牡蛎养殖技术

太平洋牡蛎具有体型大、生长快、味美、产量高、适应性强等优点,是浅海养殖的优良品种之一。本文概述了太平洋牡蛎的人工养殖技术,同时介绍了一种牡蛎的室内控温育苗技术;旨在为牡蛎养殖单位的生产实践提供参考。     

三倍体长牡蛎浮筏养殖技术的研究

本文报道了两个相邻海区近５００ｈｍ＾２三倍体长牡蛎Ｃｒａｓｓｏｔｒｅａ ｇｉｇａｓ（Ｔｈｕｎｂｅｒｇ）浮筏养殖的研究结果。三倍体牡蛎的采苗器为栉孔扇贝壳,每片采苗器采苗１０￣１２个,以１５￣２０ｃｍ间距夹于３股聚乙（丙）烯蝇间并吊养在浮筏上。三倍体牡蛎在个体重、出肉率和条件指数等养殖经济性状方面比二部体分别增加４２．１％、１６．２％、５６．７％,成活率也有一定的提高。三部体在生长等方面性状优势的生     

Spatfalls of the non-native Pacific oyster,Crassostrea gigas,in British waters

Light spatfalls of the Pacific oyster, Crassostrea gigas, have occurred in the estuaries of the Rivers Exe, Teign and Dart (Devon) and in the Menai Strait (Gwynedd), near to sites of commercial cultivation of this species. Comparisons of the sizes of the naturally settled oysters with hatchery oysters suggests that the spat from the River Teign and Menai Strait settled in 1989 and 1990. The springs and summers of these years were exceptionally warm with mean monthly air temperatures 0.8°-1.3°C above the 1951–1980 average for the period April to August. Although sitings of Pacific oyster spat were made in Loch Sween and Emsworth Harbour over 20 years ago, there is no evidence that self-sustaining populations have developed. The spatfalls which occurred in some coastal waters of Devon and Gwynedd in 1989 and 1990 are unlikely to sustain natural fisheries and are likely to die out as did the Portuguese oysters which occasionally settled in the River Blackwater, Essex.     

基于微卫星标记整合长牡蛎遗传图谱

为了提高长牡蛎遗传图谱上的微卫星标记密度,实验采用6个家系图谱间的共有微卫星标记作为锚定标记,构建了长牡蛎的整合图谱.该整合图谱共有161个微卫星标记,覆盖10个连锁群,图谱长度和平均间距分别为615.4和3.8 cM.各连锁群的标记数介于10 ～ 24个之间,连锁群长度为47.3～73.3 cM,是目前密度最高的长牡蛎微卫星图谱.不同作图家系连锁群上的标记分组保持一致,但标记顺序出现差异,可能与长牡蛎自然群体中存在大量的染色体重排现象有关.结果表明,该图谱可以为今后长牡蛎的遗传育种研究提供新的遗传工具.     

Genetic parameters of growth and survival in the Pacific oyster Crassostrea gigas

The Pacific oyster Crassostrea gigas is a representative bivalve mollusc that is widely cultured in the world and is the largest molluscan group cultured in China. In order to assess the feasibility of improving survival of C. gigas through genetic selection, the heritability and genetic correlations for growth and survival traits between different life stages were examined. Genetic parameters were estimated based on intraclass correlations of 49 full‐sib families (29 half‐sib families) in larvae (4 and 20 days after fertilization) and spat (140 days after fertilization) stages. The heritability for growth traits in larvae and spat was 0.30–0.86 and 0.53–0.59, respectively, and varied with ages. The heritability of survival was low in larvae (0.13 ± 0.05 and 0.17 ± 0.04, respectively for 4 and 20 days after fertilization) but medium (0.39 ± 0.07) in spat, suggesting that selection for increasing spat survival was feasible. The genetic correlation between growth traits within age was medium to high and positive (ranging from 0.47 to 0.96, respectively, between shell length (SL) and shell height (SH) at 20 days and between SL and SH at 140 days after fertilization), suggesting that selection to improve single growth trait will cause positive response in another growth traits in C. gigas. The genetic correlations between survival and growth traits at 140 days were low but positive (ranging from 0.23 to 0.27, respectively, between survival and SH and between survival and SL at 140 days after fertilization), suggesting that selection for survival may not have a negative response in growth. Overall, this study suggests that survival traits should be taken as improving target of next selection breeding programme in C. gigas.     

