Genetic linkage map of bay scallop, Argopecten irradians irradians (Lamarck 1819)

The bay scallop (Argopecten irradians irradians Lamarck 1819) has become one of the most important aquaculture species in China. Genetic improvement of cultured bay scallop can benefit greatly from a better understanding of its genome. In this study, we developed amplified fragment length polymorphisms (AFLPs) and simple sequence repeat markers from expressed sequence tags (EST‐SSRs) for linkage analysis in bay scallop. Segregation of 390 AFLP and eight SSR markers was analysed in a mapping population of 97 progeny. Of the AFLP markers analysed, 326 segregated in the expected 1:1 Mendelian ratio, while the remaining 74 (or 19.0%) showed significant deviation, with 33 (44.6%) being deficient in heterozygotes (A/a). Among the eight polymorphic EST‐SSR loci, one marker (12.5%) was found skewing from its expected Mendelian ratios. Eighteen per cent of the markers segregating from female parent were distorted compared with 21% of the markers segregating from male parent. The female map included 147 markers in 17 linkage groups (LGs) and covered 1892.4 cM of the genome. In the male map, totally 146 AFLP and SSR markers were grouped in 18 LGs spanning 1937.1 cM. The average inter‐marker spacing in female and male map was 12.9 and 13.3 cM respectively. The AFLP and SSR markers were distributed evenly throughout the genome except for a few large gaps over 20 cM. Although preliminary, the genetic maps presented here provide a starting point for the mapping of the bay scallop genome.     

Crosses between two subspecies of bay scallop Argopecten irradians and heterosis for yield traits at harvest

In order to improve the yield of bay scallop Argopecten irradians by exploiting geographic subspecies heterosis, crosses between and within two subspecies, the northern A. i. irradians (Lamarck) and the southern A. i. concentricus (Say), were created and the offspring were cultured under the same environmental conditions. The two parental populations were collected from Bohai Bay in northern China and Beibu Bay in southern China, which were distinct in particular shell colours. The results indicated that the shell colour of bay scallop was inheritable and could be used as a morphological mark to distinguish hybrid and purebred individuals. At harvest, hybrid offspring always produced a significantly higher yield than purebred offspring. Positive heterosis was achieved for shell length, shell height, shell width, total weight and adductor weight, which was 5.02, 5.22, 3.88, 7.53 and 9.47 respectively. Hybrid gain was 10.86% for shell length, 10.48% for shell height, 9.77% for shell width, 34.90% for total weight and 41.69% for adductor weight, respectively, and all were significantly >5%. The present study reveals that it is effective for improving yield by hybridization between different geographic subspecies in the bay scallop.     

塔玛亚历山大藻对海湾扇贝胚胎发育过程的影响

研究了塔玛亚历山大藻（Alexandrium tamarense）ATHK株对海湾扇贝受精卵孵化的影响，并探讨了可能的影响机制。将海湾扇贝受精卵暴露于不同密度的塔玛亚历山大藻ATHK中，观察其对胚胎孵化各阶段的影响，并利用光镜和透射电镜对实验组和对照组胚胎的外部形态和内部结构进行连续观察。结果表明：该藻对海湾扇贝受精卵孵化有显著的抑制作用，其IC50约为800 mL-1；2000 mL-1的ATHK延缓或破坏了胚胎的正常发育，胚胎内部出现大量溶酶体，原肠胚腔不能形成，且部分细胞出现胞质肿胀、线粒体自溶的现象，细胞不能进行正常的功能性分化；观察发现实验组中有些担轮幼虫的外形畸变，鞭毛发育迟缓；至24 h（D型幼虫）时，ATHK组中的D型幼虫数量远远低于对照组（P<0.05），且死亡率明显高于对照组。观察还发现ATHK藻细胞和胚胎碰撞接触的现象，这种碰撞接触可能对有害物质的释放和转移有一定的刺激作用。     

在海湾扇贝亲贝促熟培养中混养海参的研究

首次在海湾扇贝亲贝的促熟培育中，在池底放养海参，利用海参来摄食扇贝的粪便和残饵，改善亲贝蓄养水质。经42天混养试验表明：实验组比对照组性腺指数明显提高，水质得到了明显的改善，换水量降低了25％-30％，降低了生产成本，同时海参也增重了约30％，取得了比较好的效果。     

