泛影葡胺密度梯度离心法纯化近江牡蛎类立克次体

用国产泛影葡胺做介质,通过差速离心和密度梯度离心从患病近江牡蛎的鳃、外套膜、肝胰腺组织中纯化类立克次体。纯化的类立克次体在透射电镜下观察,20％-25％和25％-30％之间的条带为纯净的类立克次体,大多数呈球形、椭球形,偶见哑铃状（处于二分裂阶段）。纯化的类立克次体细胞形态完整,在光滑的细胞壁外围有一层疏松的粘液层,而且多个类立克次体常聚集在一起。利用APIZYM半定量法对类立克次体进行酶谱分析,检测到了11种酶,包括碱性磷酸酶、酸性磷酸酶、酯酶（C4）、类脂酯酶（C8）、亮氨酸芳胺酶、萘酚AS—BI-磷酸水解酶、β-半乳糖苷酶、N-乙酰葡萄糖胺酶、β-果糖酶、β-糖醛酸苷酶和缬氨酸芳胺酶。本实验证明,国产泛影葡胺是直接从患病贝类组织中纯化类立克次体的良好介质。     

Estimates of Linkage Disequilibrium and Effective Population Size in Wild and Selected Populations of the Pacific Oyster Using Single‐nucleotide Polymorphism Markers

The level and extent of linkage disequilibrium (LD) and effective population size (Ne) were studied in three selected lines and a wild population of Pacific oyster, Crassostrea gigas, using 61 single‐nucleotide polymorphisms. Significant differences were detected in the average r² between the selected lines and wild population for both syntenic and nonsyntenic loci with LD beyond population‐specific critical values (P<0.05). Moreover, the proportions of syntenic and nonsyntenic loci with the expected LD level in the wild population were lower than that in the selected lines. Taken together, the LD level of the selected lines was higher than that of the wild population. The extent of LD analysis showed that a short range of LD (0–0.23 cM) was detected in the four populations, and the decay distance was lower in the wild population than in the selected lines. Ne values ranged from 47.6 to 58.5 in the selected lines and ranged from 527.9 to 709.6 with infinite upper limits in the wild population. Further variance analysis of LD demonstrated that genetic drift and epistatic selection might account for the increased LD levels in selected lines. The LD information will be valuable for further association study and marker‐assisted selection in oysters.     

太平洋牡蛎三倍体诱导及苗种培育技术研究

本文报道了采用细胞松弛素B（CB）诱导太平洋牡蛎三倍体的研究结果。研究结果表明，CB浓度为0．25mg／L，处理时间约20分钟，诱导三倍体的倍化率可达75％，至D型幼虫的孵化率为40－50％。1992－1996年其培育出三倍体贝苗1846．4万枚。     

Risk factors associated with increased mortality of farmed Pacific oysters in Ireland during 2011

The Pacific oyster, Crassostrea gigas, plays a significant role in the aquaculture industry in Ireland. Episodes of increased mortality in C. gigas have been described in many countries, and in Ireland since 2008. The cause of mortality events in C. gigas spat and larvae is suspected to be multifactorial, with ostreid herpesvirus 1 (OsHV-1, in particular OsHV-1 μvar) considered a necessary, but not sufficient, cause. The objectives of the current study were to describe mortality events that occurred in C. gigas in Ireland during the summer of 2011 and to identify any associated environmental, husbandry and oyster endogenous factors. A prospective cohort study was conducted during 2010–2012, involving 80 study batches, located at 24 sites within 17 bays. All 17 bays had previously tested positive for OsHV-1 μvar. All study farmers were initially surveyed to gather relevant data on each study batch, which was then tracked from placement in the bay to first grading. The outcome of interest was cumulative batch-level mortality (%). Environmental data at high and low mortality sites were compared, and a risk factor analysis, using a multiple linear regression mixed effects model, was conducted. Cumulative batch mortality ranged from 2% to 100% (median = 16%, interquartile range: 10–34%). The final multivariable risk factor model indicated that batches imported from French hatcheries had significantly lower mortalities than non-French hatcheries; sites which tested negative for OsHV-1 μvar during the study had significantly lower mortalities than sites which tested positive and mortalities increased with temperature until a peak was reached. There were several differences between the seed stocks from French and non-French hatcheries, including prior OsHV-1 μvar exposure and ploidy. A range of risk factors relating to farm management were also considered, but were not found significant. The relative importance of prior OsHV-1 μvar infection and ploidy will become clearer with ongoing selection towards OsHV-1 μvar resistant oysters. Work is currently underway in Ireland to investigate these factors further, by tracking seed from various hatchery sources which were put to sea in 2012 under similar husbandry and environmental conditions.     

