Sea cucumber taxonomy and systematics has in the past heavily relied on gross external and internal anatomy, ossicle assemblage in different tissues, and molecular characterisation, with coloration, habitat, and geographical and bathymethric distribution also considered important parameters. In the present paper, we made these observations and techniques in detail and complemented them with the novel technique of micro-computed tomography of the calcareous ring. We investigated a single European species, the so-called gravel sea cucumber, Neopentadactyla mixta (Östergren, 1898), using recently collected material from the Chausey Islands, Normandy, France. We redescribed the species, illustrated its ossicle assemblage through scanning electron microscopy, and visualised the calcareous ring through stacking photography and through micro-CT scanning. Additionally, a DNA fragment of 955 base pairs of the 18S ribosomal RNA gene was sequenced from one specimen, which showed a high similarity with the only sequence of N. mixta publicly available. We completed this integrative study by providing a detailed distribution of the occurrence of N. mixta based on published, verifiable accounts.

中文翻译：

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探索微计算机断层扫描 (micro-CT) 在海参分类学中的应用：砾石海参 Neopentadactyla mixta（Östergren，1898）（棘皮动物、海参科、叶状海参科）的案例研究

海参分类学和系统学过去严重依赖外部和内部大体解剖学、不同组织中的小骨组合和分子特征，其中颜色、栖息地以及地理和深海分布也被视为重要参数。在本文中，我们详细地进行了这些观察和技术，并用钙质环的显微计算机断层扫描新技术对其进行了补充。我们使用最近从法国诺曼底 Chausey 群岛收集的材料调查了一种单一的欧洲物种，即所谓的砾石海参 Neopentadactyla mixta（Östergren，1898 年）。我们重新描述了该物种，通过扫描电子显微镜说明了它的小骨组合，并通过堆叠摄影和显微 CT 扫描可视化了钙质环。此外，从一个样本中对 18S 核糖体 RNA 基因的 955 个碱基对的 DNA 片段进行了测序，该片段与唯一公开的 N. mixta 序列具有高度相似性。我们根据已发表的可验证帐户提供了 N. mixta 发生的详细分布，从而完成了这项综合研究。