Identification of quantitative trait loci for growth-related traits in the Pacific abalone Haliotis discus hannai Ino

The locations and effects of quantitative trait loci (QTL) were estimated for nine characters for growth‐related traits in the Pacific abalone (Haliotis discus hannai Ino) using a randomly amplified polymorphic DNA (RAPD), amplification fragment length polymorphism (AFLP) and SSR genetic linkage map. Twenty‐eight putatively significant QTLs (LOD>2.4) were detected for nine traits (shell length, shell width, total weight, shell weight, weight of soft part, muscle weight, gonad and digestive gland weight, mantle weight and gill weight). The percentage of phenotypic variation explained by a single QTL ranged from 8.0% to 35.9%. The significant correlations (P<0.001) were found among all the growth‐related traits, and Pearson's correlation coefficients were more than 0.81. For the female map, the QTL for growth were concentrated on groups 1 and 4 linkage maps. On the male map, the QTL that influenced growth‐related traits gathered on the groups 1 and 9 linkage maps. Genetic linkage map construction and QTL analysis for growth‐related traits are the basis for the marker‐assisted selection and will eventually improve production and quality of the Pacific abalone.     

Quantitative trait locus mapping of growth‐related traits in inter‐specific F1 hybrid grouper (Epinephelus fuscoguttatus × E. lanceolatus) in a tropical climate

Growth‐related traits are the main target of genetic breeding programmes in grouper aquaculture. We constructed genetic linkage maps for tiger grouper (Epinephelus fuscoguttatus) and giant grouper (E. lanceolatus) using 399 simple sequence repeat markers and performed a quantitative trait locus (QTL) analysis to identify the genomic regions responsible for growth‐related traits in F₁ hybrid grouper (E. fuscoguttatus × E. lanceolatus). The tiger grouper (female) linkage map contained 330 markers assigned to 24 linkage groups (LGs) and spanned 1,202.0 cM. The giant grouper (male) linkage map contained 231 markers distributed in 24 LGs and spanned 953.7 cM. Six QTLs affecting growth‐related traits with 5% genome‐wide significance were detected on different LGs. Four QTLs were identified for total length and body weight on Efu_LG8, 10, 13 and 19 on the tiger grouper map, which explained 6.6%–12.0% of the phenotypic variance. An epistatic QTL with a reciprocal association was observed between Efu_LG8 and 10. Two QTLs were identified for body weight on Ela_LG3 and 10 on the giant grouper map, which explained 6.9% of the phenotypic variance. Two‐way analysis of variance indicated that the QTL on Efu_LG13 interacts with the QTLs on Ela_LG3 and 10 with large effects on body weight. Furthermore, these six QTLs showed different features among the winter, summer and rainy seasons, suggesting that environmental factors and fish age affected these QTLs. These findings will be useful to understand the genetic structure of growth and conduct genetic breeding in grouper species.     

池塘养殖三疣梭子蟹的生长规律

为探讨池塘养殖三疣梭子蟹的生长规律和雌雄差异，本研究对1～6月龄池塘养殖三疣梭子蟹各生长指标进行了比较分析，并采用Logistic模型分别拟合三疣梭子蟹的体重(BW)、体长(BL)、体高(BH)、全甲宽(FCW)、甲宽(CW)、大螯长节长(MLC)、大螯不动指长(FFLC)、第一步足长节长(MLFP)等8个形态性状的生长特征。结果显示，三疣梭子蟹雌性和雄性的生长存在差异，早期雄性生长较快，后期雌性生长较快，而雌雄混合分析介于二者之间。三疣梭子蟹各生长性状的Logistic模型拟合结果显示，除雌性MLC和MLFP以及雌雄混合分析的MLFP之外，其余性状R²均达到0.990以上；雌性和雄性体质量的极限生长值分别为290.27和195.91g，快速生长区间分别为2.74～5.10月龄和2.33～4.14月龄，拐点分别为3.92和3.24月龄。研究表明，三疣梭子蟹的生长过程均符合“慢-快-慢”的特征，雄性比雌性更早进入快速生长期，但是快速生长期的持续时间不及雌性。本研究对三疣梭子蟹不同生长指标的规律特征，以及各指标在混合养殖条件下雌性和雄性的优势阶段进行了研究，为实现三疣...     

