore aquaculture, promote the high-quality development of fisheries and alleviate the offshore pressure which relies on offshore facilities and pieces of equipment. Most fish find it difficult to resist severe winter in northern of China, and the ingestion and growth will be significantly influenced even if they can tolerate the low temperature. Therefore, it is an efficient way to conduct continuous aquaculture during land-sea relay. The method was applied to most marine fishes, which were cultivated in RAS and transported to OSCS and OANPS. Besides, the new aquaculture model during land-sea relay aimed to promote developments, utilization of natural resources and extension of culture spaces. Oplegnathus punctatus was popular with high economic value and broad prospects. According to previous researchers, transport stress significantly influenced the cortisol and glucose concentration in Ictalurus punctatus, Pelteobagrus fulvidraco, and Thunnus orientalis. Our research group had confirmed that handling stress as the primary stressor would influence the physiology function of O. punctatus. Meanwhile, O. punctatus of OSCS had better growth performance, physiology condition and immunity activity than RAS cultured in OANPS. So, we predicted that they would obtain optimal tolerance to stress after transport to OSCS. The study compared and explained the physiological response mechanism of O. punctatus subjected to transport stress under RAS and OSCS, aiming to explore the physiological response features and mechanisms during land-sea relay under different two kinds of culture models. Plasma cortisol (Cor), glucose (Glu) concentration, white blood cell numbers (WBC)and red blood cell numbers (RBC), hemoglobin (Hb) content, hematocrit (Hct) were analyzed by the automatic hematology analytical method. Hepatic and muscular glycogen content, hepatic superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), alanine transaminase (ALT), aspartate aminotransferase (AST) activity, malonaldehyde (MDA) content were detected by commercial kits. The hepatocyte apoptosis rate was evaluated using the TUNEL technique with a commercial kit of Fluorescein Tunel Cell (FITC) apoptosis detection. The results showed that RBC numbers, Hb content, and Hct under OSCS were significantly higher than RAS before transportation, whereas other parameters indicated no significant differences under OSCS and RAS. During transportation, plasma Cor and Glu concentration, plasma and hepatic ALT and AST, hepatic CAT and GSH-Px activity, MDA content, and hepatocytes apoptosis significantly increased under two kinds of models, whereas hepatic glycogen was significantly decreased and muscular glycogen and SOD activity had no significant changes during the whole experiment. The rate of changes of RBC number, Hb, hepatic MDA and glycogen content, Glu concentration, plasma and hepatic ALT and AST, CAT, GSH-Px and hepatocytes apoptosis rate in O. punctatus of OSCS was significantly lower than RAS. The above significant parameters accounted for 70.59% of the total indexes. The different changes of physiological indicators would recover after transportation 48 h, while RAS needed 72 h. Simultaneously, O. punctatus under OSCS had better physiological performances and stronger anti-stress characteristics than RAS during transportation and recovery. These findings offer important references and data support to optimize transportation and model during land-sea relay.

Abstract:Transcriptome sequencing was performed on eight developmental stages of Macrobrachium rosenbergii embryos, including cleavage stage Ⅰ, cleavage stage Ⅱ, blastocyst stage, gastrula stage, naupliusproprionalis, naupliusproprionalis, and flea like larva to explore the molecular regulatory mechanism of embryonic development of M. rosenbergii. A total of 156.37 Gb clean data was obtained, and 22 964 unigenes were predicted. A two-by-two comparative analysis of the embryonic samples from eight evelopmental stages of M. rosenbergii was performed, and the number of differentially expressed genes in eight embryonic samples of M. rosenbergii at different development stages were between 587 and 8 620. GO enrichment analysis of differentially expressed genes showed that up-regulated expressed genes were mainly enriched in GO functional categories related to cell development, growth, and motility. Meanwhile, the down-regulated expressed genes were mainly enriched in GO functional categories related to translational regulation, chemotaxis, antioxidant, and detoxification activities of cells. KEEG enrichment analysis found that differentially expressed genes pathways were mainly enriched in metabolic pathways related to cell growth and normal physiological and biochemical processes. This study obtained a large amount of transcriptome information on M. rosenbergii embryo and discovered differentially expressed genes related to embryonic development and their main enrichment functions and pathways, providing useful transcriptome resources for the embryo research of M. rosenbergii.

