Characteristics of Echinodermata
One of the most basic traits on the basis of which you can identify echinoderms, is their radial symmetry. All the species are typically characterized by a central structure surrounded by 5-part symmetry. This trait can be easily observed in starfish and brittle stars. Even though it is not so obvious in sea urchins and sea cucumbers, a closer examination of their anatomy shows that even they have a radial symmetry. Yet another common trait observed in these species, is their internal skeleton covered with spines and skin. This, however, tends to differ from one species to another. In sea cucumbers, the skeleton is made of degenerated calcareous plates, buried in the fleshy body. Similarly, the anatomy of the starfish reveals that its skeleton is made from movable calcareous plates, thus forming flexible joints. The third, but the most important characteristic trait is their water vascular system. It is most important, because almost all the functions of these creatures, including locomotion, respiration, and feeding, are facilitated by this process. The water vascular system is basically a hydraulic network of canals, which runs through their body. They carry out various life functions by varying the internal water pressure in this hydraulic network. Read more at Buzzle: http://www.buzzle.com/articles/echinoderms-characteristics.html |