Many diatoms form long chains and the distribution of chain lengths within a species depends on several environmental factors, among them grazing risk. Larger grazers, such as copepods, efficiently handle and ingest even very long chains but are less efficient with individual cells, whereas most smaller grazers are unable to feed on chains exceeding a few cells in length. Copepod cues make several species shorten their chain length, and theory predicts that cues from small grazers should induce increased, but this remains to be tested, despite the importance of diatoms in marine food webs. Here, we expose three species of chain‐forming diatoms, Skeletonema marinoi, Chaetoceros affinis, and Thalassiosira rotula to cues from various actively feeding micrograzers and record their response. The effect of grazer presence on chain length varies depending on both the type of grazer and the diatom species. For example, S. marinoi increased its chain length when exposed to grazing cues from the heterotrophic dinoflagellate Gyrodinium dominans and the ciliate Euplotes sp. but not to a copepod nauplii (Temora longicornis). C. affinis also responded to cues from grazing G. dominans by increasing chain length, and the response increased with exposure time. Finally, T. rotula did not respond to grazing cues from G. dominans, but rather inhibited the dinoflagellates' ability to feed, presumably through the release of chemical compounds. Our results suggest that some chainforming diatoms can sense and appropriately respond to fast‐growing micrograzers, thus contributing to the success of diatoms in marine environments.

中文翻译：

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微型浮游动物食草动物诱导群落硅藻的链长可塑性

许多硅藻形成长链，物种内链长度的分布取决于多种环境因素，其中包括放牧风险。较大的食草动物，例如桡足类，可以有效地处理和摄取甚至很长的链，但对于单个细胞的效率较低，而大多数较小的食草动物无法以长度超过几个细胞的链为食。桡足类线索使一些物种缩短了它们的链长，理论预测来自小型食草动物的线索应该会导致链长增加，但这仍有待测试，尽管硅藻在海洋食物网中很重要。在这里，我们暴露了三种链形成硅藻，马里诺骨条虫,亲缘角毛藻， 和圆状海链藻来自各种积极进食的小食草动物的线索并记录它们的反应。食草动物的存在对链长的影响取决于食草动物的类型和硅藻种类。例如，马里诺沙门氏菌当暴露于异养甲藻的放牧信号时，其链长度增加显性陀螺藻和纤毛虫游标动物sp。但对于桡足类无节幼体则不然（长角鲽鱼）。亲缘线虫也对放牧的暗示做出反应多米南斯通过增加链长度，响应随着暴露时间的增加而增加。最后，圆叶红藻没有对放牧的暗示做出反应多米南斯，而是抑制了甲藻的进食能力，可能是通过释放化合物来抑制的。我们的研究结果表明，一些链形成硅藻可以感知快速生长的微食动物并对其做出适当反应，从而有助于硅藻在海洋环境中的成功。