Abstract:The deep scattering layer (DSL) is crucial for marine ecosystems and oceanographic studies. It consists of dense aggregations of organisms such as zooplankton and micronekton, which form a key link in the food web, transferring energy from primary producers to higher trophic levels. Understanding the DSL is essential for assessing ecosystem health, global biogeochemical cycles, and the effects of climate change on ocean dynamics. Based on the acoustic data from October 2012 to July 2020 in the southwestern Indian Ocean, hotspot analysis and maximum entropy model were used to study the potential habitats’ distribution on hotspots of deep scattering layers under different IODs. The results showed that the maximum entropy model had a good performance with the accuracy of the model was more significant than 0.9. Dissolved oxygen had the highest contribution rate to habitat distribution, and the average contribution rate was 50.88%. The gravity centre of DSL hotspot habitats mainly moved in the northwest to southeast direction, and the most significant changes were observed during the first cold phase of IOD. DSL hotspot habitat was distributed between 30 °-45 ° S and 11-22 °C isotherms, which indicated a specific latitude correlation. This research showed that the suitable habitat changes on DSL hotspots were influenced by dissolved oxygen. The maximum entropy model could effectively predict the distribution of DSL hotspots' habitats. This study can provide new references for elucidating the spatial distribution and resource variation patterns of DSL.

Abstract:Ecological capacity assessment is an important prerequisite for fishery resource restoration and conservation. Based on the survey data of the Oujiang estuary fishery resources and ecological environment survey in March, May, August and November 2021, the Ecopath model consisting of 24 functional groups was constructed to analyze the trophic level structure and energy flow and calculated the ecological carrying capacity for Konosirus punctatus, Coilia nasus and Liza haematocheila. The results showed that the trophic level of the Oujiang estuary ecosystem ranged from 1.00 to 3.55, the trophic level of K. punctatus (2.46), C. nasus (2.97) and L. haematocheila (2.44) were lower than other fish. The evaluation of the ecosystem structure and function showed that the total primary production/total respiration (TPP/TR) was 2.276, connectance index (CI) and system omnivory index (SOI) were 0.367 and 0.217, respectively. The results indicated that most of the trophic in the ecosystem were not utilized, the primary productivity utilization efficiency was low, and the system was still immature. The current ecological carrying capacity for K. punctatus, C. nasus and L. haematocheila was 0.0189, 0.0379 and 0.0055 t/km², and the potential ecological carrying capacity, based on the Ecopath model, was estimated at 0.070, 0.065 and 0.132 t/km². When reaching the ecological carrying capacity, the TPP/TR, CI and SOI changed marginally. The stability and structure of the ecosystem of Oujiang estuary were not altered significantly, the system has a potential for continuous enhancement.

Abstract:Fish species diversity is rich across the Yangtze River basin, but fishery catches are rapidly increasing in the past decades, and declining fish biodiversity poses risks for fishes resources. However, the degree of reduction in fish diversity and the change-drove factors of fish communities in the Yangtze River are still unknown. The data from the investigation and the retrieved literature were analysed the diversity and structure of the fish community to explore the driving factors of fish diversity change and measure the change degree of fish diversity in the Yangtze River. Meanwhile, compared α and β diversity changes of fish communities at species and phylogeny levels during historical and current periods were analyzed. The results showed that 174 species, belonging to 92 genus, 22 families, and 9 orders were found in the main channel of the Yangtze River to date. Compared to the historical period, 47 native species and 27 endemic species decreased, but 11 invasive species increased in the current period. The diversity of fish community in the upper stream was significantly higher than that of the middle (P<0.05), and 43 species contributed to the diversity rates of community construction. All species and native species showed that the average taxonomic distinctness increased from history to the current at the α level, but the taxonomic distinct diversity decreased, and the loss of native species resulted in a decrease in community diversity. The β_sør values of the upper and middle communities showed significant changes at the β level, which was driven by β_sne. The β_sne.phy that changed from 0.054 to 0.085 mainly contributed to the changes of β_sor.phy between the upper and middle communities from 0.290 to 0.314 at the phylogenetic β level. The β_sor.phy for the native species did not change significantly, and the acquisition of exotic invasive species gave rise to changes in community taxonomic units, further resulting in significant changes between communities at the phylogenetic β level. By comparing the changes in fish diversity between historical and current periods, it suggested that the loss of indigenous species and the invasion of alien species had changed the spatial and temporal patterns of fish communities and significantly affected the phylogenetic diversity of fish communities, which was expected to provide theoretical support for ecological restoration in the Yangtze River.

