Molecular study for symbiosis of the Polycystine radiolarians

利用18S rDNA(小亚单位rDNA)基因序列分析方法，对独生型多囊线虫的系统发育进行了研究。结果表明，多囊线虫至少可分为两个不同的谱系：(1)群体和无骨架多囊线虫，包括粘虫科、海绵虫和海绵；(2)有壳的多囊线虫，包括海螺科。因此，“多囊线虫”清楚地显示了海克尔放射虫中的一种特殊情况。此外，NJ、MP和ML分析中相对较高的自举值支持包括棘区和孤立贝壳的“Polycystina”分支的单系化，尽管SiO_2和SrSO_4的化学成分不同，但这一谱系的特征是具有矿化的辐射骨架。到目前为止，虽然棘区和单壳多囊线虫还没有被归类为一个组，但如果根据这两个支系的单系性建立一个新的放射虫分类群，它可能会声称找到其他可能在这些生物中潜伏的分类标准。这些结果表明，目前使用的放射虫分类系统可能需要认真修订。

The phylogeny of the solitary polycystinean Radiolaria, which includes Dictyocoryne profunda Ehrenberg, D. truncatum (Ehrenberg), and Spongaster tetras Ehrenberg, with skeletons of opaline silica, was examined using 18S r DNA (small-subunit rDNA) gene sequence analysis.The 18S rDNA molecular phylogeny among Radiolaria suggested that the Polycystinea was divided into at least two distinct lineages consisting of the following taxa :(1)the colonial and skeletonless Polycystinea including the Collospaeridae, Sphaerozoidae, and Thalassicollidae ; and (2) the shell-bearing solitary Polycystinea including the Spongodiscidae. The "Polycystinea" thus clearly shows a paraphyly among Haeckel's Radiolaria. Moreover, the monophyly of the clade including the Acantharea and the solitary shell-bearing "Polycystinea" was supported by relatively high bootstrap values in the NJ, MP, and ML analyzes.This lineage is characterized by having mineralized radiate skeletons though there is a difference in the chemical components between SiO2 and SrSO4. Until now, although the Acantharea and the solitary shell-bearing "Polycystinea" have not been categorized into as one group, if a new taxonomic group among Radiolaria will be established based on the monophyly of the both clades, it may claim to find out other taxonomic criteria which could be latent in these organisms. The results thus suggested that the currently used taxonomic system in Radiolaria may need serious revision.