How many arms does a typical starfish have? A typical starfish has five arms radiating from a central disc. This five-part arrangement is called pentameral symmetry and is one of the most recognizable features of the echinoderm group, which includes starfish, sea urchins, and sea cucumbers.
Five arms are common, but they are not universal. Some starfish species have six, seven, or many more arms. The Antarctic Labidiaster annulatus, for example, can have more than 50. A starfish may also regrow an arm after injury, provided enough of the central disc remains. In some species, a detached arm containing part of the central disc can develop into a new animal.
Starfish use rows of tiny tube feet on the underside of their arms for movement, gripping surfaces, and handling food. They are not fish at all: they are marine invertebrates. The older name “starfish” remains common, although many scientists and aquariums prefer “sea star” to emphasize that distinction.