Abstract:Artificial reefs positively affect on creating habitat, improving the water ecological environment, and enhancing biodiversity. The performance of artificial reef deployment is closely related to its biological influence scope. A total of eleven cruises of field surveys were conducted from 2019 to 2021 in the artificial reefs to explore the impact of artificial reefs on the distribution of benthic swimming species. Trap and visual census methods were both used to sample benthic swimming organisms. The response relationships between biological indicators (e.g., occurrence probability, abundance, body length and weight of individual common species, and community richness) and the distance with artificial reefs were explored based on species distribution models (SDMs). This study summarized the influence scope of artificial reefs and fitted the spatial distribution of the occurrence probability for each species to verify the scope. The results indicated species could be divided into reef-dependent, intermediate, and off-reef species types according to the response curve between species occurrence probability and the distance with reefs. The reef-dependent species preferred to locate at 0-375 m away from the reefs, and the intermediate and off-reef species types were 50-375 m and 225-879 m, respectively. The abundance of reef-dependent and intermediate species types was higher at 0-225 m away from reefs, while that of reef-off species was higher at 325-879 m. The body length and weight of reef-dependent and reef-off species were more significant at 0-225 m away from the reefs, while those of intermediate species were larger at 0-525 m. The community richness was higher at 0-225 m. The spatial distribution pattern of each species was consistent with the response relationships between indicators and the distance with reefs. This study revealed the changes in response characteristics of different benthic swimming organisms to the distance from the reefs, explored the influence scope of artificial reefs under different indicators, and provided a reference for the construction, planning, and management of artificial reef areas.

Abstract:Hippocampus abdominalis is the largest known species of seahorse, primarily distributed in the seas of Australia and New Zealand. It had faster growth rates, higher survival rates, stronger stress resistance, and easier breeding, thus introducing to China in 2016. Current research primarily focused on reproductive physiology, pharmacological effects and aquaculture ecology, while there had been no reports on genetic breeding research. Under high-density single-species breeding conditions, many breeding varieties would face the fate of germplasm degradation and restricted industrial development space unless selection of superior varieties was carried out promptly. Accordingly, this article launched the research on selecting superior varieties of H. abdominalis. We sought to identify the main phenotypic morphological traits that affect weight to explore the growth characteristics of H. abdominalis and analyze the impact of phenotypic morphological traits on weight at different ages. We randomly selected 60 individuals from 1 to 5-month-old H. abdominalis pools each month for four consecutive months, measured their weight and seven phenotypic traits, used correlation analysis, multiple regression analysis, and path analysis to analyze the relationships between traits, and used stepwise regression analysis to establish weight models for H. abdominalis of different ages. The results showed that the correlation coefficients between the measured phenotypic traits and weight at 1, 2, 3, and 4 months of age were highly significant (P<0.01), while at 5 months of age, except for the snout length, which was not correlated with weight, the other phenotypic traits were significantly correlated with weight (P<0.01). The phenotypic traits that most directly affected weight at 1 and 2 months of age were the length from the posterior margin of the cephalic branchial covered to the tail tip (r₁=0.615, r₂=0.334), with the highest degree of direct determination of weight (r₁²=37.8%, r₂²=11.2%). At 3, 4, and 5 months of age, the phenotypic traits that most directly affected weight were the width at the dorsal fin (r₃=0.792, r₄=0.619, r₅=0.397), with the highest degree of direct determination of weight (r₃²=62.7%, r₄²=38.3%, r₅²=15.8%). The regression coefficients R₁²=0.932, R₂²=0.915, R₃²=0.958, R₄²=0.932, R₅²= 0.877 for the selected phenotypic traits at different ages indicated that these selected traits were the main traits affecting weight. Using the dorsal fin width (DFW), cephalic gill covered long from posterior margin to caudal tip (CPCT), dorsal fin thickness (DFT), dorsal fin long from posterior margin to caudal tip (DFPCT), head and neck thickness (HNT), head length (HL) and snout length (SL) as independent variables, we established a regression equation to estimate the weight of H. abdominalis at 1-5 months of age. This research showed that in selecting H. abdominalis by weight, their growth characteristics should be fully considered, and the traits selected at different ages should be based on different criteria. This research could provide theoretical guidance for the weight selection of H. abdominalis, thereby improving selection accuracy and efficiency.

