Selective factors in the evolution of multicellularity in choanoflagellates
Selective factors in the evolution of multicellularity in choanoflagellates
复制标题
领鞭毛虫多细胞进化的选择因素
DOI：
10.1002/jez.b.22941
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Koehl, M. A. R.
中科院分区：
文献类型：
--
作者：
Koehl, M. A. R.
Choanoflagellates，单细胞真核生物，可以通过细胞分裂形成多细胞菌落，并与动物共享一个共同的祖先，被用作模型系统，以研究功能的后果是单细胞与殖民地。本文综述了单细胞和多细胞领鞭毛虫在游泳、摄食和躲避捕食等方面的表现差异，为多细胞原生动物祖先的选择优势提供了新的见解。每个领鞭毛虫细胞通过击打单个鞭毛来推动水，并在鞭毛周围的微绒毛项圈上捕获细菌猎物。多细胞集落的形成并不能提高游泳能力，但某些配置的集落中的一些细胞的项圈的携带猎物的水的流量可能大于单细胞。殖民地的几何形状似乎影响是否在殖民地的细胞捕捉更多的猎物每细胞每一次比单细胞choanoflagellates。虽然多细胞领鞭毛虫表现出响应氧气的化学动力学行为，但只有单细胞扩散阶段（没有项圈的快速游泳者）使用pH信号在细菌猎物可能丰富的地方聚集。菌落产生更大的流体动力学信号比单细胞，和捕食原生动物捕食者捕获菌落，而忽略单细胞。与此相反，纤毛虫捕食者夹带单细胞和殖民地在他们的喂养电流，但拒绝较大的殖民地，而被动heliozoan捕食者没有表现出偏好。因此，后领鞭毛虫细胞分化成不同形态型（包括多细胞形式）的能力，可能为动物祖先提供了选择优势。
Choanoflagellates, unicellular eukaryotes that can form multicellular colonies by cell division and that share a common ancestor with animals, are used as a model system to study functional consequences of being unicellular versus colonial. This review examines performance differences between unicellular and multicellular choanoflagellates in swimming, feeding, and avoiding predation, to provide insights about possible selective advantages of being multicellular for the protozoan ancestors of animals. Each choanoflagellate cell propels water by beating a single flagellum and captures bacterial prey on a collar of microvilli around the flagellum. Formation of multicellular colonies does not improve the swimming performance, but the flux of prey‐bearing water to the collars of some of the cells in colonies of certain configurations can be greater than for single cells. Colony geometry appears to affect whether cells in colonies catch more prey per cell per time than do unicellular choanoflagellates. Although multicellular choanoflagellates show chemokinetic behavior in response to oxygen, only the unicellular dispersal stage (fast swimmers without collars) use pH signals to aggregate in locations where bacterial prey might be abundant. Colonies produce larger hydrodynamic signals than do single cells, and raptorial protozoan predators capture colonies while ignoring single cells. In contrast, ciliate predators entrain both single cells and colonies in their feeding currents, but reject larger colonies, whereas passive heliozoan predators show no preference. Thus, the ability of choanoflagellate cells to differentiate into different morphotypes, including multicellular forms, in response to variable aquatic environments might have provided a selective advantage to the ancestors of animals.