三疣梭子蟹(Portunus trituberculatus)CTL基因SNP位点E4-205 C/T与抗溶藻弧菌相关性分析

C-型凝集素(C-typelectin,CTL)是甲壳类动物体液免疫中重要的免疫因子之一。但CTL基因在溶藻弧菌对三疣梭子蟹(Portunus trituberculatus)感染的过程中的表达及抗病机制尚有待进一步研究。为初步阐明CTL基因SNP E4-205 C/T位点与抗溶藻弧菌感染相关的分子机制,对不同基因型梭子蟹进行溶藻弧菌感染,通过绝对定量方法分析不同基因型梭子蟹肝胰腺、肌肉组织中溶藻弧菌的复制情况。发现溶藻弧菌感染后12 h内梭子蟹肝胰腺、肌肉组织中C/C组细菌数量显著高于T/T组,结果表明T/T组梭子蟹抗感染能力显著高于C/C组。进一步对该位点非同义突变(ACT-ATT)导致的一个氨基酸改变(Thr-Ile)的两种蛋白进行体外重组表达,并对两种重组蛋白CTL-ATT及CTL-ACT进行活性分析。发现两种重组蛋白对溶藻弧菌生长均具有一定的抑制作用,CTL-ATT的抑菌活性显著高于CTL-ACT。重组蛋白CTL-ATT与PAMPs的结合活性高于CTL-ACT与PAMPs的结合活性,同时两种蛋白与PAMPs和溶藻弧菌的结合活性具有浓度依赖性。结果表明三疣梭子蟹CTL基因参与机体感染溶藻弧菌后的免疫应答过程,其单核苷酸多态性与抗溶藻弧菌感染存在一定的关联性,三疣梭子蟹CTL基因SNPE4-205C/T位点为T/T基因型时的抗溶藻弧菌感染能力强于C/C型。

Long-term in-vitro culture and subculture of the hemocytes of swimming crab Portunus trituberculatus

Crab cell line,especially continuous crab cell line,can provide us a useful tool for studies on the virology,immunology,and molecular biology of crabs.However,no continuous crab cell line has been available due to the lacking of suitable medium and the occurrence of mitosis-arrest.In this study,long-term in vitro culture conditions for both two-(2D)and three-dimensions(3D)were successfully developed for the circulating hemocytes of swimming crab Portunus trituberculatus,designated as PTH cells.In 2D culture,a novel crab basic medium in osmolarity of 990–1100 mOsm/kg was optimized for the first time,which is different from Leibovitz's L-15 medium in mainly the components of amino acids,containing double strengths of the contents of free amino acid mixture in the crab serum.Then an optimal crab growth medium was developed by supplementing 5%fetal bovine serum,50-g/L yeast extract powder,20-μg/L basic fibroblast growth factor and epidermal growth factor into the optimal crab basic medium,and found that it could support a long-term survival of PTH cells in a healthy monolayer up to 347 days and partially break through the mitosis-arrest of crab cells evidenced by the obvious increase of proliferating potential detected in the 10-d primarily cultured PTH cells.These 2D cultured PTH cells could be successfully sub-cultured for 11 times by physical flushing method and well cryopreserved in liquid nitrogen.In 3D culture,using the same crab growth medium,the PTH cell aggregates could be easily formed and healthily maintained on the surface of solidified Matrigel or in the ultra-low-attachment plate with a survival rate of 50%–60%on Day 103.This work largely improved the primary culture and subculture of crab cells and will facilitate the establishment of continuous crab cell line.