Early detection of triploidy in the larvae of Pacific oysters,Crassostrea gigas,by flow cytometry

Triploidy may provide a means to neuter the Pacific oyster, C. gigas, genetically thereby increasing survival and marketability during periods of reproduction. Pressure treatments administered 10 min after fertilization for 10 min duration at 6000–8000 psi consistently produced triploids. The highest proportion obtained was 57%. Triploidy was assayed in all experiments at the larval stage and again as spat (metamorphosed larvae) using flow cytometry. A technique to assay larvae as small as 250 μm is described. Results obtained by flow cytometry were verified by chromosome counts. Analysis of triploidy at the larval stage provides reliable estimates of the proportion of triploids, eliminating several weeks of culture time.     

Effects of developmental stage, seawater concentration and rearing temperature on cryopreservation of Pacific oyster Crassostrea gigas larvae

ABSTRACT: For the development of a stepwise cryopreservation technique for larvae of the Pacific oyster Crassostrea gigas , various conditions were examined. Larvae at 9, 12, 15, 18 and 21 h after insemination were cooled at a rate of −1°C/min (seeding at −8°C for 15 min) and then plunged into liquid nitrogen at −35 or −40°C using 1.5 M dimethyl sulfoxide (DMSO) and 250 mM trehalose as cryoprotectants. Among these larvae, 15 h after insemination (the trochophore stage before formation of the shell gland) showed the highest motility and the best external appearance after thawing. Trochophore larvae were cryopreserved in preservation media containing different dilutions (1/4, 1/6, 1/8, 1/10 and 1/30) of seawater. Larvae preserved in the 1/4 seawater medium showed the highest appearance of shelled larvae 4 days after thawing. Trochophore larvae reared in seawater at 21, 25 or 29°C were cryopreserved for 8 months and then reared at 26°C after thawing. Larvae reared at 25°C showed the highest survival rate and normal larval ratio at day 6 after thawing, although larvae reared at 21°C showed the highest rates until day 4. One larva developed at 25°C succeeded to settle.     

Genetic improvement of the Pacific oyster Crassostrea gigas (Thunberg) in Australia

The Pacific oyster industry in Australia is derived from importations from Japan in the late 1940s and early 1950s to Tasmania and is almost completely hatchery based. This makes it a good target for developing and deploying genetically improved strains. An allozyme survey comparing hatchery stocks with self‐recruiting Tasmanian stocks and with two collections from Japan found abundant variation and no significant evidence of allele loss. The subsequent selection programme (initiated in the summer of 1996/97) had several strands. We wanted to take advantage of the increased power that marker‐assisted selection could bring and, therefore, needed to develop a linkage map and isolate flanking markers around quantitative trait loci (QTLs). Several types of markers (allozymes, microsatellites and AFLPs) were used, and single‐pair crosses were set up; QTLs have been detected. Conventional selection programmes, one based on mass selection and one on family selection, have been established. Triploid Pacific oysters produced via chemical means have been available for several years, but rates of triploidy achieved by such means are usually less than 100%. In 1999, we will assess whether our tetraploid 2‐year‐old broodstock can be crossed with diploids to give 100% triploid offspring.     

A comparison of the gametogenic cycle between the Pacific oyster Crassostrea gigas and the Suminoe oyster Crassostrea rivularis in Washington State

The gamotogenic cycle of the Suminoe oyster, Crassostrea rivularis, was compared with that of two groups of Pacific oysters (Crassostrea gigas) on an intertidal oyster bed in Oakland Bay, Washington. The Pacific oysters exhibited an earlier and more extensive development of gonad relative to C. rivularis. Resulting carbohydrate depletion was much greater in C. gigas relative to C. rivularis. Both groups of Pacific oysters spawned completely in mid-August. C. rivularis did not spawn but, rather, initiated phagocytosis of gametes by leucocytes. The implications of the results on the development of a marketable “summer” oyster are discussed.     

Suspended culture evaluation of Pacific oyster Crassostrea gigas in a tropical estuary

The growth and survival of Crassostrea gigas were evaluated in hanging culture in the Chone River estuary (Bahía de Caráquez), Manabí province, Ecuador. Oyster seeds (~10 mm) were confined in lantern nets at a density equal to the occupation of half the surface of the basket base, until reaching commercial size (80 mm). A sample for oyster biometric, parasitic and bacterial analysis was obtained monthly. Temperature, salinity, oxygen concentration, seston and phytoplankton biomass were determined. At the end of the study, the oysters were analysed for heavy metal concentration. The commercial oyster production was extrapolated to estimate the possible economic performance of a family production module (a 7 × 7 m bamboo raft). The results show a great biological feasibility of culture of C. gigas with harvests of commercial size oysters in only 5 months and acceptable survivals (accumulated >70%, after 3 weeks of crop seed selection). The heavy metal concentrations and the parasitological and bacteriological analyses did not indicate levels of contamination. The economic projections suggest that, even with a profitability of 57%, the initially invested capital could be recovered within the first harvest.     

