Centro de Investigación en Enfermedades Tropicales, University of Costa Rica, San José, Costa Rica 11501-2060.
Laboratory of Helminthology, Faculty of Microbiology, University of Costa Rica, San José, Costa Rica 11501-2060.
Acta Trop. 2024 Oct;258:107337. doi: 10.1016/j.actatropica.2024.107337. Epub 2024 Aug 5.
Angiostrongylus vasorum is a metastrongylid parasite infecting wild canids and domestic dogs. Its patchy distribution, high pathogenicity and taxonomical classification makes the evolutionary history of A. vasorum intriguing and important to study. First larval stages of A. vasorum were recovered from feces of two grey foxes, Urocyon cinereoargenteus, from Costa Rica. Sequencing and phylogenetic and haplotypic analyses of the ITS2, 18S and cytochrome oxidase subunit 1 (cox1) fragments were performed. Then p- and Nei´s genetic distance, nucleotide substitution rates and species delimitation analyses were conducted with cox1 data of the specimens collected herein and other Angiostrongylus spp. Cophylogenetic congruence and coevolutionary events of Angiostrongylus spp. and their hosts were evaluated using patristic and phenetic distances and maximum parsimony reconciliations. Specimens from Costa Rica clustered in a separate branch from European and Brazilian A. vasorum sequences in the phylogenetic and haplotype network analyses using the ITS2 and cox1 data. In addition, cox1 p-distance of the sequences derived from Costa Rica were up to 8.6 % different to the ones from Europe and Brazil, a finding mirrored in Nei´s genetic distance PCoA. Species delimitation analysis supported a separate group with the sequences from Costa Rica, suggesting that these worms may represent cryptic variants of A. vasorum, a new undescribed taxon or Angiocaulus raillieti, a synonym species of A. vasorum described in Brazil. Moreover, nucleotide substitution rates in A. vasorum were up to six times higher than in the congener Angiostrongylus cantonensis. This finding and the long time elapsed since the last common ancestor between both species may explain the larger diversity in A. vasorum. Finally, cophylogenetic congruence was observed between Angiostrongylus spp. and their hosts, with cospeciation events occurring at deeper taxonomic branching of host order. Altogether, our data suggest that the diversity of the genus Angiostrongylus is larger than expected, since additional species may be circulating in wild canids from the Americas.
血管圆线虫是一种寄生在野生犬科动物和家犬体内的后圆线虫。其分布不均、高致病性和分类学分类使得血管圆线虫的进化历史令人着迷，值得深入研究。本研究首次从哥斯达黎加的两只灰狐粪便中回收了血管圆线虫的第一期幼虫。对 ITS2、18S 和细胞色素氧化酶亚基 1（cox1）片段进行了测序和系统发育及单倍型分析。然后，利用本文收集的标本和其他血管圆线虫属的 cox1 数据进行了 p-和 Nei 的遗传距离、核苷酸替代率和物种划分分析。利用 patristic 和 phenetic 距离和最大简约性协调评估了血管圆线虫属及其宿主的共进化关系和共进化事件。利用 ITS2 和 cox1 数据进行的系统发育和单倍型网络分析表明，来自哥斯达黎加的标本与欧洲和巴西的血管圆线虫序列聚类在一个单独的分支中。此外，来自哥斯达黎加的序列的 cox1 p-距离与来自欧洲和巴西的序列差异高达 8.6%，这一发现反映在 Nei 的遗传距离 PCoA 中。物种划分分析支持来自哥斯达黎加的序列为一个单独的群体，表明这些蠕虫可能代表血管圆线虫的隐种、一个新的未描述的分类单元或在巴西被描述为血管圆线虫同义词的 Angiocaulus raillieti。此外，血管圆线虫的核苷酸替代率比近缘种 Angiostrongylus cantonensis 高 6 倍。这一发现以及自两种物种的最后一个共同祖先以来的很长时间可能解释了血管圆线虫更大的多样性。最后，观察到血管圆线虫属与宿主之间存在共进化关系，共进化事件发生在宿主目更深的分类分支上。总之，我们的数据表明，血管圆线虫属的多样性比预期的要大，因为美洲野生犬科动物中可能存在其他未被发现的物种。
