Echinodermata:
Echinodermata are a phylum of marine animals that are found at every depth of the oceans. They are easily recognized by their radial symmetry and include well known animals such as sea stars.
Starfish Respiration:
Respiration of a starfish occurs through tube feet and the papillae which are the tiny dots covering the body of the starfish reaching from the inside through the layer of muscle, and into the ocean water which contains oxygen as well as nutrients for the starfish to eat. The same way as any other animal, it releases carbon dioxide into the water after it is finished processing oxygen. Starfish use the same organs in the excretion of waste.
Sea Cucumber Respiration:
A sea cucumber is one of the few organisms in the echinoderm phylum that doesn't have a characteristic or radial symmetry. The cucumber actually uses its anus as a respiratory organ. It is one of the only organisms that combines both the excretory and respiratory system into one. Once again it works the same way as any other animal - it gets oxygen by inhaling through the anus, and as it is releasing waste, it also releases carbon dioxide.
Sea Urchin Respiration:
Sea urchins are small, spiny, spherical organisms that live in a marine environment. Sea urchins have 5 gills around the mouth. Their tube feet behind the spikes also serve as means of respiration. Sea urchins are one of the few echinoderms that resemble the the respiration of a fish.