The environmental analysis and site selection of mussel and large yellow croaker aquaculture areas based on high resolution remote sensing

Mussel aquaculture and large yellow croaker aquaculture areas and their environmental characteristics in Zhoushan were analyzed using satellite data and in-situ surveys.A new two-step remote sensing method was proposed and applied to determine the basic environmental characteristics of the best mussel and large yellow croaker aquaculture areas.This methodology includes the first step of extraction of the location distribution and the second step of the extraction of internal environmental factors.The fishery ranching index(FRI1,FRI2)was established to extract the mussel and the large yellow croaker aquaculture area in Zhoushan,using Gaofen-1(GF-1)and Gaofen-6(GF-6)satellite data with a special resolution of 2 m.In the second step,the environmental factors such as sea surface temperature(SST),chlorophyll a(Chl-a)concentration,current and tide,suspended sediment concentration(SSC)in mussel aquaculture area and large yellow croaker aquaculture area were extracted and analyzed in detail.The results show the following three points.(1)For the extraction of the mussel aquaculture area,FRI1 and FRI2 are complementary,and the combination of FRI1 and FRI2 is suitable to extract the mussel aquaculture area.As for the large yellow croaker aquaculture area extraction,FRI2 is suitable.(2)Mussel aquaculture and the large yellow croaker aquaculture area in Zhoushan are mainly located on the side near the islands that are away from the eastern open waters.The water environment factor template suitable for mussel and large yellow croaker aquaculture was determined.(3)This two-step remote sensing method can be used for the preliminary screening of potential site selection for the mussels and large yellow croaker aquaculture area in the future.the fishery ranching index(FRI1,FRI2)in this paper can be applied to extract the mussel and large yellow croaker aquaculture areas in coastal waters around the world.

Spatial-temporal dynamics of bacterioplankton communities in the breeding area of large yellow croaker Larimichthys crocea in Sansha Bay,China

As an important spawning ground for large yellow croaker Larimichthys crocea,Sansha Bay,South China Sea has been a research hotspot.However,studies on the influence of the bacterioplankton community and assessments of its seasonal succession of bacterioplankton in different sea areas in Sansha Bay are still limited.To address the issue,we use 16S rRNA gene amplicon sequencing and functional prediction to investigate the spatial-temporal dynamics of the bacterioplankton community in three distinct areas,i.e.,Breeding Area(BA),Yantian Harbor(YH),and Bay Margin(BM)of Sansha Bay.Results show that the structure of the bacterioplankton community in Sansha Bay had a significant seasonal succession.Moreover,the representative zero-radius Operation Taxon Units in different seasons were significantly different among the three selected sea areas.Specifically,during the breeding season,bacterioplankton communities in BA were characterized by compound-degrading bacteria,such as Rhodococcus and Owenweeksia,while in YH and BM,animal parasites or symbionts such as Vibrio and Arcobacter were dominant.Furthermore,the redundancy analysis and Spearman correlation analysis further explained that water temperature,dissolved oxygen,and ammonia nitrogen were the main environmental factors responsible for the difference.In addition,the bioindicator functions screened by Functional Annotation of Prokaryotic Taxa and random forest machine learning mainly relied on compound degradation,nitrite oxidation,and photoheterotrophy.The compound-degradationcorresponded bacterioplankton genera such as Rhodococcus had relatively higher abundance in BM,while Nitrospina corresponding to nitrite oxidation tended to be abundant in YH and BA.Based on the spatial and temporal variation in the composition and function of bacterioplankton,our findings provide a basis for understanding the theory of bacterioplankton community structure in the inner-bay habitat of the large yellow croaker in Sansha Bay.

