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While a starfish lacks a centralized brain, it has a complex nervous system with a nerve ring around the mouth and a radial nerve running along the ambulacral region of each arm parallel to the radial canal. The peripheral nerve system consists of two nerve nets: a sensory system in the epidermis and a motor system in the lining of the coelomic ...
Tube feet (technically podia) are small active tubular projections on the oral face of an echinoderm, such as the arms of a starfish, or the undersides of sea urchins, sand dollars and sea cucumbers; they are more discreet though present on brittle stars, and have only a feeding function in feather stars. They are part of the water vascular system.
Echinoderms possess a simple digestive system which varies according to the animal's diet. Starfish are mostly carnivorous and have a mouth, oesophagus, two-part stomach, intestine and rectum, with the anus located in the centre of the aboral body surface. With a few exceptions, the members of the order Paxillosida do not possess an anus.
That is, the internal organs of digestion and reproduction never enter the arms, as they do in the Asteroidea. The underside of the disk contains the mouth, which has five toothed jaws formed from skeletal plates. The madreporite is usually located within one of the jaw plates, and not on the upper side of the animal as it is in starfish. [5]
Novodinia antillensis perches on the branches of arboreal deep water corals, extending its arms into the water column to catch small crustaceans drifting past. [4] The arms form a feeding fan, the pedicellariae grasp and secure the prey, and the arms form loops that surround the food item and take it to the mouth.
Madreporite of Asterias. In sea stars, water enters the system through a sieve-like structure on the upper surface of the animal, called the madreporite.This overlies a small sac, or ampulla, connected to a duct termed the stone canal, which is, as its name implies, commonly lined with calcareous material.
Choriaster granulatus is a carnivore that, like other sea stars, has its mouth on the underside of its body. Food is digested and absorbed outside of its body by forcing its stomach out of its mouth onto the food. [11] Its food includes small invertebrates such as coral polyps as well as carrion. [12]
The common starfish, common sea star or sugar starfish (Asterias rubens) is the most common and familiar starfish in the north-east Atlantic. Belonging to the family Asteriidae, it has five arms and usually grows to between 10–30 cm across, although larger specimens (up to 52 cm across) are known. The common starfish is usually orange or ...