Interesting facts about starfish

Photo taken in Trinidad CA.

Starfish (or sea stars) are beautiful marine animals found in a variety of colors, shapes, and sizes. All starfish resemble stars, and though the most common have only five arms, some of these animals can grow up to 40 arms. The amazing sea creatures—part of a group of animals known as echinoderms—travel using their tube feet. They can regenerate lost limbs, and they can swallow large prey using their unusual stomachs.

Instead of blood, sea stars have a circulatory system made up primarily of sea water.
Sea water is pumped into the animal's water vascular system through its sieve plate. This is a sort of trap door called a madreporite, which is often visible as a light-colored spot on the top of the starfish.
From the madreporite, the sea water moves into the sea star's tube feet, causing the arm to extend. Muscles within the tube feet are used to retract the limb.