- Genus: Asteroidea
- Conservation Status: Not endangered
- Location: All the oceans of the world.
Blood That Is Water
The starfish is not a fish at all, and in fact, today most people call them sea stars. This is because starfish do not have gills, scales, or fins like fish do and they move quite differently from fish. Over 2,000 species of sea stars or starfish live in all the world’s oceans, from tropical seas to the cold seafloor. Most starfish have five arms but there are species with 10, 20, and even 40 arms. While some appear smooth, they all have spines covering their upper surface and a soft underside. If you gently turn over a live Starfish, you'll see its tube feet wiggling back at you. Starfish come in a variety of colors that help them either to hide from their enemies- or to scare them off. They are famous for their ability to grow their limbs back- which means that if a starfish loses one of its arms, it will promptly grow another one. Starfish have a very simple eye that looks like a red spot at the end of each arm. The eye doesn't see much detail, but can sense light and dark.
Starfish come is different sizes. Some can be larger than your face; others may be smaller than your palm. They generally feed on meat, decomposed plant and animal materials and algae. Mussels, crustaceans, worms and echinoderms- which are other starfish or sea urchins- are their favorite treats. Starfish have tiny, suction-cupped tube feet which they use to open clams or oysters. Then their sack-like stomach emerges from their mouths, envelops the prey to digest it, and finally withdraws back into the body! The biggest threats to starfish are a reduction of coral reef habitat, pollution, and marked changes in water temperature.
Did You Know?
- Starfish have no brains and no blood.
- The nervous system of a starfish is spread through its arms and its “blood” is actually filtered sea water.
- While fish propel themselves with their tails, starfish have tiny tube feet to help them move along.
- Starfish have most of their vital organs in their arms, so some can even regenerate an entirely new body from just one arm and a portion of the central disc.