Phylogenetic analyses over the last two decades have united a few small, and previously orphan clades, the nematodermatids, acoels and xenoturbelids, into the phylum Xenacoelomorpha. Some phylogenetic analyses support a sister relationship between Xenacoelomorpha and Ambulacraria (Xenambulacraria), while others suggest that Xenacoelomorpha may be sister to the rest of the Bilateria (Nephrozoa). An understanding of the cell type complements of Xenacoelomorphs is essential to assessing these alternatives as well as to our broader understanding of bilaterian cell type evolution. Employing whole organism single-cell RNA-seq in the marine xenacoelomorph worm Xenoturbella bocki, we show that Xenambulacrarian nerve nets share regulatory features and a peptidergic identity with those found in cnidarians and protostomes and more broadly share muscle and gland cell similarities with other metazoans. Taken together, these data are consistent with broad homologies of animal gland, muscle, and neurons as well as more specific affinities between Xenoturbella and acoel gut and epidermal tissues, consistent with the monophyly of Xenacoelomorpha.

过去二十年的系统发育分析将一些小的、以前的孤儿进化枝，即线虫类、无腔动物类和异涡类动物，统一到异类动物门中。一些系统发育分析支持 Xenacoelomorpha 和 Ambulacraria (Xenambulacraria) 之间的姐妹关系，而其他分析则表明 Xenacoelomorpha 可能是其他两侧对称动物 (Nephrozoa) 的姐妹关系。了解异腔体细胞类型的补充对于评估这些替代方案以及我们对两侧对称动物细胞类型进化的更广泛理解至关重要。通过对海洋异腔蠕虫Xenoturbella bocki进行全生物体单细胞 RNA 测序，我们发现异腔蠕虫神经网络与刺胞动物和原口动物中发现的神经网络具有调节特征和肽能特性，并且与其他后生动物更广泛地具有肌肉和腺细胞相似性。总而言之，这些数据与动物腺体、肌肉和神经元的广泛同源性以及异涡虫与无腔肠道和表皮组织之间更具体的亲和力一致，与异腔虫的单系一致。