University of Ljubljana, Biotechnical Faculty, Department of Biology, Večna pot 111, SI-1000 Ljubljana, Slovenia.
J Struct Biol. 2012 Oct;180(1):216-25. doi: 10.1016/j.jsb.2012.05.014. Epub 2012 May 29.
Crustaceans form a variety of calcium deposits in which they store calcium necessary for the mineralization of their exoskeletons. Calcium bodies, organs containing large amounts of calcium, have been reported in some terrestrial isopod crustaceans, but have not yet been extensively studied. We analyzed the architecture of these organs during the molt cycle in the isopod Titanethes albus. Two pairs of calcium bodies are positioned ventrolaterally in posterior pereonites of T. albus. Individual organs are epithelial sacs that contain material arranged in concentric layers delimited by thin laminae. As demonstrated by electron microscopy and fluorescence in situ hybridization, abundant bacteria are present within the calcium bodies. Regardless of the molt cycle stage, crystalline concretions are present in the central areas of the calcium bodies. Energy dispersive X-ray spectrometry of the concretions demonstrated that they are composed predominantly of calcium and phosphorus and selected area electron diffraction indicated the presence of hydroxyapatite. In molting animals, a glassy layer of mineralized matrix is formed between the envelope and the outermost lamina of the calcium body. This layer consists of an amorphous calcium mineral which contains less phosphorus than the central concretions and is resorbed after molt. Since changes in the mineralized matrix are synchronized with the molt cycle, the calcium bodies likely function as a storage compartment that complements sternal deposits as a source of calcium for the mineralization of the exoskeleton. Bacteria associated with the mineralized matrix of calcium bodies are evidently involved in calcium dynamics.
甲壳动物在各种钙沉积物中形成，这些沉积物储存着它们外骨骼矿化所需的钙。在一些陆生等足目甲壳动物中，已经报道了含有大量钙的钙体器官，但尚未得到广泛研究。我们分析了等足目 Titanethes albus 蜕皮周期中这些器官的结构。两对钙体位于 T. albus 后胸节的腹侧外侧。单个器官是含有以同心层排列的物质的上皮囊，由薄的薄片分隔。正如电子显微镜和荧光原位杂交所证明的那样，大量细菌存在于钙体中。无论蜕皮周期阶段如何，钙体的中心区域都存在结晶结石。结石的能谱分析表明它们主要由钙和磷组成，选区电子衍射表明存在羟基磷灰石。在蜕皮动物中，在外壳和钙体最外层之间形成一层矿化基质的玻璃状层。该层由非晶态钙矿物质组成，其磷含量低于中心结石，并且在蜕皮后被吸收。由于矿化基质的变化与蜕皮周期同步，钙体可能作为一个储存室，与胸骨沉积物一起作为外骨骼矿化的钙源。与钙体矿化基质相关的细菌显然参与了钙的动态变化。
