Part alien-looking creature, part commonly spotted beach icon, the starfish is an echinoderm. About 1,500 different species of starfish exist in the world, and they can survive in a wide range of climates, from the icy arctic waters to the tropics.
A typical starfish has a central disk and five arms, though some types of starfish have more or fewer arms. As marine invertebrates, they lack a backbone like humans have, but they make up for this with a spiny, outer layering often covered with overlapping plates like scales.
