Trichomonads are flagellate protozoa that contain an intracellular fibrous rod composed of thousands of microtubules termed the axostyle.

Keywords: flagellates; protozoa; parasite; parabasilids; axostyle; costa

Figure 1.

Scanning electron micrograph of dorsal (left) and dorsolateral (right) views of Trichomonas vaginalis. Characteristic structures include four anterior flagella (AF). The recurrent flagellum (RF) can be seen emerging from the periflagellar canal (PC). The margin of the undulating membrane (UM) is typically shorter than the body and consists of the attached part of the recurrent flagellum and the outer accessory filament. The axostyle (A) is well developed and extends beyond the posterior end of the cell. Bar, 5 μm. (Reproduced with permission from BM Honigberg (ed.) Trichomonads Parasitic in Humans. New York: Springer‐Verlag.)

Figure 2.

Transmission electron micrograph of Trichomonas vaginalis. Section through the anterior part of the organism showing the Golgi apparatus (G), a hydrogenosome (H), the axostyle (A), and the costa (C). (Courtesy of Dr M. Vannier‐Santos, Universidade Federal do Rio de Janeiro, Brazil.)



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Further Reading

Biagini GA, Finlay BJ and Lloyd D (1997) Evolution of the hydrogenosome: mini review. FEMS Microbiology Letters 155: 133–140.

Bui ET, Bradley PJ and Johnson PJ (1996) A common evolutionary origin for mitochondria and hydrogenosomes. Proceedings of the National Academy of Sciences of the USA 93: 9651–9656.

Cavalier‐Smith T (1987) The simultaneous symbiotic origin of mitochondria, chloroplasts and microbodies. Annals of the New York Academy of Sciences 503: 55–72.

Horner DS, Hirt RP, Kilvington S, Lloyd D and Embley TM (1996) Molecular data suggests an early acquisition of the mitochondrion endosymbiont. Proceedings of the Royal Society of London Series B 262: 1053–1059.

Karlin S and Brocchieri L (1998) Heat shock protein 70 family: multiple sequence comparisons, function, and evolution. Journal of Molecular Evolution 47: 565–577.

Müller M (1992) Energy metabolism of ancestral eukaryotes: a hypothesis based on the biochemistry of amitochondriate parasitic protists. BioSystems 28: 33–40.

Müller M (1997) Evolutionary origins of trichomonad hydrogenosomes: comment. Parasitology Today 13: 166–167.

Roger AJ, Clark CG and Doolittle WF (1996) A possible mitochondrial gene in the early‐branching amitochondriate protist Trichomonas vaginalis. Proceedings of the National Academy of Sciences of the USA 93: 14618–14622.

Sogin ML and Silberman JD (1998) Evolution of the protistan parasites from the perspective of molecular systematics. International Journal of Parasitology 28: 11–20.

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Yarlett, Nigel(Apr 2001) Trichomonads. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1038/npg.els.0001989]