Analysis of Key Physiological Characteristics of Portunus trituberculatus in Response to Short-Term Low Salinity Stress

Salinity is a significant environmental factor that can affect the survival,metamorphosis,growth and feeding of Portunus trituberculatus.In order to analyze the key physiological characteristics of P.trituberculatus in response to short-term low salinity stress,the experiments of gradually decline and recovery as well as abrupt decline in salinity were carried out.The results showed that P.trituberculatus could survive in a certain low salinity range in the short term,and salinity 12 was the lowest tolerable salinity under the present experimental conditions.The change of the hemolymph osmotic pressure displayed significant positive correlations with water salinity,and the pressure was always higher than seawater osmotic pressure.Short-term low salinity stress changed the structure and morphology of gill tissue.The expansion of gill filament ends and epithelial cell shedding were conducive to osmotic adjustment.The activities of key ion transport enzymes such as Na^(+)-K^(+)-ATPase,carbonic anhydrase and V-ATPase also changed with the osmotic regulation,while Na^(+)-K^(+)-ATPase played a dominant role.In summary,as an osmotic adjustment species,P.trituberculatus rapidly adapt to the short-term low-salinity environment by osmotic adjustment in vivo,but salinity below salinity 12 is not conducive to its survival.Our result enriched the theoretical mechanism of osmotic regulation of P.trituberculatus,providing reference for the development of aquaculture technology of P.trituberculatus.

Biological Characteristics of Serum Agglutinin from Portunus trituberculatus

The agglutination characteristics of serum agglutinin from Portunus trituberculatus were studied in this paper. The results showed that the serum agglutinin had no agglutination to crucian carp, Chinese soft shell turtle, grass carp, chicken or human group A, B or O blood cells, but had strong agglutination to blood cells of mice and rabbits. The activities of serum agglutinin from Portunus trituberculatus to mice blood cells reached 210, and to rabbit blood cells reached 28. Salinity had a greater effect on agglutinin activity. When the Na Cl concentration exceeded 0.6 mol/L,the serum agglutinin from Portunus trituberculatus was basically inactivated. The optimum p H for agglutinin activity was 6.0-7.4. The serum agglutinin from Portunus trituberculatus had obvious dependence to Ca2 ＋and Mg2 ＋, and EDTA could significantly inhibit its activity. The results of sugar inhibition test showed that the activity of agglutinin from Portunus trituberculatus can be specifically inhibited by N-acetylglucosamine and N-acetylmannosamine. The serum agglutinin from Portunus trituberculatus was isolated by ammonium sulfate gradient precipitation, and its activity was highest by the 25% ammonium sulfate precipitation system. The SDS polyacrylamide gel electrophoresis（SDS-PAGE） showed that the protein bands were mainly distributed within 72-95 ku.

Phylogenetic Relationships between Purple and Tea-green Individuals of the Blue Swimming Crab Portunus trituberculatus by PCR-SSCP Analysis

As an important commercial species, the blue swimming crabs with different body-colors were discovered along the coast of East China in recent years. Both purple and tea-green crabs have similar, even the same physical characteristics except for the carapace color. In order to identify the relationships between them, we amplified and compared two conserved mitochondrial gene fragments of color-different crab individuals through PCR-SSCP and DNA sequencing analyses. The results showed that there was no distinct variation of DNA bands of both the COl and 16srRNA genes detected in polyacrylamide gels through SSCP analysis between purple and tea-green crab samples, and the following sequence analysis of color-different crab individuals presented 99.81% and 99.91% nucleotide sequence identity of the COl and 16srRNA genes respectively, which indicated that there was no species or subspecies differentiation between them. In addition, the purple individuals were more conserved in DNA sequence in compadson with that of the tee-green ones.

RAPD analysis between color-different crab individuals of Portunus trituberculatus

The blue swimming crabs Portunus trituberculatus with tea-green and/or purple carapace color have been discovered on the shore of eastern part of China these days, In this paper, 40 color-different crab individuals were evaluated using 80 RAPD primers. 30 primers were selected using bulk segregation analysis （BSA） and RAPD-PCR analysis. The results showed that the ratio of polymorphic loci was 61.29%, and Nei＇s gene diversity was 0.375 6, and Shannon＇s information index was 0.554 5 among purple crab individuals; and the ratio of polymorphic loci was 62.44%, and Nei＇s gene diversity was 0.3451, and Shannon＇s information index was 0.5099 among tea-green crab individuals. It was clear that the genetic diversity between purple and tea-green crabs was similar, which indicated close phylogenetic relationships between the purple and tea-green crabs. In addition, two primers （SBS A09 and SBS G16） got specific DNA bands by comparing forty individuals of color-different crab individuals through RAPD-PCR analysis and the following electrophoresis. They indicated close phylogenetic relationships between purple and tea-green crabs.

