Gregg Jacob L, Powers Rachel L, Purcell Maureen K, Friedman Carolyn S, Hershberger Paul K
Marrowstone Marine Field Station, US Geological Survey, 616 Marrowstone Point Road, Nordland, Washington 98358, USA.
Dis Aquat Organ. 2016 Jul 7;120(2):125-41. doi: 10.3354/dao03017.
Despite their widespread, global impact in both wild and cultured fishes, little is known of the diversity, transmission patterns, and phylogeography of parasites generally identified as Ichthyophonus. This study constructed a phylogeny based on the structural alignment of internal transcribed spacer (ITS) rDNA sequences to compare Ichthyophonus isolates from fish hosts in the Atlantic and Pacific oceans, and several rivers and aquaculture sites in North America, Europe, and Japan. Structure of the Ichthyophonus ITS1-5.8S-ITS2 transcript exhibited several homologies with other eukaryotes, and 6 distinct clades were identified within Ichthyophonus. A single clade contained a majority (71 of 98) of parasite isolations. This ubiquitous Ichthyophonus type occurred in 13 marine and anadromous hosts and was associated with epizootics in Atlantic herring, Chinook salmon, and American shad. A second clade contained all isolates from aquaculture, despite great geographic separation of the freshwater hosts. Each of the 4 remaining clades contained isolates from single host species. This study is the first to evaluate the genetic relationships among Ichthyophonus species across a significant portion of their host and geographic range. Additionally, parasite infection prevalence is reported in 16 fish species.
尽管它们对野生和养殖鱼类具有广泛的全球影响，但对于通常被鉴定为鱼怪虫属（Ichthyophonus）的寄生虫的多样性、传播模式和系统地理学却知之甚少。本研究基于内部转录间隔区（ITS）核糖体DNA序列的结构比对构建了系统发育树，以比较来自大西洋和太平洋以及北美、欧洲和日本的几条河流及水产养殖场所的鱼类宿主中的鱼怪虫属分离株。鱼怪虫属ITS1-5.8S-ITS2转录本的结构与其他真核生物表现出若干同源性，并且在鱼怪虫属内鉴定出6个不同的进化枝。一个单一的进化枝包含了大部分（98个中的71个）寄生虫分离株。这种普遍存在的鱼怪虫属类型出现在13种海洋和溯河产卵宿主中，并与大西洋鲱鱼、奇努克鲑和美洲西鲱的 epizootics 有关。第二个进化枝包含了所有来自水产养殖的分离株，尽管淡水宿主在地理上有很大的隔离。其余4个进化枝中的每一个都包含来自单一宿主物种的分离株。本研究首次评估了鱼怪虫属物种在其宿主和地理范围的很大一部分中的遗传关系。此外，还报告了16种鱼类的寄生虫感染率。
