Structure and Function

In general, echinoderms respire through simple diffusion. They do this by using either gills or other specialized organs to circulate water and oxygen through their bodies. Many echinoderms also use a hemal system, a series of pockets and tubes which act like a net of veins and arteries.

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Sea Stars

Starfish have gills called dermal branchiae, which allow gas exchange to occur through diffusion. In order to get water into the starfish, the organism’s feet need to move back and forth. The starfish does this through the water vascular system. This system is controlled by the maderoprite, a porous plate that periodically takes in water in order to replenish the system. The grooves in the maderoprite prevent large particles from entering, while cilia detect smaller particles and push them back into the ocean. Once the water has entered the starfish, it flows through the radial canal into lateral branches, which connect the feet inside each arm. Inside the arm, there is a valve that creates pressure, which allows for the feet to move. When the valve is closed, the foot extends and when it is open, pressure is released, causing the foot retracts. As water flows through the coelom, it circulates through gills, which allow for the oxygen to be taken in and carbon dioxide waste to be expelled from the tissues (Echinodermata Respiratory System).

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While looking through the evolutionary lense for respiration, the Echinodermata Phylum is more complex than the previously mentioned phyla. Although echinoderms respire through diffusion, they have a special mechanism called the water vascular system, which expedites the process. This system permits echinoderms to move certain parts of their body in order to obtain the maximum amount of water, which allows oxygen to easily permeate the body. All of the organisms in the previously mentioned phyla have to rely on the current of the water to aid in their respiratory efforts, while echinoderms obviously do not, based on the aforementioned specialized system.