Sex-specific growth and condition of the Pacific oyster (Crassostrea gigas Thunberg)

In order to study the possibility of gaining commercial benefit from culturing an excess of one sex of the Pacific oyster (Crassostrea gigas), comparative data on the growth rate and condition of male and female oysters are reported. Historically, measurement of sex‐specific growth rate in oysters has been overlooked or confounded by protandric sex. The recent conclusion that the sex ratio of Pacific oysters is predominantly under genetic rather than environmental control introduces the possibility of manipulating sex ratio for commercial gain if they exhibit asynchronous sex‐specific growth rates. Pacific oysters were cultured intertidally in Smoky Bay, south Australia. The observations, made over the 7‐month gametogenic cycle from August to February to ensure no sex reversal, were of growth rates of male and female oysters and ambient chlorophyll a concentrations. Mean shell growth of female oysters was significantly faster than that of males (4.5 ± 3.3 compared with 3.8 ± 3.2 μm day^?1 mm^?1 total length). Sex‐specific asymmetries in length and weight were generally significant and increased in magnitude during the 7‐month study period, suggesting potential commercial benefits from increasing the proportion of cultured female oysters. The fastest increase in the sex‐specific disparity in growth and condition came after the October chlorophyll a peak, suggesting that females utilize blooms more efficiently than males. Our results compare favourably with methods currently used to increase oyster growth (e.g. triploidy can provide growth gains of 13–51%).     

福建漳浦太平洋牡蛎微卫星等位基因比较

本文采用Ucdcg153、157、202微卫星分子标记对福建漳浦从广东饶平引人的太平洋牡蛎育苗亲贝进行等位基因比较.两组样品(Cg♀和cg♂)携带的等位基因在微卫星重复区间及其附近存在高度相似的变异特征.这些特征区间分别是:Ucdcg153 23～40位碱基区间,Ucdcg157 73～100位碱基区间,Ucd-cg2...     

Changes in volatile compounds of living Pacific oyster Crassostrea gigas during air-exposed storage

Fisheries Science - The changes in volatile compounds of living oysters Crassostrea gigas with shells under air-exposed storage for 7 days at 5 and 20 °C were investigated...     

Pathology and significance of fatal inflammatory bacteraemia in the Pacific oyster, Crassostrea gigas Thünberg

Abstract. Inflammatory bacteraemia was found in 27–31% of Pacific oysters in two bays over 2 years in Puget Sound, Washington, USA. Mantle discolouration and raised yellow to green nodules are associated with the disease in 52% and 85% of the observed cases, respectively. The disease is caused by systemically distributed, branching. Gram-positive, acid-fast bacteria suggestive of an actinomycete. Clusters of the bacteria elicit a marked inflammatory response. Glycogenic degeneration of host vesicular cells occurs in the advanced infections and results in the formation of the characteristic nodules comprised of lipid filled cells. The disease is, thus, significant to the health of individual oysters and also appears to be an important factor in the historically observed phenomenon of summer mortality in certain areas of Puget Sound.     

Application of sperm cryopreservation in selective breeding of the Pacific oyster,Crassostrea gigas (Thunberg)

The robustness of Pacific oyster, Crassostrea gigas (Thunberg), sperm cryopreservation in the context of selective breeding based on family lines was investigated. Irrespective of egg density, high fertilization success was achieved with cryopreserved sperm when sperm:egg ratios of 1000:1 to 10 000:1 were used. Variation among replicate runs on the same oyster batches was minimal, indicating that cryopreservation and larval rearing procedures were repeatable. Twenty independent single male–female crosses were made to assess the utility of cryopreserved sperm in selective breeding. The fertility of unfrozen sperm was generally a poor predictor of cryopreserved sperm fertility. Based on D‐larval yields, 17 of the 20 crosses were likely to yield adequate spat for selective breeding (>10⁵ D‐larvae from 1 million eggs), two were marginal (5 × 10⁴ D‐larvae) and one was inadequate (4 × 10³ D‐larvae). An alternative fertilization strategy to improve D‐yield from a given number of sperm was then tested. Fertilizing 10 million eggs at a sperm:egg ratio of 200:1 increased the total D‐yield when compared with fertilizing 1 million eggs at a sperm:egg ratio of 2000:1 for the same male–female pair. We conclude that, despite wide variation in fertility, cryopreserved sperm is useful for family production.     

