Micrasterias truncata

The typical variety of Micrasterias truncata is a unicellular alga which are somewhat flattened, thus appearing spindle-shaped when viewed from the top and elliptical when viewed from the side. Cells are (60–)85–120(–145) μm long and (60–)80–110(–135) μm wide, slightly longer than wide. They consist two identical halves, termed semi-cells, which are joined together at the center of the cell (the isthmus) with closed sinuses separating the two semi-cells. Semi-cells are trapezoidal to semicircular in outline. Each semi-cell has three deeply divided lobes, one polar and two lateral. The polar lobe is strongly widened near the cell apex. The side lobes are generally divided twice; lobes are short and broad and separated by narrow, shallow incisions. The angles of the apical lobes and the angles of the highest-order side lobes are denticulate. The incisions between the apical and side lobes are closed or narrowly open. Each semi-cell has a chloroplast with raised, longitudinal ridges and a few pyrenoids. The cell wall is punctate; the pores secrete a mucilaginous sheath around the cell.

Like other desmids, Micrasterias truncata reproduces asexually via cell division. Two new semi-cells are formed between the parental semi-cells. The developing semi-cells first contain only cytoplasm, then the divided nuclei migrate into them. The chloroplast migrates in later. Sexual reproduction in Micrasterias truncata results in the formation of zygospores, which are spherical and armed with long, sometimes curved spines. The zygospores are 75–80 μm in diameter without spines, and 118–130 μm including spines.