温度对海湾扇贝与虾夷扇贝及其杂交受精、胚胎和早期幼体发育的影响

本文报道了温度对海湾扇贝和虾夷扇贝及其杂交受精胚胎和早期幼体发育的影响结果。在实验温度下，各亲本组合受精的适温和最适温度范围分别为：海湾扇贝１０～３０℃和１９～２８℃，虾夷扇贝５～２２℃和１０～１９℃；海湾扇贝♀×虾夷扇贝♂１０～３２℃和１９～２８℃，虾夷扇贝♀×海湾扇贝♂１０～２５℃和１５～１９℃。在适温范围内，海湾扇贝和虾夷扇贝受精率达１００％，两杂交组合可达７０％以上，高温或低温对受精都不利。各亲本组合胚胎发育的适温和最适温度范围分别为：海湾扇贝１５～２５℃和１７～２２℃，虾夷扇贝１０～１９℃和１３～１７℃；海湾扇贝♀×虾夷扇贝♂１５～２５℃和１７～２２℃，虾夷扇贝♀×海湾扇贝♂１０～１９℃和１５～１７℃。温度过高或过低对各亲本组合胚胎发育速度和成活率都有明显的影响。     

Growth and mortality of cultured bay scallops in the Damariscotta River, Maine (USA)

Growth and mortality of hatchery-reared bay scallops, Argopecten irradians, were determined over an 18 month period (July 1994-December 1995) at two locations in the Damariscotta River, Maine, north of its natural distribution. Growth occurred primarily between May and October when mean water temperature exceeded 10 °C. Final mean shell height (56.3 mm) was significantly greater (p 0.0005) at the upriver site than at the downriver site in association with a higher mean water temperature. Cumulative mortality (43-49%) over this period occurred primarily over the winter months, in conjunction with mean water temperatures below 5 °C. Although it is possible to rear bay scallops to commercial size in Maine, the short growing season, high winter mortality, and costs associated with over-wintering and fouling will likely deter commercial culture.     

Production of bactericidal substances by a marine vibrio isolated from cultures of the scallop Argopecten purpuratus

A marine vibrio (strain C33) having inhibitory effects on the growth of the pathogen Vibrio anguillarum-VAR was isolated from seawater used in mass culture of the north-Chilean scallop Argopecten purpuratus. This bacterial isolate demonstrated broad inhibitory activity on several bacterial strains, including some pathogenic vibrios. Ethyl acetate extracts of extracellular products of strain C33 were separated by thin layer chromatography (TLC), and three fractions thus obtained were found to have antimicrobial activity when tested using microplate bioassays. One of the fractions (A2) having marked antimicrobial activity, was further purified using TLC and analyzed by IR spectrophotometry and NMR'H and was characterized on a preliminary basis as an aliphatic hydroxyl ether. This compound demonstrated bacteriostatic activity against the important marine pathogens Vibrio parahaemolyticus and V. splendidus, and as discussed in the paper, may be useful in developing natural strategies for the control of pathogens in mass cultures of Argopecten purpuratus and possibly other molluscs affected by these bacteria.     

海湾扇贝杂交后代的微卫星鉴定

海湾扇贝(Argopecten irradians)是典型的雌雄同体型贝类,行体外受精,因此杂交育种过程中存在非目标配子污染的问题。本研究筛选10对多态性微卫星引物对海湾扇贝两个亲本及正反交两个F1子代群体各100个个体进行了分析。基因型分析结果表明,所有后代等位基因均来源于双亲,不存在外源等位基因污染情况。卡方检验表明,杂交后代基因型比例符合孟德尔遗传分离比,即微卫星标记符合孟德尔遗传。其中对AIMS026扩增位点的分析结果表明,杂交后代基因型均为双亲互补型,没有出现自交后代基因型,即杂交过程中没有自身配子的污染。该研究证实了微卫星在海湾扇贝中分离的孟德尔遗传规律,同时验证了海湾扇贝杂交过程中一系列避免异源配子污染方法的有效性,为海湾扇贝定向杂交配子隔离的可靠性提供了分子生物学证据。     

