Jaleta Tegegn G, Rödelsperger Christian, Abanda Babette, Eisenbarth Albert, Achukwi Mbunkah D, Renz Alfons, Streit Adrian
Department for Evolutionary Biology, Max Planck Institute for Developmental Biology, Max-Planck-Ring 9, 72076, Tübingen, Germany.
Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, 3800 Spruce Street, Philadelphia, PA, 19104, USA.
Parasitol Res. 2018 Apr;117(4):1069-1077. doi: 10.1007/s00436-018-5783-0. Epub 2018 Feb 5.
Onchocerca ochengi is a nodule-forming filarial nematode parasite of cattle. It is the closest known relative of the human parasite Onchocerca volvulus, with which it shares the black fly vector Simulium damnosum. Onchocerca sp. "Siisa" was described in black flies and in cattle and, based on limited mitochondrial sequence information, appeared to be about equally phylogenetically distant from O. ochengi and O. volvulus. Based on molecular genetic markers and apparent interbreeding, we later proposed that O. sp. "Siisa" belongs to the species O. ochengi. However, we did not demonstrate directly that the hybrids were fertile, and we were still unable to resolve the phylogenetic relationship of O. ochengi, O. sp. "Siisa," and O. volvulus, leaving some concerns with the conclusion mentioned above. Here, we present fully assembled, manually curated mitochondrial genomes of O. ochengi and O. sp. "Siisa," and we compare multiple individuals of these two taxa with respect to their whole mitochondrial and nuclear genomes. Based on the mitochondrial genomes, O. ochengi and O. sp. "Siisa" are phylogenetically much closer to each other than to O. volvulus. The differences between them are well within the range of what is expected for within-species variation. The nuclear genome comparison provided no indication of genetic separation of O. ochengi and O. sp. "Siisa." From this, in combination with the earlier literature, we conclude that O. ochengi and O. sp. "Siisa" should be considered one species.
奥氏盘尾丝虫是牛的一种形成结节的丝状线虫寄生虫。它是已知与人类寄生虫旋盘尾丝虫亲缘关系最近的物种，二者共享黑蝇传播媒介恶蚋。盘尾丝虫属“Siisa”种是在黑蝇和牛体内发现的，基于有限的线粒体序列信息，它在系统发育上与奥氏盘尾丝虫和旋盘尾丝虫的距离似乎大致相等。基于分子遗传标记和明显的杂交情况，我们后来提出盘尾丝虫属“Siisa”种属于奥氏盘尾丝虫物种。然而，我们没有直接证明杂交后代是可育的，而且我们仍然无法解决奥氏盘尾丝虫、盘尾丝虫属“Siisa”种和旋盘尾丝虫之间的系统发育关系，因此对上述结论仍存在一些疑虑。在此，我们展示了奥氏盘尾丝虫和盘尾丝虫属“Siisa”种完全组装并经过人工整理的线粒体基因组，并比较了这两个分类群多个个体的整个线粒体基因组和核基因组。基于线粒体基因组，奥氏盘尾丝虫和盘尾丝虫属“Siisa”种在系统发育上彼此之间的关系比它们与旋盘尾丝虫的关系更为密切。它们之间的差异完全在种内变异预期的范围内。核基因组比较没有显示出奥氏盘尾丝虫和盘尾丝虫属“Siisa”种存在遗传分离的迹象。据此，结合早期文献，我们得出结论，奥氏盘尾丝虫和盘尾丝虫属“Siisa”种应被视为一个物种。
