Catalano Stefano, Lejeune Manigandan, van Paridon Bradley, Pagan Christopher A, Wasmuth James D, Tizzani Paolo, Duignan Pádraig J, Nadler Steven A
Department of Ecosystem and Public Health, Faculty of Veterinary Medicine, University of Calgary, 3280 Hospital Drive NW, Calgary, AB T2N 4Z6, Canada.
J Parasitol. 2015 Apr;101(2):182-92. doi: 10.1645/14-621.1. Epub 2014 Dec 30.
The hookworms Uncinaria rauschi Olsen, 1968 and Uncinaria yukonensis ( Wolfgang, 1956 ) were formally described from grizzly ( Ursus arctos horribilis) and black bears ( Ursus americanus ) of North America. We analyzed the intestinal tracts of 4 grizzly and 9 black bears from Alberta and British Columbia, Canada and isolated Uncinaria specimens with anatomical traits never previously documented. We applied morphological and molecular techniques to investigate the taxonomy and phylogeny of these Uncinaria parasites. The morphological analysis supported polymorphism at the vulvar region for females of both U. rauschi and U. yukonensis. The hypothesis of morphological plasticity for U. rauschi and U. yukonensis was confirmed by genetic analysis of the internal transcribed spacers (ITS-1 and ITS-2) of the nuclear ribosomal DNA. Two distinct genotypes were identified, differing at 5 fixed sites for ITS-1 (432 base pairs [bp]) and 7 for ITS-2 (274 bp). Morphometric data for U. rauschi revealed host-related size differences: adult U. rauschi were significantly larger in black bears than in grizzly bears. Interpretation of these results, considering the historical biogeography of North American bears, suggests a relatively recent host-switching event of U. rauschi from black bears to grizzly bears which likely occurred after the end of the Wisconsin glaciation. Phylogenetic maximum parsimony (MP) and maximum likelihood (ML) analyses of the concatenated ITS-1 and ITS-2 datasets strongly supported monophyly of U. rauschi and U. yukonensis and their close relationship with Uncinaria stenocephala (Railliet, 1884), the latter a parasite primarily of canids and felids. Relationships among species within this group, although resolved by ML, were unsupported by MP and bootstrap resampling. The clade of U. rauschi, U. yukonensis, and U. stenocephala was recovered as sister to the clade represented by Uncinaria spp. from otariid pinnipeds. These results support the absence of strict host-parasite co-phylogeny for Uncinaria spp. and their carnivore hosts. Phylogenetic relationships among Uncinaria spp. provided a framework to develop the hypothesis of similar transmission patterns for the closely related U. rauschi, U. yukonensis, and U. stenocephala.
钩虫鲁氏钩口线虫（Uncinaria rauschi Olsen，1968）和育空钩口线虫（Uncinaria yukonensis (Wolfgang，1956)）最初是从北美洲的灰熊（棕熊指名亚种Ursus arctos horribilis）和黑熊（美洲黑熊Ursus americanus）中描述的。我们分析了来自加拿大阿尔伯塔省和不列颠哥伦比亚省的4只灰熊和9只黑熊的肠道，并分离出具有此前从未记录过的解剖学特征的钩口线虫标本。我们应用形态学和分子技术来研究这些钩口线虫寄生虫的分类学和系统发育。形态学分析支持鲁氏钩口线虫和育空钩口线虫雌性在阴门区域存在多态性。通过对核糖体DNA的内部转录间隔区（ITS-1和ITS-2）进行遗传分析，证实了鲁氏钩口线虫和育空钩口线虫形态可塑性的假设。鉴定出两个不同的基因型，ITS-1（432个碱基对[bp]）有5个固定位点不同，ITS-2（274 bp）有7个固定位点不同。鲁氏钩口线虫的形态测量数据显示出与宿主相关的大小差异：黑熊体内的成年鲁氏钩口线虫比灰熊体内的明显更大。考虑到北美熊的历史生物地理学，对这些结果的解释表明，鲁氏钩口线虫相对较新地从黑熊宿主转换到灰熊宿主，这一事件可能发生在威斯康星冰川期末期之后。对串联的ITS-1和ITS-2数据集进行系统发育最大简约法（MP）和最大似然法（ML）分析，有力地支持了鲁氏钩口线虫和育空钩口线虫的单系性以及它们与窄头钩口线虫（Uncinaria stenocephala (Railliet，1884)）的密切关系，后者主要是犬科动物和猫科动物的寄生虫。尽管ML分析解析了该类群中物种间的关系，但MP分析和自展重抽样未支持这些关系。鲁氏钩口线虫、育空钩口线虫和窄头钩口线虫的分支被发现是海狗科鳍足类动物的钩口线虫属分支的姐妹分支。这些结果支持钩口线虫属及其食肉动物宿主不存在严格的宿主 - 寄生虫共系统发育关系。钩口线虫属物种间的系统发育关系为提出鲁氏钩口线虫、育空钩口线虫和窄头钩口线虫这三种亲缘关系密切的物种具有相似传播模式的假设提供了框架。
