Asari clam (or Manila clam) Ruditapes philippinarum is an important bivalve for local fisheries. This species exhibits a large variation in shell morphology, and the shell roundness tends to be greater in more unsuitable habitats. To test whether the increments in shell size parameters (length, height and width) were affected solely by environmental conditions or by internal factors such as initial shell shapes or growth rate, a field caging experiment was conducted at two different sites of unsuitable and suitable habitats in Matsukawaura Lagoon, Japan, where shell shapes of wild clams were significantly different between the habitats. In the experiment, clams were released from the two sites to the same site or to the other site and were re-collected after 3, 6 and 12 months of caging. Caged clams originating from unsuitable habitats and released to suitable habitats showed a reduction in shell height relative to shell length, while clams from suitable habitats introduced to unsuitable habitats showed marked increases in both shell height and width. Generalized linear mixed models suggested that the increase in shell height was affected largely by the release habitat (environment) whereas the increase in shell width was affected largely by the individual growth rate. These results suggest that marginal growths in shell height and width respond differently to external and internal factors of clams, resulting in plasticity in their shell shapes according to the environments to which they are translocated.

中文翻译：

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细辛蛤壳生长方向的生态表型可塑性 Ruditapes philippinarum

Asari 蛤蜊（或马尼拉蛤蜊）菲律宾蛤仔是当地渔业的重要双壳类动物。该物种在贝壳形态上表现出很大的变化，并且在更不合适的栖息地中，贝壳的圆度往往更大。为了测试贝壳尺寸参数（长度、高度和宽度）的增加是否仅受环境条件或初始贝壳形状或生长速率等内部因素的影响，在两个不合适和合适的栖息地的不同地点进行了野外笼养实验在日本松川浦泻湖，野生蛤蜊的贝壳形状在不同栖息地之间存在显着差异。在实验中，将蛤蜊从两个地点释放到同一地点或另一个地点，并在关笼 3、6 和 12 个月后重新收集。来自不适宜栖息地并被释放到适宜栖​​息地的笼中蛤蜊的壳高相对于壳长减少，而来自适宜栖息地的蛤蜊被引入不适宜栖息地的蛤壳高度和宽度均显着增加。广义线性混合模型表明，壳高的增加主要受释放栖息地（环境）的影响，而壳宽的增加主要受个体生长速率的影响。这些结果表明，贝壳高度和宽度的边际增长对蛤蜊的外部和内部因素的反应不同，导致它们的壳形状根据它们易位的环境而具有可塑性。而来自适宜栖息地的蛤蜊被引入不适宜的栖息地，其壳高和宽度均显着增加。广义线性混合模型表明，壳高的增加主要受释放栖息地（环境）的影响，而壳宽的增加主要受个体生长速率的影响。这些结果表明，贝壳高度和宽度的边际增长对蛤蜊的外部和内部因素的反应不同，导致它们的壳形状根据它们易位的环境而具有可塑性。而来自适宜栖息地的蛤蜊被引入不适宜的栖息地，其壳高和宽度均显着增加。广义线性混合模型表明，壳高的增加主要受释放栖息地（环境）的影响，而壳宽的增加主要受个体生长速率的影响。这些结果表明，贝壳高度和宽度的边际增长对蛤蜊的外部和内部因素的反应不同，导致它们的壳形状根据它们易位的环境而具有可塑性。