Myxomycetes constitute one of the major lineages within the supergroup Amoebozoa. At the end of their life cycles, most myxomycetes produce spore-bearing fruiting bodies, in which additional structures develop, like the capillitium, a system of sterile filaments intermingled with the spores. The capillitium is a relevant structure in the taxonomy of the order Trichiales, the target group in this study. However, the introduction of molecular phylogenies in Myxomycetes systematics is challenging our comprehension of this structure. We studied the capillitium of 25 species representing nine Trichiales genera, with both scanning and transmission electron microscopy. In this order, the capillitium showed higher diversity than so far recognized. Thus, we distinguished and described five capillitium types and two subtypes based on the presence or absence of a lumen and the wall ultrastructure. These types followed the evolutionary history reported in recent phylogenies, although not all of them defined monophyletic groups. Besides, the spiral ornamentation, which most taxonomists considered to have appeared once, occurred in three different capillitium types. The ultrastructural approaches in Myxomycetes systematics enable the reconsideration of their morphological features in the new phylogenetic scenario.

粘菌纲是变形虫超群中的主要谱系之一。在它们的生命周期结束时，大多数粘菌产生带有孢子的子实体，其中会形成额外的结构，如毛状体，这是一种与孢子混合的无菌细丝系统。毛状体是本研究的目标群体 Trichiales 分类学中的一个相关结构。然而，黏菌系统学中分子系统发育的引入正在挑战我们对这种结构的理解。我们使用扫描和透射电子显微镜研究了代表 9 个 Trichiales 属的 25 个物种的毛状体。按照这个顺序，毛状体表现出比迄今为止公认的更高的多样性。因此，我们根据管腔和壁超微结构的存在与否区分并描述了五种毛细血管类型和两种亚型。这些类型遵循最近系统发育报告的进化历史，尽管并非所有类型都定义了单系群。此外，大多数分类学家认为曾经出现过的螺旋纹出现在三种不同的毛状体中。粘菌纲系统学中的超微结构方法能够在新的系统发育情景中重新考虑它们的形态特征。发生在三种不同的毛状体类型中。粘菌纲系统学中的超微结构方法能够在新的系统发育情景中重新考虑它们的形态特征。发生在三种不同的毛细血管中。粘菌纲系统学中的超微结构方法能够在新的系统发育情景中重新考虑它们的形态特征。