Abstract:Distribution pattern of living resources depends on the spatial scale, and inappropriate scales may lead to misleading results. As a key species in the Antarctic ecosystem, Antarctic krill (Euphausia superba) distribution demonstrates significant spatial-temporal heterogeneity. Therefore, the distribution pattern of this species cannot be predicted effectively. In order to understand the spatial-temporal distribution pattern of E. superba resources at different spatial scales, this study preprocessed scientific survey data into 12 spatial scales (5′×5′ - 60′×60′) at 5′ intervals of latitude and longitude and carried out multi-scale analysis of this species in the Antarctic Peninsula, which is the main distributional region of E. superba resources. And the Moran's I index of E. superba density distribution at different spatial scales was also calculated. The results showed that the spatial patterns of E. superba differed in spatial scales. The density distribution of resources showed a clustering trend at 11 spatial scales. According to the correlogram between Moran's I index and spatial scale, the characteristic spatial scales of E. superba density distribution were determined as 25′× 25′, which was determined by the Moran's I index crossing the point y=0 for the first time, and 15′× 15′, which was determined by the smallest scale with no significant difference between Moran's I index and zero, respectively. This study showed that the method with no significant difference between Moran's I index and zero value was more consistent with the characteristics of E. superba resources. It was, therefore, suggested that 15′× 15′ could be the optimum spatial scale for studying the distribution of E. superba density in this region.

Abstract:Acute hepatopancreatic necrosis disease (AHPND) is the major bacterial disease of cultured shrimps, mainly caused by Vibrio parahaemolyticus associated with acute hepatopancreatic necrosis disease (Vp_AHPND). The aim of this study was to explore the anti-AHPND effect and its mechanism of immunoglobulin of yolk (IgY). Different doses of Vp_AHPND IgY agent (0, 0.2% and 0.5%) were added to shrimp feeds and immunized the juvenile L. vannamei for 28 d. The growth rate and survival rate of the juveniles, the activity of immune enzymes and the relative expression level of immune genes in shrimp hepatopancreas were measured. The resistance to Vp_AHPND infection of immunized juveniles was determined by the immersion infection. The growth experiment results showed that after 28 d of immunization, there was no significant difference in the average growth rate, specific growth rate and survival rate of the juveniles between the immunized group and the control group. The immune function test results showed that after 14 d of immunization, compared with the control group, the 0.2% immunized group (0.2% IgY agent) generated significantly higher enzyme activities for phenoloxidase (PO), superoxide dismutase (SOD) and lysozyme in the hepatopancreas. The relative expression level of antibacterial peptide (Crustin) gene was also significantly increased, while the relative expression level of β-1,3-glucan binding protein-lipoprotein (β-GBP-HDL) gene was significantly reduced in the 0.2% IgY agent group. The results of the immersion infection showed that the survival rate of the juveniles in the 0.2% IgY agent group was significantly higher than that of the control group, and the relative percentage of survival (RPS) of 0.2% IgY agent was 63.77%. In conclusion, oral administration of Vp_AHPND IgY agent will not adversely affect the growth and survival of L. vannamei. The 0.2% IgY agent can significantly enhance the immune function of L. vannamei by increasing the enzyme activities of PO, SOD, LZM and the expression level of Crustin gene, thereby improving the ability of shrimps to resist Vp_AHPND infection. This study implied that Vp_AHPND IgY agent has a strong application potential for the prevention of AHPND.

Abstract:In order to explore the relationship between spatial and temporal distribution of potential habitats of marine economic species and environmental conditions and effectively help enterprises to utilize and develop fishing grounds. Dosidicus gigas is widely distributed in the Eastern Pacific Ocean, from California (30°N) to Chile (45°S), and can reach 125°W in Equator. Based on the fisheries data of Chinese squid-jigging fishing vessels in equatorial waters from 2012 to 2018, and environmental data including sea surface temperature (SST), sea surface salinity (SSS), chlorophyll-a (Chl-a), net primary production (NPP), photosynthetically active radiation (PAR), eddy kinetic energy (EKE) and sea level anomaly (SLA), this study established the maximum entropy model (MaxEnt) to analyze the spatial and temporal variations of habitat and the influence of environmental factors from month to month. The results showed that CPUE was higher from January to March, while the fishing effort was higher from July to August. AUC of the MaxEnt model were more than 0.8 in each month, indicating that the simulation results were accurate. The spatial and temporal distribution characteristics of suitable habitat were significant in different months. The suitable habitat of D. gigas was distributed between 3°N-3°S, and gradually moved eastward from January to May. Suitable habitat began to shift to the southeast (85°-102°W, 2°-5°S) in June and moved northwestward in August. The results of contribution rate for environmental factors showed that impacts of environmental variables on habitat distribution of D. gigas in different months were significantly different. The cumulative contribution rate of key environmental factors to the model was more than 60% in each month. Overall, SST, NPP, PAR and EKE were the key environmental factors that strongly affected the habitat distribution of D. gigas. Suitable range of each key environmental factor showed significantly monthly variations. In addition, it was speculated that the distribution of suitable habitat of D. gigas was extremely sensitive to SST patterns, and currents and eddies might have a great impact on the distribution of D. gigas. The results showed that there were obvious monthly distribution characteristics in the D. gigas habitat in the equatorial waters, and the effects of environmental factors on the habitat distribution were significantly different.

