The scientific name for a starfish, also called a sea star, is Asteroidea. These creatures are members of the phylum Echinodermata. Echinoderms live in the ocean and have radial symmetry, with appendages usually appearing in multiples of five.
More than 2,000 types of starfish exist. While most have five arms, some have as many as 50. Arms grow to be as long as 23 inches in some starfish. They are able to reproduce both asexually and sexually. Asexual reproduction occurs when an appendage and part of the body break off and form a new creature. Most of the respiration of a starfish happens in the tube feet, and though they have senses, they do not have a "true centralized brain," according to the Marine Education Society of Australasia.