Mapping quantitative trait loci for infectious salmon anaemia resistance in a North American strain of Atlantic salmon

Infectious salmon anaemia (ISA) is a highly virulent viral disease of Atlantic salmon that causes massive economic losses to infected aquaculture operations. Our goal was to detect and map quantitative trait loci (QTL) that confer resistance to ISA in an admixed commercial strain of Atlantic salmon that was largely founded from the Saint John River (SJR) in North America. Full‐sibling families were challenged with a virulent strain of ISA virus. Mortality was tracked during two annual trials with individual fish that survived to the end of the trial being classified as ‘resistant’, and those that died were classified as ‘susceptible’. Ten families with intermediate levels of mortality and an average size of 54.2 individuals were chosen for genotyping with a 50K SNP array designed for the SJR strain. Single nucleotide polymorphisms that were segregating within families were first used to make a composite 11K female linkage map that was then used to find the positions of QTL for ISA resistance using a half‐sib model. The dam‐based HS model detected a total of three QTL for ISA resistance including an experiment‐wide significant QTL on Ssa25 that accounted for 8.3% of the phenotypic variance and chromosome‐wide significant QTL on Ssa03 and on Ssa04 that accounted for 6.0% and 6.6% respectively. We conclude that classic linkage mapping within families continues to be an important method of detecting QTL for oligogenic traits in strains founded from multiple populations. Single nucleotide polymorphisms with moderate trait effects are being used to select within families for more ISA‐resistant strains of Atlantic salmon.     

iTRAQ‐based identification of differentially expressed proteins related to growth in the swimming crab,Portunus trituberculatus

The swimming crab, Portunus trituberculatus, is an important farmed species in China, and it has been studied extensively, which requires more information on its genetic background. To date, information on the proteomics of P. trituberculatus is scarce. In this study, we used isobaric tags for relative and absolute quantitation (iTRAQ)‐based proteomics to investigate growth regulation in P. trituberculatus. Total proteins were isolated from five tissues (eyestalk, gill, heart, hepatopancreas and muscle). Equal quantities of protein from each tissue were pooled at the proteome level using the iTRAQ method. A total of 961 proteins were identified using liquid chromatography coupled with tandem mass spectrometry and de novo sequencing data. Using a 1.2‐fold change in expression as a physiologically significant benchmark, 30 differentially expressed proteins (DEPs) were found to undergo differential expression related to the growth of P. trituberculatus, and most of the growth‐related proteins, including those involved in metabolism, immune responses, DNA duplication and protein synthesis, were upregulated, indicating that conservation of energy is an important strategy to cope with growth. There was a high consistency between the expression levels determined using iTRAQ and mRNA, highlighting the high reproducibility of our proteomic approach and its great value in elucidating the molecular mechanisms of P. trituberculatus.     

Genotyping‐by‐sequencing for construction of a new genetic linkage map and QTL analysis of growth‐related traits in Pacific bluefin tuna

Pacific bluefin tuna (Thunnus orientalis) has high market value, but its wild populations have decreased in recent years. The broodstock of Pacific bluefin tuna that were hatched artificially and reared under aquaculture conditions is beginning to be used for production. The creation of broodstock with commercially valuable traits, such as rapid growth, is therefore of great interest. Genetic linkage map‐based identification of markers associated with quantitative trait loci (QTLs) facilitates marker‐assisted selection (MAS) breeding and allows efficient genetic improvement of broodstock. Single nucleotide polymorphism (SNP)‐based genetic linkage map construction using the genotyping‐by‐sequencing method can expand the number of mapped markers and help identify growth‐related QTLs. In this study, we constructed sex‐specific maps for 24 linkage groups consisting of 677 SNP and 651 microsatellite markers. The total lengths of 93 progenies in the mapping population followed normal distribution, with an average length of 9.4 mm. We performed composite interval mapping in the mapping population. QTL analysis revealed one significant QTL in LG10 on the female linkage map. The genetic linkage map—the second such map generated for Pacific bluefin tuna—and the growth‐related QTLs detected in this study will be useful for tuna aquaculture MAS programs.     

