Table 1. Comparative morphology of considered organisms.

Species	Cell size, µm	Cell shape	Comparative length ofanterior flagellum inrelation to body length	Comparative length ofposterior flagellum inrelation to body length	Ventral groove	Anteriorrostrum	Contractilevacuole	Nucleusposition
Colponema vietnamica	10.5–14.5×5.0–6.5(up to 9.0 forsatiated cells)	elongated-oval, not flattened;satiated cells bean-shapedor ovoid	2 times shorter	1.5 times longer	short, weaklypronounced	present	present atthe anteriorend	cell center or closerto the anterior end
Colponema edaphicum	8–12×2.5–4.5	oval, flattened	about the cell length	2 times longer	short, well-markedat starvingspecimens	present	present atthe anteriorend	anterior or centralcell part
Colponema marisrubri	8.5–14×4.0–6.5	elongated-oval, not flattened	about the cell length	2 times longer	short, pronounced	absent	absent	anterior cell part
Colponema loxodes	17–30×8–15	ovoid or bean-shaped,not flattened	about the cell length	1.5 times longer	Long, pronounced	present	present atthe anteriorend	anterior cell part
Colponema globosum	15×13–14	wide-oval, flattened	slightly shorter than cell	2 times longer	long, deep, withwide curvilinearmargins	absent	present atthe anteriorend	no data
Colponema symmetricum	9–15	elliptical with widely roundedends, flattened	1.5–2 times longer	3–4 times longer	long, well-visible	absent	no data	slightly below thecell center
Acavomonas peruviana	9.5–13.5	elongated-oval or egg-shaped,not flattened	about the cell length	2 times longer	Absent	present	absent	anterior cell part