The Starfish are star-shaped echinoderms that belong to the class Asteroidea. There are also roughly 1,500 species of Starfish that we know of and are present in all of the world’s oceans. Further, they also reside in areas from the intertidal zone, down to depths of as much as 20,000 ft. (6,000 m) below the ocean surface.
Starfish are marine invertebrates. The majority of them possess a central disc and five arms but there are some types with many more arms. Also, they move with many small tube feet.
Most animals can regenerate lost limbs and shed limbs as a method of defense.
The body wall of the animal consists of a thin cuticle, an epidermis, a rather thick dermis of connective tissue, and a thin layer which provides the musculature. The dermis contains an internal skeleton from components called ossicles which are honeycombed structures arranged in a lattice.
The starfish does not have blood as such. Instead, they circulate water through a network of canals which serve in food manipulation, locomotion, and gas exchange.
Most of these animals cannot move quickly. In fact, typical speed averages about 6 in (15 cm) per minute. Apart from their function in locomotion, the unique feet act as accessory gills. Some species are able to reproduce asexually.
Most starfish are predatory and prey upon sponges, snails, bivalves and other small creatures. Others are detritivores – indeed, they consume decomposing organic material and fecal matter.
The processes of feeding and capture may be aided by specialized body parts. Interestingly, one species endemic to the West Coast of the United States uses a set of specialized tube feet to dig itself deep into the soft substrate to extract prey which is typically clams. When feeding, the animal turns its stomach out of its body and then thrusts it into a crack in the shell of its prey.
Starfish Distribution and Habitat
All echinoderms, including starfish, maintain a delicate internal electrolyte balance which only sea water can maintain in equilibrium. Therefore, it is only possible for them to live in a marine environment and there are none of them dwelling in fresh water.
Their regions of habitation include rocky shores, tropical coral reefs, tidal pools, kelp forests, and seagrass meadows. Nonetheless, by far the greatest diversity of species occurs in coastal regions.