A first genetic linkage map of bluegill sunfish (<Emphasis Type="Italic">Lepomis macrochirus</Emphasis>) using AFLP markers

Genetic linkage maps were constructed for bluegill sunfish, Lepomis macrochirus, using AFLP in a F₁ inter-population hybrid family based on a double-pseudo testcross strategy. Sixty-four primer combinations produced 4,010 loci, of which 222 maternal loci and 216 paternal loci segregated at a 1:1 Mendelian ratio, respectively. The female and male framework maps consisted of 176 and 177 markers ordered into 31 and 33 genetic linkage groups, spanning 1628.2 and 1525.3 cM, with an average marker spacing of 10.71 and 10.59 cM, respectively. Genome coverage was estimated to be 69.5 and 69.3% for the female and male framework maps, respectively. On the maternal genetic linkage map, the maximum length and marker number of the linkage groups were 122.9 cM and 14, respectively. For the paternal map, the maximum length and marker number of the linkage groups were 345.3 cM and 19, respectively, which were much greater than those on the maternal genetic linkage map. The other genetic linkage map parameters of the paternal genetic linkage map were similar to those in the maternal genetic linkage map. For both the female and male maps, the number of linkage groups was greater than the haploid chromosome number of bluegill (2n = 48), indicating some linkage groups may distribute on the same chromosome. This genetic linkage mapping is the first step toward to the QTL mapping of traits important to cultured breeding in bluegill.     

长牡蛎出肉率与壳形性状的 QTL 定位分析

本研究以长牡蛎(Crassostrea gigas)F1全同胞家系为作图群体,在已构建的基于120个微卫星和66个SNP标记的长牡蛎性别平均连锁图谱上,利用PROC QTL 2.0软件对出肉率和壳形(壳宽和壳深)性状进行QTL定位分析。结果表明,共检测到13个相关的QTL,分布在3个连锁群上;其中,与出肉率相关的4个QTL定位在1号和3号连锁群上(LG1和LG3),表型解释率为0.25%~47.53%;与壳宽相关的3个QTL定位在10号连锁群上(LG10),表型解释率为0.71%~45.39%;与壳深相关的6个QTL也定位在LG10,表型解释率为3.37%~24.78%。根据QTL连锁群分析和性状相关性分析结果可以推测,出肉率与糖原含量性状以及壳宽与壳深性状分别具有相近的遗传特征,利用与相关性状共同关联的分子标记可以同时对出肉率与糖原含量性状、壳宽与壳深性状进行遗传改良。本研究结果为今后长牡蛎相关性状候选基因克隆和分子标记辅助育种提供了参考。     

Ovarian development and nutritional quality changes of the wild‐caught Portunus trituberculatus during the artificial fattening period

A female swimming crab (Portunus trituberculatus) with fully developed ovaries is considered one of the most nutritious types of seafood. The fishing yield of P. trituberculatus in China has always been high; however, its economic value has been low and unreliable due to poor ovarian development and low nutritional value. Artificial fattening is an effective way to improve the value of wild‐caught crabs, and this study focused on analysing the ovarian development and nutritional quality of the female P. trituberculatus during an artificial fattening period. Therefore, this study provides scientific evidence on the effects of artificial fattening on female P. trituberculatus and can guide the development of nutritional quality regulations for wild‐caught female crabs during the fattening process. The results showed that the ovaries of the wild female P. trituberculatus developed gradually. The ovarian morphology became bulkier, while the gonadosomatic index (GSI) and total edible yield (TEY) were significantly improved after artificial fattening. Significant changes in the nutritional components of the edible tissues were observed, and the moisture content in the ovaries and hepatopancreas decreased continually, while both the protein and fat content in the ovaries significantly increased. Moreover, the fat content in the hepatopancreas significantly increased. The saturated fatty acids(ΣSFA) in the ovaries and hepatopancreas had an increasing trend after fattening, while ΣPUFA and Σn‐3PUFA first decreased and then increased. In contrast, the ratio of Σn‐3PUFA to Σn‐6PUFA decreased steadily. However, the fatty acid composition of the muscles did not change significantly. The levels of all the amino acids increased continuously during the fattening process, and EAA increased significantly in the early stages of the fattening period. Consequently, all amino acids became nonlimiting amino acids after fattening. Furthermore, the ratio of EAA/NEAA in the ovaries increased continually until the end of the fattening period. On the other hand, the fatness and TEY increased significantly after artificial fattening. In addition, the nutritional value significantly improved with the exception of the high‐quality fatty acids in the ovaries and hepatopancreas, which were slightly lower in both.     