Abstract:Filter-feeding bivalves provide habitats for microbial colonization. Microbes also affect the growth and development of host organisms. Mytilus coruscus not only has economic importance in China but also shows powerful immune tolerance to environmental changes. However, the underlying tissue-specific pattern of microbial communities of M. coruscus is still poorly understood. To fill these knowledge gaps, we collected 7 tissues of M. coruscus cultured in Shengsi breeding area. These tissues included hemolymph, digestive glands, kidneys, gills, mantles, gonads and feet. Through the 16S rRNA gene amplicon sequencing targeting the V3-V4 variable region on the Illumina MiSeq platform, we characterized the community structure and distribution of microbiota. On average, a total of 36 860 high-quality reads were obtained from 21 samples of M. coruscus. The highest number of OTU (1 237) was detected in hemolymph, followed by digestive glands and kidneys (1 014 and 1 015 OTUs), and the gonad had the lowest (only 553 OTUs). Although the number of OTU in hemolymph was the highest, there was only 9 unique OTUs in hemolymph. The kidney had a maximum of 172 unique OTUs, followed by digestive glands (144 unique OTUs). Compositional distribution showed that Proteobacteria, Bacteroidetes and Verrucomicrobia were the main phyla in all tissues. The Bray-Curtis distance results indicated that the bacterial composition of hemolymph, digestive gland, kidney and foot were clustered and the bacterial community from gills, gonads and mantle had higher similarity. Analysis of alpha diversity indicated that the microbiota in hemolymph, digestive glands and kidneys were more diverse than those in other tissues. The variation of indigenous microbiome was attached to different tissues of M. coruscus. Overall, our results will help improve the knowledge of mussel-associated microbial community, and provide a better understanding for revealing the interaction between the mussel and its host-associated microbiota.

Abstract:This study was conducted to evaluate and improve model performance for estimating abundance and occurrence of small yellow croaker (Larimichthys polyactis) based on the data collected from fishery independent bottom trawl surveys data in Haizhou Bay in the spring of 2011 and 2013-2016. According to different methods of processing spatial data, five species distribution models were formulated by combining the delta method with structured additive regression framework, they were compared in terms of their performance on fitness, predictive capacity and independdence of residuals for two commonly used response variables, namely, occurrence and abundance. Result showed that models with spatial covariates had significantly better fitting effect and lower residual spatial correlation, and positve model and delta model showed more improvement than binomial model. The AIC of geoadditive models was the lowest in both binomial model and positive model (respectively lower than GAM without the spatial term by 7.60 and 144.90). Varying coef?cient models had the highest R² (0.68) and fitting AUC (0.94). Geoadditive model had the highest AUC (0.793±0.100) and the lowest RMSE (21.65±4.83), indicating that geoadditive model's estimation n the occurrence probability and resource density of L. polyactis were most accurate. Therefore, we predicted the spatial distribution of L. polyactis in Spring using delta-geoadditive model based on FVCOM simulation data. Prediction result reflected the distribution and variations of L. polyactis was mainly distributes in the southern and western coastal areas (34.0°N-34.5°N，121.0°E-121.5°E), decreasing with the water depth increase and varying significantly over the years. This study aimed to provided a scientific basis for the development and protecttion of L. polyactis fishery resources in Haizhou Bay.

