Intra-epithelial spicules in a homosclerophorid sponge
Intra-epithelial spicules in a homosclerophorid sponge
复制标题
同核海绵中的上皮内针
DOI：
10.1007/s00441-007-0385-7
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发表时间：
2007
影响因子：
3.6
通讯作者：
A. Riesgo
中科院分区：
文献类型：
--
作者：
M. Maldonado;A. Riesgo
试图了解海绵中生物硅化的复杂性受到分离和培养其硬细胞的困难的阻碍，硬细胞是在海绵体内以低密度徘徊的特化细胞，并且被认为是唯一负责硅质骨架结构（骨针）的分泌。通过调查homosclerophorid的Corticium candelabrum，传统上包括在类Demospongiae，我们表明，两个丰富的细胞类型的上皮细胞（pinacocytes），除了硬细胞，包含骨针胞内。这些细胞内骨针的小尺寸，连同它们的二氧化硅层的超微结构，表明它们的硅化是未完成的，并支持这样的想法，即它们是由上皮细胞“原位”产生的，而不是从细胞间的mesohyl被纳入。小骨针的起源也发生（虽然很少）在核细胞和细胞质的后囊细胞是更不确定的。这种海绵的骨针不仅在位置上，而且在结构上都是非常规的。横截面的针状体显示出一个近圆形的轴向细丝，外部被二氧化硅层包围，然后是两个同心的轴外有机层，每个层又被二氧化硅环包围。我们解释这种结构模式作为一个独特的三步过程的结果，包括一个初始（轴向）硅化波周围的轴向丝和两个随后的（轴外）硅化波。这些研究结果表明，骨针生产的细胞机制不同的海绵，并揭示了需要仔细重新检查迄今为止的单系状态归因于生物硅化的门多孔动物。
Attempts to understand the intricacies of biosilicification in sponges are hampered by difficulties in isolating and culturing their sclerocytes, which are specialized cells that wander at low density within the sponge body, and which are considered as being solely responsible for the secretion of siliceous skeletal structures (spicules). By investigating the homosclerophorid Corticium candelabrum, traditionally included in the class Demospongiae, we show that two abundant cell types of the epithelia (pinacocytes), in addition to sclerocytes, contain spicules intracellularly. The small size of these intracellular spicules, together with the ultrastructure of their silica layers, indicates that their silicification is unfinished and supports the idea that they are produced “in situ” by the epithelial cells rather than being incorporated from the intercellular mesohyl. The origin of small spicules that also occur (though rarely) within the nucleus of sclerocytes and the cytoplasm of choanocytes is more uncertain. Not only the location, but also the structure of spicules are unconventional in this sponge. Cross-sectioned spicules show a subcircular axial filament externally enveloped by a silica layer, followed by two concentric extra-axial organic layers, each being in turn surrounded by a silica ring. We interpret this structural pattern as the result of a distinctive three-step process, consisting of an initial (axial) silicification wave around the axial filament and two subsequent (extra-axial) silicification waves. These findings indicate that the cellular mechanisms of spicule production vary across sponges and reveal the need for a careful re-examination of the hitherto monophyletic state attributed to biosilicification within the phylum Porifera.
影响因子：
3.6
作者：
Müller, WEG;Rothenberger, M;Schröder, H
通讯作者：
Schröder, H