Spiralians represent the least studied superclade of bilaterian animals, despite exhibiting the widest diversity of organisms. Although spiralians include iconic organisms, such as octopus, earthworms and clams, a lot remains to be discovered regarding their phylogeny and biology. Here, we review recent attempts to apply single-cell transcriptomics, a new pioneering technology enabling the classification of cell types and the characterisation of their gene expression profiles, to several spiralian taxa. We discuss the methodological challenges and requirements for applying this approach to marine organisms and explore the insights that can be brought by such studies, both from a biomedical and evolutionary perspective. For instance, we show that single-cell sequencing might help solve the riddle of the homology of larval forms across spiralians, but also to better characterise and compare the processes of regeneration across taxa. We highlight the capacity of single-cell to investigate the origin of evolutionary novelties, as the mollusc shell or the cephalopod visual system, but also to interrogate the conservation of the molecular fingerprint of cell types at long evolutionary distances. We hope that single-cell sequencing will open a new window in understanding the biology of spiralians, and help renew the interest for these overlooked but captivating organisms.

中文翻译：

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单细胞转录组学推动螺旋生物学的探索

尽管螺旋动物表现出最广泛的生物多样性，但它代表了研究最少的两侧对称动物的超进化枝。尽管螺旋虫包括章鱼、蚯蚓和蛤等标志性生物，但它们的系统发育和生物学仍有很多待发现。在这里，我们回顾了最近将单细胞转录组学应用于几个螺旋类群的尝试，单细胞转录组学是一种新的开创性技术，能够对细胞类型进行分类并表征其基因表达谱。我们讨论了将这种方法应用于海洋生物的方法挑战和要求，并从生物医学和进化的角度探讨了此类研究可以带来的见解。例如，我们表明单细胞测序可能有助于解决螺旋虫幼虫形式的同源性之谜，而且还可以更好地表征和比较不同类群的再生过程。我们强调单细胞研究进化新颖性的起源的能力，如软体动物外壳或头足类视觉系统，而且还可以探究长进化距离下细胞类型分子指纹的保守性。我们希望单细胞测序能够为理解螺旋虫的生物学打开一扇新的窗口，并帮助重新燃起人们对这些被忽视但迷人的生物体的兴趣。