Explain the asterias of echinodermata which belongs to non chordate phyla?

The asterias is also known as star fish. They are carnivorous and reside in the rocky areas. They have a higher power of regeneration and autotomy. There body is divided into two parts. The upper surface is known as aboral surface while the lower surface is known as oral surface. The oral surface has a mouth with multiple ambulacral grooves which have a bright red eye at the terminal end. The upper surface has a many spines which are present in irregular fashion. There are also dermal branchiae in between spines. They act as a respiratory and excretory organ. In between the arms a perforated circular plate known as madreporite is present. The pedicellariae are also present which have microscopic pincer structure. They act as an organ of offence. They also remove the foreign materials. They are rich in calcium and nitrogen which are used to make fertilizers. They are saprophytic which feed on dead materials. They also kill the pearl producing organisms. They help in cleaning the surface.