The name starfish is a little deceiving, as these marine creatures are more closely related to sea urchins than to clown fish. Also known as sea stars, these bloodless, heartless, brainless creatures are marine-dwellers, found throughout the worlds oceans. There are a wide variety of starfish, each with adaptions that make them suited to their own corner of the world.
Most starfish live in marine environments. The salty sea water is crucial to their survival, as it is drawn into their bodies and filtered, running through their veins like blood and acting in much the same way blood does in other creatures. As the water is drawn into the starfish's body, a vacuum is created at the point of entry; it is this effect that allows the starfish to cling to rocks and other underwater structures. Temperature is not a concern to the starfish, as there are types found from the warmest equatorial waters to some of the coldest regions of the ocean.
Coral reefs are a favorite home for several varieties of starfish, notably the crown of thorns. These starfish, which have many more than the typical five appendages, are carnivorous like others in their species. However, when large number of starfish take up residence in coral reefs, they can begin to do some serious damage to these delicate ecosystems.
Starfish digest their food outside of their bodies. Stomach pockets are extended, delivering a fatal amount of digestive juices to the prey. As this prey begins to liquefy, it is drawn into the starfish's body. The crown of thorns--and other types of starfish--prey on the soft tissues of the coral that exists in abundance in the reef environments. This abundance of food can result in a population boom, putting more of a dent in the numbers of coral.
Starfish are always found foraging along the bottom of whatever marine environment they are in, whether it's in the shallows of a rock pond or at the bottom of the cold Atlantic Ocean. Because they have no head, every direction they can move in is considered forward; they cling to rocks, reefs and even sandy ocean bottoms with the suction created when they draw water into their bodies.
This same suction allows the starfish to feed. The ocean floor is the starfish's environment of choice as well as its dining room. Starfish prey on other bottom-dwelling creatures such as clams and whelks, which it encounters as it moves along the bottom.
Starfish can easily thrive in the shallows of the ocean, including the area long beaches and in rock pools. These extremely hardy creatures can survive for some time when they are washed up on shore and out of the water, where they can become a meal for seabirds and other land-dwelling predators. This close proximity to the shore -- and potentially dangerous predators -- is not the threat to a starfish that it could be to another species. Starfish can regenerate lost limbs, even if as little as a fifth of the entire starfish remains, even if it is only one of the legs. Each of the legs of the starfish contain at least part of the vital organs, allowing it to rebuild itself from virtually any part of its body.