Environmental hypoxia induces apoptosis in large yellow croaker Larimichthys crocea via both intrinsic and extrinsic pathways

Hypoxia has become an unfavorable factor affecting the sustainable development of the large yellow croaker Larimichthys crocea,an economically important mariculture fish in China.Apoptosis is a consequence of hypoxia on fish.However,the effects of hypoxia stress on apoptosis in L.crocea remain largely unknown.We investigated the effect of environmental hypoxia on apoptosis in L.crocea.Results show that hypoxia induced apoptosis in L.crocea both in vivo and in vitro.The mitochondrial membrane potential was significantly reduced in large yellow croaker fry(LYCF)cells.The expression levels of Bcell lymphoma/leukemia-2(Bcl-2)m RNA and protein were also significantly decreased in the liver and LYCF cells during 96 h and 48 h of hypoxia stress,respectively,whereas the expression level of Bcl-2 associated X(Bax)mRNA,Casp3 mRNA,and activity of caspase-3/7/9 were significantly increased,indicating that hypoxia induced caspase-dependent intrinsic apoptosis in L.crocea.The expression level of the apoptosis-inducing factor(AIF)protein was significantly increased in the liver and LYCF cells.The level of AIF protein was significantly decreased in the cytoplasm but increased in the nuclei of L.crocea,demonstrating that hypoxia induced the AIF-mediated caspase-independent intrinsic apoptosis.In addition,the activity of caspase-8 was significantly increased,indicating that hypoxia stress induced extrinsic apoptosis in L.crocea.Therefore,hypoxia induced apoptosis in L.crocea through both the intrinsic and extrinsic pathways.The present study accumulated basic biological information to help elucidate the mechanism of hypoxia response in marine fish.

Establishment of a Spleen Cell Line from Large Yellow Croaker Pseudosciaena crocea and its Primitive Application in Foreign Gene Transfection

A large yellow croaker,Pseudosciaena crocea,spleen(LYCS)cell line was established and the feasibility of using it for foreign gene transfection was evaluaed in this study.Primary culture of LYCS cells was initiated from spleen tissue pieces,which were cultured at 25℃ in Dulbecco's modiced Eagle medium/F12 medium(DMEM/F12,1:1)(pH7.2),supplemented with 20% fetal bovine serum,carboxymethyl chitosan,chondroitin sulfate,basic fibroblast growth factor(bFGF)and insulin-like growth factor-I(IGF-I).The cultured LYCS cells,in fibroblast shape,proliferated to 100% confluency 20 days later.Chromosome analyses indicated that the LYCS cells exhibited chromosomal aneuploidy with a modal chromosome number of 48 which displayed the normal diploid karyotype of P.crocea(6m+6sm+36t,NF=60).A LYCS cell line,with a population doubling time of 48.7 h at passage 60,has been established and subcultured to passage 70.Transgenic feasibility test demonstrated that positive green fluorescence protein(GFP)expression was observed in LYCS cells after pcDNA3.1-GFP plasmid transfection.In conclusion,a continuous foreign gene trans-fection feasible LYCS cell line has been established successfully.The cell line might serve as a valuable tool for studies of transgenic breeding and has potential applications for different kinds of cytotechnological studies.

Large yellow croaker(Larimichthys crocea)mitofusin 2 inhibits type I IFN responses by degrading MAVS via enhanced K48‑linked ubiquitination

In mammals,mitofusin 2(MFN2)is involved in mitochondrial fusion,and suppresses the virus-induced RIG-I-like receptor(RLR)signaling pathway.However,little is known about the function of MFN2 in non-mammalian species.In the present study,we cloned an MFN2 ortholog(LcMFN2)in large yellow croaker(Larimichthys crocea).Phylogenetic analysis showed that MFN2 emerged after the divergence of amphioxus and vertebrates.The protein sequences of MFN2 were well conserved from fsh to mammals.LcMFN2 was expressed in all the tissues/organs examined at diferent levels,and its expression was upregulated in response to poly(I:C)stimulation.Overexpression of LcMFN2 inhibited MAVS-induced type I interferon(IFN)promoter activation and antiviral gene expression.In contrast,knockdown of endogenous LcMFN2 enhanced poly(I:C)induced production of type I IFNs.Additionally,LcMFN2 enhanced K48-linked polyubiquitination of MAVS,promoting its degradation.Also,overexpression of LcMFN2 impaired the cellular antiviral response,as evidenced by the increased expression of viral genes and more severe cytopathic efects(CPE)in cells infected with spring viremia of carp virus(SVCV).These results indicated that LcMFN2 inhibited type I IFN response by degrading MAVS,suggesting its negative regulatory role in cellular antiviral response.Therefore,our study sheds a new light on the regulatory mechanisms of the cellular antiviral response in teleosts.

