Dinema platysomum

Cells are elliptical, 20 to 32 microns long, flattened and flexible. There are about 20 pellicular striations on ventral and dorsal faces of the cell. The ventral striations are more distinct than the dorsal ones. The two flagella are unequal in length. The anterior flagellum is slightly thickened, is about 1.2 times the length of the cell and sweeps from side to side. The trailing posterior flagellum is thicker and is most strongly developed proximally. It lies in a ventral groove and is about 2 to 2.5 times the length of the cell. The flagellar pocket is located in the left side of the cell and the large elliptical nucleus is located on the right half in the middle of the cell. The wedge-shaped ingestion apparatus may be easily seen. The cells occasionally stop and jerk when changing direction and then move again. The cells contained diatoms as food.

The flagellated alga Dinema platysomum, synonym Anisonema platysomum, is the first eukaryote in which magnetotactic structures have been discovered. Monje & Baran (2004) describe how this euglenoid alga stores magnetite in a similar way that already discovered magnetotactic bacteria do. It has been shown that the cells contain magnetite particles aligned with the longitudinal axis of the alga, and each magnetite chain is a permanent dipole. The observed magnetic momentum of the cell has been estimated to be 1000 times stronger than those of typical magnetotactic bacteria.

The species was first described in 1939 as Anisonema platysomum, and transferred to the genus Dinema in 2000.