Evaluation of resistance to Dermo in eastern oyster strains tested in Chesapeake Bay

We investigated growth, Dermo disease, and survival for nine groups of oysters, Crassostrea virginica (Gmelin) cultivated in Chesapeake Bay (CB). Five regional strains (upper CB, North Carolina (NC), South Carolina (SC), Louisiana (LA) and LA triploids) and four additional hybrid strains (CB oysters mated with NC, SC, LA and Texas (TX) oysters) were held in floating rafts at three locations representative of lower CB: ‘low’ salinity (3–14 g L^?1), ‘moderate’ salinity (5–20 g L^?1) and ‘high’ salinity (14–24 g L^?1). At each site, patterns of growth and incidence of infection with Perkinsus marinus (Levine), the causative agent of Dermo disease, were similar. However, mortality trends were markedly different at each site; the CB strain being notable for accelerated mortality following infection with P. marinus. In addition, hybrids between CB and all four of the regional strains exhibited similar accelerated mortality in response to infection. Mortality was strongly correlated with infection only at the high salinity site implicating interaction of differences in both oyster strain and virulence of Dermo between moderate and high salinity areas as factors in differential mortality across sites.     

响应面法优化牡蛎复合酶水解工艺研究

采用响应面法优化牡蛎的复合酶水解工艺.结果表明:中性蛋白酶与风味蛋白酶按照2∶1复配,在水解温度40℃,水解时间5.68h,水解pH值7.0条件下,牡蛎蛋白水解度可达到32.24%,水解效果最优.验证试验表明,实际蛋白质的水解度与模型预测值相近,因此采用响应面法优化牡蛎酶解工艺,准确可靠.     

太平洋牡蛎人工诱导雌核发育精子遗传失活的初步研究

用紫外线照射法对太平洋牡蛎Crassostrea gigas精子进行不同照射剂量和照射时间的处理，并将处理后的精子与正常的太平洋牡蛎的卵进行授精实验。实验结果表明，在精子厚度为1mm时，紫外线的最佳照射时间为1min、最佳照射剂量为1500μW／cm^2，受精率为87．74％，早期胚胎成活率为92．97％，单倍体率为96．24％。实验中，在担轮幼虫期利用染色体计数和流式细胞仪测定单倍体率，并从早期胚胎存活率上观察到“Hertwig”效应的存在。     

温度对不同规格长牡蛎三倍体和二倍体代谢影响的比较

用试验生态学方法研究了温度对不同规格的长牡蛎Crassostrea gigas三倍体(3n)和二倍体(2n)呼吸和排泄的影响。试验设12、18、24、30℃4个温度水平,并根据牡蛎倍性、规格分别设3n-L、3n-M、3n-S、2n-L、2n-M、2n-S 6个组别。结果表明:在12~24℃条件下,牡蛎的耗氧率随着温度的升高而增加,并在24℃时达最大值,之后,耗氧率随温度的升高而降低;3n和2n牡蛎软体部干重(W)与耗氧率(R)的回归关系符合幂函数方程R=aWb-1,3n的a值为1.532~1.737,b值为0.728~0.887,2n的a值为1.197~2.173,b值为0.823~0.854。牡蛎软体部干重(W)与排氨率(N)的关系符合幂函数N=c Wd-1,2n的c平均值为194.992,d平均值为0.669;3n的c平均值为251.746,d平均值为0.611。以体重为协变量进行协方差分析结果表明:温度引起耗氧率和排氨率的差异达到显著水平;倍性效应引起排氨率的差异达到显著水平,且3n的排氨率大于2n,倍性效应引起的耗氧率的差异不显著。     

溢油对贝类的毒害效应以及生态风险评价

通过磁力搅拌和超声波乳化等手段模拟海上溢油事故,采用常见的4种原油和4种燃料油开展对贝类的毒害效应以及生态风险评价。结果表明：根据8种油品对褶牡蛎的96h-LC50得出这8种油对褶牡蛎的整体上毒害作用的大小顺序是：F120=F180〉-20#〉F380〉TJ015〉TJ014〉TJ002〉TJ016;根据8种油品对缢蛏的96h-LC50得出这8种油对褶牡缢蛏蛎的整体上毒害作用的大小顺序是：F180〉F120〉-20#〉F380〉TJ002〉TJ015〉TJ014〉TJ016;根据8种油品对褶牡蛎的96h-LC50得出TJ016和TJ002对褶牡蛎属于低毒中风险,TJ015和TJ014对褶牡蛎属于低毒高风险,F380和-20#对褶牡蛎柴油属于中毒高风险,F180和F120对褶牡蛎属于高毒极高风险;根据8种油品对缢蛏的96h-LC50得出TJ016对缢蛏属于低毒中风险,TJ015、TJ014、TJ002和F380对缢蛏属于中毒高风险,-20#、F180和F120对缢蛏属于高毒极高风险。总之,对贝类而言,燃料油毒性比原油更大,缢蛏相对褶牡蛎对油品毒害作用更为敏感。     

Hot water immersion lowers survival,shell growth rate and lysosomal membrane stability of oysters Crassostrea virginica (Gmelin)

