Pyrocystis fusiformis is a unicellular eukaryotic alga belonging to the dinoflagellate phylum. As a protist species, dinoflagellates like P. fusiformis are characterized by the presence of two flagella, one longitudinal and another transverse, which they use for movement in water. This marine plankton species is capable of bioluminescence, a phenomenon triggered by water movement and high shear flow, often observed around ships, breaking waves, or in response to the presence of predators.The cells of P. fusiformis are fusiform in shape, meaning they are elongated with tapered ends. They typically have an average length and width of 970 x 163 µm, and their equivalent spherical diameter is approximately 374 µm3. While P. fusiformis possesses a cell wall, it lacks an additional sheathing of rigid polysaccharide plates, known as thecae, which form the cytoskeleton.