Population structure and genome‑wide evolutionary signatures reveal putative climate‑driven habitat change and local adaptation in the large yellow croaker

The large yellow croaker(Larimichthys crocea)is one of the most economically valuable marine fsh in China and is a notable species in ecological studies owing to a serious collapse of wild germplasm in the past few decades.The stock division and species distribution,which have important implications for ecological protection,germplasm recovery,and fshery resource management,have been debated since the 1960s.However,it is still uncertain even how many stocks exist in this species.To address this,we evaluated the fne-scale genetic structure of large yellow croaker populations distributed along the eastern and southern Chinese coastline based on 7.64 million SNP markers.Compared with the widely accepted stock boundaries proposed in the 1960s,our results revealed that a climate-driven habitat change probably occurred between the Naozhou(Nanhai)Stock and the Ming-Yuedong(Mindong)Stock.The boundary between these two stocks might have shifted northwards from the Pearl River Estuary to the northern area of the Taiwan Strait,accompanied by highly asymmetric introgression.In addition,we found divergent landscapes of natural selection between the stocks inhabiting northern and southern areas.The northern population exhibited highly agminated signatures of strong natural selection in genes related to developmental processes,whereas moderate and interspersed selective signatures were detected in many immune-related genes in the southern populations.These fndings establish the stock status and genome-wide evolutionary landscapes of large yellow croaker,providing a basis for conservation,fsheries management and further evolutionary biology studies.

Effective CRISPR/Cas9-based genome editing in large yellow croaker (Larimichthys crocea)

The large yellow croaker (Larimichthys crocea) is an economically important marine species with the highest annual production among the farmed marine fishes in China. However, the aquaculture industry of this species is suffering from severe problems that include weakened disease resistance, decreased growth rate, and reduced meat quality due to frequent inbreeding. Genome editing, which has a huge potential for solving those problems by introducing favorable genetic changes, is not yet available for the large yellow croaker. Here, we pioneered the techniques of embryo microinjection and genome editing using the CRISPR/Cas9 system in this species. Recombinant plasmids encoding green fluorescent protein (GFP) were introduced into the fertilized eggs of L. crocea by microinjection before the chorion had hardened. A high survival rate (40%) and GFP-positive larvae rate (81.8%) were achieved, indicating that the microinjection technique in L. crocea was successfully established. On this basis, Cas9 mRNA and sgRNA targeting the tyrosinase a gene in L. crocea (Lc-tyra) were co-injected into fertilized eggs of L. crocea. Mutant individuals with insertion and deletion mutations of Lc-tyra were detected. These results indicated that the CRISPR/Cas9-based genome editing technology established herein could efficiently introduce mutations at a specific site in the L. crocea genome. This method provides the potential for genetic improvement and functional genomic study in this species. This is the first report on effective CRISPR/Cas9-based genome editing in L. crocea.

Sex-biased gene discovery from the gonadal transcriptomes of the large yellow croaker(Larimichthys crocea)

The investigation of sex determination in fish is not only of great scientific value,but also has important practical significance,especially in fishes grown in aquaculture exhibiting obvious growth-related sexual dimorphism,such as the large yellow croaker(Larimichthys crocea).While growth of the female large yellow croaker is faster than that of the male,little information exists on the mechanisms that drive the differentiation of the testis and ovary in this species.In this study,the gene expression profiles of large yellow croaker testis and ovary were analysed using RNA-Seq technology.A total of 222 million reads were mapped to the reference genome(89.80%).The differential gene expression analysis identified 13 genes specifically expressed in ovary and 897 specific to testis.Among these,were candidate sex determining genes,such as Dmrt1,Gsdf,Sox9,Amh.This study explored gene expression profiles in large yellow croaker gonads at the transcriptome level by RNA-Seq technology.We found many DEGs related to the development of each specific organ,including the candidate testis differentiation genes Dmrt1,Gsdf,Sox9,Sox3,Amh and ovary differentiation gene Foxl2 by analogy with other fish species,providing essential foundation clarifying the molecular mechanism involved in early sex differentiation.

