中文摘要：

对寄生于鲴亚科鱼类肠道中的多泡肠袋虫的超微结构进行了研究，描述了其体表皮层、胞口、核与胞器及腹中凹板各部分的精细构造。结果显示其体表及口区皮层均由表膜和表膜下纤维系统两部分组成：“V”形胞口密被纤毛、对称排布，其咽微丝较体纤毛处更为发达。大核内具多个核仁，异染色质散布核质内；小核内染色质则呈均匀致密分布。另在腹中凹板内质中发现大量支链淀粉粒，并由不连续的微管束沿凹陷边缘将此区域包围起来。同时，对皮层组分和腹中凹板进行了相近物种间的比较分析并对其功能进行了讨论。

英文摘要：

Balantidium polyvacuolum Li, 1963, an obligatory intestinal symbiont of Xenocyprinae fish, mainly inhabits in the luminal contents of the middle and hindgut. Though the description and some revisions are given at both light and scanning electronic microscopic levels, the morphological data are still incomplete since fine structural data with taxo nomic values are still unavailable. This study examined the ultrastructural anatomy of this Chinese balantidium that inhabits in the intestines ofXenocypris davidi collected from the Jialing River in Sichuan province during fish parasite surveys in August 2011. All fish samples were dissected, and intestines were cut to collect the luminal contents into petridishes for further examination with the aid of a dissecting microscope. The luminal contents of the hindgut con- taining numerous B. polyvacuolum were selected and fixed directly in 2.5% glutaraldehyde in 0.2 M phosphate buffered saline （PBS, PH 7.4） for 2h at 4℃, then postfixed in 1% （v/v） osmium tetroxide in PBS for 2h at 4℃, this step was fol lowed by a series of dehydration in acetone and embedded in Araldite. Ultrathin sections were cut on a Leica Ultracut R ultramicrotome, stained with uranyl acetate and lead citrate before being observed in a Philips Tecnai G2 20 Transmis sion Electron Microscope （Netherlands）. Its somatic cortex, vestibulum, nuclei, cytoplasmic organelles and the cen troventral concave platelet were well described here. Our results indicated that both somatic cortex and vestibulum were composed of pellicle （the outermost cell membranes, pellicular alveoli and the layer of microtubules） and infraciliature （kinetosomes and associated fibrils such as kinetodesmal fibril, postciliary microtubules, transverse microtubules and nematodesmata）. However, the nematodesmata of vestibular kinetids were much longer than those of somatic kinetids and usually extended deeply into the endoplasm. As for the nuclei, the macronucleus was club-shaped with several nu- cleoli and heterochro