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.     

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。     

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。     

提高海湾扇贝孵化率技术

实验表明,海湾扇贝卵的孵化率与换水量有关,孵化率以12小时倒池一次最高,为81．2％。亲贝的流产主要是由NH33-N较高引起的,COD只是间接因素。高COD引起NH3-N过高。加大换水量会使亲贝流产减少、培养良好的亲贝,在亲贝培育过程中加入3×10-6的“去氨净”,经常倒池,有利于提高亲贝孵化率。     

Use of marine by‐product meals in diets for juvenile longfin yellowtail Seriola rivoliana

A 60‐day feeding trial to determine the nutritional value of marine by‐product meals in diets for longfin yellowtail Seriola rivoliana juveniles (48.1 ± 0.6 g initial weight) was conducted. Five diets were evaluated: a reference diet (RD; 500 g kg^?1 CP, 130 g kg^?1 L), containing 500 g kg^?1 of fish meal (FM); three experimental diets with 125 g kg^?1 of shrimp head (SM), Catarina scallop viscera (CM) or Pen shell viscera (PM) meals; and one diet (SCP) containing 125 g kg^?1 of each of the experimental meals, to partially replace FM. Survival was not significantly affected by any treatment. Individual weight gain per day was high for the PM (5.3 ± 0.51 g d^?1) and SM (4.7 ± 0.32 g d^?1) diets, being significantly higher than the RD (3.5 ± 0.23 g d^?1) and the other treatments (<1.2 g d^?1). Feed intake was high in PM and SM diets, and very low in SCP and CM diets. Biochemical and haematological parameters were similar among treatments RD, PM and SM, while fish fed CM and SCP exhibited lower levels of total protein, cholesterol, haematocrit and haemoglobin. The results indicate that SM or PM can be used to partially replace FM in diets for yellowtail juveniles.     

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。

     

Accumulation, biotransformation, histopathology and paralysis in the Pacific calico scallop Argopecten ventricosus by the paralyzing toxins of the dinoflagellate Gymnodinium catenatum

The dinoflagellate Gymnodinium catenatum produces paralyzing shellfish poisons that are consumed and accumulated by bivalves. We performed short-term feeding experiments to examine ingestion, accumulation, biotransformation, histopathology, and paralysis in the juvenile Pacific calico scallop Argopecten ventricosus that consume this dinoflagellate. Depletion of algal cells was measured in closed systems. Histopathological preparations were microscopically analyzed. Paralysis was observed and the time of recovery recorded. Accumulation and possible biotransformation of toxins were measured by HPLC analysis. Feeding activity in treated scallops showed that scallops produced pseudofeces, ingestion rates decreased at 8 h; approximately 60% of the scallops were paralyzed and melanin production and hemocyte aggregation were observed in several tissues at 15 h. HPLC analysis showed that the only toxins present in the dinoflagellates and scallops were the N-sulfo-carbamoyl toxins (C1, C2); after hydrolysis, the carbamate toxins (epimers GTX2/3) were present. C1 and C2 toxins were most common in the mantle, followed by the digestive gland and stomach-complex, adductor muscle, kidney and rectum group, and finally, gills. Toxin profiles in scallop tissue were similar to the dinoflagellate; biotransformations were not present in the scallops in this short-term feeding experiment.