Abstract:Cephalopods possess the most complex brain structures among invertebrates. Due to the distinct functions regulated by various brain lobes, studying the anatomical structure of the brain and the distribution of neurotransmitters can lay the foundation for further in-depth research in neurobiology. Anatomy and histology were used to obtain three consecutive slice images of the sagittal plane, coronal plane and transverse plane, and constructed the brain atlas of Amphioctopus fangsiao to investigate the brain structure and neuronal distribution characteristics for this speicies. Neuron nuclear antigen (NeuN) was used as the primary antibody to label the mature neurons by immunohistochemical technique, and the brain tissue structure and internal neuron distribution characteristics were analyzed. The results showed that the central brain of A. fangsiao surrounded the esophagus, which could be divided into the supraesophageal mass and subesophageal mass, optic lobes were located on both sides and were connected to the central brain through the optic nerve tract. According to the structure and function of each lobe, supraesophageal mass was divided into vertical lobe complex, basal lobe complex, buccal lobe complex, optic tract complex and other regions. Subesophageal mass was consisted of anterior subesophageal mass, middle subesophageal mass and posterior subesophageal mass. NeuN immunoreactivity was observed in the central brain, and mainly concentrated in the large cells in the perinuclear layer of the subesophageal mass, and there was no NeuN immunoreactivity in the optic lobe. The brain structure and division of the A. fangsiao showed typical octopus brain characteristics, and there were structural differences in the neuronal cell types in the lobe of the brain.

Abstract:Global marine fishery resources are declining due to the effects of overfishing, climate change, and environmental pollution. Stock enhancement is considered to be an effective means of increasing the number of biological populations and promoting the sustainable development of fisheries. However, the effectiveness of stock enhancement is affected by many factors. Among them, the habitat conditions at the releasing waters directly affect the released fish's survival rate and growth rate. Therefore, before the fish were released in large numbers, it is important to evaluate the suitability of this water area. At present, the research on evaluating the suitability of the release waters is mainly to carry out the background investigation of the proposed releasing waters by sampling before releasing, including water quality, food organisms, fishery resources and other aspects. However, this investigation method was expensive. A small batch of Plectropomus leopardus was first released into the waters and then recaptured them in this study to develop a method for evaluating the suitability of fish-releasing waters. The growth characteristics and muscle nutrients of the recaptured P. leopardus and the farmed P. leopardus were compared to evaluate whether the waters were suitable for the growth of released fish. The results showed that the allometric growth factor b value of the recaptured and farmed populations of P. leopardus was close to 3, showing an isokinetic growth state. The growth condition factor a value of recaptured P. leopardus was more significant than that of farmed P. leopardus. The condition factor K value was also greater than that of farmed P. leopardus. There were no significant difference in moisture, crude ash, crude protein, crude fat, essential amino acid content, and total amino acid content in the recaptured and farmed P. leopardus muscles. The contents of monounsaturated fatty acids, C20:4n6, C20:5n3 and C22:6n3, in muscle of recaptured P. leopardus were significantly higher than those in farmed P. leopardus. There were no significant differences in other elements except manganese and selenium in the recaptured and farmed P. leopardus muscles. The lead content in the muscle of recaptured P. leopardus was significantly lower than that of farmed P. leopardus, and there were no significant differences in other heavy metals. In short, this study indicated that the habitat conditions of the releasing waters could ensure the balance and accumulation of various nutrients to meet the growth and development needs of P. leopardus. This study verified the feasibility of evaluating the suitability of fish-releasing waters based on the fish growth characteristics and nutrient composition and formed the evaluation process. It can provide new insight for evaluating the suitability of fish-releasing waters in the future and can also be used for other aquatic species.

