Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea. Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or "basket stars". sea stars have an eye spot at the end of each arm. While they can't see as well as we do. The five-armed varieties of sea star are the most well known, not all sea stars have 5 arms. Some have many more. Take the sun star for instance, which has up to 40 arms! This is a very simple eye that looks like a red spot. The eye doesn't see much detail, but can sense light and dark. The heart beats about six times a minute and is at the apex of a vertical channel (the axial vessel) that connects the three rings. Speaking of prey, sea stars have a rather unique way of eating theirs. A sea star's mouth is on its underside. They prey on bivalves like mussels and clams, as well as small fish, snails, and barnacles.Instead of blood, sea stars have a water vascular system, in which the sea star pumps sea water through its sieve plate, or madreporite, into its tube feet to extend them. Muscles within the tube feet retract them.This starfish have five-point radial symmetry, which means that their body plan has five sections (or multiples thereof) arranged around a central disk.They are not fish. They do not have gills, scales, or fins like fish do and they move quite differently from fish. While fish propel themselves with their tails, sea stars have tiny tube feet to help them move along.There are about 2,000 species of sea stars. Some live in the intertidal zone, some in deep water, some in tropical areas, some in cold water. Muscles within the tube feet retract them. Many starfish wear striking colors that camouflage them or scare off potential attackers. They use color, pattern and texture to camouflage on sand, coral, rocks and the ocean floor. Some starfish also have the ability to change colors to camouflage themselves from other enemies.
No comments:
Post a Comment