海湾扇贝杂交家系与自交家系生长和存活的比较

2002年春季,利用国内现有的海湾扇贝两个不同遗传背景的养殖群体A和B的种贝为材料,采用自体受精和异体受精两种交配策略,建立了海湾扇贝的自交系和杂交系。实验由AA(A♀×A♂)、BB(B♀×B♂)、AB(A♀×B♂)、BA(B♀×A♂)四个组组成。杂交使两个表型性状———生长和存活都得到了改良。就生长而言,杂交组比自交组快,杂种优势在幼虫期为35.34%、养成阶段为21.17%;杂交组AB的生长速度比自交组AA的提高了35.53%(幼虫期)和43.32%(养成阶段),杂交组BA的生长速度比自交组BB的提高了35.13%(幼虫期)和12.34%(养成阶段)。就存活而言,两个杂交组的存活率都高于相应的自交组,杂种优势的平均值在幼虫期为19.93%,养成阶段为31.46%;杂交组AB的存活率比自交组AA的提高了25.23%(幼虫期)和49.44%(养成阶段),杂交组BA的存活率比自交组BB的提高了12.36%(幼虫期)和21.29%(养成阶段)。A、B两个群体间存在的遗传差异是它们能够获得杂种优势和性状得到改良的基础。     

海湾扇贝引种及展望

海湾扇贝原产于美国大西洋海岸,自1982年引种以来,取得了巨大的经济社会效益和生态效益.随着海湾扇贝的大规模养殖,制约海湾扇贝养殖的一系列问题逐渐显现,尤其是种质退化,虽然采取了一系列的相应措施,取得了一定的成效,但没有从根本上解决这些问题.通过新品种的引进可以遏制种质退化,促进生态平衡,提高单位养殖水体的效益,预防传...     

Chlamydiosis: a newly reported serious disease of larval and postmetamorphic bay scallops, Argopecten irradians (Lamarck)

Abstract. Diseases of bivalve molluscs characterized by the presence of prokaryotic intra-cytoplasmic inclusion bodies in epithelial cells are reviewed. The paper reports the history, clinical and pathological findings during hatchery epizootics of chlamydiosis in larval and postmetamorphic bay scallops, Argopecten irradians (Lamarck), and enzootic infection in wild, captive and cultured adult and juvenile bay scallops during a 15-year period (1972–1987) of surveillance for scallop diseases in the northeastern Atlantic coastal region of the United States. The disease was found in 44·4% of adult bay scallop laboratory accessions as an endemic disease without overt clinical signs or mortalities, and as a highly fatal epizootic disease with a rapid course in 20% of hatchery-reared larval and postmetamorphic bay scallop accessions. The pathogenesis and development of the chlamydial agent during hatchery epizootics are described. The importance of the congenital 'childhood' diseases of larval bay scallops and other species of bivalve molluscs is discussed.     

Strategies for enhancement of natural bay scallop, Argopecten irradians irradians, populations; A case study in the Niantic River estuary, Connecticut, USA

We investigated strategies to enhance populations of bay scallops,Argopecten irradians irradians (Lamarck, 1819), in a presumablyrecruitment-limited natural habitat. At present, the Niantic Riverestuary supports only a minor bay scallop population that is harvestedrecreationally. Three enhancement strategies were evaluated; (1)collection and redistribution of natural spatfall, (2) introduction andover-wintering of hatchery-reared stock into natural habitat to providenew spawning stock, and (3) over-wintering of hatchery-reared stock insuspension culture for creation of mobile spawner sanctuaries. Anassessment of natural bay scallop recruitment in the Niantic Riverconducted in 1997 indicated that few spat were found, they were widelydispersed within the river, and peak spawning occurred in late July1997. Direct re-seeding was evaluated as an enhancement measure byplanting hatchery-reared scallops ( 38 mm shell height) insmall-scale, 100-m² plots at different times and densities.Time of planting and the inferred predation intensity were major factorsaffecting survival; whereas, planting density had no significant effect.Approximately 9,000 scallops (35–45 mm shell height), broadcastwithin an eelgrass bed in November 1997, had high over-winter survivaland underwent gametogenesis and spawning during 1998. Of 26,000 bayscallops ( 45 mm shell height) over-wintered in suspensionculture from 1998–1999, approximately 60–80%survived, and these scallops spawned in mobile sanctuaries, during thesummer of 1999. There is good potential for using aquacultural methodsfor enhancement of bay scallop populations when natural recruitment ispoor and habitat and environmental conditions are not limiting.     