Abstract:This experiment was conducted to investigate the effects of dietary γ-aminobutyric acid (GABA) on growth performance, serum biochemistry, body composition, digestive enzyme activity, lpl and tor gene expression of yellow catfish (Pelteobagrus fulvidraco). Four isonitrogenous and isolipidic diets were formulated to contain graded levels of GABA (0, 50, 100 and 200 mg/kg of diet) by adding GABA. A total of 480 fish with an initial average body weight of (1.26±0.01) g were randomly divided into four groups with three replicates of 40 fish each, and each group was fed with one of the diets for 56 d. The results showed that: (1) The final body weight, weight gain rate and specific growth rate of the 100 mg/kg group were significantly higher than those of the control group and 200 mg/kg group. The protein deposition rate, fat deposition rate, calcium deposition rate, and phosphorus deposition rate of the 100 mg/kg group were significantly higher than those of the control group, and the feed ratio was significantly lower than that of the control group. (2) The liver-body ratio of the 50 mg/kg group and 100 mg/kg group was significantly higher than that of the control group. Ash in the 200 mg/kg group was significantly higher than in the control group. (3) There were no significant differences in total protein, triglyceride, cholesterol, glucan, urea, aspartate aminotransferase and alanine aminotransferase among the three groups. (4) The gastric lipase in the 100 mg/kg group was significantly higher than in other groups. Trypsin in the hepatopancreas of the 100 mg/kg group was significantly higher than that of the control group. The 100 mg/kg group had a significantly higher level of intestinal lipase than the control and 50 mg/kg groups (P<0.05). (5) The tor gene expression in the hepatopancreas of the 100 mg/kg group was significantly higher than that of other groups. The tor gene expression in the intestine was significantly higher in the 200 mg/kg group than in the other groups. The intestinal lpl gene expression was significantly higher in the 100 mg/kg group than in the other groups. The study showed that the dietary addition of 50-100 mg/kg γ-aminobutyric acid significantly improved the growth performance and body composition of P. fulvidraco , and the dietary addition of 100 mg/kg significantly increased the digestive enzyme activity, lpl and tor gene expression levels. Combined with the comprehensive evaluation of growth, body composition, digestive enzyme activity, lpl and tor gene expression levels, the dietary addition of 50-100 mg/kg γ-aminobutyric acid significantly increased the digestive enzyme activity of P. fulvidraco. The optimal amount of GABA added to the diet of yellow catfish was 100 mg/kg. In summary, adding GABA to feed improved the growth performance, digestive enzyme activity, body composition and nutrient retention of P. fulvidraco, and played a positive role in the growth of P. fulvidraco.

