Get in My Belly!

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Echinoderms feed with much variety.  Crinoids, the sea lillies, filter-feed, lying upside-down, with oral side up and arms outstretched, using cilia-lined ambulacral grooves to bring food to mouth. Asteroidea, most commonly known as Sea Stars, are mostly predators or scavengers, but a few exceptions filter feed.  Brittle stars use podia on arms or arms themselves to push small or large food to mouth for ingestion. Urchins use a masticatory apparatus called "Aristotle's lantern" inside mouth; in many forms this can be everted to scrape detritus off substrate, stones, etc. Holothurians are mostly suspension or deposit feeders, and use tentacles to bring food to mouth

Excretion

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 In most Echinoderms, solid wastes are released as feces through the anus. Nitrogen containing cellular wastes are excreted primarily in the form of ammonia. This waste product is passed into surrounding wateer through tissue of tube feetand skin gills.    Excretion in echinoderms is accomplished by simple diffusion of metabolic wastes (ammonia) across thin permeable regions of the body wall.   A variety of gas exchange structures, including the tube feet, is found in various echinoderms. A hemal system is present but its role in transport is still poorly understood. The hemal system may be through transport system that delivers nutrients from the gut to these compartments for local distribution. Echinoderms are gonochoric and fertilization is usually external.