三疣梭子蟹(Portunus trituberculatus)肝胰腺内源酶性质的初步研究

内源酶是三疣梭子蟹(Portunus trituberculatus)体内重要的酶,往往会导致梭子蟹死后肌肉组织迅速软化,严重影响了蟹肉的贮藏品质。为了探明该酶的基本特性,本试验从三疣梭子蟹肝胰腺中提取了粗酶,优化了提取方法,并对其部分酶学性质进行初步研究。结果表明:三疣梭子蟹肝胰腺内源酶最佳浸提时间段为4～12 h,酶比活显著高于0～4 h和12～14 h;以酪蛋白为水解底物,内源酶作用最适温度为65℃、最适p H范围为7.0～8.0;丝氨酸蛋白酶特异性抑制剂,包括大豆胰蛋白酶抑制剂(SBTI)和苯甲基磺酰氟(PMSF),对内源酶活力的相对抑制率分别为100%、70.46%±6.27%,显著高于其他抑制剂的相对抑制率,推测丝氨酸蛋白酶为主要内源酶;在硫酸铵分级沉淀中,分别以酪蛋白和Boc-Phe-Ser-Arg-MCA为底物,前者最适盐析浓度为0～70%,后者为30%～70%,酶比活显著高于其他盐浓度;当硫酸铵浓度为40%～60%时,盐析蛋白质含量、粗酶酶活和丝氨酸蛋白酶活均显著高于其他盐浓度。

三疣梭子蟹(Portunus trituberculatus)CYP4C基因的cDNA克隆及表达分析

采用RT-PCR及Smart-TM Race技术,首次获得三疣梭子蟹CYP4C基因cDNA全长序列。该基因全长1888bp,编码一个由514个氨基酸组成的多肽,预测分子量大小为59.54kDa,理论等电点为8.08。氨基酸序列中含有CYP基因家族特有的K螺旋保守序列(ExxR)和血红素结合区(FxxGxxxCxG)。同源性及系统进化分析表明,三疣梭子蟹CYP4C基因与岸蟹、凡纳滨对虾、日本沼虾、中国对虾、沟虾、红螯螯虾的同源性分别为88%、72%、66%、59%、60%、59%。荧光定量RT-PCR结果表明,CYP4C在肝胰腺、肌肉、眼柄、鳃和心脏中均有分布,在肝胰腺中表达量最高。高盐(45)胁迫后,三疣梭子蟹CYP4C的表达量显著高于对照组,随着胁迫时间的延长出现逐渐降低的趋势,在胁迫48h后表达量达到对照组水平;低盐(11)胁迫条件下,CYP4C的表达水平随着胁迫时间的延长呈现逐渐下降的趋势,且从胁迫6h开始显著低于对照组。研究推测,CYP4C基因参与三疣梭子蟹盐度适应调节,是蜕皮机制的调控因子之一。

三疣梭子蟹(Portunustrituberculatus)冻藏过程中肌肉蛋白质生化特性的变化

以三疣梭子蟹肌肉基本营养成分、蛋白质组成、肌原纤维蛋白含量、Ca^(2+)-ATPase活性、总巯基含量、二硫键含量以及肌原纤维蛋白的SDS-PAGE分析作为指标,研究了三疣梭子蟹在不同冻藏温度下肌肉蛋白质生化特征的变化。结果表明,三疣梭子蟹是典型的高蛋白食品;随着冻藏时间的延长,水溶性蛋白含量先增加后减少,盐溶性蛋白和不溶性蛋白含量逐渐减少,碱溶性蛋白含量逐渐增加;肌原纤维蛋白含量、Ca^(2+)-ATPase活性、总巯基含量随着冻藏时间的延长,均呈现下降趋势,而二硫键含量则呈上升趋势,且–20℃和–40℃两组之间差异显著(P<0.05)。SDS-PAGE分析结果表明,组成肌原纤维蛋白的各种蛋白质均有不同程度降解,且–20℃比–40℃组降解更明显。因此,–40℃冻藏对梭子蟹肌肉蛋白质生化特性的影响较小。

