Grenier Christian, Griesshaber Erika, Schmahl Wolfgang, Berning Björn, Checa Antonio G
Departamento de Estratigrafía y Paleontología, Universidad de Granada, 18071 Granada, Spain.
Department of Earth and Environmental Sciences, Ludwig-Maximilians Universität, 80333 Munich, Germany.
Mar Life Sci Technol. 2024 Jun 7;6(3):405-424. doi: 10.1007/s42995-024-00233-1. eCollection 2024 Aug.
Gymnolaemata bryozoans produce CaCO skeletons of either calcite, aragonite, or both. Despite extensive research, their crystallography and biomineralization patterns remain unclear. We present a detailed study of the microstructures, mineralogy, and crystallography of eight extant cheilostome species using scanning electron microscopy, electron backscatter diffraction, atomic force microscopy, and micro-computed tomography. We distinguished five basic microstructures, three calcitic (tabular, irregularly platy, and granular), and two aragonitic (granular-platy and fibrous). The calcitic microstructures consist of crystal aggregates that transition from tabular or irregularly platy to granular assemblies. Fibrous aragonite consists of fibers arranged into spherulites. In all cases, the crystallographic textures are axial, and stronger in aragonite than in calcite, with the c-axis as the fiber axis. We reconstruct the biomineralization sequence in the different species by considering the distribution and morphology of the growth fronts of crystals and the location of the secretory epithelium. In bimineralic species, calcite formation always predates aragonite formation. In interior compound walls, growth proceeds from the cuticle toward the zooecium interior. We conclude that, with the exception of tabular calcite, biomineralization is remote and occurs within a relatively wide extrapallial space, which is consistent with the inorganic-like appearance of the microstructures. This biomineralization mode is rare among invertebrates.
The online version contains supplementary material available at 10.1007/s42995-024-00233-1.
裸唇目苔藓虫会产生方解石、文石或两者皆有的碳酸钙骨骼。尽管进行了广泛研究，但其晶体学和生物矿化模式仍不清楚。我们使用扫描电子显微镜、电子背散射衍射、原子力显微镜和显微计算机断层扫描，对八种现存唇口目物种的微观结构、矿物学和晶体学进行了详细研究。我们区分出五种基本微观结构，三种方解石质的（板状、不规则片状和粒状），以及两种文石质的（粒状片状和纤维状）。方解石质微观结构由晶体聚集体组成，这些聚集体从板状或不规则片状过渡到粒状集合体。纤维状文石由排列成球粒的纤维组成。在所有情况下，晶体学织构都是轴向的，文石中的比方解石中的更强，c轴为纤维轴。我们通过考虑晶体生长前沿的分布和形态以及分泌上皮的位置，重建了不同物种的生物矿化序列。在双矿物物种中，方解石的形成总是早于文石的形成。在内部复合壁中，生长从角质层向虫室内部进行。我们得出结论，除了板状方解石外，生物矿化是远距离的，并且发生在相对较宽的外套膜外空间内，这与微观结构的无机样外观一致。这种生物矿化模式在无脊椎动物中很少见。
在线版本包含可在10.1007/s42995-024-00233-1获取的补充材料。
