Description of Cryothecomonas

Circumscription: Biflagellated heterotrophic flagellate moving by swimming or gliding, with one anteriorly directed and one posteriorly directed flagellum, body surface coated in delicate theca except at site of emergence of flagella and in area of food ingestion. Theca not visible by light microscopy. Feeding by ingestion by ventral face of body often involving pseudopodia. Ultrastructural identity: Mitochondria with tubular cristate, two flagella inserting as inclined basal bodies interconnected by a striated band, giving rise to several microtubular arrays, one of which links basal bodies to nucleus, transition zone with constriction, cell with dictyosomes and osmiophilic bodies. Cell surface with thin organic coating. During mitosis, the nuclear envelope disintegrates, spindle microtubules arise from basal bodies. Synapomorphy: Not specified-this is a tubulocristate flagellate with body enclosed by delicate mucoid theca and a large ventral groove, but neither feature is unique to this taxon. Composition: One genus, several species.