Development and evolution of the shell in cephalopods is difficult to establish as there is few species with a calcified shell that could be fossilized (stable in geological time). Internal cuttlebone of sepiids is so particular that homologies are difficult to find. The developmental sequence in embryos give some response elements by comparison with adult cuttlebone. The macro and microstructure of adult shell is well known but an approach at nanostructural level allows to determine structure and composition of the two main parts, the dorsal shield and chambered part. We evidence in the embryonic shell, mainly organic, a light calcification of the shell, which occurs directly as aragonite, as it is all along the formation of the shell and whatever the parts. In embryonic shell, the prismatic and/or lamellar layers, present in adult, are not differentiated and the dorsal shield grows progressively, from posterior to anterior. Despite microstructural differences, all layers of both chambered part and dorsal shield are composed of rounded nanogranules (between 50 and 100 nm), similar to what is found in other mollusc shells. Finally, the presence of pillars evidenced in embryo suggests either that their absence in extinct lineages of sepiids is the result of a diagenetic process or that they are a novelty in present sepiid species.

中文翻译：

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Sepia officinalis (Cephalopoda, Mollusca) 胚胎和成体壳的比较

头足类动物壳的发育和进化很难确定，因为很少有具有钙化壳的物种可以化石化（地质时间稳定）。sepiids 的内部墨鱼骨非常特殊，很难找到同源性。与成体墨鱼骨相比，胚胎的发育顺序给出了一些反应要素。成人壳的宏观和微观结构是众所周知的，但纳米结构水平的方法可以确定两个主要部分的结构和组成，背盾和腔室部分。我们在胚胎壳（主要是有机壳）中证明了壳的轻微钙化，它直接以文石的形式出现，因为它一直伴随着壳的形成和任何部分。在胚胎壳中，棱柱和/或层状层，存在于成虫中，没有分化，背盾逐渐生长，从后到前。尽管微观结构存在差异，但腔室部分和背盾的所有层均由圆形纳米颗粒（50 至 100 nm）组成，类似于其他软体动物壳中的颗粒。最后，在胚胎中证实存在柱子表明它们在已灭绝的 sepiids 谱系中的缺失是成岩过程的结果，或者它们是目前 sepiid 物种中的新奇事物。