Abstract:Prolyl endopeptidase (PEP) is a serine protease which has been implicated in many biological processes, such as learning and memory, cell proliferation and differentiation, and glucose metabolism. A small number of reports have also suggested PEP participates in mammalian reproductive process by specifically degrading peptide hormones and gonadal hormones containing proline residues. Compared with mammals, research on PEP of molluscs is relatively scarce at home and abroad. This observation led us to investigate PEP and whether it is related to reproductive development of mollusk. We analyzed the natural PEP of Haliotis discus hannai and the protein expression level changes during gonad development. Fluorescence quantitative PCR (qRT-PCR) and enzyme activity analysis were used to detect the expression of the PEP in tissues of H. discus hannai. The enzyme activity and the expression level of PEP were the highest in H. discus hannai gonad, followed by the muscle. PEP was purified from the gonad by column chromatography with a molecular weight of 82 ku. The isoelectric point of PEP was determined to be 5.5 by two dimensional electrophoresis, and it was similar to the isoelectric point of predicted PEP of abalone. The 182 peptides were obtained by liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis, which were consistent with the H. discus hannai prolyl endopeptidase of NCBI (KY214290). The analysis of enzymatic properties showed that the optimum temperature and pH of PEP were 25 °C and 6.0, respectively, and high enzyme activity can be maintained at 15-25 °C and pH 5-8. Circular dichroism was used to analyze the effect of temperature on structure of PEP. The results showed that the secondary structure of PEP changed significantly as the temperature increased. When the temperature increases from 25 °C to 95 °C, the content of α-helix structure decreases from 12.5% to 5.8%, and the random coil increases from 24.4% to 28.0%. When the temperature was lowered from 95 °C to its optimum temperature (25 °C), the content of α-helical structure decreased by 1%, β-folding decreased by 4.6%, β-turn and random coiling structure increased by 1.5% and 2.4%, respectively, compared with the initial secondary structure at the same temperature. The secondary structure could not be restored, indicating that the thermal denaturing of PEP was irreversible. The fitting thermal denaturation temperature was (51.4±0.2) °C. In order to further analyze the protein and gene expression level of PEP in the development of H. discus hannai gonad, we divided abalone gonad development into different growth stages (preliminary, early, middle and late growth stages), and the results of Western blot and qRT-PCR analysis showed that PEP could be detected in all stages of male and female. The expression level was the highest in the middle stage of maturity of male gonad and the late stage of maturity of female gonad. These results indicated that the difference of PEP at developmental stages of H. discus hannai gonad demonstrated that it may be involved in the process of gonad development. The current study analyzed PEP of mollusks and speculated that PEP is associated with gonad development in H. discus hannai. It provides a theoretical reference for further research of the function of PEP in H. discus hannai gonad development.

Abstract:In order to scientifically predict the distribution of Sthenoteuthis oualaniensis and to utilize its resources,this study established the PCA-GAM prediction model of S. oualaniensis was established based on the production data of light seine in the open sea Arabian Sea from 2017 to 2019, combined with the data of salinity, temperature, 0, 50, 100, 150 and 200 m water layers, mixed layer thickness, sea level anomaly, chlorophyll a concentration, sea surface velocity, longitude and latitude. The correlation between environmental factors will cause multicollinearity, resulting in over-fitting of the model, and reducing the prediction ability of the model. The environmental data were transformed into a few unrelated principal components (PCs) which retained important information of these environmental factors based on the application of dimension reduction techniques such as principle component analysis (PCA). The average variance explanation rate of the top 8 PCs accounted for 87.34% (±0.86%). The top 8 PCs were taken as explanatory variables of the GAM model to construct the prediction model of the distribution of S. oualaniensis. The establishment of PCA-GAM prediction model was divided into two-stage GAM. The first stage GAM is to estimate the presence probability of S. oualaniensis. The second stage GAM is to estimate the log-transformed CPUE of S. oualaniensis. The overall log-transformed CPUE was the product of the results from the first and second stages of the GAM. The eight fold cross-validation results showed that the mean of the correlation coefficients between the predicted values and the practical CPUE (log-transformed) was 0.532 7, the mean of the slopes of the regression models was 0.708 7, and the mean of truncation values was 1.471 1. The degree of overlap between the predicted values and the practical CPUE (log-transformed) from January to April and September to December 2019 was very high in spatial distribution, which indicated that the PCA-GAM model was able to predict the spatial distribution of S. oualaniensis in the Arabian Sea.

Abstract:Preparation of marine active substances by bioprocessing technologies is a hot research topic in recent years. During the bioprocessing, it is of great significance to achieve rapid detection of the target products, while the traditional detection methods are faced with many limitations, so there is an urgent need for novel and simple analytical methods. In this study, phosphatidylserine (PS) was chosen as the model target, a colorimetric aptamer-based biosensor (aptasensor) was developed for the rapid detection of PS in bioprocessing system. The positively-charged chitosan oligosaccharides and negatively-charged aptamers firstly bound through electrostatic adsorption. In the presence of PS, the aptamers specifically bound with the PS, causing the release of chitosan oligosaccharides, which in turn adsorbed onto the negatively-charged gold nanoparticles to form nanozymes with high peroxide catalytic activity towards 3,3',5,5'-tetramethyl benzidine (TMB), producing colorimetric signals which were positively correlated with the concentration of PS. The absorbance values were collected and processed into rate of change with comparison to that of the negative samples without PS, and the rapid quantification was thus achieved. The concentration of aptamers, the concentration of chitosan oligosaccharides, and the conditions of nanozyme catalysis reaction were optimized in detail. Under optimal conditions, the developed aptasensor exhibited a good linear detection range (0.50-50.00 nmol/L) and high sensitivity, with a limit of detection (LOD) as low as 93.84 pmol/L. Moreover, the aptasensor showed high selectivity, accuracy, and repeatability. Recovery rates of 95.63%-110.76% and RSD less than 9.00% were obtained, when analyzing the PS in the actual bioprocessing samples. Only 40 min was needed for the entire analysis. In short, an aptasensor was successfully developed for highly sensitive and rapid detection of PS. The study can provide new ideas and research basis for the rapid detection method of PS as well as other biological processed products.