盐度对香港巨牡蛎摄食和代谢的影响

为了探明香港巨牡蛎(Crassostrea hongkongensis)的摄食和代谢与盐度的关系,在实验室条件下采用流水系统研究了不同盐度(S)条件下香港巨牡蛎的滤水率(FR)、摄食率(IR)、吸收率(AE)、耗氧率(OR)和排氨率(NR)的变化规律。结果显示:在盐度6～27范围内,盐度对香港巨牡蛎的滤水率、摄食率的影响都极显著,随着盐度的升高,滤水率与摄食率先增大后减小,盐度13时最大,分别为5.93 L/g.h和38.26×106cell/g.h;盐度对吸收率的影响不显著,吸收率为74.77%～78.41%。盐度对香港巨牡蛎的耗氧率和排氨率的影响极显著,随着盐度的升高,耗氧率与排氨率先增大后减小,盐度20时最大,分别为1.76 mg/g.h和0.11 mg/g.h;盐度对O∶N比的影响不显著,不同盐度下O∶N平均值为17.89,表明在本试验条件下香港巨牡蛎代谢所需要的能量主要由脂肪和碳水化合物提供。根据研究结果可以判断,香港巨牡蛎的摄食和代谢活动在盐度13~20之间处于较适宜水平。     

Experimental assessment of oyster transfers as a vector for macroalgal introductions

Introduction of non-indigenous species can alter marine communities and ecosystems. In shellfish farming, transfer of livestock, especially oysters, is a common practice and potentially constitutes a pathway for non-indigenous introductions. Many species of seaweeds are believed to have been accidentally introduced in association with these transfers, but there is little direct evidence.We experimentally simulated the transfer of oysters from the Thau Lagoon (France). These transfers involved increasing periods of aerial emersion and additional brine and hot water treatments. The brine and hot water treatments were evaluated as a means of reducing the probability of algal introductions with oyster transfers. Shells were cultured for 40 days in experimental tanks to identify the macroalgae likely to be introduced with any oyster transfer.A total of 57 macroalgal taxa, including 16 taxa not indigenous to the Thau Lagoon, were recorded across all treatments and experiments. The abundance of some species increased in several cases following aerial emersion. Elimination treatments (immersion in brine or hot water) significantly reduced algal diversity, with hot water treatments resulting in no species or only tubular Ulva spp. present.The results support the hypothesis that oyster transfers are effective as primary and secondary vectors of macroalgal introductions. Relatively simple changes to the transfer practice (particularly hot water treatments) are suggested as a means of reducing the risk of non-indigenous algal introductions.     

