Gómez Fernando, López-García Purificación, Nowaczyk Antoine, Moreira David
Observatoire Océanologique de Banyuls sur Mer, Université Pierre et Marie Curie, CNRS-INSU UMR 7621, BP 44, 66651 Banyuls sur Mer, France.
Syst Parasitol. 2009 Sep;74(1):65-74. doi: 10.1007/s11230-009-9199-1. Epub 2009 Jul 25.
The Ellobiopsidae are enigmatic parasites of crustaceans that have been grouped together exclusively on the basis of morphological similarities. Ultrastructural studies have revealed their affiliation within the alveolates, which was confirmed by the phylogenetic analysis of the ribosomal RNA gene (SSU rDNA) sequences of two species of Thalassomyces Niezabitowski, 1913. However, their precise systematic position within this group remains unresolved, since they could not be definitively allied with any particular alveolate group. To better determine the systematic position of ellobiopsids by molecular phylogeny, we sequenced the SSU rDNA from the type-species of the Ellobiopsidae, Ellobiopsis chattoni Caullery, 1910. We found E. chattoni infecting various copepod hosts, Acartia clausi Giesbrecht, Centropages typicus Kröyer and Clausocalanus sp., in the Bay of Marseille, NW Mediterranean Sea, which allowed us to study several stages of the parasite development. A single unicellular multinucleate specimen provided two different sequences of the SSU rDNA gene, indicating the existence of polymorphism at this locus within single individuals. Ellobiopsis Caullery, 1910 and Thalassomyces formed a very divergent and well-supported clade in phylogenetic analyses. This clade appears to be more closely related to the dinoflagellates (including the Syndiniales/Marine Alveolate Group II and the Dinokaryota) and Marine Alveolate Group I than to the other alveolates (Ciliophora, Perkinsozoa and Apicomplexa).
艾氏虫科是一类寄生于甲壳类动物的神秘寄生虫，它们仅根据形态相似性被归为一类。超微结构研究揭示了它们属于顶复门，这一点通过对1913年尼扎比托夫斯基描述的两种海生艾氏虫核糖体RNA基因（小亚基核糖体DNA，SSU rDNA）序列的系统发育分析得到了证实。然而，它们在这一门类中的精确系统位置仍未确定，因为它们无法明确地与任何特定的顶复门类群联系起来。为了通过分子系统发育更好地确定艾氏虫科的系统位置，我们对艾氏虫科的模式种——1910年考勒里描述的查氏艾氏虫的SSU rDNA进行了测序。我们发现查氏艾氏虫感染了地中海西北部马赛湾的各种桡足类宿主，包括克氏纺锤水蚤、典型真刺水蚤和克劳氏哲水蚤属，这使我们能够研究寄生虫发育的几个阶段。一个单细胞多核标本提供了SSU rDNA基因的两种不同序列，表明单个个体内该位点存在多态性。在系统发育分析中，1910年考勒里描述的艾氏虫属和海生艾氏虫属形成了一个差异很大且得到充分支持的分支。这个分支似乎与甲藻（包括聚缩虫目/海洋顶复门第二组和双核甲藻）以及海洋顶复门第一组的关系比与其他顶复门（纤毛虫纲、 Perkins 虫纲和顶复虫纲）更为密切。