Abstract:Xenocypris davidi is one of the most economically important freshwater fish in China. In recent decades, owing to the construction of dams, overfishing, habitat degradation, pollution of water, and other human disturbances, the number and biomass of X. davidi local populations declined sharply. On the other hand, X. davidi can effectively restrain the aggravation of eutrophication and control the abnormal proliferation of algae. To restore fishery resources of X. davidi and improve water quality, restocking enhancement activities of X. davidi have been conducted in natural waters since the 1980s. It is urgent to carry out the evaluation of the effect of restocking enhancement of X. davidi, as well as the potential genetic risk assessment of breeding population to wild population of X. davidi under large-scale proliferation and release. However, there has been few report on the effect of restocking enhancement of X. davidi. In order to assess the effect of restocking enhancement of X. davidi and provide guidance and suggestions for the breeding and releasing of X. davidi in Qiantang River, the potential genetic risks of X. davidi in the upper reaches of Qiantang River were evaluated by using 11 polymorphic microsatellite loci. We collected 33 breeding parents and 105 recaptured individuals. Microsatellite DNA molecular marker technology was used. The number of mean alleles (N_a), the mean observed heterozygosity (H_o) , mean expected heterozygosity (H_e) and mean polymorphic information content (PIC) were 8.64, 0.708, 0.739 and 0.703, respectively. It was proved that 11 pairs of microsatellite primers as an effective tool for parentage identification. The combined non-exclusion probability (CEP) of 11 loci was 99.999 980 % by Cervus software. Five individuals were confirmed to be released. The return capture rate of the offspring is 4.76%. The comparative analysis of genetic diversity between the cultured and wild populations of X. davidi showed that the two populations had high genetic diversity, and the genetic parameters of population differed little, indicating that their genetic diversity levels were close; AMOVA analysis showed that genetic variation mainly came from within the population (95.92%), the genetic differentiation coefficient F_ST is 0.053 59, and the gene exchange value (N_m) was 4.42. The results showed that it was a low degree of differentiation and gene communication was barrier-free. So our study suggested that the stock enhancement of X. davidi in Qiantang River had produced a good resource recovery effect, and there was no potential genetic risk caused by the release. In the following studies, on the basis of making full use of microsatellite genotype data, we should strengthen the long-term and continuous tracking of the release population and the field population, so as to provide basic support for the scientific evaluation of the stock enhancement and the conservation of seed resources of X. davidi.

Abstract:Shanghai smoked fish is a traditional Chinese dish with crispy crust, delicious taste and rich nutrition, belonging to Shanghai cuisine. Traditional Shanghai smoked fish uses Mylopharyngodon piceus or Ctenopharyngodon idella as raw materials. In recent years, the amount of M. piceus farmed has declined, C. idella is a typical herbivorous fish with a strong earthy smell, and both M. piceus and C. idella have intermuscular spines, which is not convenient for the elderly and children to eat. Micropterus salmoides with abundantly nutritional values is an omnivorous freshwater bass with meat as the main food. The earthy smell of M. salmoides is lighter than that of M. piceus and C. idella. The meat of M. salmoides is tender and has no intermuscular spines, also its mouthfeel and flavor are better than C. idella, which is popular among the public. In this experiment, on the basis of the original technology, better raw materials were selected to develop new processed products for M. salmoides. In order to overcome the shortcomings of processing Shanghai smoked fish by M. piceus and C. idella, M. salmoides was used to replace C. idella in processing Shanghai smoked fish. Single factor experimental design and orthogonal experimental design were used to improve the processing technology of Shanghai smoked fish. Headspace solid phase micro-extraction gas chromatography-mass spectrometry (SPME-GC-MS) was to analyze the changes of volatile flavor active substances in deep-fried Shanghai smoked fish, Shanghai smoked fish with no spices in the fried soaking liquor and Shanghai smoked fish (final product). Key volatile compounds were detected by qualitative and quantitative analysis of gas chromatography-mass spectrometry and high-performance liquid chromatography (HPLC) was used to determine flavor nucleotides. The result showed that, better processing method is to fry M. salmoides for 6 min and then to soak it in the soaking liquor of soy sauce / white sugar=4 ∶ 3. The volatile compounds in three samples are 37, 47 and 55 kinds. Aldehydes, ketones, alcohols, hydrocarbons, aromatics and nitrogen, sulfur-containing substances are the main flavor compounds of Shanghai smoked fish. IMP is the main umami nucleotide. In conclusion, first soaking, deep-frying, and soaking after frying were the key processes for removing and concealing the earthy smell of freshwater fish. At the same time, the Maillard Reaction in the process of frying can increase the aroma of the fish and make cooked dishes with excellent aroma and rich nutrition. The Maillard Reaction, thermal degradation and fatty acid oxidation that happened in the deep-frying process help to reduce fishy smell and form the characteristic flavor of Shanghai smoked fish. Soaking and deep-frying are excellent processing methods to improve the quality of fish products.