干露胁迫对长牡蛎基因组DNA甲基化的影响

为探讨干露胁迫对海产贝类基因组DNA甲基化的影响,应用荧光标记甲基化敏感扩增多态性(fluorescencelabeled methylation sensitive amplified polymorphism,F-MSAP)技术,比较了不同干露条件下(0 d、0.5 d、1 d、3 d、5 d、7 d、9 d和11 d)长牡蛎(Crassostrea gigas)基因组DNA甲基化的变化。结果表明,对照组(干露处理0 d)闭壳肌与鳃组织的总体甲基化水平分别为29.76%和29.82%;干露处理0.5 d、1 d、3 d、5 d、7 d、9 d和11 d的长牡蛎全基因组甲基化水平呈现先增高后降低的趋势,其中,闭壳肌组织的总体甲基化水平分别为36.59%、38.86%、43.02%、39.30%、51.13%、46.79%和35.06%,鳃组织总体甲基化水平分别为39.39%、42.13%、39.36%、43.54%、56.19%、38.57%和28.99%;干露处理7 d的长牡蛎甲基化水平明显高于其他时期(P0.05),11 d时甲基化水平基本恢复至初始状态。甲基化变异模式分析发现,闭壳肌与鳃组织DNA甲基化变异位点存在差异,甲基化升高位点变化程度较大(P0.05)。以上结果表明,长牡蛎通过改变DNA甲基化模式来应答干露胁迫,发生了不同程度的甲基化与去甲基化反应,DNA甲基化与长牡蛎的抗逆性状密切相关。     

Heritability estimates for nutritional quality‐related traits of the Pacific oyster,Crassostrea gigas

Pacific oysters, Crassostrea gigas, are the most abundantly harvested shellfish in the world and are ecologically significant. The content of nutrients, including protein, glycogen, lipid, zinc (Zn), and selenium (Se), is important for oyster meat quality, but heritability estimates of such traits have rarely been reported. In this study, 64 full‐sib families were generated using a nested mating design. Finally, 18 full‐sib families, of which there were nine half‐sib families, with each containing 2 full‐sib families, were sampled for heritability estimates. The narrow‐sense heritabilities of glycogen, protein, lipid, Zn, and Se contents were 0.29 ± 0.02, 0.38 ± 0.02, 0.58 ± 0.08, 0.02 ± 0.02, and 0, respectively. Negative genetic correlations existed between both glycogen and protein content (?0.95 ± 0.004) and between lipid and protein content (?0.59 ± 0.05), whereas a positive correlation was observed between lipid and glycogen content (0.16 ± 0.06). Weak genetic and phenotypical correlations (r = 0–0.2) were observed between shell height and nutritional quality traits. These data demonstrated that glycogen, protein, and lipid content can be chosen in a selective breeding program, but glycogen and lipids cannot be selected together with protein. Furthermore, performing indirect selective breeding for quality traits by selecting traits related to growth is impossible. This study provides information for the development of breeding strategies for oyster quality traits.     

Comparative growth of Pacific oyster (Crassostrea gigas) postlarvae with microfeed and microalgal diets

Two trials were carried out in the laboratory in order to assess the effect of microparticulated feed (F) and live (Thalassiosira pseudonana, M) diets on the growth of recently set (396 ± 13 μm shell height) and 2 mm Crassostrea gigas postlarvae. Different proportions of M and F (100:0, 75:25, 50:50; 25:75, 0:100) were delivered in a single dose of 3 h d⁻¹ in trial 1. Dietary M:F proportions of 100:0, 50:50, and 0:100 were delivered as a single pulse of 8 h d⁻¹ (P1) or two pulses of 4 h⁻¹ (P2) in trial 2. Maximal daily M ration was 296 cells μl⁻¹ d⁻¹ (trial 1), 150 M cells μl⁻¹ d⁻¹ (trial 2), or their equivalent F dry weight. Shell height (SH), dry (DW), and organic weight (AFDW) were evaluated weekly. Oysters from trial 1 significantly increased their size after 28 days, and exhibited no significant dietary differences in terms of DW (1.21 ± 0.15 to 2.01 ± 0.28 mg) or AFDW (0.091 ± 0.022 to 0.166 ± 0.029 mg). Newly set postlarvae (trial 2) also exhibited significant growth after 25 days. No dietary differences were observed in trial 2, yet P2 oysters attained significantly higher shell heights (825–912 μm) than P1 oysters (730–766 μm) after 25 d. Pulse effects were marginally not significant in terms of AFDW and growth rate. Together, these findings showed that balanced microfeeds have a practical potential for the culture of early C. gigas postlarvae, when they are delivered in pulse-feeding schemes