Abstract:Sea cucumber (Apostichopus japonicus) is an aquatic economic variety with great nutritional value, and its polysaccharide is one of the main functional substances in the body of A. japonicus, which has the function of anti-oxidation and immunity promotion. With the development of A. japonicus breeding industry, the formula feed of A. japonicus puts forward higher requirements. Fucoidan is rich in fucoses, which can regulate animals’ immunity and lipid metabolism. This study investigated the effects of dietary fucoidan on growth performances, digestion, immunity, antioxidant and glucolipid metabolism of A. japonicus. A total of six isonitrogen and isoenergetic experimental diets were formulated to contain graded levels of fucoidan, which named 0.00% (D0), 0.44% (D1), 0.88% (D2), 1.41% (D3), 1.89% (D4) and 2.38% (D5) dry diets. Each diet was randomly assigned to triplicate tanks of A. japonicus with initial body weight of (16.75±0.07) g for 60 days. The result showed: ① The weight gain rate of sea cucumber in D2 and D3 groups was significantly higher than in D0 group (P<0.05). The body wall crude fat and polysaccharide contents of A. japonicus reached the maximum in D2 and D3 groups, respectively. Lipase activity in D1 and D2 groups was significantly higher than in other groups (P<0.05). Amylase activity in D3 group was significantly higher than in other groups (P<0.05). ② The activities of intestinal lysozyme and superoxide dismutase reached the maximum value in D4 group. Malondialdehyde content in group D1 was significantly lower than in other groups (P<0.05). ③ Phosphofructokinase activity in D2 group was significantly lower than that in D0 and D1 groups (P<0.05), pyruvate kinase in D3 group was significantly lower than that in other groups (P<0.05). The activity of phosphoenolpyruvate carboxykinase reached the minimum value in D2 group. The activities of fatty acid synthase and carnitine palmitoyl transferase-1 in D1 and D2 groups were significantly higher than those in other groups (P<0.05). ④ The fluorescence quantitative results showed that the expression level of GDP-mannose-4, 6 dehydrase in D2 group was significantly lower than that in D0 group (P<0.05), while fucokinase, sulfotransferase, chondroitin sulfate and synthase in D2 group were significantly higher than that in D0 group (P<0.05). The effects of dietary fucoidan could promote the growth of A. japonicus, improved the digestive, immune and antioxidant capacity of the body, increased the efficiency of lipid metabolism, and decreased the efficiency of glucose metabolism. It was found that the fucoidan could inhibit the de novo pathway of GDP-fucose, promote the salvage pathway, and up-regulate the synthesis pathway of chondroitin sulfate polysaccharide. With the weight gain rate as an evaluation indicator, quadratic regression analysis showed that the optimum dietary fucoidan of A. japonicus with body weight 16.75 g was 1.116% diet. This study can provide theoretical basis for the rational utilization of Fucoidan and the deposition of chondroitin sulfate polysaccharide in the diet of A. japonicus, and promoting the high-quality development of A. japonicus aquaculture.

Abstract:In recent years, due to the high density of mariculture, the water circulation is not smooth, the sea area's pollution is becoming more and more serious and the disease occurs frequently. Visceral white spot disease caused by Pseudomonas plecoglossicida is a common bacterial disease of Larimichthys crocea in cage culture. A recombinant Tol C domain protein named B6 was obtained by prokaryotic expression to evaluate the immunoprotective effect of Tol C (GenBank: EPB97112.1). The immunogenicity of B6 was preliminarily detected by rabbit anti-P. plecoglossicida polyclonal antiserum. Following this, a subunit vaccine was prepared by mixing B6 with alum adjuvant, and L. crocea was immunized by intraperitoneal injection. The relative protection rate (RPS) was detected 4 weeks after immunization. Meanwhile, the serum, head kidney and spleen of fish were collected at 2, 4, 6 and 8 weeks after immunization, and the serum antibody titer and the expression level of immune-related genes were determined. Finally, the head kidney and spleen of healthy and challenged individuals were both collected and made into paraffin sections to compare histopathological changes. The results showed that the molecular weight of B6 was 22 ku. The Western blot results showed that the rabbit antiserum against P. plecoglossicida could strongly bind to B6 with a single unique band. A total of four weeks after inoculation with B6 subunit vaccine, the RPS reached 72.22%. ELISA showed that the serum antibody titer increased significantly since the second week after immunization, peaked at the fourth week (log₂ value 8.65), and decreased slightly to log₂ value 6.98 in the eighth week. RT-PCR showed that the expression level of immune-related genes in the head kidney and spleen were both up-regulated with varying degrees at 2, 4, 6 and 8 weeks after immunization. Among them, the up-regulation rates of IL-1β and MHCⅠα was the largest, with 93.33 and 77.02 times each in the head kidney, and 241.13 and 131.95 times each in the spleen, respectively. Except for CD8, the expression up-regulation trend of IgM, IL-1β, CD4, MHC Ⅰ α and MHC Ⅱ β in the spleen was all higher than that in the head kidney. Paraffin sections showed that severe bleeding spots and nodules appeared in the head kidney and spleen of the control group after the challenge, accompanied by different degrees of siderophore deposition. Comparatively, there were only a few bleeding spots in the head kidney and spleen of the B6 immunized group, and no nodules and siderophore deposition. In conclusion, our study first reported the prokaryotic expression and immune protection evaluation of the outer membrane protein Tol C from P. plecoglossicida. The results showed the recombinant Tol C protein had strong immunogenicity and good immune protection in L. crocea, with a RPS of 72.22 % 4 weeks after immunization, thus was a potential candidate of subunit vaccine.