Abstract:In order to analyze the association between mitochondrial protein-coding genes and body color traits of black carp (Mylopharyngodon piceus) and screen out SNP markers related to body color, this study selected the skin tissues of five Foshan gray black carp samples and five Hanjiang black M. piceus samples and detected the relative expression of 13 mitochondrial protein-coding genes in the skin tissues of the two color populations by qPCR, and then performed the significance analysis. The study designed primers for the CDS region sequence of the protein-coding gene with the most obvious expression difference, and then selected 78 Foshan gray M. piceus samples and 92 Hanjiang black M. piceus samples for sequencing, and screened out SNP markers based on the sequencing peak map. The results showed that among the 13 mitochondrial protein coding genes, the relative expression of ND4L gene is the most significant, the relative expression of COⅡ gene is the highest, and the relative expression of ND5 gene is the lowest. Two SNPS (C252T and A243G) were detected in the mitochondrial ND4L gene of 170 M. piceus samples. The frequencies of A and G genotypes at A243G in Foshan gray body color population are 96.2% and 3.8%, while the frequencies of T and C genotypes at C252T are 38.5% and 61.5%. The frequencies of A and G genotypes of C252T locus in Han Jiang normal body color population are 100% and 0%, while the frequencies of T and C genotypes of C252T locus are 15.2% and 84.8%. Three haplotypes, AC, AT and GC were detected. AC shows the highest frequency; AC and AT are distributed in both body colors, while GC shows the lowest frequency and only appeares in normal body colors. This study studied the distribution of genotypes and haplotypes of two SNPS in mitochondrial ND4L gene related to body color of M. piceus and provided theoretical guidance for the study of body color and growth traits of M. piceus as well as the breeding of M. piceus.

Abstract:The length-weight relationship of fish stock is one of the commonly used formulas in fishery ecology study. The length-weight relationship is significant for the assessment of fishery resources. It is often used to estimate the average weight of a given length and estimate the status of the fish stock. The accuracy of the estimates of length-weight relationship parameters for fish stock affects the stock assessment and management. Data obtained with different sampling design may have influence on the estimation of length-weight relationship parameter b of Chaemrichthys stigmatias. In order to find out the affect of sampling season and sample size on the length-weight relationship parameters, this study based on the biological data on the length and weight of C. stigmatias obtained from fishery-independent surveys conducted between 2013 and 2014 in the Yellow River Estuary, examined the influence of sampling designs on the estimation of parameter b of the length-weight relationship of C. stigmatias by using a computer simulation study. Based on the actual situation of fishery resources survey in different seasons, 15 sampling design schemes were simulated, and then the influence of different sampling designs on the estimated body length-weight relationship parameter b was compared by selecting two indexes, namely, relative estimation error and relative deviation. The results showed that the estimation accuracy of the length-weight relationship parameter can be effectively improved with the sample size increasing. The length and weight data in different seasons showed different impacts on the estimation accuracy of the parameter, and the data in summer were particularly important in improving the accuracy and precision of estimation of length-weight relationship parameter b for C. stigmatias. The precision and accuracy of parameter estimates based on the data from more seasons were usually higher than those using data in a single season. Scheme 9 (sampling in summer and winter) performed the best at the same sample size among all the fifteen sampling design schemes. The relative estimation error of parameter b of the length-weight relationship was 2.08%, and the absolute value of the relative bias was 0.71% for scheme 9 at the sample size of 540 individuals. The study indicated that enough biological data from representative seasons that have a great effect on the estimation of the parameter should be obtained when we estimate the length-weight relationship for fish populations like C. stigmatias in the Yellow River estuary. In this paper, using C. stigmatias as an example, the influence of sampling design on the estimation of length-weight relationship parameter was explored, which would provide a reference for the estimation of length-weight relationship parameter of other fish stocks.

