For many years, Paramacrobiotus richtersi was reported to consist of populations with different chromosome numbers and reproductive modes. To clarify the relationships among different populations, the type locality of the species (Clare Island, Ireland) and several Italian localities were sampled. Populations were investigated with an integrated approach, using morphological (LM, CLSM, SEM), morphometric, karyological, and molecular (18S rRNA, cox1 genes) data. Paramacrobiotus richtersi was redescribed and a neotype designed from the Irish bisexual population. Animals of all populations had very similar qualitative and quantitative characters, apart from the absence of males and the presence of triploidy in some of them, whereas some differences were recorded in the egg shell. All populations examined had the same 18S haplotype, while 21 haplotypes were found in the cox1 gene. In four cases, those qualitative characters were correlated with clear molecular (cox1) differences (genetic distance 14.6–21.8%). The integrative approach, which considered the morphological differences in the eggs, the reproductive biology and the wide genetic distances among putative species, led to the description of four new species (Paramacrobiotus arduus sp. n., Paramacrobiotus celsus sp. n., Paramacrobiotus depressus sp. n., Paramacrobiotus spatialis sp. n.) and two Unconfirmed Candidate Species (UCS) within the P. richtersi complex. Paramacrobiotus fairbanksi, the only ascertained parthenogenetic, triploid species, was redescribed and showed a wide distribution (Italy, Spain, Poland, Alaska), while the amphimictic species showed limited distributions. The difference in distribution between apomictic and amphimictic populations can be explained by the difference in the dispersal potentials associated with these two types of reproduction.

中文翻译：

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Paramacrobiotus richtersi 复合体（Eutardigrada、Macrobiotidae）的物种、繁殖模式和分布具有高度多样性

多年来，据报道，副巨生物（Parmacrobiotus richtersi）由具有不同染色体数目和繁殖模式的种群组成。为了阐明不同种群之间的关系，对该物种的模式产地（爱尔兰克莱尔岛）和意大利的几个地点进行了采样。使用形态学（LM、CLSM、SEM）、形态测定、核学和分子（18S rRNA、cox1 基因）数据，采用综合方法对群体进行研究。Paramacrobiotus richtersi 被重新描述，并从爱尔兰双性恋群体中设计了一个新类型。所有种群的动物除了不存在雄性且其中一些存在三倍体之外，具有非常相似的定性和定量性状，而在蛋壳中记录了一些差异。所有检查的群体都具有相同的 18S 单倍型，而 cox1 基因中发现了 21 个单倍型。在四种情况下，这些定性特征与明显的分子 (cox1) 差异相关（遗传距离 14.6–21.8%）。综合方法考虑了卵的形态差异、生殖生物学和假定物种之间的广泛遗传距离，从而描述了四个新物种（Paramacrobiotus arduus sp. n.、Paramacrobiotus celsus sp. n.、Paramacrobiotus depressus sp. n.、Paramacrobiotus spaceis sp. n.）和 P. richtersi 复合体内的两个未经证实的候选物种（UCS）。Paramacrobiotus fairbanksi是唯一确定的单性生殖三倍体物种，被重新描述并显示出广泛的分布（意大利、西班牙、波兰、阿拉斯加），而两栖物种则显示出有限的分布。无融合生殖和两性生殖种群之间的分布差异可以通过与这两种繁殖类型相关的扩散潜力的差异来解释。