Andree K B, Székely C, Molnár K, Gresoviac S J, Hedrick R P
Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis 95616, USA.
J Parasitol. 1999 Feb;85(1):68-74.
Sequences representing approximately 1,700 base pairs of the 18S rRNA gene from 10 different species in the genus Myxobolus were found to group them into 3 clusters that showed little correlation with spore morphology and size or host specificity, criteria currently used for both higher and lower taxonomic placements in the Myxozoa. Of the phenotypic criteria examined, tissue tropism was most correlated with the rRNA groupings observed. Spores of similar size and shape (Myxobolus cerebralis vs. Myxobolus squamalis) were distantly related in some instances, whereas spores with divergent morphology and size were sometimes found to be closely related (M. cerebralis and Myxobolus insidiosus). These initial investigations into the phylogenetic relationships of putative members of the genus Myxobolus clearly indicate the potential limitations of groupings based on size and morphological properties of the spores and host species infected. We propose that 18S rRNA gene sequences, combined with information on tissue tropism, host species infected, and developmental cycles in the fish and alternate host (when and if known) be given greater consideration in taxonomic placements of myxosporeans.
已发现来自黏液孢子虫属10个不同物种的约1700个碱基对的18S rRNA基因序列将它们分为3个簇，这些簇与孢子形态、大小或宿主特异性几乎没有相关性，而这些标准目前用于黏液虫纲的高级和低级分类定位。在所检查的表型标准中，组织嗜性与观察到的rRNA分组最相关。在某些情况下，大小和形状相似的孢子（脑黏液孢子虫与鳞黏液孢子虫）亲缘关系较远，而形态和大小不同的孢子有时却亲缘关系很近（脑黏液孢子虫和阴险黏液孢子虫）。这些对黏液孢子虫属假定成员系统发育关系的初步研究清楚地表明了基于孢子大小、形态特征和受感染宿主物种进行分组的潜在局限性。我们建议，在黏液孢子虫的分类定位中，应更多地考虑18S rRNA基因序列，以及组织嗜性、受感染宿主物种和鱼类及替代宿主（如果已知）的发育周期等信息。
