Paparini Andrea, Macgregor James, Ryan Una M, Irwin Peter J
Vector- and Water-Borne Pathogen Research Group, School of Veterinary & Life Sciences, Molecular and Biomedical Sciences, Murdoch University, Murdoch WA, 6150, Australia.
College of Veterinary Medicine, School of Veterinary and Life Sciences, Murdoch University, 90 South Street, Murdoch, Western Australia, 6150.
Protist. 2015 Dec;166(6):609-20. doi: 10.1016/j.protis.2015.10.001. Epub 2015 Oct 22.
Piroplasms, tick-transmitted Apicomplexa of the genera Theileria, Babesia and Cytauxzoon, are blood-borne parasites of clinical and veterinary importance. The order Piroplasmida shows a puzzling systematics characterized by multiple clades, soft polytomies and paraphyletic/polyphyletic genera. In the present study, screening of platypuses (Ornithorhynchus anatinus), was performed to infer the parasite molecular phylogeny. DNA was extracted from blood, ectoparasites and tick eggs and the 18S rRNA- hsp70-genes were used for the phylogenetic reconstructions. Microscopic analyses detected pleomorphic intra-erythrocytic organisms and tetrads consistent with previous descriptions of Theileria ornithorhynchi Mackerras, 1959, but observation of possible schizonts could not be confirmed. DNA sequences obtained from blood and ticks allowed resolving the systematics of the first piroplasm infecting a monotreme host. Molecularly, T. ornithorhynchi formed a novel monophyletic group, basal to most known piroplasms' clades. The ancestral position of this clade, isolated from an ancient lineage of mammalian host appears particularly fascinating. The present paper discusses the inadequacies of the current molecular systematics for the Piroplasmida and the consequences of incomplete sampling, morphology-based classification and ambiguous microscopic identifications. Likely when the current sampling bias is rectified and more sequence data is made available, the phylogenetic position of T. ornithorhynchi will be further contextualized without ambiguity.
梨形虫是由泰勒虫属、巴贝斯虫属和嗜吞噬细胞无形体属通过蜱传播的顶复门寄生虫，是具有临床和兽医重要性的血源寄生虫。梨形虫目呈现出一个令人费解的系统发育特征，其特点是有多个分支、软多歧分类和并系/多系属。在本研究中，对鸭嘴兽（Ornithorhynchus anatinus）进行了筛查，以推断寄生虫的分子系统发育。从血液、外寄生虫和蜱卵中提取DNA，并将18S rRNA - hsp70基因用于系统发育重建。显微镜分析检测到多形性红细胞内生物体和四联体型，与1959年Mackerras对鸭嘴兽泰勒虫（Theileria ornithorhynchi）的先前描述一致，但无法确认观察到的可能裂殖体。从血液和蜱中获得的DNA序列有助于解析感染单孔目宿主的第一种梨形虫的系统发育。在分子层面上，鸭嘴兽泰勒虫形成了一个新的单系群，位于大多数已知梨形虫分支的基部。这个从古老的哺乳动物宿主谱系中分离出来的分支的祖先位置显得特别引人入胜。本文讨论了当前梨形虫目分子系统发育的不足之处，以及采样不完整、基于形态学的分类和显微镜鉴定不明确所带来的后果。当当前的采样偏差得到纠正并获得更多序列数据时，鸭嘴兽泰勒虫的系统发育位置可能会在没有歧义的情况下得到进一步的背景化。
