Symmetry around a central axis; organisms with radial symmetry have a dorsal and ventral surface but are roughly similar on every side, though they may show fourfold, fivefold, sixfold, or eightfold symmetry. Radial symmetry is a trait of organisms that live in an environment that has an 'up' or 'down' due to gravity, or live on a substrate, or have lighting from one constant direction, but are either sessile or very slow moving. On Old Earth, many plants are radially symmetric, as are slow moving or sessile animals like coelenterates or echinoderms. Analogous xenobionts have this form, as do slow moving or aquatic xenobionts. It is also common trait of sessile or slow neogens created for microgravity environments. Compare to bilateral symmetry or spherical symmetry.