牙鲆遗传作图及生长性状QTL定位

采用牙鲆日本群体和韩国群体杂交的92个F₁个体作为分离群体, 利用微卫星标记和Joinmap 4.0作图软件构建了牙鲆遗传连锁图谱。共有221个SSR标记用于连锁图谱构建, 雌性图谱中, 共178个微卫星标记定位到22个连锁群上, 观测总长度为(G _oa )599.0 cM, 覆盖率(C _oa )达76.27%。雄性图谱中, 共194个微卫星标记定位到23个连锁群上, G _oa 为693.4 cM, C _oa 为78.82%。对全长、体质量、体高3组数据进行主成分分析处理, 得到可解释3个性状的89.6%特征的一组数据, 命名为牙鲆生长性状GT。用WinQTLCart 2.5软件的复合区间作图,在已构建的遗传连锁图谱上对牙鲆生长性状GT进行QTL定位, 取LOD经验值2.5为QTL存在的阈值; 对微卫星标记进行性状—标记之间的回归分析。本研究共定位3个与牙鲆生长性状GT相关的QTLs, qGT-f4 qGT-m20 qGT-f20,可解释表型变异率分别为27.60%, 13.74%, 10.27%。在性状—标记之间的回归分析中, 得到22个与生长性状GT相关(P<0.05)的微卫星标记, 单个标记可解释表型变异率介于3.70%~10.42%, 其中6个微卫星标记scaffold558_51720、scaffold558_26183、scaffold903_69232、scaffold485_47120 、scaffold1262_77386、scaffold809_65154与生长性状GT之间呈极显著相关(P><0.01), 可解释表型变异率分别为10.42%、7.31%、10.07%、10.07%、8.39%和11.26%。     

东海近海蟹笼网目尺寸对三疣梭子蟹的选择性

不断壮大的东海近海笼壶渔业对三疣梭子蟹（Portunus trituberculatus）等甲壳类资源造成了巨大的压力,实施养护幼蟹的管理措施已成为渔业管理者和生产者的共同呼声。本研究通过海上对比试验,分析了放大网目尺寸对蟹笼渔获效率的影响,运用SELECT模型估算了蟹笼对三疣梭子蟹的尺寸选择性,结合混合影响模型探讨了作业时间和可捕群体对选择性分析的影响。结果显示,对照蟹笼（网目尺寸32.0 mm）与试验蟹笼（网目尺寸分别为52.3 mm和59.7 mm）的三疣梭子蟹渔获甲宽分布存在显著性差异;SELECT模型拟合结果显示试验蟹笼与对照蟹笼的相对作业强度无显著性差异,网目尺寸分别为52.3 mm和59.7 mm的试验蟹笼对三疣梭子蟹的50%选择甲宽（CW₅₀）分别为86.9 mm和90.9 mm,选择范围分别为15.9 mm和9.2 mm。试验蟹笼的CW₅₀远未达到浙江省等当前的最小可捕尺寸规定,表明蟹笼渔业中仅依靠放大网目尺寸可能难以实现幼蟹的有效释放。结果分析显示,在此次试验中作业时间和可捕群体的数量对蟹笼的选择性没有显著性影响。     