Abstract:Botiidae (Actinopterygii: Cypriniformes) is a group of small and medium-sized fish with eight genera and 62 species, which is widely distributed in Southeast Asia, East Asia and South Asia. A total of 240 sequences were obtained by PCR amplification and downloading from GenBank, covering eight genera and 20 species of Botiidae to clarify the phylogenetic relationships and the origin evolution of the family Botiidae. In this study, phylogenetic tree reconstruction, divergence time estimation and biogeographic analysis were performed using the combination of two mitochondrial genes (CO I, Cytb) and three nuclear genes (IRBP, RAG1, RH). The topology of Maximum Likehood (ML) and Bayesian inference (BI) trees based on different datasets consistently showed that the family Botiidae was a monophyletic taxa and all genera were also monophyletic taxa. The family Botiidae was divided into two major brances of the subfamily Botiinae and Leptobotiinae, of which Botiinae included Sinibotia, Ambastaia, Yasuhikotakia, Syncrossus, Botia and Chromobotia and Leptobotiinae included Parabotia and Leptobotia. The above results were well supported. The results of divergence time and geographic ancestral reconstruction indicated that the family Botiidae originated in Southeast Asia in the Early Oligocene (about 28.85 million years ago), and the genera began to diverge in the Miocene (about 24.25 million years ago), with obvious divergence of species within genera in the Late Miocene and Pliocene (about 17.17-3.79 million years ago). With the movement of the Himalayas, the family Botiidae spread and evolved westward and northward from Southeast Asia, among which the genus Botia entered the South Asian region westward, and the genera of Leptobotia, Parabotia, and Sinibotia entered the Yangtze River and Pearl River basin in China to the north. The differentiation of the family Botiidae was closely related to the movement of the Himalayas. This research has important implications for the phylogenetic relationships and evolutionary processes in the origin of Botiidae.

Abstract:The sustainable utilization and benefit-sharing of aquatic genetic resources (AGRs) is a key theme of the Convention on Biological Diversity, as well as an important topic in the negotiation on an international legally binding instrument under the Convention on the Law of the Sea on the conservation and sustainable use of marine biological diversity of areas beyond national jurisdiction. While there is consensus on its significance, the the value composition of AGRs becomes challenging to define since its connotation continuously evolves with technological progress and new applications. Different opinions on its value composition have resulted in divergence in the conceptualization and difficulties in international negotiation as well as the framing of key mechanisms in domestic law. In this context, this study aimed to analyze the value composition of AGRs from the perspective of value realization. Specifically, it developed an approach to define and evaluate the value of AGRs based on Total Economic Value (TEV) framework. To assess the value realization of AGRs, information was collected and analyzed through publicly accessible information. By categorizing and evaluating the means to utilize aquatic genetic resources, as well as its derivative and digital sequence information through the collected information, it could identify the value of AGRs. The result showed that the value of AGRs could be realized through five significant ways: commercial development, breeding, ecological use, management, and cultural value. For commercial development, the current use of AGRs was found in the fields of medicine, cosmetics and health. Combining the results with the TEV framework found that the means to realize the value of AGRs were not completely consistent with those of natural resources at the above-species level. The classic TEV framework could not be used to fully cover the value of AGRs, especially the value coming from the use of derivatives and digital sequence information. To better frame the TEV model and allow this classic model to fully contain the value of AGRs, this article proposed the modification of the TEV framework to meet the utilization of AGRs. The value of AGRs could be then composed of consumptive use value, non-consumable use value, selection value, existence value, and genetic value under TEV framework. The non-consumptive value would entail more connotation than analysis on the above-species level, such as the use of AGRs for breeding and management purposes. In comparison to resources above-species level, the value of AGRs might be reflected more on the non-consumptive level. Given the particularity of the value realization of AGRs, the modified TEV framework matched the current usage of AGRs more than the classic model and could effectively address the conceptual divergence in AGRs in the negotiation and mechanism design. With better-framed value composition of AGRs, it can lay a solid foundation for the value assessment of AGRs and promotes the establishment of a fair and reasonable benefit-sharing mechanism in an international forum.