海湾扇贝南部亚种闭壳肌质量的双性状选择效应

采用双性状选择方法在经群体继代大壳高选育的海湾扇贝(Argopecten irradians concentricus Say)南部亚种F₃养殖群体中进行闭壳肌定向选育, 以评价闭壳肌的选择效果和现实遗传力, 为海湾扇贝南部亚种育种提供理论依据。结果表明, 在以壳高为第一选择性状、体质量为第二选择性状、壳高选择压力为10%、体质量选择压力为1%情况下, 正、负向选择组、对照组在产卵量、受精率、孵化率、幼虫期壳长增长率、中培期存活率、成体各形态参数等方面的差异不显著(P>0.05); 在稚贝育成率、养成期存活率、成体各质量性状等方面均存在显著差异(P<0.05), 各指标值均呈现正向选择组>对照组>负向选择组; 正、负向选择组中, 体质量与闭壳肌质量均出现较高的现实遗传力, 且正向选择组高于负向选择组; 双性状选择时, 体质量与闭壳肌质量的当代遗传获得明显高于单性状选择结果。壳高和体质量对闭壳肌质量均具有密切的遗传相关, 任何一个性状的选择均可对闭壳肌质量产生显著影响, 双性状同时选择可对闭壳肌质量产生叠加效应, 使闭壳肌质量性状的遗传进展达到最大。

     

Effect of parental stock size on F1 genetic structure in the bay scallop, Argopecten irradians (Lamarck, 1819)

Three F₁ families of the bay scallop, Argopecten irradians, were produced from one, two and 10 individuals. The genetic changes in these populations, which suffered recent and different levels of bottleneck, were analysed using amplified fragment length polymorphism (AFLP) techniques. In the parental stock, a total of 330 bands were detected using seven AFLP primer pairs, and 70% of the loci were polymorphic. All F₁ groups had a significantly lower proportion of polymorphic loci when compared with the initial stock, and loss of the rare loci and reduction in heterozygosity both occurred. The progeny of the larger population (i.e., N=10) exhibited a lesser amount of genetic differentiation compared with the progeny from N=2, which showed lesser differentiation than progeny from N=1. The effective population sizes (N_e) in N=1, 2 and 10 were estimated as 1.50, 1.61 and 2.49. Based on regression analysis, we recommend that at least 340 individuals be used in hatchery populations to maintain genetic variation.     

墨西哥湾扇贝与华贵栉孔扇贝的远缘杂交

为进一步研究扇贝属间远缘杂交的可行性,以墨西哥湾扇贝(Argopecten irradians concentricus)与华贵栉孔扇贝(Chlamys nobilis)作为亲本,建立了两种扇贝的正交组MH、反交组HM、墨西哥湾扇贝自交组MM和华贵栉孔扇贝自交组HH。对各实验组的胚胎发育速度、受精率、孵化率、D形幼虫发生率和幼虫生长速度进行比较,分析了不同温度、盐度和精子浓度对各实验组配子亲和力及合子育性的影响,并尝试运用BP神经网络模型预测杂交组浮游幼虫的生长趋势。结果表明,两种扇贝的正反杂交均可获得早期杂交子代(F_1)。从胚胎发育情况看,正反杂交组幼虫发育到D形幼虫的时间均少于两个自交对照组;其受精率、孵化率、D形幼虫发生率也低于两个自交对照组;即使在不同温度、盐度和不同精子浓度下正反交组的受精率和孵化率也均低于两个自交组。从浮游幼虫生长情况看,正反交组D形幼虫的壳长和壳高均高于两个自交组,具有显著的差异性(P0.01),表现出较明显的杂种优势。运用BP神经网络模型对正反交组的浮游幼虫进行预测,其预测值与实测值的误差率均小于4%。     

人工养殖栉孔扇贝和海湾扇贝血淋巴中部分免疫因子的比较研究

采用分光光度技术对人工养殖的栉孔扇贝和海湾扇贝血淋巴中部分免疫因子进行了比较研究。结果表明,海湾扇贝血清和血细胞中溶菌酶、非特异性酯酶(NSE)、过氧化氢酶(CAT)、髓性过氧化物酶(MPO)、一氧化氮(NO)、一氧化氮合酶(NOS)、活性氧和H2O2的活力或含量均高于栉孔扇贝,两种扇贝除血清中MPO活力差异不显著外,其他各组均差异极显著或显著。表明人工养殖海湾扇贝较栉孔扇贝的免疫力强。     

