Pentagonal or star-shaped echinoderms. The value ranges from 2 cm to 1m, although the majority - 12-25 cm Many species are brightly colored.
This is a slow-moving animals, having from 5 to 50 rays. From the central flat or slightly convex disc with starfish depart 5 (rare - up to 40) rays, or arms. When shortening the rays of the body shape is close to pentagonal. Hands embody the digestive processes of the outgrowths of the stomach and genitals, inside the arms is the longitudinal number of vertebrae. The skin is equipped with properly arranged skeletal plates, which are armed with thorns, needles, sometimes pedicellariae.
The mouth is located on the oral side of the disc and converted to the substrate. A broad furrow or ambulakr (ambulacral groove) runs radially from the mouth along each ray. Each ambulakr contains two or four rows of small tubular outgrowths - ambulacral feet. Legs are flexible tubular outgrowths, usually with suckers on the end, and driven by the water pressure in the inner channels and ampoules ambulacral system. The edges are protected ambulakrov movable spines that can close its cover (from Lat. Ambulacrum - sheltered pathway). The thin tip of each hand is completed by one or more small tentacular sensory ambulacral feet and a red eye spot.
The upper, aboral, the party is the anus (in some stars it is not) in the center and a large madreporite located between the bases of the two hands. The entire surface may be smooth or covered with spines, tubercles or ridges. Some types of arms and drive bordered by wide marginal plates.\
Source
No comments:
Post a Comment