The genus Trichomonas
includes polymorphic parabasalid flagellates (5-30 Âµm) with four free anteriorly directed flagella and a short recurrent flagellum associated with an undulating membrane shorter than the body; no free posterior recurrent flagellum. Costa relatively slender, axostylar trunk protruding posteriorly; parabasal body V-shaped with one or two long parabasal filaments. Amoeboid and polymastigotes forms present in natural or culture conditions. Several species living in the genitor-urinary tract of humans such as T. vaginalis
, the mouth such as T. tenax
or in the instestine of birds such as T. gallinae
. Image of Trichomonas vaginalis
with short undulating membrane, posterior axostyle, nucleus (Giemsa).