Czerneková Michaela, Jönsson K Ingemar, Chajec Lukasz, Student Sebastian, Poprawa Izabela
School of Education and Environment, Kristianstad University, Kristianstad, Sweden.
Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
Protoplasma. 2017 May;254(3):1367-1377. doi: 10.1007/s00709-016-1027-2. Epub 2016 Sep 27.
Tun formation is an essential morphological adaptation for entering the anhydrobiotic state in tardigrades, but its internal structure has rarely been investigated. We present the structure and ultrastructure of organs and cells in desiccated Richtersius coronifer by transmission and scanning electron microscopy, confocal microscopy, and histochemical methods. A 3D reconstruction of the body organization of the tun stage is also presented. The tun formation during anhydrobiosis of tardigrades is a process of anterior-posterior body contraction, which relocates some organs such as the pharyngeal bulb. The cuticle is composed of epicuticle, intracuticle and procuticle; flocculent coat; and trilaminate layer. Moulting does not seem to restrict the tun formation, as evidenced from tardigrade tuns that were in the process of moulting. The storage cells of desiccated specimens filled up the free inner space and surrounded internal organs, such as the ovary and digestive system, which were contracted. All cells (epidermal cells, storage cells, ovary cells, cells of the digestive system) underwent shrinkage, and their cytoplasm was electron dense. Lipids and polysaccharides dominated among reserve material of storage cells, while the amount of protein was small. The basic morphology of specific cell types and organelles did not differ between active and anhydrobiotic R. coronifer.
隐生形成是缓步动物进入脱水状态所必需的形态适应，但对其内部结构的研究却很少。我们通过透射电子显微镜、扫描电子显微镜、共聚焦显微镜和组织化学方法，展示了干燥的冠状富氏熊虫器官和细胞的结构及超微结构。还展示了隐生阶段身体组织的三维重建。缓步动物脱水过程中的隐生形成是一个前后身体收缩的过程，这会使一些器官（如咽球）重新定位。角质层由外表皮、内表皮和原表皮、絮状层和三层结构组成。蜕皮似乎并不限制隐生形成，处于蜕皮过程中的缓步动物隐生个体就证明了这一点。干燥标本的储存细胞充满了内部的自由空间，并围绕着收缩的内部器官，如卵巢和消化系统。所有细胞（表皮细胞、储存细胞、卵巢细胞、消化系统细胞）都发生了收缩，其细胞质电子密度较高。储存细胞的储备物质中脂质和多糖占主导，而蛋白质含量较少。活跃的和处于脱水状态的冠状富氏熊虫特定细胞类型和细胞器的基本形态没有差异。