墨西哥湾扇贝亲代选择对自交子一代的影响

试验从来自同一养殖群体的1000个随机个体墨西哥湾扇贝(Argopecten irradians concentricus Say)中选取规格最大(壳长58.3~61.9 mm)、中等(壳长49.5~50.8 mm)、最小(壳长38.9~41.1 mm)的性成熟个体各3个作为亲贝,按规格分成大、中、小3组,利用该贝雌雄同体的特性分别进行各组内亲本个体自交。在相同环境及试验条件下通过比较各自交组受精率、孵化率、稚贝育成率、海上暂养及标粗期存活率、养成期存活率、壳长壳高体重日增长率和选择反应等指标的差异,分析亲本选择对自交子代生产性能的影响。结果表明,从上述各指标看,大规格亲贝优于中规格亲贝(P<0.01);中规格亲贝优于小规格亲贝(P<0.01)。大规格亲贝壳高、壳长和体重的选择反应分别为6.0 mm、5.4 mm和6.3 g,中规格亲贝分别为-0.4 mm、-0.1mm和-0.7 g,小规格亲贝分别为-4.7 mm-、5.3 mm和-7.6 g。大规格亲贝壳高、壳长和体重的实现遗传力分别为0.52、0.49和0.40。研究证明,墨西哥湾扇贝亲代选择对自交子一代生产性能具有极显著影响(P<0.01),大规格亲贝自交后代表现出明显生长优势,截断选择策略有效。     

The culture of the southern bay scallop in Tampa Bay, an urban Florida estuary

Bay scallop, Argopecten irradians concentricus (Say), stocks were collected from a Homosassa (Florida) population in 1991 and were kept in seawater from Bayboro Harbor on Tampa Bay, an urban Florida estuary. They were fed with Isochrysis galbana and Tetraselmis sp. Spawning was allowed to occur after the scallops became ripe. The hatching rate of the F1 eggs to D-shaped larvae was 72%. Settlement and metamorphosis began 11 days after fertilization. When spat reached a shell height of 0.8 mm in the laboratory, they were placed with substrates into 300 and 800 m mesh bags, and later in lantern nets, suspended from a dock in Bayboro Harbor. The F1 scallops successfully survived to gonad maturity in the fall of 1992, with mean (sd) shell height of 49.8 (4.0) mm on 6 September 1992. The scallops experienced heavy mortality during the summer, partially as a result of heavy fouling. From early August to October of 1992, F1 scallops grown in Bayboro Harbor were successfully spawned in the laboratory. Growth and survival of the F2 scallops were comparable to those of the F1 scallops. Results have shown that bay scallops can complete an entire life cycle in an urban estuary such as Tampa Bay, and a hatchery for bay scallops on the estuary can assist in the restoration of the population. Fouling represents a possible severe limitation and alternatives to caging for grow-out should be considered.     

海湾扇贝一种球形病毒的形态发生及细胞病理学观察

2001年3-5月,青岛海区养殖海湾扇贝发生外套膜"糜烂病"并导致约50%亲贝死亡,主要表现为外套膜糜烂;严重者,约2/3的外套膜溃烂呈胶水状.电镜检测发现病贝体内感染有病毒等病原微生物.本文报道了该病毒粒子的形态、发生及宿主细胞由此所产生的细胞病理学变化.成熟的病毒粒子近球形,直径150～180nm,具囊膜,在细胞核附近的溶酶体内发生和增殖.发生初期溶酶体内形成板层髓样结构,随后形成块状、泡状、絮状等多形态的病毒发生基质及具有正方形花样的蛋白质晶格结构.最后,大量的病毒粒子装配形成,填充在溶酶体内.该病毒粒子主要存在于消化盲囊上皮细胞及结缔组织细胞的胞质中.受感染的宿主细胞线粒体肿胀、嵴溶解,内质网肿胀、核糖体脱落,溶酶体数量增多,核膜膨胀、溶解等,大部分细胞器受损.     

间接免疫荧光法检测栉孔扇贝急性病毒性坏死症病毒

用纯化栉孔扇贝(Chlamys farrei)急性病毒性坏死症病毒(AVNV)免疫兔子,以兔抗血清为一抗,荧光标记的羊抗兔抗体为二抗,采用冰冻切片技术,建立了栉孔扇贝AVNV的间接免疫荧光检测方法。用该方法分析栉孔扇贝和海湾扇贝(Argopecten irradians)体内AVNV感染强度,并对感染率进行统计。结果表明,栉孔扇贝的肾脏、肝胰腺中,AVNV阳性信号最强,呈现中度到重度感染,其AVNV感染率100％。鳃丝、性腺及闭壳肌中未检测到阳性信号。在海湾扇贝的肝胰腺及肾中AVNV的感染率也较高。提示AVNV感染扇贝的靶器官主要是肾脏、肝胰腺。对与栉孔扇贝同一海区养殖的海湾扇贝在栉孔扇贝发病期间存活率较高的原因进行了讨论。     

