背景:鱼翅目科(螺旋藻:鱼翅目)的线虫通常寄生在所有主要脊椎动物群体的消化道中。然而,许多叶翅目物种没有被充分描述,特别是关于头端的详细形态。目前,鱼翅目物种的遗传数据库仍然非常有限,这严重阻碍了基于分子的物种鉴定。此外,鱼翅目科中某些属的系统状态和亚科的进化关系仍在争论中。
方法:根据中国新收集的猪badgeArctonyxcollarisCuvier(食肉动物:Mustelidae)的标本,使用光学和扫描电子显微镜收集了西伯利亚鱼翅目的新形态数据。六种不同的遗传标记,包括核小核糖体DNA(18S),大核糖体DNA(28S)和内部转录间隔区(ITS),线粒体细胞色素c氧化酶亚基1(cox1)和亚基2(cox2),据我们所知,本文首次对西氏疟原虫12S小亚基核糖体RNA基因进行了测序和分析。此外,构建鱼翅目的基本分子系统发育框架,使用最大似然(ML)和贝叶斯推断(BI)方法,基于cox1和18Scox1基因进行系统发育分析。
结果:扫描电子显微镜(SEM)观察显示了头部结构的详细信息,Deirids,排泄孔,尾乳头,外阴,这是我们第一次了解到的。对获得的P.sibirica序列的成对比较没有发现关于18S的种内差异,28S,COx1和12S遗传标记在ITS(0.16%)和COx2(2.39%)区域的分歧水平较低。最大似然性和贝叶斯推断分析表明,Physalopteridae的代表形成了两个主要的进化枝(Physalopterinae+Thubunaeinae寄生在陆生脊椎动物中,Proleptinae仅发生在海洋或淡水鱼中)。在鱼翅目的代表中发现了Turgidaturgida。黄翅目与P.rara聚集在一起。鱼柳。(Thubunaeinae)与短缩子宫形成了姐妹关系。
结论:重新描述了翼翅目,这是猪badgeA.collaris报告的第四种线虫寄生虫,和A.collaris代表了新的宿主。系统发育结果挑战了Thubunaeinae亚科和Turgida属的有效性,并支持将Physalopteridae科分为两个亚科,Physalopterinae和Proleptinae。然而,我们不会立即对鱼翅目进行任何系统的改变,因为需要进行更严格的研究,以更广泛的代表Physalopteridae。这些发现有助于更准确地从形态上鉴定sibirica,并为Physalopteridae的系统学提供新的见解。
BACKGROUND: Nematodes of the family Physalopteridae (Spirurida: Physalopteroidea) commonly parasitize the alimentary canal of all major vertebrate groups. However, many physalopterid species are not adequately described, especially regarding the detailed morphology of the cephalic end. The current genetic database for Physaloptera species is still very limited, which seriously hampers molecular-based species identification. Additionally, the systematic status of some genera and the evolutionary relationships of the subfamilies in the Physalopteridae remain under debate.
METHODS: New morphological data for Physaloptera sibirica was gathered using light and scanning electron microscopy based on newly collected specimens from the hog badger Arctonyx collaris Cuvier (Carnivora: Mustelidae) in China. Six different genetic markers, including nuclear small ribosomal DNA (18S), large ribosomal DNA (28S) and internal transcribed spacer (ITS), mitochondrial cytochrome c oxidase subunit 1 (cox1) and subunit 2 (cox2), and the 12S small subunit ribosomal RNA gene of P. sibirica were sequenced and analyzed for the first time to our knowledge. Additionally, to construct a basic molecular phylogenetic framework for the Physalopteridae, phylogenetic analyses were performed based on the cox1 and 18S + cox1 genes using maximum likelihood (ML) and Bayesian inference (BI) methods.
RESULTS: Scanning electron microscopy (SEM) observation displayed the details of the cephalic structures, deirids, excretory pore, caudal papillae, vulva, phasmids and egg of P. sibirica for the first time to our knowledge. Pairwise comparison of the sequences obtained for P. sibirica did not reveal intraspecific divergence regarding the 18S, 28S, cox1 and 12S genetic markers and a low level of divergence in the ITS (0.16%) and cox2 (2.39%) regions. Maximum likelihood and Bayesian inference analyses showed that the representatives of Physalopteridae formed two major clades (species of Physalopterinae + Thubunaeinae parasitic in terrestrial vertebrates and Proleptinae only occurring in marine or freshwater fishes). Turgida turgida was found nested among representatives of Physaloptera. Physaloptera sibirica clustered together with P. rara. Physalopteroides sp. (Thubunaeinae) formed a sister relationship to the physalopterine Abbreviata caucasica.
CONCLUSIONS: Physaloptera sibirica was redescribed, which is the fourth nematode parasite reported from the hog badger A. collaris, and A. collaris represents a new host for P. sibirica. The phylogenetic results challenged the validity of the subfamily Thubunaeinae and of the genus Turgida and supported dividing the family Physalopteridae into two subfamilies, Physalopterinae and Proleptinae. However, we do not make any immediate systematic changes in the Physalopteridae, because a more rigorous study with broader representation of the Physalopteridae is required. These present findings contribute to morphologically identifying P. sibirica more accurately and provide new insights into the systematics of the Physalopteridae.