Tetraselmis is a relatively large unicellular algae species characterized by its ellipsoidal-ovoidal shape. It is easily identified by the presence of four flagella of equal length that emerge from an anterior depression in the cell body. The coloration of this species is typically greenish.The cellular structure of Tetraselmis cordiformis is noteworthy. The cells are flattened and exhibit a cordiform (heart-shaped), elliptical, or almost spherical shape. At the apical base, four flagella of equal length extend, contributing to the distinctive appearance of the species. The anterior end of the cell features an invagination, and a conspicuous eyespot is present on the flattened side of the cell.Within the cell, there is a single large cup-shaped chloroplast housing a pyrenoid at the base. Additionally, a nucleus is positioned parallel to the pyrenoid. Tetraselmis cordiformis is equipped with a single large stigma and two contractile vacuoles located at the base of the flagella.Asexual division in this species occurs during the nonmotile stage of its life cycle, contributing to its reproductive process. Overall, Tetraselmis cordiformis exhibits distinctive characteristics in terms of its morphology and cellular features.