Department of Astronomy and Earth Sciences, Tokyo Gakugei University, Koganei, Tokyo 184-8501, Japan.
Department of Astronomy and Earth Sciences, Tokyo Gakugei University, Koganei, Tokyo 184-8501, Japan.
Eur J Protistol. 2014 Apr;50(2):194-204. doi: 10.1016/j.ejop.2013.12.001. Epub 2013 Dec 15.
Reproductive swarmers of the polycystine radiolarian Sphaerozoum punctatum (Huxley) collected from the East China Sea were examined using light, scanning and transmission electron microscopy. The swarmer cells were about 8-10 μm in length with a pear-like shape and a conical end with two flagella. A nucleus, mitochondria, Golgi body, lipid droplets and, characteristically, a single, large, vacuole-bound SrSO₄ crystal were present in the cytoplasm. Centering on the crystal inclusion, swarmers swam in a rapid rotational movement both clockwise and anticlockwise. Small subunit (SSU) rDNA sequences obtained for the reproductive swarmer cells from S. punctatum show a monophyletic group together with colonial spumellarians and grouped with S. punctatum from Bermuda in the clade. The morphological features and molecular phylogeny of the reproductive swarmers of S. punctatum show evidence of ancestral traits of radiolarians; acantharians and polycystines have a common ancestry. In addition, SrSO₄ inclusion of the swarmer cell may be a form of ballast deposited by the swarmer to allow proper positioning in the water column. We hypothesize that radiolarian-affiliated sequences from SSU rDNA clone libraries of marine picoeukaryotes may be derived from the picoplanktonic cells of radiolarians; i.e., small flagellated life stages such as reproductive swarmers or gametes.
从东海采集的多房放射虫 Sphaerozoum punctatum (Huxley) 的繁殖游仆虫，通过光镜、扫描电镜和透射电镜进行了检查。游仆虫细胞长约 8-10 μm，呈梨形，前端为锥形，有两根鞭毛。细胞质中存在细胞核、线粒体、高尔基体、脂滴和特征性的单个大、与液泡结合的 SrSO₄ 晶体。围绕着晶体包含物，游仆虫以顺时针和逆时针方向快速旋转游动。从 S. punctatum 的繁殖游仆虫细胞中获得的小亚基 (SSU) rDNA 序列显示出一个单系群，与群体盘形虫和百慕大的 S. punctatum 一起聚类。S. punctatum 繁殖游仆虫的形态特征和分子系统发育表明它们具有放射虫祖先特征的证据；刺丝胞动物和多房放射虫具有共同的祖先。此外，游仆虫细胞中的 SrSO₄ 包含物可能是游仆虫为了在水柱中正确定位而沉积的一种压载物。我们假设海洋微微体古菌 SSU rDNA 克隆文库中的放射虫相关序列可能来自放射虫的微微浮游细胞，即小鞭毛生命阶段，如繁殖游仆虫或配子。