Scope for growth of Texas Bay scallop Argopecten irradians amplicostatus

Bivalves have exceptional potential as sentinel organisms because their sedentary benthic lifestyle and ability to pump large volumes of water in short periods of time results in bioaccumulation of pollutants and toxins present in the water column. Scope for Growth (SFG) is an instantaneous measure of production that ranges from maximum positive values under optimal conditions to negative valves when the organism is stressed and utilizing its body reserves for maintenance. We determined baseline SFG for the Texas bay scallop Argopecten irradians amplicostatus so that this species might be used to determine sublethal effects of toxins, contaminants, or other environmental stressors in light of recent harmful algal bloom events in the Gulf of Mexico. We also quantified the effects of different diets (phytoplankton, zooplankton, mixed phytoplankton/zooplankton) on Texas bay scallop SFG. SFG of starved animals was negative, indicating that body reserves were used for maintenance. SFG varied significantly (P < 0.001) by diet, with rotifers yielding the highest value (mean = 14.88 Joules hr^?1g dry weight, SE = 0.72). We determined that the Texas bay scallop has presently unrecognized potential as sentinel organisms to define effects of various environmental and anthropogenic perturbations.     

熊本牡蛎多嵴和无嵴品系F3生长性状的连续选择效应

为进一步检测熊本牡蛎(Crassostrea sikamea)多嵴和无嵴品系F3的连续选择反应,以2个品系F2上选组为材料,开展2个品系F3混合上选研究,评估2个品系F3生长性状的选择反应、现实遗传力及遗传改进量,解析选育过程中选择效应、品系效应及二者交互作用对生产性状的影响。结果表明:多嵴品系F3生长性状具有较高的现实遗传力,表现出较好的遗传改良效果;无嵴品系F3表现出中等现实遗传力水平,但仍具有一定程度的遗传改良潜能。养成期360日龄时,多嵴品系子代壳高、鲜重的选择反应分别为0.70、0.76;现实遗传力分别为0.40、0.43;遗传改进量分别为7.02%、12.29%;无嵴品系的选择反应分别为0.36、0.33;现实遗传力分别为0.20、0.19;遗传改进量分别为3.74%、5.72%。经过双因子分析模型检测发现:品系来源是影响F3生长性状的主要因子,选择效应是次要因子,二者间不存在明显的交互作用。由此可见,随着连续选择的进行,选择反应逐渐降低,品系来源作用增强,本研究为熊本牡蛎遗传改良和新品系培育奠定了基础。     

Chlamydia-like organisms in the digestive diverticula of the bay scallop, Argopecten irradians (Lmk)

Abstract. The morphology of a chlamydia-like organism from the digestive diverticula of the bay scallop, Argopecten irradians (Lmk), is described. This organism was found in about 40% of bay scallops introduced to the quarantine unit at Ellerslie, Prince Edward Island, Canada and also in about 40% of the F₁ and F₂ generations. Procaryote infections were also found in the northern quahog, Mercenaria mercenaria (L.), the soft-shelled clam, Mya arenaria L., and the Atlantic deepsea scallop, Placopecten magellanicus (Gmelin).     

Utility of high-density plantings in bay scallop, Argopecten irradians irradians, restoration

Two different methods of establishing high-density spawner sanctuaries for bay scallop (Argopecten irradians irradians) restoration were evaluated over 2 years at a site in Northwest Harbor, East Hampton, New York, USA. Hatchery-reared scallops, which had been overwintered at nearby sites, were free-planted directly to the bottom in late March/early April at an initial target density of 94?C128 scallops/m². In addition, scallops were stocked in off-bottom culture units consisting of three vertically stacked 15-mm mesh ADPI^® bags at densities of 50, 100, or 200 scallops/bag (=117, 234, or 468 scallops/m²), respectively. Survival of scallops differed significantly by year, planting method, and scallop source. Survival of free-planted scallops was generally lower than caged scallops. Better survival of free-planted scallops in 2005 versus 2006 likely reflected the presence of luxuriant eelgrass beds in 2005, which were absent in 2006. Survival of scallops in ADPI bags was not appreciably related to stocking density. Shell growth was highest for free-planted scallops; in cages, growth was somewhat better at 50 versus 200 scallops/bag. Wet weights of epibionts were significantly higher in caged versus free-planted scallops. Reproductive condition of scallops stocked at 50/bag was usually higher than at 200/bag. Both free-planting and off-bottom systems yielded high densities of adult bay scallops at the time of spawning, which ensures a higher probability of successful fertilization of spawned eggs and thus a greater potential for success of restoration efforts.