Jakoba incarcerata Bernard et al., 2000. Cells are 4 to 10microns Two flagella arise slightly sub-apically. They may be slightly acronematic. The anterior flagellum is usually shorter than the length of the cell. The posterior flagellum is up to one and a half times the length of the cell and may appear proximally thickened. The nucleus is located subapically. Food vacuoles containing bacteria are common. A refractile granule is frequently located in the middle of the cell. Typical cells are crescent-shaped with a groove occupying three quarters of the ventral face. The posterior flagellum beats with a short wavelength and amplitude pattern within the groove, often attaching to the posterior margin but with the distal portion free. Some cells lack a groove, have an ovoid to irregular profile, but have usually a posterior tail. Transformation from a grooved to a tailed profile has been observed. Grooved or tailed cells may attach to the substrate by a hooked anterior flalgellum or the tip of the posterior flagellum. Tailed cells often stick to the substrate by the tail, the cell body or irregular extensions thereof. Grooved, or more commonly, tailed cells may swim with a smooth spiral path, with the anterior flagellum directed forward. Occasionally, non-grooved cells were observed with anterior flagella up to four times the length of the cell directed posteriorly in a curving arc. These cells swim or attach to the substrate by the cell body. Electron-micrographs of cells from the type culture shows a single vane on the dorsal side of the posterior flagellum.
