Starfish, or sea stars, are a marine creature that are echinoderms. Echinoderms are animals which have no head, a hard skeleton under its skin, a body that resembles a star with at least five legs and a mouth in the center, and tubular feet to help them to move. Sea urchins and sea cucumbers are also considered echinoderms. There are two distinct families of starfish, soft bodied starfish from the class Asteroidea and the harder, more brittle starfish from the class Ophiuroidea. There are 2000 living species of starfish in the oceans around the world including in the arctic circles. Despite their name starfish are not actually fish as they do not possess any of the anatomical characteristics of fish such as scales, gills and fins.
What Do Starfish Eat?
Starfish eat mainly bivalves such as clams, mussels and oysters. They will also eat small fish, sea snails and barnacles. A starfish will basically eat any sea creature that is too slow to avoid being captured by it. Some starfish eat decomposing animals, algae and plant matter. Other species such as the Crown of Thorns Starfish eat coral polyps and sponges destroying large sections of coral reef. Starfish have an interesting way of eating their prey. When they find a clam, mussel or oyster, they pry the shell open with their arms and then insert their stomach into the shell. They do this by extending their stomachs out through their mouths and digesting their prey before pulling their stomach back inside via the mouth opening on the bottom of their bodies.
Interesting Facts about Starfish
- They are able to regenerate an arm when lost or injured. Some starfish use this as a defense mechanism as when threatened by a predator they can shed an arm and while this is distracting the predator they can escape. Much the same was as some lizards drop their tails.
- Not all starfish have only five arms. Many have more than five arms; the sun start has up to 40 arms.
- Starfish do not have blood. Instead of blood they have a water vascular system.
- Starfish have eyes. They have an eye spot on the end of each arm allowing them to see in many different directions at once. These eyes cannot see very much detail but can sense light and dark.