Levels of Metabolic Enzymes and Nitrogenous Compounds in the Swimming Crab Portunus trituberculatus Exposed to Elevated Ambient Ammonia-N

This study investigated the effects of ammonia-N(control and 1 and 5 mg L^(-1)) on the changes of metabolic enzymes activities and nitrogenous compounds levels in the gills, hepatopancreas, muscles, and hemolymph of the swimming crab Portunus trituberculatus. Results showed that the levels of hemolymph ammonia increased significantly at 6 h and then decreased to control level at 12 h. The activities of key enzymes involved in biosynthesis pathways of glutamine(Gln) and urea, such as glutamate dehydrogenase(GDH), glutamine synthetase(GS), and arginase(ARG), increased remarkably in different tissues of P. trituberculatus. Gln level was the highest in muscles, while urea content was the largest in hepatopancreas. The m RNA expression level of xanthine dehydrogenase(XDH) was downregulated sharply in gills but upregulated in the hepatopancreas and muscles. A small amount of uric acid was detected in the hemolymph. This result suggests that Gln in muscles may be used as an intermediary nitrogen repository, while urea may be primarily synthesized in the hepatopancreas and then transferred to other tissues via the hemolymph. Uric acid could be synthesized by the anabolism of purine nucleotides, in additon to the inhibitory activities of gills. In addition, the levels of Gln, urea and uric acid exhibited dose-and time-dependent effects with ammonia content. Therefore, P. trituberculatus could possibly convert ammonia into Gln, urea, or uric acid to detoxify ammonia during high ambient ammonia-N stress.

Impacts of the sampling design on the abundance index estimation of Portunus trituberculatus using bottom trawl

In the survey of fishery resources,the sampling design will directly impact the accuracy of the estimation of the abundance.Therefore,it is necessary to optimize the sampling design to increase the quality of fishery surveys.The distribution and abundance of fisheries resource estimated based on the bottom trawl survey data in the Changjiang River(Yangtze River)Estuary-Hangzhou Bay and its adjacent waters in 2007 were used to simulate the"true"situation.Then the abundance index of Portunus trituberculatus were calculated and compared with its true index to evaluate the impacts of different sampling designs on the abundance estimation.Four sampling methods(including fixed-station sampling,simple random sampling,stratified fixed-station sampling,and stratified random sampling)were simulated.Three numbers of stations(9,16 and 24)were assumed for the scenarios of fixed-station sampling and simple random sampling without stratification.While 16 stations were assumed for the scenarios with stratification.Three reaction distances(1.5 m,3 m and 5 m)of P.trituberculatus to the bottom line of trawl were also assumed to adapt to the movement ability of the P.trituberculatus for different ages,seasons and substrate conditions.Generally speaking,compared with unstratified sampling design,the stratified sampling design resulted in more accurate abundance estimation of P.trituberculatus,and simple random sampling design is better than fixed-station sampling design.The accuracy of the simulated results was improved with the increase of the station number.The maximum relative estimation error(REE)was 163.43%and the minimum was 49.40%for the fixed-station sampling scenario with 9 stations,while 38.62%and 4.15%for 24 stations.With the increase of reaction distance,the relative absolute bias(RAB)and REE gradually decreased.Resource-intensive area and the seasons with high density variances have significant impacts on simulation results.Thus,it will be helpful if there are prior information or pre-survey results about density distribution.The current study can provide reference for the future sampling design of bottom trawl of P.trituberculatus and other species.

