Sakashita Misaki, Sato Mao, Kondo Shigeru
Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan.
Laboratory of Marine Biology, Faculty of Science, Kochi University, Kochi, Japan.
J Morphol. 2019 Jun;280(6):778-795. doi: 10.1002/jmor.20983. Epub 2019 Apr 4.
Vertebral bodies of teleost fish are formed by the sclerotomal bone covering the chordacentrum. The internal part of the sclerotomal bone is composed of an amphicoelous hourglass shaped autocentrum, which is common in most fish species. In contrast, the external shape of the sclerotomal bone varies extensively among species. There are multiple hypotheses regarding the composition and formation of the external structure. However, as they are based on studies of few extant or extinct species, their applicability to other species remains to be clarified. To understand the morphology, formation, and composition of vertebral bodies in teleosts, we performed a comparative analysis using micro-CT scans of 32 species from 10 orders of Teleostei and investigated the detailed morphology of the sclerotomal bone, especially its plate-like ridge and trabeculae. We discovered two structural characteristics that are shared among most of the examined species. One was the sheet-like trabeculae that extend radially from the center of the vertebral body with a constant thickness. The other was the presence of hollow spaces on the internal parts of the lateral ridge and trabeculae. The combination of different arrangements of sheet-like trabeculae and internal hollow spaces formed different shapes of the lateral structure of the vertebral body. The properties of these two characteristics suggest that the external part of the sclerotomal bone grows outward by deposition at the bone tip, and that, concurrently, bone absorption occurs in the internal part of the sclerotomal bone. The vertebral arches were also formed by the sheet-like trabeculae, indicating that both, the vertebral body and the arches, are formed by the same component. The micro-CT scanning data were uploaded to a public database so they can be used for future studies on fish vertebrae.
硬骨鱼的椎体由覆盖脊索中心的骨化骨形成。骨化骨的内部由双凹形沙漏状的自体中心组成，这在大多数鱼类中很常见。相比之下，骨化骨的外部形状在不同物种之间差异很大。关于外部结构的组成和形成有多种假说。然而，由于这些假说基于对少数现存或已灭绝物种的研究，其对其他物种的适用性仍有待阐明。为了了解硬骨鱼椎体的形态、形成和组成，我们对硬骨鱼纲10个目32个物种进行了显微CT扫描，并进行了比较分析，研究了骨化骨的详细形态，特别是其板状嵴和小梁。我们发现了大多数被检查物种共有的两个结构特征。一个是从椎体中心径向延伸且厚度恒定的片状小梁。另一个是侧嵴和小梁内部存在中空空间。片状小梁和内部中空空间的不同排列组合形成了椎体侧部结构的不同形状。这两个特征的特性表明，骨化骨的外部通过在骨尖沉积向外生长，同时，骨化骨内部发生骨吸收。椎弓也由片状小梁形成，这表明椎体和椎弓都是由相同的成分形成的。显微CT扫描数据已上传至公共数据库，以便用于未来关于鱼椎的研究。