湛江北部湾养殖墨西哥湾扇贝的形态增长规律

采用模型拟合方法研究了墨西哥湾扇贝(Argopecten irradians concentricusSay)在湛江北部湾水温18.2~30.8℃、盐度27.8~30.4、透明度1.5~5.7 m、水深9.7 m、浮游植物细胞丰度平均4.3×104L-1、采用"秋冬春"养殖等条件下,一个养殖周期的形态增长规律。结果表明:墨西哥湾扇贝各形态性状生长过程遵循Logistic生长模型,平方复相关系数R2均大于0.98(P<0.001),根均方误差RMSE平均0.897,各形态性状模型都具有统计学意义(ANOVA,P<0.001)。通过Levenberg-Marquardt迭代法求出模型中3个生长参数,并得出各形态性状的生长极限值为壳长53.8 mm、壳高54.6 mm、壳宽27.1 mm、铰合线长28.4 mm、闭壳肌长26.1 mm、闭壳肌直径16.2 mm;快速生长区间及生长拐点则分别是壳长1.5~5.7个月及3.6个月、壳高1.4~5.9个月及3.6个月、壳宽2.0~6.4个月及4.2个月、铰合线长0.7~4.8个月及2.8个月、闭壳肌长1.9~6.5个月及4.2个月、闭壳肌直径1.6~5.5个月及3.5个月;绝对增长速度为壳长>壳高>壳宽>闭壳肌长>闭壳肌直径;相对增长速度性状间存在差异并随生长逐渐趋于0。研究发现主要经济性状壳宽及闭壳肌长出现生长延缓、不同地理种群形态增长存在显著差异、形态性状生长速度受温度及生长阶段共同调控等现象。提出了根据壳宽及闭壳肌生长适时收获,及把快速生长期安排在水温最适合生长的季节以最大程度挖掘生长潜能的新观点。研究结果可为墨西哥湾扇贝养殖生态研究、选择育种及养殖生产提供理论指导。     

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。     

扇贝幼虫附着基的细菌组成及其作用

自海湾扇贝幼虫附着基表面分离到99株附着细菌。经鉴定、分类至9属包括弧菌属、假单胞菌属、无色杆菌属,芽孢杆菌属、气单胞菌属、葡萄球菌属、微球菌属、棒杆菌属和黄杆菌属。扇贝幼虫的附着基表面具有一定数量的附着细菌。单一菌株菌膜实验表明,不同菌株形成的菌膜对幼虫附着的吸引力大小不一。有的细菌促进幼虫附着,有的却有抑制作用。     

Repopulation and culture of the Pacific Calico scallops in Bahia Concepcion, Baja California Sur, Mexico

The Pacific Calico scallop, Argopecten ventricosus (Sowerby), is the most important commercial species in Bahia Concepcion. Catches declined steadily from 1991 to 1993 as a result of overexploitation, forcing the adoption of management measures. The Government has now established regulations for exploitation and scallop culture development. In 1994, Centro Interdisciplinario de Ciencias Marinas (CICIMAR) and the Fisheries Department of the Mexican Government initiated research on the feasibility of increasing scallop biomass through a reseeding programme to protect artisanal fishing. The use of onion bags to collect spat in Bahia Concepcion (1988-1994) demonstrated that settlement was cumulative from January to March. At Punta Coloradito, there were two peaks, in January and early March. Commercial collectors were deployed in February at El Indio and in April at El Remate. In June, about one million juvenile scallops were placed in an enclosure, held until mid-August and then released. Mass mortality (>80%) of the scallops was observed in September, increasing to 99% in October. The high water temperature and predators may be responsible for the mortalities.     

Sources of Vibrio bacteria in mollusc hatcheries and control methods: a case study

Results of a 1‐year intensive monitoring of Vibrio bacteria, as thiosulphate citrate billar salt sucrose (TCBS) counts, in a hatchery for molluscs, are presented. Surface seawater, well seawater, tap water from a freshwater well, microalgae system, including pasteurized well seawater, f/2 medium, starter cultures of eight micro algal species, mass‐produced microalgae and compressed air were studied as possible sources of Vibrio. Additionally, recently collected broodstock of the catarina scallop Argopecten ventricosus (Sowerby II 1842) was also subjected for investigation for their possible role in discharging Vibrio during spawning. Efficiency of a cartridge–ultraviolet (UV)‐filtration system and of a steam gun employed for sterilizing tanks, hoses and utensils was also determined. Results indicated that Vibrio were present in surface seawater throughout the year. In well seawater these bacteria were only found during the first 5 months soon after construction of the well and before commencement of continuous operations, but not after this period. Vibrio was never detected in pasteurized well seawater, f/2 medium, starter cultures of microalgae and compressed air. However, mass‐produced microalgae contained Vibrio, possibly as a result of the use of contaminated tap water for washing and rinsing the fibreglass culture tanks. Scallop broodstock was found to be an important source of Vibrio in the hatchery. Biopsy on female gonads of live organisms demonstrated higher numbers of colony‐forming units than male gonads. At spawning, Vibrio was released into water, producing bacterial blooms in tanks after 24 h. The cartridge–UV‐filteration system was not sufficient to eliminate the bacteria from seawater, but the steam gun proved to be a good tool to eliminate Vibrio biofilms on tank walls or tools used in the hatchery. Some recommendations are given, which could be useful for other mollusc hatcheries.     

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.