Fire Urchin: Astropyga radiata
The digestive system begins at Aristotle's Lantern (Strongylocentrotus droebachiensis eats by using a special appendage called Aristotle’s Lantern to scrape or tear their food into digestible bits), where food enters the body. An esophagus starts from the mouth, through the center of Aristotle's Lantern, where it meets with the intestine. The intestine is organized into bundles that adhere to the inside of the intestine in a counter-clockwise circuit, around Aristotle's Lantern. Once the intestine gets back to itself, it doubles over itself and reverses directions in a second clockwise direction. Digestive enzymes are formed by the intestinal walls, and begin the breakdown of food. This is almost completely extracellular. From the intestine, what is left of the food moves out of the intestine into the short rectum, and out the anus. S. droebachiensis gets its green color from the pigments of its plant food.