Genome-wide association study identifies loci for body shape in the large yellow croaker(Larimichthys crocea)

The large yellow croaker(Larimichthys crocea)is an important maricultured fish species in southeast China.Body shape is an important economic trait for this species,because consumers prefer to purchase fish that have a slender shape.Furthermore,investigating the genetic basis of this trait may be useful for understanding the evolution of fish body shape in general.This study randomly selected 500 large yellow croakers to perform genome-wide association study of this trait.We used Genotyping-By-Sequencing technology combined with a genome-wide prediction model(BayesC)to identify and test QTLs.We also compared the association results using BayesC and single-marker analysis,and found that BayesC outperformed single-marker analysis in detecting significant SNPs explaining a proportion of the total genetic variance in this experiment.Using 124,419 SNP markers,10 candidate genes,correspond to 4 QTL regions located around 3.5,1.8,23.9 and 10.8 Mb on chromosomes 2,4,8 and 22 respectively,were suggested to be relevant to the trait.All of these genes may directly or indirectly participate in bone development.These genes may provide a valuable reference for marker-assisted selective breeding and investigating the genetic basis of the evolution of fish body shape.

Influence of industrial organizational structure on farming performance of large yellow croaker farmers

This paper determines the cost-benefit levels of yellow croaker farming households by comparing and analysing responses to questionnaires distributed to 405 households located in nine breeding regions of three counties(cities)in the Chinese provinces of Fujian and Zhejiang.A transcendental logarithmic stochastic frontier production function model is used to perform a quantitative analysis on the large yellow croaker production technique efficiency of different forms of industry organisation,with the farming household as the basic production unit.The findings indicate that the average production technology efficiency of the farming households is 84.33% and room for improvement remains;and there are significant differences between the production technique efficiency of farming households from different regions and under different forms of organisation.An analysis of the factors that affect farming household production technique efficiency found that capital input has a greater effect than labour input.Family participation and the number of individuals involved in the rearing of large yellow croakers,participation in technical training,and joining a closely-knit industry organisation all have a significant positive effect on increasing the production technique efficiency.These empirical results provide a basis and practical reference for optimising the development of the large yellow croaker farming industry,enhancing the degree of closeness of the organisations in the industry,and improving aquaculture performance.

Identification of a TGF-β1 homologue in the large yellow croaker(Larimichthys crocea)revealed its role in regulation of immune response

Mammalian TGF-β1 plays a crucial role in maintaining immune tolerance and inhibiting autoimmunity.Although several TGF-β1 homologues have been identified in teleosts,their immunosuppressive functions remain unclear.Herein,we identified and characterized LcTGF-β1,a TGF-β1 homologue from the large yellow croaker(Larimichthys crocea).LcTGF-β1 possesses several features characteristic of the TGF-βsuperfamily,including an RGD integrin binding site,an RSKR tetrabasic cut site,and nine conserved cysteines in the mature peptide.The LcTGFβ1 gene was constitutively expressed in all examined tissues,with the highest expression in the spleen,which is rich in immune cells.LcTGF-β1 was significantly upregulated in the head kidney and spleen after Vibrio alginolyticus stimulation.LcTGF-β1 was also expressed in primary head kidney lymphocytes(PKLs),monocytes/macrophages(MO/Mφs),and granulocytes(PKGs),and was significantly upregulated in the MO/Mφs after lipopolysaccharide(LPS)stimulation.Recombinant LcTGF-β1 protein(rLcTGF-β1)significantly suppressed reactive oxygen species(ROS)and nitrogen oxide(NO)production in LPS-activated head kidney MO/Mφs.Furthermore,in these MO/Mφs,rLcTGF-β1 strongly inhibited the expression of pro-inflammatory cytokine(TNFα)and inducible NO synthase(iNOS),while it induced anti-inflammatory cytokines(TGF-β1 and IL-10),arginase1,and CD206.The phagocytic activity of LPS-activated MO/Mφs was also increased by rLcTGF-β1.Finally,rLcTGF-β1 significantly inhibited the proliferation of T cells(ZAP70þcells)and downregulated T-cell activation genes(CD3ζ,TCRα,and ZAP70),T-cell marker genes(CD4 and CD8),and IL-2 in PKLs.These results thus provide strong evidence that LcTGF-β1 promotes the alternative activation of head kidney MO/Mφs and inhibits T-cell proliferation in PKLs,highlighting its role in the regulation of immune response in large yellow croaker.