Valigurová Andrea, Diakin Andrei, Seifertová Mária, Vaškovicová Naděžda, Kováčiková Magdaléna, Paskerova Gita G
Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic.
Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic.
J Invertebr Pathol. 2023 Nov;201:107997. doi: 10.1016/j.jip.2023.107997. Epub 2023 Sep 27.
Urosporid eugregarines (Apicomplexa: Urosporidae) are unicellular eukaryotic parasites inhabiting the coelom or the intestine of marine invertebrates such as annelids, molluscs, nemerteans, and echinoderms. Despite the availability of published morphological and phylogenetical analyses of coelomic gregarines, their long-term survival in the host body cavity and dispersal routes into the marine environment remain unclear. Here, we focus on Urospora gametocysts and oocysts with sporozoites, which were found viable inside the so-called brown bodies floating in the body cavity of the polychaete Travisia forbesii. Brown bodies form as a result of host defence where coelomocytes encapsulate dead host cells and foreign objects including potential pathogens. We hypothesise the long-term persistence of Urospora eugregarines in brown bodies through evasion of the host immunity and outline possible pathways for their egress into the marine environment, applicable as dispersal routes for other parasites as well. Unique features revealed by detailed ultrastructural analysis of detected eugregarine stages include asynchronous sporogony, a massive sporozoite secretion apparatus, as well as the presence of free (possibly autoinfective) sporozoites within the gametocyst. The assignment to the genus Urospora and the complete identity with U. ovalis and U. travisiae were confirmed by analysing 18S rDNA sequences obtained from isolated gametocysts. The 18S rDNA phylogeny confirmed the affiliation of Urosporidae to Lecudinoidea and the grouping of all Urospora sequences with Difficilina from nemerteans and environmental sequences from the Artic region. We also enriched the Apicomplexa set by partial 28S rDNA sequences of two Urospora species enabling more complex phylogenetic analyses prospectively.
尿孢子虫目真簇虫（顶复门：尿孢子虫科）是单细胞真核寄生虫，寄生于海洋无脊椎动物的体腔或肠道，如环节动物、软体动物、纽形动物和棘皮动物。尽管已有关于体腔真簇虫的形态学和系统发育分析报道，但它们在宿主体腔内的长期存活情况以及进入海洋环境的传播途径仍不清楚。在此，我们聚焦于含有子孢子的尿孢子配子囊和卵囊，它们在多毛纲动物福布斯特拉维西亚虫体腔内漂浮的所谓褐色体中被发现具有活力。褐色体是宿主防御反应的产物，其中体腔细胞包裹死亡的宿主细胞和包括潜在病原体在内的异物。我们推测尿孢子虫目真簇虫通过逃避宿主免疫在褐色体中长期存活，并概述了它们进入海洋环境的可能途径，这些途径也适用于其他寄生虫的传播。对检测到的真簇虫阶段进行详细超微结构分析所揭示的独特特征包括异步孢子生殖、大量的子孢子分泌装置，以及配子囊内存在游离（可能具有自身感染性）的子孢子。通过分析从分离的配子囊中获得的18S rDNA序列，确认了其属于尿孢子属，并与卵形尿孢子和特拉维西亚尿孢子完全一致。18S rDNA系统发育分析证实了尿孢子虫科隶属于勒库迪虫总科，以及所有尿孢子序列与来自纽形动物的迪菲利纳属和北极地区环境序列的聚类。我们还通过两个尿孢子物种的部分28S rDNA序列丰富了顶复门数据集，从而有望进行更复杂的系统发育分析。
