Karagodina N P, Vishnyakov A E, Kotenko O N, Maltseva A L, Ostrovsky A N
1Department of Invertebrate Zoology, Faculty of Biology, Saint Petersburg State University, Universitetskaja nab. 7/9, 199034 Saint Petersburg, Russia.
2Department of Palaeontology, Faculty of Earth Sciences, Geography and Astronomy, Geozentrum, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria.
Symbiosis. 2018;75(2):155-164. doi: 10.1007/s13199-017-0516-1. Epub 2017 Nov 3.
Autozooids of the cheilostome bryozoan contain rod-like bacteria in the funicular bodies - the complex swellings of the funicular strands. Each funicular body contains symbionts in the central cavity surrounded by a large, synthetically active internal "sheath-cell" (bacteriocyte) and a group of the flat external cells. The tightly interdigitating lobes of these cells form a capsule well-isolated from the body cavity. Slit-like spaces between bacteria are filled with electron-dense matrix and cytoplasmic processes of various sizes and shapes (often branching) produced by the "sheath-cell". The cell ultrastructure and complex construction of the funicular bodies as well as multiplication of the bacteria in them suggest metabolic exchange between host and symbiont, involving the nourishment of bacteria. We suggest that the bacteria, in turn, influence the bryozoan mesothelial tissue to form the funicular bodies as capsules for bacterial incubation. We present ultrastructural data, discuss possible variants in the development of the funicular bodies in Bryozoa, and propose the possible role of bacteria in the life of their bryozoan host.
唇口目苔藓虫的自个虫在索状体（索状丝的复杂肿胀部分）中含有杆状细菌。每个索状体在中央腔中含有共生体，中央腔被一个大型的、具有合成活性的内部“鞘细胞”（细菌细胞）和一组扁平的外部细胞包围。这些细胞紧密交错的叶形成了一个与体腔完全隔离的囊。细菌之间的狭缝状空间充满了电子致密基质以及由“鞘细胞”产生的各种大小和形状（通常为分支状）的细胞质突起。细菌的细胞超微结构和索状体的复杂构造以及其中细菌的增殖表明宿主与共生体之间存在代谢交换，涉及细菌的营养供应。我们认为，反过来，细菌会影响苔藓虫间皮组织形成索状体作为细菌孵化的囊。我们展示了超微结构数据，讨论了苔藓虫纲中索状体发育的可能变体，并提出了细菌在其苔藓虫宿主生命中的可能作用。
