Cryptomonas paramecium

Colourless cryptomonads, with stiff elongate-ovate body, 19 to 30 microns long. Two subequal flagella, shorter than the length of the body, insert in an anterior pocket which is surrounded by rows of extrusomes. Small extrusomes are also visible under the cell membrane. The nucleus is located posteriorly to the pocket. A contractile vacuole is located anteriorly and empties into the pocket. Cells contain refractile storage products and often two refractile Maupas' bodies. Cells rotate while swimming, and can also swim backwards.

Elongate ovate cell, broader anteriorly than posteriorly, slightly concave, measuring 14-28 µm long. With two flagella equal in length and slightly shorter than cell length inserting subapically near the opening of a pocket that extends almost to half the length of the cell and is lined by refractile ejectisomes. Viewed laterally, dorsal anterior portion of cell is more prominent, and is the site of the contractile vacuole. Several refractile crystals may also be present in the cell. Body frequently with many starch grains. Usually observed resting with flagella against the substrate or actively swimming. Cell occasionally jumps backwards. This species has usually be referred to as Chilomonas paramecium, with Chilomonas being one of two heterotrophic genera of cryptomonads (the other being Goniomonas)