辽南沿海牡蛎科Ostreidae种类的调查及其增养殖前景研究

经过调查，确定辽南地区沿海分布有６种牡蛎，其中猫爪牡蛎Ｃｒａｓｓｏｓｔｒｅａ Ｐｅｓｔｉｇｇｒｉｓ Ｈａｎｌｅｙ在辽宁省为首次记录。对各种牡蛎的分布情况作了简要描述，并对其生产状况和增养殖前景进行了研究，提出今后主要增养殖的种类和途径。     

三倍体长牡蛎(Crassostrea gigas)不育性研究

三倍体长牡蛎(Crassostrea gigas)雌性怀卵量在0～2000万,雄性精量在0～1亿,大大低于正常二倍体。三倍体生殖腺发育受阻,大部分停留在增殖期和休止期,一部分虽发育至生长期和成熟期,但与同期的二倍体比较,生殖腺发育差。部分三倍体配子能完成受精作用,并发育至D形幼虫,但不能继续正常发育。卵子减数分裂后为含14～16条染色体的非整倍体。因此,三倍体长牡蛎是不育的。     

The effect of size on the response of Pacific oysters (<Emphasis Type="Italic">Crassostrea gigas</Emphasis>) to changes in water temperature and air exposure

To further improve the technology used in Pacific oyster farming, information is required on the response of different sized and aged oysters to various environmental changes. In this study a neutral red retention (NRR) assay was used to investigate the effects of size and age on the response of Pacific oysters to changes in water temperature and their recovery after exposure to different air temperatures. Results from moving oysters directly between water temperatures of 5°C and 15°C, 10°C and 20°C and 15°C and 25°C demonstrated that different water temperature change affect the lysosomal membrane integrity differently. The NRR times of large and small oysters transferred directly between 10°C and 20°C initially decreased significantly, and then increased to levels corresponding to the new temperature. In addition, NRR times in large oysters responded at a significantly slower rate than small oysters when they were transferred from 5°C and 25°C to 15°C water and between 10°C and 20°C water. Results from the air exposure experiments showed that, after exposure to air temperatures of 5°C, 15°C or 25°C, the lysosomal membrane integrity of large oysters recovered at a slower rate in 15°C water compared to small oysters. It therefore appears necessary to develop different management strategies for large (old) and small (young) oysters. Results from this and previous research also indicate that the NRR assay could potentially be used to develop a model to monitor and predict the performance of oysters on farms.     

An insulin-like system involved in the control of Pacific oyster Crassostrea gigas reproduction: hrIGF-1 effect on germinal cell proliferation and maturation associated with expression of an homologous insulin receptor-related receptor

The putative involvement of insulin-like peptides in the control of the reproduction of the Pacific oyster Crassostrea gigas was investigated using different approaches. In conjunction with a monthly histological analysis of the oyster reproductive cycle, in vitro biological effects of the human recombinant IGF-1 (hrIGF-1) on dissociated germinal cells were mesured over 1 year using [³H]-thymidine and [¹⁴C]-amino acid mixture as tracers for DNA and protein synthesis. DNA synthesis was stimulated by hrIGF-1 in November (114 ± 11% for 10^− 7M), December (46 ± 6% for 10^− 7 M) and January, which was identified as the highest gonial mitosis period. A clear dose-effect was observed in January with a maximum activation of 68 ± 7% for 10^− 12 M. Germinal cell protein synthesis was also stimulated in March (20 ± 1% for 10^− 10 M), April (41 ± 5% for 10^− 13 M), May (25 ± 4% for 10^− 13 M), and by almost all of hrIGF-1 doses in June (21.5 ± 2% for 10^− 13 M) and July (34 ± 1% for 10^− 13 M). This suggests the involvement of insulin-like substances in gonadal tubule rebuilding (December), as well as in the development of germinal cells (March, April), and in the summer maturation of gametes (May, June, July). These insulin-like effects conform with the expression pattern of the recently identified C. gigas insulin receptor-related receptor (CIR): It appeared highly expressed in the gonadal area during gonial mitosis phase, but also in maturating oocytes, suggesting the involvement of an insulin-like system in gonial proliferation and maturation. Moreover, CIR showed differential expression during embryogenesis and larval developmental stages. The expression of maternal CIR during the embryonic and early larval development, followed by the increasing zygotic CIR expression from D larvae to 11-day-old veliger larvae, then a decrease until metamorphosis, also suggest that insulin-like peptide is involved in organogenesis.