Urceolus cyclostomus

Urceolus cyclostomus is a species of flagellate, a single-celled protist that exhibits an emergent flagellum for movement. Members of the genus Urceolus are distinguished by the presence of a 'neck' at the anterior end of their oval-shaped cell, followed by a wide aperture or 'mouth' into a deep canal where the feeding groove and the flagellum originate. In addition, like other euglenids, the cell surface or pellicle is spiral-striped. In particular, U. cyclostomus is distinguished from other species of the genus by its more or less rigid and regular body shape, a less developed 'ingestive organelle' or feeding apparatus, and a more conspicuous 'hatching' (i.e. more pronounced stripes) of the pellicle. The posterior end of the cell is narrow, as is common in other euglenids. The cells are ovate, measuring 14–30 μm long and 4–18 μm wide. The cells move by crawling through the substrate, with the posterior end raised. The flagellum is around 1.5 times longer than the cell itself, 40–50 μm.

Urceolus cyclostomus inhabits the bottom sediment of freshwater bodies with a wide distribution. It has been recorded in bogs of the Central Russian forest-steppe region and numerous ponds in the Czech Republic, where it feeds on epipelic cyanobacteria and other kinds of algae. It is also present in brackish waters, such as salt marshes and intertidal sand of England.