The asteroid, more commonly known as the starfish, or sea star, is an invertebrate that lives mainly in an oceanic environment. These unique and unusual creatures have a number of arms that protrude away from their spiny skinned bodies. The exact number of arms depends on the species; some have only three, and the most is 42. Most people commonly associate the starfish with having five arms. However, there are many species of starfish that have 3, 4, 6, 7, and 8 arms. Each arm that extends out of the “body” is covered on the bottom by many tube-like feet.
These feet help convey the starfish but taking water in and the pumping it out, therefore enabling it to move. When the water is pumped, the feet extend and contract. The pumping of the water is implemented by a complex structure of internal valves that use hydraulic pressure. The tube feet help the starfish in feeding, as well as locomotion. Most species of starfish eat a variety of foods, some being meat, and others plants, therefore making it an omnivore. Its diet includes plankton, coral, and oysters.
The larger species tend to eat birds, predominantly the sea gull. The starfish will catch the bird while it is searching for fish to feed on and then proceed to drown it. It then eats and digests its prey. These large starfish also tend to feed on sea urchins, fish, and crabs. This makes the larger species carnivores, as opposed to omnivores. Even though the starfish has the ability to regenerate body limbs that have been torn away from their body, if any internal tissue is even slightly damage, the creature will most likely die.
Other than this limitation, the starfish is subject to immortality. The starfish can vary in color, from the bright and vivid designs of the tropical species, to the dull oranges and yellows of the deep-ocean dwellers. Blue, red, and green are very common colors that appear on the star. The sea star has to practices of reproduction. First, the opposite sexes can mate by spawning the sperm and the eggs into the water. After this, the female usually protects the eggs.
When the eggs hatch, however, the larvae are on their own. The second way that the starfish uses to reproduce ties in with their ability to regenerate limbs. The sea star will move the two halves of their body by crawling in separate directions. The body will split apart, and each half will become a new body. This cold-blooded creature can weigh as little as 5 ounces, of as much as 5 1/2 pounds. The can measure as little as 1-2 cm, and can reach sizes as large as 3 feet.
Each of these starfish lives somewhere in the wide expanse of oceans, but only in the warmer areas. Some live very near the ocean’s bottom, while others live very close to the shore. Starfish are members of the phylum echinoderma, and they belong to the class of asteroidea. Some stars are known as linkia multiflore, linkia laevigata, oreaster reticulatu, and acnthaster planci. Some belong to the genus linka, and others to oreaster, culcita, choriaster, acanthaster, and pycnopodia.