What Are the Diets of Echinoderms?

Echinodermata is a phylum of sea creatures that are very symmetrical. They often gain five or more arms that come from a central body. This body is also divided into sections, each with its own identical set of organs. There are five classes of echinoderms. These classes often share similar diet habits, but individual classes may focus on different food types.

Sea Stars

Sea stars, also known as starfish, are echinoderms that are usually carnivorous. Their diet mostly consists of sponges, bryozoans, ascidians and mollusks. However, some sea stars eat detritus from the ocean floor. Detritus is the film that covers rocks on the ocean floor. This film is rich in organic matter. Sea stars have no mouths but instead lie atop their food. They then extend their stomach over their prey. The stomach acid liquefies the food and sucks it back into the starfish to be completely digested.

Feather Stars

Feather stars have long, feathery arms that give them their common name. These arms are covered with mucus, a sticky substance that grabs any piece of food that floats into its grasp. Feather stars' food consists of plankton, plant life matter or any small, easily digested sea creatures, such as very small snails. After being caught, the food is thrown into a section of the body called the ambulacral groove. It is pushed toward the mouth for digestion. Feather stars have no stomach, so their food is digested in their intestines.

Brittle Stars

Brittle stars are highly flexible echinoderms with five long and narrow arms. They use these arms to move, capturing prey with the tube feet on the end of their arms. The arms then place the food directly into the mouth for digestion. Their prey varies depending on the species. Some are suspension feeders, hanging from rocks and filtering plankton from ocean currents. Others move on the ocean floor, eating coral mucus and detritus. Others are capable of eating larger prey, such as mollusks, crustaceans and worms.

Sea Urchins

Sea urchins are circular-shaped echinoderms with small spikes covering their upper body. Their movement arms are located on the bottom of their body. They move by crawling. These slow-moving echinoderms are generally sea floor grazers. A majority of sea urchins graze on algae, using their mouths to break off segments of algae. However, other sea urchins feed on bryozoans, ascidians and detritus.

Sea Cucumbers

Sea cucumbers are long, cylindrical echinoderms that resemble the vegetable that shares their name. They have a series of tube feet underneath their body in rows. These feet help them move across the ocean floor, which is where they feed. Modified tube feet surround their mouth for feeding. Their feeding habits are similar to sea urchins. Sea cucumbers filter organic material from the sand, expelling the sand from their anus. Their diet consists of plankton, foraminifera and bacteria.