Domain: Eukaryota
Kingdom: Animalia
Subkingdom: Eumetazoa
Superphylum: Deuterostomia
Phylum: Echinodermata
Class: Asteroidea
Order: Clypeasteroida
Family: Asterinidae
Habitat:starfish prefers to live in more sheltered areas such as lagoons, and in deeper water along reef fronts. They generally avoid shallow water on the tops of reefs where the water conditions are likely to be more turbulent. Occasionally they may feed in these areas, particularly when the weather is calm. Consequently care should be taken when reef walking as they can produce a toxic and inflammatory reaction if trodden upon.
Predator: The predators most commonly observed to feed on crown-of-thorns starfish are: the giant triton shell (Charonia tritonis), a puffer fish (Arothron hispidus), two species of trigger fish (Balistoides viridescens, Pseudobalistes flavimarginatus), a shrimp (Hymenocera picta) and a worm (Pherecardia striata).
Prey:They eating clams, and oysters; or any animal too slow to evade the attack (e.g. dying fish). Some species are detritivores, eating decomposed animal and plant material or organic films attached to substrate. The others may consume coral polyps (the best-known example for this is the infamous Acanthaster planci), sponges or even suspended particles and planktons (starfish from the Order Brisingida). The processes of feeding and capture may be aided by special parts; Pisaster brevispinus or Short-spined Pisaster from the west coast of America may use a set of specialized tube feet to extend itself deep into the soft substrata to extract prey (usually clams)[9]. Grasping the shellfish, the Starfish slowly pries open the shell by wearing out the Adductor muscle and then inserts its stomach into an opening to devour the organism.
Anatomy:The body cavity also contains the water vascular system that operates the tube feet, and the circulatory system, also called the hemal system. Hemal channels form rings around the mouth (the oral hemal ring), closer to the top of the starfish and around the digestive system (the gastric hemal ring). A portion of the body cavity called the axial sinus connects the three rings. Each ray also has hemal channels running next to the gonads.Starfish are composed of a central disc from which arms sprout in pentaradial symmetry. Most starfish have 5 arms, but some have more or fewer. Some starfish have shown differing numbers of limbs within a single species. The mouth is located underneath the starfish, on its ventral surface. The spiny upper surface is called the aboral or dorsal surface. On the aboral surface there is a structure called the madreporite, a small white spot located slightly off-center on the central disc which acts as a water filter and supplies the starfish's water vascular system with water to move. Porcellanasteridae employ additional cribriform organs used to generate current in the burrows made by these infaunal starfish.
Reproduction: Starfish are capable of both sexual and asexual reproduction. Individual starfish are male or female. Fertilization takes place externally, both male and female releasing their gametes into the environment. Resulting fertilized embryos form part of the zooplankton.Starfish are developmentally (embryologically) known as deuterostomes. Their embryo initially develops bilateral symmetry, indicating that starfish probably share a common ancestor with the chordates, which includes the fish. Later development takes a very different path however as the developing starfish settles out of the zooplankton and develops the characteristic radial symmetry. Some species reproduce cooperatively, using environmental signals to coordinate the timing of gamete release; in other species, one to one pairing is the norm.some species of starfish also reproduce asexually by fragmentation, often with part of an arm becoming detached and eventually developing into an independent individual starfish. This has led to some notoriety. Starfish can be pests to fishermen who make their living on the capture of clams and other mollusks at sea as starfish prey on these. The fishermen would presumably kill the starfish by chopping them up and disposing of them at sea, ultimately leading to their increased numbers until the issue was better understood. A starfish arm can only regenerate into a whole new organism if some of the central ring of the starfish is part of the chopped off arm.
Link: http://www.starfish.ch/reef/echinoderms.html
http://www.aims.gov.au/pages/reflib/cot-starfish/pages/cot-000.html
http://en.wikipedia.org/wiki/Starfish
