深海六放海绵大骨针的结构与特性

在海绵动物(多孔动物)中,六放海绵和寻常海绵为硅质骨骼.生活在深海(1 000 m)中的六放海绵是最古老的海绵动物,其中间单根海绵和春氏单根海绵有长达3 m的骨针,是地球上最长的生物硅结构.利用电子显微技术观测, 这些直径达8 mm的巨大根须骨针具有同心层状结构,其横截面显示明显的构造分界:中间为含有轴丝的轴管,外围是一50-150 μm厚的轴筒,最外面为区状区(300-500层,每层厚度3-5 μm).生物化学研究显示其主要的蛋白质为35 kD大分子,另外,还检测到23-24 kD 多肽,可能是硅蛋白相关蛋白.依据现有的红血球凝聚活性,从骨针提取物中也检测到了凝集素.由电子探针获得其化学成分主要为Si,K和Na.此外,骨针的光传输实验表明,该巨大根须骨针用作光纤可传输600 nm至1 400 nm范围的光,而滤掉小于600 nm的光(类似高通滤波器)和大于1 400 nm 的红外光(类似低通滤波器).另外,从六放海绵的空囊泡沫海绵中分离出一个基因并确证了其推导的编码蛋白序列,该蛋白编码一个光裂合酶相关蛋白,蛋白相似性比较结果显示属于光裂合酶相关蛋白中多细胞动物隐色素一类.基于以上数据给出了六放海绵硅质骨针形成的示意图.另外,由单根海绵骨针可作为波导传输光/电和/或化学信号,推断在海绵动物中有类似神经系统的网络系统动物学报 53(3):557-569,2007].

Structure and characteristics of giant spicules of the deep sea hexactinellid sponges of the genus Monorhaphis (Hexactinellida: Amphidiscosida: Monorhaphididae)

Two classes of sponges (phylum Porifera) are characterized by a siliceous skeleton, the Hexactinellida and the Demospongiae. The phylogenetically oldest sponge taxon, the Hexactinellida, lives in the deep-sea (1 000 m). The species Monorhaphis intermedia and Monorhaphis chuni, comprise with their 3 m long spicules the longest bio-silica structures on earth. These giant basal spicules have been analyzed by electron microscopical techniques. All spicules have a concentric lamellar organization. Cross sections through the spicules show a structural division of the spicules: in the center is an axial canal which harbors the axial filament; around this canal an axial cylinder of 50 to 150 μm width can be distinguished; and finally the lamellar region (300 to 500 lamellae; size between 3 and 5 μm). Biochemical studies revealed that the dominant protein in the spicules is a 35 kDa large molecule; in addition, a 23-24 kDa polypeptide, which is possibly silicatein-related, can be identified. Electron microprobe analysis revealed that three main elements compose the spicules: silicon, potassium and sodium. Furthermore, the giant basal spicules have been used as a waveguide for light within the spectral range 600 nm and 1 400 nm. Light transmission studies revealed that the spicules act as optical fibers (like a high pass filter) cutting off the light of wavelengths below about 600 nm; a similar cut-off of the spicule is observed in the infrared wavelength range above 1 400 nm. Finally the gene encoding a photolyase-related protein from the hexactinellid Aphrocallistes vastus is described. Sequence similarity studies suggested that the protein can be subdivided to the photolyase-related proteins which comprise also the metazoan cryptochromes. Based on these data a schematic outline of the formation of the siliceous spicules of hexactinellids is given; in addition, it is proposed that in Monorhaphis the spicules act as waveguides for the transmission of light/electrical and/or chemical signals, thus providing these animals with a neuronal-like network systemActa Zoologica Sinica 53(3):557-569,2007].