Phylactolaemate bryozoans are the sister-group to all remaining bryozoan taxa. Consequently, their study is essential to reveal and analyze ancestral traits of Phylactolaemata and Bryozoa in general. They are the only bryozoans to possess an epistome which traditionally has been regarded as shared with phoronids and brachiopods. Contrary to older observations, an epistome was recently reported to be missing in the early branching phylactolaemate Lophopus crystallinus. In this study, the ontogeny of the lophophoral base and also its three-dimensional structure in adult specimens was reinvestigated to assess whether an epistome is never formed during ontogeny and absent in adult specimens. The results show that organogenesis during the budding process in this species is similar to other, previously investigated, species. The epistome anlage in L. crystallinus forms in early buds from the outer budding layer which penetrates the two shanks of the u-shaped gut. This ingression of the epithelium further proceeds distally and starts to wrap over the forming ganglion. The adult epistome is a rather short, but present bulge above the cerebral ganglion with prominent muscle bundles traversing its cavity. Distally it is arched by the forked canal that in L. crystallinus has a particularly thick and prominent epithelium in the three median tentacles. This study shows that neither during ontogeny nor in the adult stage an epistome is absent. The epistome is less pronounced than in other phylactolaemates, but otherwise similar in its general structure. Consequently, an epistome can be assumed to be present in the ground pattern of Phylactolaemata.

中文翻译：

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Lophopus crystallinus lophophore 的形态学和个体发育支持了 phylactolaemate 苔藓虫的祖先特征

Phylactolaemate 苔藓动物是所有剩余苔藓动物分类群的姐妹群。因此，他们的研究对于揭示和分析一般的藻类和苔藓虫的祖先特征至关重要。它们是唯一拥有一个传统上被认为与phoronids 和brachiopods 共享的树状体的苔藓动物。与较早的观察相反，最近有报道称，在早期分枝的 phylactolaemate Lophopus crystallinus 中缺少一个认识体。在这项研究中，重新研究了成虫基部的个体发育及其三维结构，以评估在个体发育过程中是否从未形成和在成虫标本中不存在的假体。结果表明，该物种在萌芽过程中的器官发生与之前研究过的其他物种相似。L 中的认识论语。晶状体从外芽层的早期芽中形成，穿透 U 形肠的两个小腿。上皮的这种侵入进一步向远端进行，并开始包裹形成的神经节。成人的上肢是一个相当短的，但在大脑神经节上方的凸起，突出的肌肉束穿过其腔。在远端，它由分叉的运河拱起，在 L.crystallinus 的三个正中触手中有一个特别厚和突出的上皮。这项研究表明，无论是在个体发育过程中还是在成年阶段，都不存在认识体。Epistome 不如其他叶门藻那么明显，但其一般结构在其他方面相似。因此，可以假设在 Phylactolaemata 的基本模式中存在一个认识体。