草鱼生长相关的微卫星标记在选育群体中的验证

生长性状是水产动物遗传育种中的重要经济性状,利用与性状相关的分子标记与育种相结合的手段,可以大大加速育种进程。在对草鱼生长性状的前期研究中,采用数量性状位点(QTL)定位的方法,在1号连锁群中发现了2个与生长相关的QTL。在此基础上,实验利用这2个QTL侧翼的2对微卫星标记(CID391_2、CID1512、CID973_1和CID254_1),对长江草鱼选育群体的480个个体进行分析,以期基于草鱼QTL定位结果,对草鱼生长相关的微卫星标记在选育群体中进行验证。结果显示:(1)4个微卫星标记在该群体中均具有高度多态性,其中各位点观测等位基因数(N_a)为12～23个,有效等位基因数(N_e)为4～12个,观测杂合度(H_o)为0.607～0.904,期望杂合度(H_e)为0.751～0.902;(2)利用方差分析及多重比较对4个多态性的微卫星标记与选育草鱼群体的生长性状(体质量和体长)进行关联分析,发现CID391_2在雌性个体中,各基因型与体质量和体长之间均无显著差异;而在雄性个体中,各基因型与体质量和体长之间差异显著。CID1512、CID973_1和CID254_1在雌性或雄性个体中,各基因型与体质量和体长之间均具有显著差异。研究表明,对草鱼生长相关的微卫星标记在选育群体中的验证结果,为进一步开展草鱼生长性状QTL定位研究和基于QTL结果的分子标记辅助育种(MAS)实践奠定理论基础。     

A genome scan of a four-way tilapia cross supports the existence of a quantitative trait locus for cold tolerance on linkage group 23

A genome scan, searching for quantitative trait loci (QTL) for the traits cold tolerance and body weight in tilapia, was performed on a cross between a (Oreochromis niloticus×Sarotherodon galilaeus) male and a (O. mossambicus×O. aureus) female. Fifty‐four microsatellites and 23 amplified fragment length polymorphism (AFLP) primer combinations were genotyped and tested for marker–trait associations. Sex‐specific linkage maps were constructed from this data. Twenty‐three point‐wise significant marker–trait associations were found in the genome scan, and putative QTL were subsequently tested in another (On×Sg) × (Om×Oa) family. None of the putative QTL from the first experiment were significant in the second experiment. However, one microsatellite, UNH130, found to be associated to weight in the first experiment, was found to be strongly associated to cold tolerance in the second experiment. Since QTL for cold tolerance and body weight were recently found on the linkage group containing UNH130 (linkage group 23) in another study, this linkage group was investigated more closely using interval mapping. The results provide indications, but not conclusive evidence, of a QTL for cold tolerance on linkage group 23.     

AFLP-based genetic linkage map of marine shrimp Penaeus (Fenneropenaeus) chinensis

This paper presents the genetic linkage map of the Chinese shrimp Penaeus (Fenneropenaeus) chinensis constructed with 472 AFLP markers. A hundred F₁ progeny from an intercross between a female from the new variety “Yellow Sea No. 1” and wild caught male used for the mapping study. Two separate maps were constructed for each parent. The female linkage map consisted of 197 marker loci forming 35 linkage groups and spanned a total length of 2191.1 cM, with an average marker space of 13.5 cM. The male map consisted of 194 marker loci mapped to 36 linkage groups and spanned a total length of 1737.3 cM, with an average marker spacing of 11.0 cM. The level of segregation distortion observed in this study was 12.2%. The estimated genome length of P. chinensis was 3150.3 cM for the female and 2549.3 cM for the male, respectively. The observed genome coverage was 69.6% for the female and 68.1% for the male map. The linkage maps constructed in this study provide basic information for further linkage studies on Chinese shrimp, and more importantly, the construction of the maps are part of the work of the genetic breeding programs which will be used for growth discovered in the QTL analysis of P. chinensis.     

