Weinberg J R, Leavitt D F, Lancaster B A, Capuzzo J M
Population Dynamics Branch, National Marine Fisheries Service, Woods Hole, Massachusetts, 02543, USA.
J Invertebr Pathol. 1997 Mar;69(2):183-94. doi: 10.1006/jipa.1996.4641.
A field experiment was conducted from 1991 to 1992 to examine induction and impact of hematopoietic neoplasia on the marine bivalve Mya arenaria in southeastern Massachusetts. Clams were collected from Little Buttermilk Bay and separated into three size classes (20-29, 30-39, and 40-49 mm shell length) in the laboratory. These sizes span the range of adults found in the population. A random subsample of these clams was taken to estimate disease prevalence at the start of the experiment, and this was found to be </=10% in all size classes. Remaining clams were assigned randomly to two groups: Control and Treated. "Controls" were injected with filtered seawater, while "Treated" clams were injected with hemocytes extracted from diseased individuals. Injection of diseased hemocytes was performed to increase disease prevalence in the Treated group. Clams were returned to New Bedford Harbor, a more contaminated field location, where hematopoietic neoplasia is more prevalent, in January 1991, and characteristics of both groups were monitored for 555 days. Among Controls, probability of survival was size-dependent, with higher survival rates in larger clams. Treated clams had a lower probability of survival than Controls, and the magnitude of treatment effect increased with size class. The impact on survival was evident after 89 days, but it was first shown to be statistically significant after 189 days. Among Controls, probability of disease was strongly season-dependent, increasing in the large size class from 0.19 in spring to 0.50 in summer. During summer, Treated clams had a higher probability of being diseased than Controls. Among survivors, no significant sublethal effects due to treatment were detected in the field experiment. Experimental manipulation of disease prevalence may be a useful tool in future studies. In addition to results pertaining to disease, this study obtained long-term growth information, by size class, on somatic and reproductive tissue and shell size.
1991年至1992年进行了一项野外实验，以研究造血肿瘤在马萨诸塞州东南部海洋双壳贝类砂海螂中的诱发情况及其影响。蛤蜊从酪乳湾采集而来，并在实验室中被分为三个大小等级（壳长20 - 29毫米、30 - 39毫米和40 - 49毫米）。这些大小涵盖了该种群中成年个体的范围。在实验开始时，从这些蛤蜊中随机抽取一个子样本以估计疾病患病率，结果发现所有大小等级的患病率均≤10%。其余的蛤蜊被随机分为两组：对照组和处理组。“对照组”注射经过滤的海水，而“处理组”的蛤蜊注射从患病个体中提取的血细胞。注射患病血细胞是为了提高处理组中的疾病患病率。1991年1月，蛤蜊被放回新贝德福德港，这是一个污染更严重的野外地点，造血肿瘤在那里更为普遍，并对两组的特征进行了555天的监测。在对照组中，存活概率与大小有关，较大的蛤蜊存活率更高。处理组的蛤蜊存活概率低于对照组，且处理效果的幅度随大小等级增加。对存活的影响在89天后就很明显，但在189天后才首次显示出具有统计学意义。在对照组中，患病概率强烈依赖季节，在大尺寸等级中从春季的0.19增加到夏季的0.50。在夏季，处理组的蛤蜊患病概率高于对照组。在野外实验中，在存活者中未检测到因处理导致的显著亚致死效应。疾病患病率的实验性操纵可能是未来研究中的一个有用工具。除了与疾病相关的结果外，本研究还按大小等级获得了关于体细胞、生殖组织和壳大小的长期生长信息。
