Menoidium pellucidum

Gliding, rigid euglenid, flattened, cell shape falciform, the dorsal side of the cell is convex and the ventral side is slightly concave or straight, about 32 - 60 microns (average 45.8 microns) long and 7 - 11 microns (average 7.6 microns) wide. Pellicle with delicate broadly spaced longitudinal ridges, very hard to see. The anterior end of the cell narrows into a short neck, forming the apical canal opening. The posterior end of cell is rounded and narrows. One flagellum about 0.5 - 0.75 the body length arises from the flagellar pocket. A contractile vacuole is present in the middle of the cell and empties in the base of the flagellar pocket. A roundish nucleus with a granular texture is located in the middle or slightly subcentral of the cell. The cell contains a number of large and small paramylon granules and typically there are 1-3 large rhomboidal granules near the front of the cell and more lens-like small granules posteriorly. The number of these granules varies a lot from one cell type to another. The posterior end of many cells contains an ovoid structure without paramylon grains, also the region around the nucleus with an empty space of paramylon grains. The cell swims quickly rotating or following an undulating path.