Mature euspermatozoan ultrastructure is described for seven species of the rissooidean family Baicaliidae (endemic to Lake Baikal, Russia)-Liobaicalia stiedae, Teratobaikalia ciliata, T. macrostoma, Baicalia carinata, Pseudobaikalia pulla, Maackia bythiniopsis, M. variesculpta, and M. herderiana. For comparison with these species and previously investigated Rissooidea, two species of the Lake Baikal endemic genus Benedictia (B. cf. fragilis and B. baicalensis; Hydrobiidae: Benedictiinae of some authors, Benedictiidae of other authors) in addition to Lithoglyphus naticoides (Hydrobiidae: Lithoglyphinae) and Bythinella austriaca (Hydrobiidae: Bythinellinae) were also investigated. Paraspermatozoa were not observed in any of the species examined, supporting the view that these cells are probably absent in the Rissooidea. In general, the euspermatozoa of all species examined resemble those of many other caenogastropods (basally invaginated acrosomal vesicle, mid-piece with 7-13 helical mitochondria, an annulus, glycogen piece with nine peri-axonemal tracts of granules). However, the presence of a completely flattened acrosomal vesicle and a specialized peri-axonemal membranous sheath (a scroll-like arrangement of 4-6 double membranes) at the termination of the mid-piece, clearly indicates a close relationship between the Baicaliidae and other rissooidean families possessing these features (Bithyniidae, Hydrobiidae, Pyrgulidae, and Stenothyridae). Euspermatozoa of Benedictia, Lithoglyphus, Bythinella, and Pyrgula all have a solid nucleus, which exhibits a short, posterior invagination (housing the centriolar complex and proximal portion of the axoneme). Among the Rissooidea, this form of nucleus is known to occur in the Bithyniidae, Hydrobiidae, Truncatellidae, Pyrgulidae, Iravadiidae, Pomatiopsidae, and Stenothyridae. In contrast, the euspermatozoa of the Baicaliidae all have a long, tubular nucleus, housing not only the centriolar derivative, but also a substantial portion of the axoneme. Among the Rissooidea, a tubular nuclear morphology has previously been seen in the Rissoidae, which could support the view, based on anatomical grounds, that the Baicaliidae may have arisen from a different ancestral source than the Hydrobiidae. However, the two styles of nuclear morphology (short, solid versus long, tubular) occur widely within the Caenogastropoda, and sometimes both within a single family, thereby reducing the phylogenetic importance of nuclear differences within the Rissooidea. More significantly, the occurrence of the highly unusual membranous sheath within the mid-piece region in the Baicaliidae appears to tie this family firmly to the Bithyniidae + Hydrobiidae + Stenothyridae + Pyrgulidae assemblage. Eusperm features of Benedictia spp. strongly resemble those of hydrobiids and bithyniids, and neither support recognition of a distinct family Benedictiidae (at best this is a subfamily of Hydrobiidae) nor any close connection with the hydrobiid subfamily Lithoglyphinae.

中文翻译：

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贝加尔特有前肢腹足动物精子超微结构比较

成熟的真子动物超微结构描述了七种 rissooidean 家族 Baicaliidae（俄罗斯贝加尔湖特有）- Liobaicalia stiedae、Teratobaikalia ciliata、T. macrostoma、Baicalia carinata、Pseudobaikalia pulla、Maackia bythiniopsis、M. variederianescence 为了与这些物种进行比较和之前研究过的 Rissooidea，贝加尔湖特有的 Benedictia 属的两个物种（B. cf. fragilis 和 B. baicalensis；Hydrobiidae：一些作者的 Benedictiinae，其他作者的 Benedictiidae）以及 Lithoglyphus naticoides（Hydrobiidae： Lithoglyphinae) 和 Bythinella austriaca (Hydrobiidae: Bythinellinae) 也进行了研究。在任何被检查的物种中都没有观察到副精子，这支持了这些细胞可能在 Rissooidea 中不存在的观点。一般来说，所检查的所有物种的真精子与许多其他盲腹足动物相似（基部内陷的顶体囊泡，具有 7-13 个螺旋线粒体的中段，一个环，具有 9 个轴突周围颗粒束的糖原片）。然而，在中段末端出现一个完全扁平的顶体囊泡和一个特化的轴突周围膜鞘（4-6 个双层膜的卷轴状排列），清楚地表明了黄蜂科与其他生物之间的密切关系。具有这些特征的 rissooidean 科（Bithyniidae、Hydrobiidae、Pyrgulidae 和 Stenothyridae）。Benedictia、Lithoglyphus、Bythinella 和 Pyrgula 的 Euspermatozoa 都有一个实心核，其表现出短的后部内陷（容纳中心粒复合体和轴丝的近端部分）。在 Rissooidea 中，已知这种形式的细胞核出现在 Bithyniidae、Hydrobiidae、Truncatellidae、Pyrgulidae、Iravadiidae、Pomatiopsidae 和 Stenothyridae 中。相比之下，Bacaliidae 的真子动物都有一个长而管状的核，不仅容纳中心粒衍生物，还容纳大部分轴丝。在 Rissooidea 中，之前曾在 Rissoidae 中观察到管状核形态，这可以支持基于解剖学基础的观点，即 Baicaliidae 可能起源于与 Hydrobiidae 不同的祖先来源。然而，两种类型的核形态（短、实心与长、管状）广泛存在于 Caenogastropoda 中，有时两者都在一个科中，从而降低了 Rissooidea 内核差异的系统发育重要性。更重要的是，在 Baicaliidae 中段区域出现非常不寻常的膜质鞘似乎将这个家族与 Bithyniidae + Hydrobiidae + Stenothyridae + Pyrguliidae 组合牢固地联系在一起。Benedictia spp 的 Eusperm 特征。与hydrobiids和bithyniids非常相似，既不支持识别不同的Benedictiidae家族（充其量这是Hydrobiidae的一个亚科），也不支持与hydrobiid亚科Lithoglyphinae的任何密切联系。