副基体纲

副基体纲
	吉姆萨染液染色的阴道滴虫活动体
科学分类
界：	古虫界 Excavata
纲：	副基体纲 Parabasalia; Honigberg 1973
目
	Trichomonadida; Cristamonadida; Spirotrichonymphida; Trichonymphida;

副基体纲 (Parabasalia) 是古虫界中一群具有鞭毛的原生生物，大部分的物种与动物共生，例如白蚁^[1]和某些蟑螂肠道内的物种，这些共生原生生物同时也与细菌共生，细菌会协助原生生物分解纤维素，间接帮助白蚁和蟑螂分解纤维素。副基体纲中某些物种为寄生性，某些则会导致人类疾病。

特征

细胞前端生有一丛或多丛的鞭毛。副机体纲的特征是基体 (basal body) 借由副基体纤维 (parabasal fibers) 与高基氏体连接。大部分物种胞内有一束维管，从细胞前端延伸至细胞末端，有些物种还会突出胞外，此构造称作轴柱 (axostyle)，副基体纲的轴柱构造与锐滴虫目的轴柱不同。

副基体纲为不具线粒体的厌氧生物，不具线粒体，副基体纲拥有一种小型的造氢体 (hydrogenosome)，学者推测这些造氢体是由退化的线粒体演化而来^[2]。其他不具线粒体的鞭毛虫也具有类似的造氢体，学者认为这些具有造氢体的鞭毛虫和副基体纲的亲缘关系接近，于是将其称作“后滴门 (metamonad)”。副基体纲不具有食槽 (feeding groove) ，这个特征和线粒体一样是在演化过程中消失的。

分类

副前基体纲分类状况凌乱，被不同的学者分类方式不同，一般分为七到十个目^[3]，现在则被分为四个目：Trichonymphida、Spirotrichonymphida、Cristamonadida，和 Trichomonadida^[4]。

毛滴虫目 (Trichomonadida) 具有4-6根鞭毛，其中一根鞭毛附着在细胞的侧面，常形成波状膜。很多物种寄生在脊椎动物中，例如阴道滴虫会经由人类性行为传播。
Trichonymphida、Spirotrichonymphida、Cristamonadida 则具有较多的鞭毛，大多栖息在昆虫的肠道内^[5]。

参考资料

^ Ohkuma M, Iida T, Ohtoko K, et al. Molecular phylogeny of parabasalids inferred from small subunit rRNA sequences, with emphasis on the Hypermastigea. Mol. Phylogenet. Evol. June 2005, 35 (3): 646–55. PMID 15878133. doi:10.1016/j.ympev.2005.02.013.
^ Bui, ET; Bradley, PJ; Johnson, PJ. A common evolutionary origin for mitochondria and hydrogenosomes. Proceedings of the National Academy of Sciences of the United States of America. Sep 3, 1996, 93 (18): 9651–6. Bibcode:1996PNAS...93.9651B. PMC 38483 . PMID 8790385. doi:10.1073/pnas.93.18.9651.
^ Yubuki, Naoji; Céza, VÍT; Cepicka, Ivan; Yabuki, Akinori; Inagaki, Yuji; Nakayama, Takeshi; Inouye, Isao; Leander, Brian S. Cryptic Diversity of Free-Living Parabasalids, Pseudotrichomonas keilini and Lacusteria cypriaca n. G., n. Sp., as Inferred from Small Subunit rDNA Sequences. Journal of Eukaryotic Microbiology. 2010, 57 (6): 554–61. PMID 20880033. doi:10.1111/j.1550-7408.2010.00509.x.
^ Adl, Sina M; et, al. The new higher level classification of eukaryotes with emphasis on the taxonomy of protists. Journal of Eukaryotic Microbiology. 2005, 52 (5): 399–451. doi:10.1111/j.1550-7408.2005.00053.x .
^ Carpenter KJ, Keeling PJ. Morphology and phylogenetic position of Eucomonympha imla (Parabasalia: Hypermastigida). J. Eukaryot. Microbiol. 2007, 54 (4): 325–32. PMID 17669157. doi:10.1111/j.1550-7408.2007.00263.x.

[pmid15878133-1] Ohkuma M, Iida T, Ohtoko K, et al. Molecular phylogeny of parabasalids inferred from small subunit rRNA sequences, with emphasis on the Hypermastigea. Mol. Phylogenet. Evol. June 2005, 35 (3): 646–55. PMID 15878133. doi:10.1016/j.ympev.2005.02.013.

[2] Bui, ET; Bradley, PJ; Johnson, PJ. A common evolutionary origin for mitochondria and hydrogenosomes. Proceedings of the National Academy of Sciences of the United States of America. Sep 3, 1996, 93 (18): 9651–6. Bibcode:1996PNAS...93.9651B. PMC 38483 . PMID 8790385. doi:10.1073/pnas.93.18.9651.

[3] Yubuki, Naoji; Céza, VÍT; Cepicka, Ivan; Yabuki, Akinori; Inagaki, Yuji; Nakayama, Takeshi; Inouye, Isao; Leander, Brian S. Cryptic Diversity of Free-Living Parabasalids, Pseudotrichomonas keilini and Lacusteria cypriaca n. G., n. Sp., as Inferred from Small Subunit rDNA Sequences. Journal of Eukaryotic Microbiology. 2010, 57 (6): 554–61. PMID 20880033. doi:10.1111/j.1550-7408.2010.00509.x.

[4] Adl, Sina M; et, al. The new higher level classification of eukaryotes with emphasis on the taxonomy of protists. Journal of Eukaryotic Microbiology. 2005, 52 (5): 399–451. doi:10.1111/j.1550-7408.2005.00053.x .

[pmid17669157-5] Carpenter KJ, Keeling PJ. Morphology and phylogenetic position of Eucomonympha imla (Parabasalia: Hypermastigida). J. Eukaryot. Microbiol. 2007, 54 (4): 325–32. PMID 17669157. doi:10.1111/j.1550-7408.2007.00263.x.

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