Na^+/K^+-ATPase α-subunit in swimming crab Portunus trituberculatus: molecular cloning, characterization, and expression under low salinity stress

Na^＋/K^＋-ATPases are membrane-associated enzymes responsible for the active transport of Na^＋ and K^＋ ions across cell membranes, generating chemical and electrical gradients. These enzymes＇ α-subunit provides catalytic function, binding and hydrolyzing ATP, and itself becoming phosphorylated during the transport cycle. In this study, Na^＋/K^＋-ATPase α-subunit eDNA was cloned from gill tissue of the swimming crab Portunus trituberculatus by reverse-transcription polymerase chain reaction （RT-PCR） and rapid amplification of eDNA end methods. Analysis of the nucleotide sequence revealed that the eDNA had a full-length of 3 833 base pairs （bp）, with an open reading frame of 3 120 bp, 5＇ untranslated region （UTR） of 317 bp, and 3＇ UTR of 396 bp. The sequence encoded a 1 039 amino acid protein with a predicted molecular weight of 115.57 kDa and with estimated pI of 5.21. It was predicted here to possess all expected features of Na^＋/K^＋-ATPase members, including eight transmembrane domains, putative ATP-binding site, and phosphorylation site. Comparison of arnino acid sequences showed that the P. tritubereulatus α-subunit possessed an overall identity of 75%-99% to that of other organisms. Phylogenetic analysis revealed that this α-subunit was in the same category as those of crustaceans. Quantitative real-time RT-PCR analysis indicated that this α-subunit＇s transcript were most highly expressed in gill and lowest in muscle. RT-PCR analysis also revealed that α-subunit expression in crab gill decreased after 2 and 6 h, but increased after 12, 24, 48, and 72 h. In addition, α-subunit expression in hepatopancreas of crab decreased after 2-72 h. These facts indicated that the crab＇s Na^＋/K^＋-ATPase α-subunit was potentially involved in the observed acute response to low salinity stress.

Effects of different dietary lipid sources on growth performance and tissue fatty acid composition of juvenile swimming crab Portunus trituberculatus

This study was conducted to evaluate the effects of dietary lipid sources on the growth performance and fatty acid composition of the swimming crab, P ortunus trituberculatus. Four isonitrogenous and isoenergetic experimental diets were formulated to contain four separate lipid sources, including fish, soybean, rapeseed, and linseed oils(FO, SO, RO, and LO, respectively). With three replicates of 18 crabs each for each diet, crabs(initial body weight, 17.00 ±0.09 g) were fed twice daily for 8 weeks. There were no significant differences among these groups in terms of weight gain, specific growth rate, and hepatosomatic index. However, the RO groups' survival rate was significantly lower than FO groups. The feed conversion and protein efficiency ratios of RO groups were poorer than other groups. The proximate compositions of whole body and hepatopancreas were significantly affected by these dietary treatments. Tissue fatty acid composition mainly reflected dietary fatty acid compositions. Crabs fed FO diets exhibited significantly higher arachidonic, eicosapentaenoic, and docosahexaenoic acid contents in muscle and hepatopancreas compared with VO crabs. Linoleic, oleic, and linolenic acids in muscle and hepatopancreas were the highest in the SO, RO, and LO groups, respectively. The present study suggested that SO and LO could substitute for FO in fishmeal-based diets for swimming crabs, without affecting growth performance and survival.

Trophic Interaction in a Portunus rituberculatus Polyculture Ecosystem Based on Carbon and Nitrogen Stable Isotope Analysis

Trophic interaction among various biomass groups in a swimming crab Portunus trituberculatus polyculture pond was investigated using carbon and nitrogen stable isotope analysis. The polycultured animal species also included white shrimp Litopenaeus vannamei, short-necked clam Ruditapes philippinarum, and redlip mullet Liza haematochila. The mean δ^(13)C value for all the biomass groups in polyculture ecosystem ranged from -25.61‰ to -16.60‰, and the mean δ^(15)N value ranged from 6.80‰ to 13.09‰. Significant difference in the δ^(13)C value was found between particulate organic matter(POM) and sediment organic matter(SOM)(P < 0.05), indicating that these two organic matter pools have different material sources. Assuming that a ^(13)C-enrichment factor of 1.00‰ and a ^(15)N-enrichment factor of 2.70‰ existed between consumer and prey, diets of the four cultured animals were estimated using a stable isotope mixing model. The estimated model results indicated that P. trituberculatus mainly feed on Aloidis laevis; L. vannamei mainly feed on shrimp feed; while A. laevis, R. philippinarum and L. haematochelia mainly feed on POM. Shrimp feed was also an important food source of R. philippinarum and L. haematochelia. The diets of P. trituberculatus, L. vannamei, R. philippinarum, and L. haematochila showed complementary effects in this polyculture ecosystem. Our finding indicated that the polyculture of these four organisms with suitable farming density could make an effective use of most of the food sources, which can make a highly efficient polyculture ecosystem.