Effects of phospholipid addition to diets with different inclusion levels of fish oil on growth and fatty acid body composition of juvenile swimming crab Portunus trituberculatus

Six experimental diets were designed with two phospholipid (PL; 0% and 1.5%) and three fish oil levels (0%, 1% and 3%) to evaluate the effects of dietary fish oil and PL levels on growth, survival and fatty acid composition of juvenile swimming crab, Portunus trituberculatus. Diets were iso‐energetic and iso‐nitrogenous and each diet was fed to triplicate groups (initially weight, 24.88 ± 0.04 g per crab) for 59 days. Weight gain (WG) and specific growth rate (SGR) increased with dietary PL addition to 0% fish oil‐supplemented diets (P < 0.05). On the other hand, WG and SGR decreased with dietary PL addition to 3% fish oil diets (P < 0.05). Crabs fed PL supplemented diets had higher haemolymph low‐density lipoprotein cholesterol concentrations and muscle crude lipid levels (P < 0.05) than crabs fed a none PL supplemented diet. The percentage of highly unsaturated fatty acids (HUFA; % total FA) in both polar and neutral lipids fractions of muscle tissue only increased in case of PL addition to 0% and 1% fish oil‐supplemented diets (P < 0.05). HUFA levels in the neutral lipids fraction of the hepatopancreas increased by dietary PL addition at each dietary fish oil level (P < 0.05). In this study, both dietary fish oil and PL addition contributed to a high n‐3/n‐6 ratio in muscle and hepatopancreas of P. trituberculatus. In conclusion, PL addition is only meaningful with fish oil‐deficient diets, in which case it enhanced lipid transport and HUFA absorption efficiency, hence improving the nutritional value of the diet.     

Effects of co‐supply ratios of swimming crab Portunus trituberculatus zoeae and Artemia on survival and growth of East Asian common octopus Octopus sinensis paralarvae under an upwelling culture system

Despite recent advances in culture technology for East Asian common octopus Octopus sinensis paralarvae using upwelling systems, securing suitable feed for the paralarvae is an unresolved issue. The zoea of the swimming crab Portunus trituberculatus is a good candidate for paralarval feed because of the high fecundity of the adult females. To investigate the effects of supplying P. trituberculatus zoeae and their feeding method on paralarvae, we cultured paralarvae with supplying different combination ratios of zoeae and Artemia (10:0, 7:3, 5:5, 3:7 and 0:10), and with or without supplementing rotifers using small‐scale (3‐L) upwelling systems. Paralarval survival rate and growth were improved when zoeae were supplied as the main feed, but reduced when the proportion of Artemia exceeded half the whole preys. Supplementing rotifers did not affect the paralarval survival and growth. Subsequently, paralarvae were cultured by supplying zoeae (partially augmented by Artemia) using three large (1‐kl) upwelling systems to assess their feeding effectiveness in juvenile octopus production. Paralarvae could be cultured at high survival rates of 77.1 ± 5.1% to reach benthic juveniles at 23 days after hatching. In conclusion, supplying P. trituberculatus zoeae augmented with Artemia under an upwelling culture system has great potential for juvenile octopus production.     

草鱼7个插入/缺失型突变多态性及与幼鱼生长性状关联分析

对草鱼生长性状进行数量性状基因座(quantitative trait locus,QTL)定位过程中,在15号连锁群中定位到一个与体质量相关的QTL,本研究根据已有的草鱼遗传连锁图谱和基因组序列,拟用短片段重复序列(short tandem repeat,STR)分型技术对该连锁群的3个scaffolds中插入/缺失型突变位点进行筛选,以降低分型成本,同时将筛选出的7个多态性位点与草鱼幼鱼生长性状进行关联分析。结果显示,(1)草鱼3个scaffolds中44个插入/缺失型突变位点中有17个简单重复序列(又称微卫星,simple sequence repeats,SSRs),2个位点引物设计不成功,设计的25对引物中仅22对扩增和分型成功;(2) 22个位点中仅有7对引物在4个亲本中存在多态性,直接测序结果发现,STR分型技术不仅可准确对插入/缺失型突变位点进行分型,同时可降低分型成本;(3)将7个插入/缺失型突变位点与323尾选育F2草鱼的生长性状进行关联分析发现,除了位点ID-10H和ID-41F以外,其余5个位点都与草鱼幼鱼的一个或多个生长性状显著相关,其中ID-6H与幼鱼肥满度性状显著相关,位点ID-11F、ID-15F、ID-32F和ID-39F分别与草鱼幼鱼体质量、体长、体宽和体高性状显著相关,可将以上5个与草鱼幼鱼生长性状相关的突变位点用于草鱼生长性状QTL加密和分子标记辅助育种。     

