Guidetti Roberto, Bonifacio Alois, Altiero Tiziana, Bertolani Roberto, Rebecchi Lorena
*Department of Life Sciences, University of Modena and Reggio Emilia, via Campi 213/D, 41124 Modena, Italy;
Department of Engineering and Architecture, University of Trieste, via Valerio 10, 34127 Trieste, Italy;
Integr Comp Biol. 2015 Aug;55(2):241-52. doi: 10.1093/icb/icv008. Epub 2015 Apr 8.
The cuticular portion of the tardigrade feeding apparatus is a complex structure that can be schematically divided into four parts: a buccal ring, a buccal tube, a stylet system (formed by two piercing stylets, each within a stylet coat, and two stylet supports), and the lining of a myoepithelial sucking pharynx. To better understand the function and evolution of the feeding apparatus, the morpho-functional traits and chemical composition of the structures forming the feeding apparatuses of eight different species of tardigrades were analyzed. These eight species are representative of almost all main phylogenetic lineages of the phylum. The calcium and chitin in the feeding apparatus were examined by light microscopy, scanning electron microscopy, confocal laser scanning microscopy, energy dispersive X-ray spectroscopy, and Raman microspectroscopy (Raman). In all species, the feeding apparatus had been subjected to biomineralization due to CaCO3 encrustations organized in the crystalline form of aragonite. Aragonite and chitin are present in different concentrations in the feeding apparatus according to the structures and species considered. Generally, where the structures are rigid there is more aragonite than chitin, and vice versa. The buccal tube and piercing stylets are rich in calcium, with the piercing stylets apparently composed exclusively of aragonite. In eutardigrades, chitin is in higher concentration in the structures subject to higher mechanical stresses, such as the crests of the buccal crown and the condyles of the stylet furca.
缓步动物进食器官的角质部分是一个复杂的结构，可大致分为四个部分：口环、口管、针系统（由两根穿刺针组成，每根针位于一个针鞘内，还有两根针支撑）以及肌上皮吸吮咽的内衬。为了更好地理解进食器官的功能和进化，分析了八种不同缓步动物物种进食器官的形态功能特征和化学成分。这八个物种几乎代表了该门所有主要的系统发育谱系。通过光学显微镜、扫描电子显微镜、共聚焦激光扫描显微镜、能量色散X射线光谱和拉曼显微光谱（拉曼）对进食器官中的钙和几丁质进行了检测。在所有物种中，进食器官都因以文石晶体形式组织的碳酸钙结壳而经历了生物矿化。根据所考虑的结构和物种不同，进食器官中文石和几丁质的浓度也不同。一般来说，结构坚硬的地方文石比几丁质多，反之亦然。口管和穿刺针富含钙，穿刺针显然完全由文石组成。在真缓步纲动物中，几丁质在承受较高机械应力的结构中浓度较高，如口冠的嵴和针叉的髁。
