Bryozoa is a large phylum of colonial aquatic suspension feeders. The boring ctenostome Hypophorella expansa is unique and inhabits parchment-like polychaete tubes. Morphological studies date back to the nineteenth century, but distinct adaptations to this specific habitat have not been properly analysed, which prompted us to reexamine the morphology of this recently encountered species. The colony of H. expansa is composed of elongated stolonal kenozooids with a distal capsule-like expansion. A median transversal muscle is present in the latter, and one autozooid is laterally attached to the capsule. Unique stolonal wrinkles are embedded in the thin parts of the stolons. Single autozooids are attached in an alternating right–left succession on subsequent stolons. Polypide morphology including digestive tract, muscular system and most parts of the nervous system are similar to other ctenostomes. The most obvious apomorphic features of Hypophorella are space balloons and the gnawing apparatus. The former are two fronto-lateral spherical structures on autozooids, which provide space inside the tube. The latter perforates layers of the polychaete tube wall and consists of two rows of cuticular teeth that, together with the entire vestibular wall, are introvertable during the protrusion-retraction process. The apertural muscles are in association with this gnawing apparatus heavily modified and show bilateral symmetry. Adaptations to the unique lifestyle of this species are thus evident in stolonal wrinkles, autozooidal space balloons and the gnawing apparatus. The growth pattern of the colony of H. expansa may aid in rapid colonization of the polychaete tube layers.

中文翻译：

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管中的生活：栉口动物苔藓虫 Hypophorella expansa 的形态

苔藓虫是一大群群落水生悬浮饲养者。无聊的栉口动物 Hypophorella expansa 是独特的，栖息在羊皮纸状的多毛类管中。形态学研究可以追溯到十九世纪，但对这种特定栖息地的独特适应尚未得到适当的分析，这促使我们重新审视这个最近遇到的物种的形态。H. expansa 的菌落由细长的匍匐茎孔虫组成，远端有胶囊状扩张。后者存在正中横肌，并且一个自体动物横向附着在胶囊上。匍匐茎细部嵌有独特的匍匐茎皱纹。单个自生动物以左右交替的顺序附着在随后的匍匐茎上。息肉形态包括消化道、肌肉系统和神经系统的大部分部分与其他栉口动物相似。Hypophorella 最明显的非对称特征是太空气球和啃咬器。前者是自体动物上的两个额侧球形结构，在管内提供空间。后者穿过多毛类管壁的层，并由两排角质齿组成，这些齿与整个前庭壁一起在突出-缩回过程中是内倾的。孔肌与这种经过严重改造的啃咬装置相关联，并显示出双边对称性。因此，该物种对独特生活方式的适应在匍匐皱纹、自体动物太空气球和啃咬器具中表现得很明显。H. expansa 菌落的生长模式可能有助于多毛类管层的快速定殖。