Abstract:Insulin-like growth factor 2 binding proteins (IGF2BPs) are the important RNA metabolism regulators involved in many different biological processes. In order to study whether IGF2BP1 plays a role in biomineralization of pearl oysters, this study identified a Pinctada fucata martensii IGF2BP1 gene, named PfIGF2BP1-1. The cDNA length of the gene is 7 348 bp, with an ORF of 1 818 bp and encoding 605 amino acids. Multiple sequence alignments and phylogenetic analysis showed that PfIGF2BP1-1 has two RRM domains and four KH domains, which are homologous to IGF2BPs from other species. Real-time fluorescent quantitative PCR results showed that PfIGF2BP1-1 was expressed in eight tissues of P. fucata martensii, with the highest expression level in adductor muscle tissue, followed by foot and mantle tissue. The pET-32a prokaryotic expression vector was used to construct a recombinant plasmid containing the mature polypeptide region of PfIGF2BP1-1 and the protein was successfully expressed. The optimal conditions for inducing protein expression were that the bacteria were cultured at 37 ℃ for 8 hours with 0.5 mmol/L IPTG . The PfIGF2BP1-1 protein can stimulate the coat membrane primary cells of P. fucata martensii and significantly increase the expression level of cell matrix protein genes Accbp, MSI7, and Nacrein in primary mantle cells. The results indicated that the PfIGF2BP1-1 protein is involved in the biomineralization process of P. fucata martensii through inducing the expression of shell mineralization-related genes.

Abstract:Artificial reefs can be regarded as artificial structures in the sea. There are three methods to reflect bottom structures in large-scale ocean models: method of water depth modified treats artificial reefs as impermeable solids and reflects reefs by changing the water depth, which is applicable to impermeable reef mountains; method of bottom friction increased reflects the obstruction of water flow by structures on the seabed by increasing the bottom friction of the model, which is applicable to the simulation of submarine mussel beds and low oyster reefs; method of retarding force simulates the obstruction of water flow in different water layers by adding a retarding force term to the model momentum equation. In order to reasonably represent the permeable artificial reef assemblage in the large-scale ocean model, the hydrodynamic conditions of the proposed artificial reef area on Dachen Island were simulated based on the numerical ocean model FVCOM (An unstructured grid Finite-Volume Community Ocean Model), and the differences of vertical flow velocity, reef top plane flow velocity, upward transport flux and back eddy volume before and after reefing were compared among the method of water depth modified, method of bottom friction increased and method of retarding force. Based on the difference of flow velocity before and after reef casting, the empirical formula was applied to predict the bottom bed sediment flushing and siltation one year after reef casting. The numerical simulation results showed that by adding the retarding force term in the model, the flow velocity in the occupied water layer was reduced by 0.06 m/s compared with the time when the reef was not installed, and the maximum upward flow velocity was 0.005 m/s in the direction of incoming flow; the reduction of flow velocity at the back of the reef at the time of rapid rise can be more than 20 times of the combined length of the reef, and the maximum thickness of the bottom bed siltation after one year in the corresponding flow velocity reduction sea was about 0.05 m, the average upward water transport flux of single reef was 66 m³, and the back eddy volume was 1550 m³. Compared with the method of water depth modified and the method of bottom friction increased, the retarding force method can well represent the effect of the reef on water flow, avoiding the problem of overestimating the flow field effect in the simulation of permeable reefs by the method of water depth modified, and without the defect that the method of bottom friction increased is only applicable to low reefs. The hysteresis method is not only applicable to the bottom-set permeable reefs, but also to the study of hydrodynamics and ecodynamics of enrichment culture facilities such as floating reefs and net cages.

Abstract:Chromatophores are specialized cells that synthesize pigments in animals. They play an important role not only in coloration, but also have crucial functions in a series of biological processes such as warning, mating, camouflage, mimicry, concealment and environmental adaptation. Compared with amniotes that only depended on melanocytes to produce color pattern, teleost and other ectothermic vertebrates derived more than six types of chromatophores from embryonic neural crest, including melanophores, xanthophores, erythrophores, iridophores, leucophores and cyanophores. During embryonic development, neural crest cells differentiate into the precursors of chromatophores along the dorsal ventral axis and then migrate to specific sites to mature pigment cells, which can selectively absorb or reflect specific wavelength of light to form multiple pigment patterns and colors. So, the number and distribution area of pigment cells, the dispersion and contraction of pigment particles all affect body color formation. Xanthophores are the most concerned chromatophores, second only to melanophores. Xanthophores have red/yellow xanthosomes composed of carotenoids and pteridines, which produces a series of colors from white to red and is an ideal model for pigment cells interaction, pigmentation and animal evolution. Though many mechanisms of xanthophores differentiation and pigmentation are starting to be elucidated, few reports summarize the available progression in xanthophore biology and genetics. Thus, this review introduces the advances in research of origin and distribution of fish chromatophores, the development and differentiation of xanthophores, the regulatory mechanism of pteridine pigments synthesis and the inadequacies in current xanthophores researches. It provide useful information in fish coloration, chromatophores differentiation and molecular breeding of body color phenotype.