Dynamic metabolite alterations of Portunus trituberculatus during larval development

A mass mortality often occurs from molting to the megalopa stage during the larval development of the swimming crab Portunus trituberculatus. Larvae with insuffcient nutrient accumulation during the zoeal stages are probably unable to develop into juvenile swimming crabs. However, the nutritional information such as the primary metabolites is scarce for P. trituberculatus larvae. The aim of this work is to obtain an insight into the metabolite traits of P. trituberculatus at early developmental stages. 1 H nuclear magnetic resonance spectroscopy coupled with multivariate data analysis was used to determine how the metabolite pro?les shift during larval development in P. trituberculatus. Our results show that the trend of total metabolites exhibited a rise from zoea 1 to zoea 3, followed by a drop from zoea 4 to megalopa and recovery during the ?rst juvenile stage. A large-scale depletion of total metabolites in the zoea 4 and megalopa stages suggests a deep depression of metabolic activity, which may be linked to the mass mortality from molting to the megalopa stage. These ?ndings provided essential metabolic information about the larval development of P. trituberculatus and important clues for understanding the nutritional requirements of P. trituberculatus in early developmental stages.

Disruption of bacterial balance in the gut of Portunus trituberculatus induced by Vibrio alginolyticus infection

A bstract Gut microbiota impacts the health of crustaceans. V ibrio alginolyticus is a main causative pathogen that induces the vibriosis in farmed swimming crabs, Portunus trituberculatus. However, it remains unknown whether gut bacteria perform functions during the progression of vibriosis. In this study, 16 SrRNA gene amplicon sequencing was used to investigate temporal alteration of gut bacterial community in swimming crabs in response to 72-h V. alginolyticus challenge. Our results show that V. alginolyticus infection resulted in dynamic changes of bacterial community composition in swimming crabs. Such changes were highlighted by the overwhelming overabundance of V ibrio and a significant fluctuation in the gut bacteria including the bacteria with high relative abundance and especially those with low relative abundance. These findings reveal that crab vibriosis gradually develops with the infection time of V. alginolyticus and tightly relates to the dysbiosis of gut bacterial community structure. This work contributes to our appreciation of the importance of the balance of gut bacterial community structure in maintaining the health of crustaceans.

Enhanced resistance of Portunus trituberculatus to Vibrio alginolyticus by selective breeding

We established a line (screened) of Portunus trituberculatus by selectively breeding individuals that survived from challenge with Vibrio alginolyticus, and compared the response of screened and unscreened (control) P. trituberculatus challenged with V. alginolyticus. We measured superoxide dismutase, catalase, acid phosphatase, alkaline phosphatase, and peroxidase activity and the content of hemocyanin in the plasma and phenoloxidase activity in serum. The cumulative survival rate after 24-h challenge with V. alginolyticus was significantly higher in the screened crabs than in the unscreened crabs (P<0.05). T-SOD and PO activity were significantly lower in the screened stock than in the unscreened stock (P<0.05). POD, CAT, and ACP activity and hemocyanin content were significantly higher in the screened stock than in the unscreened stock. Our results suggest that the screened stock was more resistant to infection. Furthermore, the indices we measured may be used to evaluate the health state of P. trituberculatus.

Impacts of sampling design on the abundance estimation of Portunus trituberculatus using crab pots

