Dinoflagellate, euglenid, or cercomonad?: The ultrastructure and molecular phylogenetic position of Protaspis grandis n. Sp.
Dinoflagellate, euglenid, or cercomonad?: The ultrastructure and molecular phylogenetic position of Protaspis grandis n. Sp.
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DOI：
10.1111/j.1550-7408.2006.00110.x
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发表时间：
2006-09-01
影响因子：
2.2
通讯作者：
Leander, Brian S.
中科院分区：
文献类型：
--
作者：
Hoppenrath, Mona;Leander, Brian S.
Protaspis 是海洋吞噬双鞭毛虫的一个神秘属，已初步归类为几个不同的真核生物类群，包括甲藻、眼虫和尾毛虫。这种不确定性促使我们研究 Protaspis grandis n 的系统发育位置。 sp。具有超微结构和小亚基 (SSU) rDNA 序列数据。我们的结果表明，细胞背腹扁平，形状像长椭圆形，侧面平行，长32.5-55.0μm，宽20.0-35.0μm。此外，两个异动力鞭毛通过位于近顶端的漏斗出现，每个鞭毛都位于凹陷内，并由独特的突起分开。细胞周围有复杂的多层壁。与甲藻和眼虫一样，细胞核在整个细胞周期中含有永久浓缩的染色体和大核仁。含有大量具有管状嵴的线粒体的伪足通过位于突起和鞭毛器后面的纵向狭缝从腹侧沟出现。挤出体电池存在于细胞质内，并通过细胞壁的孔具有喷射位点。 SSU rDNA 系统发育表明底栖 P. grandis n. 之间存在非常密切的亲缘关系。 sp。和浮游的 Cryothecomonas longipes。 Protaspis 的这些超微结构和分子系统发育数据表明，Protaspis 和 Crythecomonas 的当前分类学需要重新评估。回顾了 Protaspis 的组成和特性，并对未来分类学的变化提出了建议。还强调了冷藻属内的问题，并澄清了解决两个属之间歧义所需的缺失数据。
Protaspis is an enigmatic genus of marine phagotrophic biflagellates that have been tentatively classified with several different groups of eukaryotes, including dinoflagellates, euglenids, and cercomonads. This uncertainty led us to investigate the phylogenetic position of Protaspis grandis n. sp. with ultrastructural and small subunit (SSU) rDNA sequence data. Our results demonstrated that the cells were dorsoventrally flattened, shaped like elongated ovals with parallel lateral sides, 32.5-55.0 mu m long and 20.0-35.0 mu m wide. Moreover, two heterodynamic flagella emerged through funnels that were positioned subapically, each within a depression and separated by a distinctive protrusion. A complex multilayered wall surrounded the cell. Like dinoflagellates and euglenids, the nucleus contained permanently condensed chromosomes and a large nucleolus throughout the cell cycle. Pseudopodia containing numerous mitochondria with tubular cristae emerged from a ventral furrow through a longitudinal slit that was positioned posterior to the protrusion and flagellar apparatus. Batteries of extrusomes were present within the cytoplasm and had ejection sites through pores in the cell wall. The SSU rDNA phylogeny demonstrated a very close relationship between the benthic P. grandis n. sp. and the planktonic Cryothecomonas longipes. These ultrastructural and molecular phylogenetic data for Protaspis indicated that the current taxonomy of Protaspis and Crythecomonas is in need of re-evaluation. The composition and identity of Protaspis is reviewed and suggestions for future taxonomic changes are presented. Problems within the genus Cryothecomonas are highlighted as well, and the missing data needed to resolve ambiguities between the two genera are clarified.