Echinoderms what do they eat

Filter feeders , like brittle stars, absorb nutrients in marine water. Suspension feeders use their arms to capture floating food particles. Grazers , like sea urchins, feed on both plants and animals, making them omnivores.

Grazers feed mostly on seaweeds and algae living in coral and decomposed fish matter. Deposit feeders , like sea cucumbers, live on the ocean floor and eat tiny matter found on the top layer of soil. Some echinoderms are predatory , like sea stars, and actively hunt their prey. This is called partial external digestion and is unique to the sea star. What Are My Predators? Sea otters, arctic fox, sharks, bony fish, and spider crabs prey on echinoderms. Their lifestyles vary greatly depending on which group of Echinoderms a species belongs to.

Sea stars are generally predators or detritivores, eating decomposing animal and plant material. Crinoids and some brittle stars are passive filter-feeders, absorbing suspended particles from passing water; sea urchins are grazing herbivores and sea cucumbers deposit feeders removing food particles from sand or mud.

Crabs, sharks, eels and other fish, sea birds, octopuses and larger starfish are predators of Echinoderms. Echinoderms use their skeltons, spines, toxins, and the discharge of sticky entangling threads by sea cucumbers as defence mechanisms against predators. Thanks to I would sincerely like to thank the many members of the Flickr community who have given me permission to use their wonderful images for this unit.

Their contributions really make this unit come alive! Next: Sea stars Echinoderms Introduction. The different groups of echinoderms. Digestive System Echinoderms have a simple digestive system with a mouth, stomachs, intestineand anus. Nervous System and Senses Echinoderms do not have brains, they have nerves running from the mouth into each arm or along the body. Examples of Echinoderms. Circulatory System Echinoderms have a network of fluid-filled canals that function in gas exchange, feeding and in movement.

Respiratory System Echinoderms have a a poorly developed respiratory system. Tube feet. Sea stars have remarkable powers of regeneration. Many species can regenerate a whole arm that breaks off Fig. These regenerated pieces are called comets Fig.

Sea stars are voracious predators, crawling over the ocean bottom in search of prey. They feed not only on sessile molluscs such as clams, oysters, and mussels, but also on dead organisms lying on the bottom. The crown-of-thorns starfish Acanthaster planci consumes so much live coral that it is considered a significant threat to coral reefs in the tropical Indo-Pacific region. The mouth of a sea star opens into the stomach in the central disc.

The anus is on the upper surface Fig. Most sea stars are carnivores. Although a sea star has no teeth, it can eat coral polyps and molluscs by pushing its stomach out of the body, spreading it over its prey, and digesting it. To eat a clam, the sea star grasps the bivalve in its arms, attaches its suction cups to both shells, pulls steadily until the shells open slightly, and extends its stomach into the clam.

In this way it preys on clams whose shells are open as little as 0. After the sea star digests and absorbs the tissue of its prey, it sucks its stomach back into its own body. Brittle stars are the most abundant echinoderms. About 2, species inhabit the ocean floor worldwide, from the shoreline to great depths. In some areas, clusters of millions of brittle stars thickly carpet the bottom.

This group is active only at night, hiding under rocks and in crevices during the day. Brittle stars have long, flexible arms attached to a small central disc Figs. Skeletal ossicles form a series of scaly plates along the arms, and a series of large cylindrical ossicles runs through the center of each arm. These ossicles look somewhat like the row of vertebrae in a fish skeleton.

They are connected by muscles that contract, producing a snakelike action. This characteristic movement gives the class its name, Ophiuroidea from the Greek root words ophio - meaning snake and - uroid meaning tail-like. It is also the basis for another common name, serpent star. Moving brittle stars can appear to be dangerous, but they are harmless to humans. A row of movable spines projecting from the sides of the arms helps the animal move along the bottom.

Although the arms appear to be radial, one or two of them usually lead in pulling the animal along while the others trail Fig. These animals got the name brittle star because an arm often breaks off if they are captured. The broken arm is left wiggling as the rest of the brittle star scoots away.

The missing arm regenerates quickly. Most brittle stars are small with a central disc diameter less than three centimeters, but the arms may be up to ten centimeters long. Brittle stars feed on detritus—small particles of food—on the bottom. Some brittle stars curve their arms up to collect food particles suspended in the water.

The tube feet, shaped like pointed tentacles, are used mainly for collecting food. One tube foot passes particles to another toward the mouth.

The food then passes into the stomach, where it is digested. Unlike the other echinoderms, brittle stars have no anus; they eject undigested material through the mouth. The class Holothruoidea is better known by as the sea cucumbers. Sea cucumbers are cylindrical echinoderm animals with feathery tentacles at the mouth end of their bodies. They are often mistakenly called worms. Some species resembles fat pickles a few centimeters long Fig. Others are like thin tubes over a meter long Fig.

These animals are common residents of reefs and rocky shorelines worldwide. A few species swim constantly in the water, seldom touching the bottom; they are the only members of this phylum to do so.

Some Pacific islanders collect sea cucumbers, remove their intestines, and dry the muscular body wall, making a food eaten in many countries. Unlike other groups of echinoderms, sea cucumbers have no large plates or ossicles forming a rigid skeleton. Because the spicules differ by species, they are useful in identification. Muscles in the body wall of many sea cucumbers are developed enough to aid in locomotion.

When the muscles contract, the body becomes firm and rigid. In some species the muscles are so thin that the internal organs show through the body wall. When these animals are taken from the water, the body wall collapses like thin plastic tubing. The digestive system has a mouth at one end, a digestive tube down the center, and an anus at the other end Fig. The mouth is ringed with tentacles that are modified tube feet. Some species use their tentacles to take in sediment particles rich in plant and animal matter Fig.

Other sea cucumbers extend their tentacles to snatch passing food particles detritus and plankton Fig. This behavior makes them look somewhat like sea anemones, and so this class is named Holothuroidea from the Greek root word holothuroid meaning like a polyp. The digestive tube has a stomach and a long, thin, coiled intestine where food is digested. Indigestible sand and other particles are expelled through the anus. Much the same happens in earthworms, which literally eat their way through soil.

The respiratory system of sea cucumbers is unusual in its arrangement. They breathe through an internal structure called a respiratory tree , which is attached to the intestine Fig.

Seawater taken in through the anus fills this branching structure, where body fluids absorb the oxygen. Because the anus is often open during this respiratory process, other organisms—small crabs and fish among them—sometimes enter and take up residence in the lower digestive tract and respiratory tree Fig.

A few species of sea cucumbers have a set of tooth-like projections around the anus to ward off invaders. Some sea cucumbers have another bizarre way of protecting themselves. Cuverian tubules are branches of sea cucumber respiratory trees in the form of long, slender threads Fig. These Cuverian tubules contain both sticky and toxic chemicals.