This study compares the effect of two anti‐fouling treatments, hot water immersion (15 s at 60°C) and air drying (72 h) on the physiological status of the Eastern oyster Crassostrea virginica. The negative impact of hot water immersion was greater than that of air drying, but varied depending on the initial size of the oysters (40 vs. 60 mm shell height) and the time of the year (June vs. August). Groups treated with hot water exhibited a higher proportion of haemocytes with destabilized lysosomal membranes (HDLM; 47.5 ± 3.1%) than those exposed to air drying (37.5 ± 2.9%). This suggests that the oyster immunocompetency may be lowered by hot water immersion. Overall, the large oysters had lower HDLM values (32.9 ± 3.5%) than the small individuals in June (45.7 ± 2.8%) but similar values in August (46.6 ± 3.5%). Small oysters subjected to hot water immersion in June exhibited a 50% reduction in shell growth and a 50% mortality rate after one month. Our results indicate that air drying is more suitable than hot water immersion as an anti‐fouling treatment for <45 mm oysters.     

水溶性牡蛎多糖的降血压活性

牡蛎中含有丰富的多糖。从牡蛎中制备的水溶性多糖经HPLC测定,其单糖组成为葡萄糖,以葡聚糖分子筛测定其分子量为(3.93~10.84)×106 Da。以牡蛎多糖(7g/kg)对高血压模型大鼠灌胃均具有较明显的降低收缩压和舒张压作用。     

微卫星标记在长牡蛎三倍体鉴定中的应用

为开发一种简单有效的倍性检测方法对长牡蛎三倍体诱导结果进行准确评估,本实验采用细胞松弛素B抑制第二极体释放诱导产生长牡蛎三倍体,选用7个微卫星位点扩增基因组DNA,通过亲子代基因分型进行倍性检测,检测结果采用流式细胞仪加以验证,以评估微卫星标记倍性检测的准确性。另外,本研究探讨了准确鉴定倍性所需的微卫星标记数量与微卫星—着丝粒重组率(y)之间的关系,以期为其他物种采用分子标记进行倍性检测提供理论依据。结果显示,细胞松弛素B诱导产生的115个长牡蛎子代经7个微卫星位点鉴定得到40个三倍体,与流式细胞仪检测结果一致,准确率达到100%,7个微卫星位点的(1-y)的乘积为0.005。随机挑选6个位点,也可鉴定出所有三倍体,(1-y)的乘积为0.005~0.042。研究表明,本研究中开发的微卫星标记可以简单高效地鉴定长牡蛎三倍体,微卫星位点的(1-y)的乘积小于0.005,倍性检测的准确率可达100%,采用微卫星标记进行倍性检测对于加速长牡蛎三倍体育种进程具有十分重要的意义。     

Larval dispersal and population connectivity among a network of marine reserves

A major challenge in marine ecology is describing patterns of larval dispersal and population connectivity, as well as their underlying processes. We used a biophysical model to simulate dispersal of eastern oyster, Crassostrea virginica, larvae and connectivity among a network of 10 no‐take reserves in a shallow, wind‐driven estuary to assess the relative importance of spawning location, spawning date, larval behavior, larval mortality, and adult reproductive output to predicted dispersal and connectivity patterns. The location (i.e., natal reserve) and date of spawning relative to physical processes, particularly frequency of wind reversals, were the dominant drivers of dispersal and connectivity patterns. To a lesser extent, larval behavior (i.e., 3D vertical advection and ontogenetic depth regulation) and mortality modified dispersal and connectivity, whereas spatiotemporal variability in adult reproductive output was of minimal importance. Over a 21‐day larval duration, mean dispersal distance of passive surface particles ranged from 5 to 40 km. Reserves were too small (1 km²) relative to mean dispersal distances to promote extensive local retention (median 2%) and spaced too far apart (typically ~50 km) to promote extensive inter‐reserve connectivity (median 2%). Limited connectivity and local retention may preclude the network from being self‐sustainable, thereby limiting its long‐term conservation and management benefits. In reserve systems characterized by limited connectivity, management efforts should focus on increasing connectivity by increasing the number or size of reserves to realize the benefits of improved adult demographics within reserves.     

盐度与pH对3种南方贝类呼吸率和钙化率的影响

测定了近江牡蛎(Crassostrea rivularis)、翡翠贻贝(Perna viridis)和波纹巴非蛤(Paphia undulata)3种南方重要养殖贝类在20、25、30和35共计4个盐度梯度和8.1、7.7、7.3和7.0共计4个pH梯度下的呼吸率和钙化率。结果表明,盐度和pH对3种贝类的呼吸率和钙化率均有显著影响(P0.05);盐度为20~35,近江牡蛎的呼吸率和钙化率均随盐度的升高而降低,而翡翠贻贝和波纹巴非蛤在盐度为20~30时,呼吸率和钙化率随盐度的升高而升高,盐度30~35时,随盐度的升高而下降。pH为8.1~7.0时,3种贝类的呼吸率和钙化率均随着pH的下降而显著性下降(P0.05)。