Trichomonas vaginalis is an anaerobic, flagellated protozoan parasite and the causative agent of trichomoniasis. Both gametes may be flagellated and therefore motile. Both gametes may be flagellated and thus motile. Colonies are spherical and motile, with motility derived from the flagellated individual cells. All members of the clade have motile flagellated swimming cells. Forams in the family Spirillinidae have amoeboid gametes rather than flagellated. The motile flagellated form is gymnodinioid and athecate. The life cycle of many planctomycetes involves alternation between sessile cells and flagellated swarmer cells. Trophozoites in the water mature and release flagellated zoospores. The location of the cytostome in most flagellated protozoa is strongly conserved. The parabasalids are a group of flagellated protists within the supergroup Excavata. All animals are posited by biologists to have evolved from a flagellated eukaryote. The flagellated microgamete fertilizes the female macrogamete to produce a diploid cell called a zygote. The ovule is fertilized by the flagellated male gametes, which can move about freely. These microspores undergo meiosis to form a flagellated sperm.