Origin
Starfish or starfish belongs to the Class Asteroidea. It's also called the fragile star. There are 2000 species that live in all the world's oceans: Pacific, Atlantic, Indian, Arctic and Southern Ocean(Antarctica).
Starfish are found at various depths, some greater than 6000m.they are most familiar to marine animals and possess a number of well-known traits, such as regeneration and feeding on mussels.
They vary according to the individual species and possess a great have a great diversity of forms and modes of feeding.
Starfish feed
The digestive system is quite complicated. I'll come back to him when I do a species classification of starfish. Until then a little summary ... the mouth is located on the lower part of the body and opens through a short esophagus.
First open the shell. Then he pulls his stomach out of his mouth and inserts it between the valves of the shell. The stomach secretes enzymes with the help of which help digest the victim.
Due to its ability to digest food outside its body, the starfish is able to hunt prey larger than its mouth such as clams, oysters, arthropods, small fish and mollusks. Starfish feed mostly on shells.
Not all species are carnivores or only carnivores. In the absence of meat they can supplement the diet with algae. It sounds strange but some algae actually graze on the bottom of the seas and oceans.
Starfish appearance
The starfish expressed in adulthood a pentaradial symmetry. However it is believed that the ancestors had bilateral symmetry. The most common star has 5 Rays or arms. There are also species with 6 or more arms due to developmental anomaly.
Other species simply have more, for example the species Solasteridae can have up to 50 Arms. These organisms are composed of calcium carbonate. The lower surface contains the oral surface and the upper surface is harder, it also has a protective role.
From the surface of the body can be identified several structures that comprise the basic anatomy of animals and can sometimes help to identify it. The 5 arms move on dozens of legs. Tubular legs move when water is pumped in and out of them.
A system of channels leads the water to the stilts. There are pumps on these channels. They regulate water circulation. The starfish absorbs water through a filter.
At the end of each arm there is a microscopic eye with which the starfish can see where it moves in light and also in darkness. There is no cornea or iris.
Starfish behavior
Many types of toxins have been extracted from various species of starfish for research and pharmaceutical or industrial fields worldwide.
Breathing occurs mainly through small tubes in the arms called papillae. The oxygen in the water is distributed throughout the body.
Excretion also occurs all through this system of tubes and papillae.
Reproduction starfish
Starfish can reproduce sexually or asexually. Most species are hermaphrodites. One of the species is born male and later turns into female.
Sexual dimorphism can not be seen from the outside. The eggs after they have been laid only need to be covered and hatched. Starfish gather during the breeding season and it is not known how they communicate but they all multiply on the same day.
If an arm is broken it regenerates only if at one end it has a part of the central disc, that is, only the part caught by the body. Life span varies between species, larger species live longer.
One species reaches sexual maturity in 2 years and lives about 10 years, another reaches maturity in 5 years and lives 30-40 years.
