Feeding & Excretion

Echinoderms have diverse methods in feeding: Some, such as the sea star, are carnivores, where their tube feet are used to pry open other animals that have shells. Once the shell is open, the starfish everts its stomach out of its mouth, secretes digestive enzymes on their prey and digests the prey in the prey's own shell. Once the starfish is finished feeding, it moves its stomach back into its shell. While, herbivores, such as sea urchins, use their five-part jaw to scrape algae off rocks. Filter feeders, such as basket stars, use their tube feet to capture floating materials in the water. Detritus feeders collect large amounts of sand along the sea floor and filters out the waste materials in the form of feces.

Excretion in echinoderms is very simple. Almost all echinoderms release solid wastes (feces) through the anus. One exception is the brittle star, which releases solid wastes through the mouth because they lack an anus. Also, nitrogenous cellular wastes (ammonia) are release through the tube feet and the skin gills.