Abstract:In order to explore the genetic diversity and genetic differentiation status of Schizothorax biddulphi, three different geographic populations of S. biddulphi in the Qarqan River, Kizil River, and Aksu Rivers were selected as the research objects. The mitochondrial DNA COII and ND4 gene sequences of 126 samples were compared and analyzed, and the differences and relationships between the two kinds of markers on the genetic diversity analysis results of S. biddulphi were discussed. The results showed that the A + T contents of the mitochondrial DNA COII and ND4 gene sequences of S. biddulphi were higher than the G + C contents, and the base composition was biased. Based on mitochondrial DNA COII and ND4 gene sequence analysis, 6 and 23 haplotypes were identified in 126 samples. In the mitochondrial DNA COII gene sequence, there were shared haplotypes in the three populations. In the mitochondrial DNA ND4 gene sequence, no shared haplotypes were found among the three populations. Based on the two kinds of markers, the haplotype diversity and nucleotide diversity of the three populations are 0.738±0.019/0.904±0.014 and 0.02129±0.00298/0.04876±0.00149, respectively. S. biddulphi is characterized by high haplotype polymorphism and high nucleotide polymorphism. The analysis of molecular variances (AMOVA) of the two kinds of markers showed that the genetic variation mainly came from the groups in all populations. Moreover, the genetic differentiation between the Qarqan River population and the other two populations reached a significant level (P <0.05). The BI tree constructed by Bayesian method (BI) is consistent with the haplotype network diagram, and S. biddulphi formed two branches. The mismatch distribution of the COII and ND4 gene sequences showed both bimodal pattern. This result indicates that the current distribution of S. biddulphi is the result of a second exchange between previously differentiated populations. The results also indicated that S. biddulphi had differentiated into 2 distinct geographic populations. In addition, when our research group studied the morphological difference analysis of different populations of S. biddulphi, it was found that the differentiation in some traditional morphological areas has reached the subspecies level. Therefore, it is suggested that the Qarqan River population should be managed as a separate population during the protection and development of germplasm resources.

Abstract:In order to explore the effects of dietary calcein (CAL) for fluorescence labeling on the levels of antioxidant enzymes, and lipid peroxidation in different tissues, juvenile Spinibarbus sinensis were fed continuously with different CAL dosages feed (including 0, 2, 8, and 32 g/kg) for 16 days (i.e., toxicity accumulation experiment), and then with feed without CAL for 32 days (ie., toxicity elimination experiment). Moreover, the recovery after CAL feeding, as well as the toxic effects of CAL were further evaluated. The results of toxicity accumulation experiment showed that the excess reactive oxygen species (ROS) could be successfully removed by the antioxidant system of juvenile S. sinensis, when the CAL dosage ≤ 32 g/kg and the cumulative feeding duration ≤ 8 days. However, long feeding period (e.g., 16 days) might cause toxic effects, and even lead to excessive oxidative stress in hepatopancreas and kidney of experimental fish. The results of toxicity elimination experiment showed that most of the antioxidant enzyme indexes, non-enzyme antioxidants and lipid peroxidation products in serum, hepatopancreas and kidney tissues of juvenile S. sinensis recovered to safe levels after 32 days. The present study confirmed that the toxic effects of CAL feeding in juvenile S. sinensis depended on cumulative feeding duration when dosage ≤ 32 g/kg. In other words, when CAL is used to mark juvenile S. sinensis by feeding, the CAL dosage and the feeding duration should be restricted to ≤ 32 g/kg and ≤ 8 days, respectively, and the marked juveniles should be reared for at least 32 days. The results are of important guiding significance for the safe and effective application of CAL in fish fluorescent labeling.

Abstract:In Epinephelus coioides, foxl3 showed the expression characteristics of gender dimorphism, and the expression level of foxl3 in testis of E. coioides was significantly higher than that in ovary and other tissues. In addition, foxl3 is considered to play an important role in ovarian and testis development. In this study, by comparing the over-expression of foxl3 gene in E. coioides with 17ɑ-methyltestosterone (MT) feeding, explored a new method of regulating gonad development in E. coioides. The gonadal development status was observed and the genes related to gonadal differentiation were detected and analyzed by real-time PCR after the injection of foxl3 recombinant plasmid and MT feeding to three-month-old E. coioides. The results showed that the ovary of the injection group is smaller than that of the control group, and there are more somatic cells in the early stage of plasmid injection, and there is a trend of development in the male direction ( there were testicular interstitial cells ). The relative expression levels of male-related gene–amh, hormone-producing genes–cyp11b, 11β-hsd2，and spermatogenesis-related genes–rec8, sycp3 genes in the early injection group after plasmid injection are significantly higher than those in the control group. In particular, gene expression in amh, cyp11b and sycp3 injection groups was twice as high as that in control group. The gonads in the late MT feeding stage are in the obvious facultative stage, and the control group is still in the O2 oocyte stage. The relative expression trend of amh, cyp11b, 11β-hsd2, rec8 and sycp3 genes in MT feeding group is consistent with plasmid injection, but the difference between the feeding group and the control group is more significant than that of plasmid injection. Under the experimental conditions, the effect of MT feeding on the regulation of gonad masculinization is more obvious than that of foxl3 plasmid injection. In conclusion, the above results showed that the over-expression of foxl3 recombinant plasmid has a clear male regulatory effect on gonadal development of juvenile E. coioides, and this regulation may have a dose-dependent effect. The results laid the foundation for further study on testis development of E. coioides.