Fishery-independent surveys can provide high-quality data and support fishery assessment and management.Optimization of sampling design is crucial to increase the quality of fishery surveys.Crab pots are important fishing gears used to catch crabs.We analyzed the impacts of sampling design of crab pots on the abundance of Portunus trituberculatus in the Changjiang(Yangtze)River estuary to the Hangzhou Bay and its adjacent waters in East China Sea.The crab pots were cylindrical,240 mm in height and 600 mm in diameter of the iron ring.Our sampling designs(including fixed-station sampling,simple random sampling,stratified fixed-station sampling,and stratified random sampling),three number of stations(9,16,and 24),and three numbers of crab pots(500,1000,and 3000)were simulated and compared with the“true”abundance that obtained from bottom trawl surveys in the study area in 2007.The scenarios with 16 stations were set in stratification as a control group for comparison with unstratified designs.Results show that simple random sampling can obtain more stable results than fixed-station sampling in the abundance estimation of P.trituberculatus.In addition,stratified sampling resulted in more accurate abundance than unstratified sampling.The accuracy of the simulated results improved with the increase of the number of stations.No remarkable differences in the results were found among the scenarios of different number of crab pots at each station.However,resource-intensive areas exerted great impacts on simulation results.Thus,prior information or pre-survey results about resource abundance and density distribution are necessary.This study may serve as a reference for future sampling designs of crab pots of P.trituberculatus and other species.

Assessment of Heavy Metals,Polycyclic Aromatic Hydrocarbons,and Perfluorinated Alkyl Substances in two Marine Crustaceans(Oratosquilla oratoria and Portunus trituberculatus)in the Zhoushan Fishing Ground of China East Sea

Heavy metals,polycyclic aromatic hydrocarbons(PAHs),and perfluorinated alkyl substances(PFASs)polluted in 155 samples of two marine crustaceans(Oratosquilla oratoria and Portunus trituberculatus)harvested in the Zhoushan fishing ground in the East China Sea were assessed.The results showed that Pb,Hg,and iAs in the whole edible parts of O.oratoria and P.trituberculatus were at trace levels,far below the limits set by the China’s national standard,whereas the exceeding standard rates of Cd in the whole edible parts of O.oratoria and P.trituberculatus were 98.6%and 75.6%,respectively.Moreover,the average Cd levels and the exceeding standard rates of Cd in the visceral tissues of O.oratoria were significantly higher than those in the muscle tissues(4.64 mg kg^(−1)vs.0.49 mg kg^(−1)and 96.7%vs 30%,respectively).PAHs with high detection frequency in the two marine crustaceans included NA,AC,FL,and PHE.Total contents of 15 PAHs(abbreviated asΣ15 PAHs)in whole edible parts of O.oratoria and P.trituberculatus were 10.75–65.9μg kg^(−1)(mean=18.7μg kg^(−1)and 13.26–181μg kg^(−1)(mean=24.2μg kg^(−1),and those in the muscle and the visceral tissues of P.trituberculatus were 9.58–160μg kg^(−1)(mean=21.1μg kg^(−1)and 18.22–201μg kg^(−1)(mean=32.7μg kg^(−1),respectively.Furthermore,PFASs that were found at high contents included PFOA,PFOS,and PFOSA,and total contents of 23 PFASs(Σ23 PFASs)ranged 0.0162–5.104μg kg^(−1)(mean=0.915μg kg^(−1).Collectively,the present work provides new data on the contamination in two marine crustaceans captured in the Zhoushan fishing ground in the China East Sea,which can be useful for making suggestions on proper consumption amounts of the two marine crustaceans.

Eff ects of climate change on the potential habitat distribution of swimming crab Portunus trituberculatus under the species distribution model

Over the last decades,the species distribution model(SDM)has become an essential tool for studying the potential eff ects of climate change on species distribution.In this study,an ensemble SDM was developed to predict the changes in species distribution of swimming crab Portunus trituberculatus across diff erent seasons in the future(2050s and 2100s)under the climate scenarios of Representative Concentration Pathway(RCP)4.5 and RCP8.5.Results of the ensemble SDM indicate that the distribution of this species will move northward and exhibit evident seasonal variations.Among the four seasons,the suitable habitat for this species will be signifi cantly reduced in summer,with loss rates ranging from 45.23%(RCP4.5)to 88.26%(RCP.8.5)by the 2100s.The loss of habitat will mostly occur in the East China Sea and the southern part of the Yellow Sea,while a slight increase in habitat will occur in the northern part of the Bohai Sea.These fi ndings provide an information forecast for this species in the future.Such forecast will be helpful in improving fi shery management under climate change.