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Description of Peranema dolichonemaCells are long sack-shaped and about 30 microns (20-45 microns) long with longitudinal pellicle striations half to one micron apart. Body narrowed anteriorly, broadening posteriorly, to a width 1/3-1/2 of the cell length. The posterior end rounded or dimpled or may be oblique. The ingestion organelle is short and relatively weakly developed. Two fine rods measure about one quarter the length of the cell and open near the posterior end of the slit of the flagellar pocket. The rods are narrow and taper posteriorly, their anterior ends are thickened and joined by an arc of cytoskeletal material. The anterior flagellum is about 1.5 - 1.8 times longer than the cell and its anterior part beats with a flailing motion, and the posterior flagellum lies in a narrow ventral groove and may or may not project from the rear of the cell - the body in this region may be depressed around the flagellum. The reservoir is situated deeply in the cell and the nucleus is located in the posterior part of the cell. The flagellar pocket opens with a short slit running along ventral surface. Cells eat diatoms, other algae and detritus. The nucleus is located near the centre of the body and has a lobed nucleolus. Extrusomes short and refractile, typically in small clusters and oriented at right-angles to cell surface; most often seen in the âneckâ region (area of ingestion rods). Extrusomes of P. dolichonema appear similar to those in P. trichophorum, those of P. dolichonema are typically found in clusters and oriented perpendicular to the cell â rather than along the direction of the grooves. Individuals with fine-spaced grooves and/or a non-projecting posterior flagellum have some similarity with P. inflexum.