This Nomarski interference microscopy shows a marine centric diatom (unicellular alga). Diatoms are photosynthesising algae that live in most aquatic environments, both fresh and salt water. They are non-motile and are restricted to shallow waters as they require sunlight for photosynthesis. A centric diatom is one that displays radial symmetry. It is likely that due to the lack of symmetry in this example that this is probably a 4-cornered mutant of normally triangular centric diatom. More diatom images are available as CIL:39032, 39033, and 39035.