Abstract:Ctenopharyngodon idella is the most productive cultured freshwater fish species in China, while the healthy development of grass carp industry has been restricted for a long time by grass carp hemorrhage disease caused by grass carp reovirus (GCRV) infection. The selective breeding of C. idella with high resistance is a research focus of industry and academia. Our previous research found that maternal immunization could significantly enhance the offspring resistance to GCRV. To investigate the expression characteristics of maternal immune factors in the female parent treated with GCRV attenuated vaccine and its offspring, the protein concentration and gene expression levels of five different immune factors (IgM, C3, LZM, MBL and Bf) were detected by ELISA and qPCR in the blood of female parent, the early development embryos and juvenile fish of offspring. The results showed that the protein concentration and gene expression level of five immune factors in female parent blood by GCRV attenuated vaccine (experimental group) were 1.5 times higher than those in the control group, but there was no significant difference between the two groups after 11 months of immunization. The gene expression level of IgM, C3, MBL and Bf in experimental group offspring were higher than those of the control group on day 4. The protein concentration level of IgM, C3 and Bf in experimental group offspring were slightly higher than those of the control group on day 15. Five immune factors were still highly expressed in experimental group offspring immune organs such as liver, spleen, kidney and head kidney at the age of 5-11 months. The results indicated that the expression levels of immune factors in the female parent treated with GCRV attenuated vaccine and its offspring significantly increased after maternal immunization by GCRV attenuated vaccine, but it has a certain time-effectiveness. The high expression of immune factors in the female parents and offspring might last up to 11 months, which provides a reference for the maternal immune procedure in C. idella and molecular information for the breeding of C. idella with viral resistance.

Abstract:Shellfish culture is one of the pillar industries of China's mariculture industry, and oyster is the species with the highest yield and output value. Crassostrea gigas, also known as Pacific oyster, is one of the leading species of oyster culture in China, which is characterized by high fertility, strong adaptability, rapid growth and rich nutrition. In order to solve the problem of diploid oysters with reduced meat quality due to spawning in summer, triploid oysters were successfully cultivated. Because of their poor fertility and high quality in breeding season, the market vacancy of diploid oysters in summer was made up for. The study of the regulatory mechanism of gonadal development has always been one of the hot research fields in developmental biology. Gonad development is accompanied by energy storage and utilization. Analysis of energy storage and consumption during gonadal development helps to reveal the regulation mechanism of gonadal development. Therefore, to carry out research on energy changes and related regulation mechanisms in the development of gonads of different fertility oysters has important scientific significance and important application value. In order to investigate the utilization and change of the main energy supply substances during the gonadal development of different fertility C. gigas, the gonadal tissues of triploid and diploid C. gigas were observed and analyzed by using the methods of PAS staining and oil red O staining. The results showed that a large amount of glycogen and lipid are accumulated in the gonadal connective tissue of both diploid and triploid C. gigas during the proliferation stage. With the development of gonad, the content of glycogen in the gonadal connective tissue of diploid and fertile triploid (3nα type) C. gigas decrease significantly, and almost no glycogen is detected at maturity stage, indicating that the glycogen in the gonadal connective tissue provides energy for gametogenesis. Lipids mainly existed in the connective tissue and cytoplasm of oocytes in the female diploid and 3nα gonad of C. gigas, indicating that lipids were an important component of oocyte development. The content of lipids in gonadal connective tissue of female diploid and 3nα type C. gigas does not decrease significantly with gonadal development, so it is speculated that glycogen may be converted into lipids to meet the material needs of gonad development. Lipids are significantly reduced during the gonadal development in diploid male C. gigas, indicating that the main function of lipids in the gonadal development of male C. gigas may be energy supply rather than structural composition. As important energy supply and components in the gonadal development of C. gigas, their content shows no significant change during the gonadal development of sterile triploid (3nβ type) C. gigas, and this is closely related to the locked gametogenesis of the 3nβ. It is speculated that glycogen and lipid accumulated at the early stage of gonadal development of 3nβ can not be transported to germ cells, but remain in connective tissue due to the blocked gametogenesis, so that the sterile triploid C. gigas can still grow rapidly during the reproductive season. The results of this study provide important information for the regulation mechanism of oyster reproductive development and fertility control breeding.