Eichinger Irmgard, Klepal Waltraud, Schmid Markus, Bright Monika
Department of Marine Biology, University of Vienna, Austria.
Biol Bull. 2011 Apr;220(2):140-53. doi: 10.1086/BBLv220n2p140.
The trophosome-an organ especially evolved to accommodate symbiotic bacteria-is a key character of the polychaete family Siboglinidae. Astonishingly, the trophosomes vary in organization and origin between the different siboglinid taxa. The trophosome of the small genus Sclerolinum was nearly unknown until now. Here we investigated the trophosome of S. contortum from the Gulf of Mexico, using light and electron microscopy. We show that this organ derives from the visceral mesoderm and propose that the trophosome of the sister clade Vestimentifera and Sclerolinum is a homologous character. Like that of juvenile vestimentiferans, the trophosome of Sclerolinum trophosome is simply organized. This study reveals that the Sclerolinum trophosome exhibits two regions that differ in the organization of host tissue and the size and shape of the symbionts. We suggest that a specific cell cycle within the symbiont-housing organ is directed along the longitudinal body axis, with a region of proliferation anteriorly and a region of degradation posteriorly. Using Raman microspectroscopy we demonstrate that the endosymbionts of S. contortum from the Gulf of Mexico contain sulfur vesicles, and we argue for a chemoautotrophic sulfur-oxidizing metabolism.
营养体是多毛纲西伯格林线虫科的一个关键特征，它是一种特别进化以容纳共生细菌的器官。令人惊讶的是，不同西伯格林线虫类群的营养体在组织结构和起源方面存在差异。直到现在，小属硬鳞虫的营养体几乎还不为人所知。在这里，我们利用光学显微镜和电子显微镜对来自墨西哥湾的扭旋硬鳞虫的营养体进行了研究。我们发现这个器官起源于内脏中胚层，并提出姐妹分支缨鳃虫目和硬鳞虫的营养体是同源特征。与幼年缨鳃虫的营养体一样，硬鳞虫的营养体结构简单。这项研究表明，硬鳞虫的营养体呈现出两个区域，这两个区域在宿主组织的组织结构以及共生体的大小和形状方面存在差异。我们认为，共生体容纳器官内的特定细胞周期沿身体纵轴定向，前部为增殖区域，后部为降解区域。利用拉曼光谱显微镜，我们证明来自墨西哥湾的扭旋硬鳞虫的内共生体含有硫小泡，并认为其具有化学自养硫氧化代谢。
