Sea Cucumbers
The water vascular system of sea cucumbers has no connection to the outside, and is thus filled with the internal coelomic fluid, rather than sea water. The madreporite is present, but lies within the body cavity, just below the pharynx. The stone canal is relatively short.
The ring canal normally has one to four polian vesicles, but in the order Apodida, there may be as many as fifty. The radial canals run through notches in the calcareous plates surrounding the mouth and then run along the ambulacral areas along the length of the body. Lateral canals run to both the tube feet and the large oral tentacles, all of which possess ampullae. The Apodida, which have no tube feet, also have no radial canals, with the canals to the tentacles branching off directly from the ring canal.
Read more about this topic: Water Vascular System
Famous quotes containing the word sea:
“All the morning we had heard the sea roar on the eastern shore, which was several miles distant.... It was a very inspiriting sound to walk by, filling the whole air, that of the sea dashing against the land, heard several miles inland. Instead of having a dog to growl before your door, to have an Atlantic Ocean to growl for a whole Cape!”
—Henry David Thoreau (1817–1862)