致急性肝胰腺坏死病副溶血弧菌(VpAHPND)自然感染三疣梭子蟹

近年来包括急性肝胰腺坏死病(AHPND)在内的多种新发疫病的流行,使我国甲壳类养殖业遭受了严重的经济损失。为了筛查导致山东潍坊某养殖场中一虾蟹混养池塘内患病三疣梭子蟹感染的可能病原,本研究采用分子生物学检测方法,对三疣梭子蟹样品进行了白斑综合征病毒(WSSV)、传染性皮下及造血组织坏死病毒(IHHNV)、虾血细胞虹彩病毒(SHIV)、致急性肝胰腺坏死病副溶血孤菌(Vp_(AHPND))、虾肝肠胞虫(EHP)、偷死野田村病毒(CMNV)、黄头病毒(YHV)和肝胰腺细小病毒(HPV)等8种病原的检测,并对样品进行了组织病理和原位杂交分析。分子生物学检测结果显示,患病三疣梭子蟹样品呈Vp_(AHPND)阳性,而呈现WSSV、IHHNV、SHIV、EHP、CMNV、YHV和HPV阴性。对样品进行Vp_(AHPND)套式PCR第二轮扩增产物的序列测定、比对和进化树分析,结果显示,扩增产物序列与致病副溶血弧菌质粒上pirA~(vp)毒力基因片段具有99%的同源性,该序列与已报道的多个致病副溶血弧菌PirA聚在进化树的同一主分支上。组织病理学分析显示,患病三疣梭子蟹的肝胰腺小管上皮细胞坏死,心肌纤维呈溶解样病变,鳃丝上皮柱突细胞明显坏死,胸神经节的神经细胞损伤严重,并且这些组织中还可见大量的细胞核固缩现象;原位杂交结果显示,肝胰腺、心肌、鳃组织及胸神经节中的病变部位均存在Vp_(AHPND)探针的蓝紫色杂交信号。以上表明,虾蟹混养池塘中三疣梭子蟹在自然状态下感染了Vp_(AHPND),并导致肝胰腺、心肌、鳃和胸神经节发生了严重病理损伤。本研究首次在养殖三疣梭子蟹中检测到Vp_(AHPND)感染并揭示了感染所致的病理变化,相关结果为揭示Vp_(AHPND)自然宿主种类和养殖三疣梭子蟹病害防控提供了基础信息。     

QTL mapping for glycogen content and shell pigmentation in the Pacific oyster Crassostrea gigas using microsatellites and SNPs

Glycogen content and shell pigmentation are two important economic traits of the Pacific oyster Crassostrea gigas. The first set of quantitative trait loci (QTLs) controlling the two traits was determined in an F1 full-sib family based on a sex-averaged linkage map. The linkage map was constructed using 120 SSRs, and 66 expressed sequence tag-derived single nucleotide polymorphisms (EST–SNPs). Two QTLs were found to be associated with glycogen content, explaining 0.27–79.05 % of the phenotypic variation. One QTL on LG9 were found to be related to shell pigmentation, the paternal and maternal alleles explaining 6.75 and 17.44 % of the phenotypic variation. The relationship of glycogen content with left shell depth and QTL linkage group analysis suggests that left shell depth and volume might be used to assist in indirect selection for glycogen content. The constructed linkage map and determined QTLs can provide a tool for further genetic analysis of the traits and be potential for marker-assisted selection in C. gigas breeding.