Cilia are evolutionarily conserved organelles that extend from the surface of cells and are found in diverse organisms from protozoans to multicellular organisms. Motile cilia play various biological functions by their beating motion, including mixing fluids and transporting food particles. Non-motile cilia act as sensors that signal cells about their microenvironment. In corals, cilia have been described in some of the cell layers but never in the calcifying epithelium, which is responsible for skeleton formation. In the present study, we used scanning electron microscopy and immunolabelling to investigate the cellular ciliature of the different tissue layers of the coral Stylophora pistillata, with a focus on the calcifying calicoblastic ectoderm. We show that the cilium of the calcifying cells is different from the cilium of the other cell layers. It is much shorter, and more importantly, its base is structurally distinct from the base observed in cilia of the other tissue layers. Based on these structural observations, we conclude that the cilium of the calcifying cells is a primary cilium. From what is known in other organisms, primary cilia are sensors that signal cells about their microenvironment. We discuss the implications of the presence of a primary cilium in the calcifying epithelium for our understanding of the cellular physiology driving coral calcification and its environmental sensitivity.

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初级纤毛在珊瑚钙化中的作用？

纤毛是进化上保守的细胞器，从细胞表面延伸出来，存在于从原生动物到多细胞生物的各种生物中。运动纤毛通过它们的跳动运动发挥各种生物学功能，包括混合液体和运输食物颗粒。非运动纤毛充当传感器，向细胞发出有关其微环境的信号。在珊瑚中，纤毛在一些细胞层中被描述过，但从未在负责骨骼形成的钙化上皮中被描述过。在本研究中，我们使用扫描电子显微镜和免疫标记来研究珊瑚 Stylophora pistillata 不同组织层的细胞纤毛，重点是钙化的 calicoblastic 外胚层。我们表明钙化细胞的纤毛不同于其他细胞层的纤毛。它更短，更重要的是，它的基部在结构上不同于在其他组织层的纤毛中观察到的基部。基于这些结构观察，我们得出结论，钙化细胞的纤毛是初级纤毛。从其他生物体中已知的情况来看，初级纤毛是向细胞发送有关其微环境的信号的传感器。我们讨论了钙化上皮中初级纤毛的存在对我们理解驱动珊瑚钙化及其环境敏感性的细胞生理学的影响。我们得出结论，钙化细胞的纤毛是初级纤毛。从其他生物体中已知的情况来看，初级纤毛是向细胞发出有关其微环境的信号的传感器。我们讨论了钙化上皮中初级纤毛的存在对我们理解驱动珊瑚钙化及其环境敏感性的细胞生理学的影响。我们得出结论，钙化细胞的纤毛是初级纤毛。从其他生物体中已知的情况来看，初级纤毛是向细胞发送有关其微环境的信号的传感器。我们讨论了钙化上皮中初级纤毛的存在对我们理解驱动珊瑚钙化及其环境敏感性的细胞生理学的影响。