Central Facility for Electron Microscopy, University of Ulm, Albert-Einstein-Allee 11, 89069 Ulm, Germany.
Central Facility for Electron Microscopy, University of Ulm, Albert-Einstein-Allee 11, 89069 Ulm, Germany.
Arthropod Struct Dev. 2021 Nov;65:101101. doi: 10.1016/j.asd.2021.101101. Epub 2021 Sep 6.
Generally, the mineralisation of the crustacean cuticle occurs when the cuticle has expanded after moulting. However, in the partes incisivae of Porcellio scaber, cuticle mineralisation with calcium phosphate already occurs before the moult. We investigated the ultrastructure and distribution of organelles within the epidermis cells and searched for calcium-containing organelles using EDX and EFTEM analysis. We found two different cell types. Calcium carbonate-secreting C-cells, which resemble the epithelial cells of the general integument, and the P-cells, which, as an unusual feature, have cell extensions up to 400 μm long. During secretion of the partes incisivae, these extensions end at the unmineralised tip and the phosphate-containing middle region. Their cell bodies contain most of the mitochondria located in basal folds and a high amount of endoplasmic reticulum. The cell extensions contain many microtubules, endoplasmic reticulum, large and small vesicles and densely stained rod-shaped cisternae. The rod-shaped cisternae and the endoplasmic reticulum contain calcium. During cuticle mineralisation, vesicles, which probably belong to the endo-lysosomal system, contain calcium and phosphorus. They occur at some distance and close to the cuticle. The mineral in these vesicles has a similar composition to that within the cuticle, suggesting that they play a role in cuticle mineralisation.
通常情况下，甲壳动物外骨骼的矿化发生在外骨骼蜕皮后扩张的时候。然而，在 Porcellio scaber 的切齿中，磷酸钙在外骨骼蜕皮前就已经开始矿化。我们通过电子显微镜研究了表皮细胞内细胞器的超微结构和分布，并利用 EDX 和 EFTEM 分析寻找含钙细胞器。我们发现了两种不同的细胞类型。一种是分泌碳酸钙的 C 细胞，它类似于一般表皮的上皮细胞；另一种是 P 细胞，它有一个不寻常的特征，即细胞延伸长达 400 μm。在切齿分泌过程中，这些延伸在未矿化的尖端和含磷酸盐的中间区域结束。它们的细胞体包含大部分位于基底褶皱中的线粒体和大量的内质网。细胞延伸部分含有许多微管、内质网、大的和小的囊泡以及密集染色的杆状内质网。杆状内质网和内质网含有钙。在甲壳矿化过程中，可能属于内体-溶酶体系统的囊泡含有钙和磷。它们在一定距离处靠近外骨骼。这些囊泡中的矿物质与外骨骼中的矿物质组成相似，表明它们在外骨骼矿化过程中发挥了作用。
