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Echinoderms

Echinoderms. Maria Alva and Maria V illasmil Period # 2. Characteristics :. Echinoderms are characterized by radial symmetry and amount of arms. They have no heart, brains, or eyes. However some have some light sensitive spots called eyespots.

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Echinoderms

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  1. Echinoderms Maria Alva and Maria Villasmil Period # 2

  2. Characteristics : • Echinoderms are characterized by radial symmetry and amount of arms. • They have no heart, brains, or eyes. However some have some light sensitive spots called eyespots. • Their mouth is located on the dorsal side (bottom) and the anus on top (ventral). (Except on feather stars, sea cucumbers and some urchins) • “Echinoderms have tentacle-like structures called tube feet with suction pads situated at their extremities. These tube feet are controlled by a vascular system. • This system supplies water through canals of small muscular tubes to the tube feet. As the tube feet press against a moving object, water is withdrawn from them, resulting in a suction effect. When water returns to the canals, suction is released. The resulting locomotion is generally very slow.”

  3. Environment: • Echinoderms live in marine environments. “They occur in various habitats from the intertidal zone down to the bottom of the deep sea trenches and from sand to rubble to coral reefs and in cold and tropical seas.”

  4. Consumption: • Some Echinoderms are carnivorous; such as starfishes. • Others are detritus foragers -feed on the debris on rocks- like sea cucumbers. • Some others are planktonic feeders (for example basket stars).

  5. reproduction • Reproduction: Is carried out by releasing the eggs and sperm into the water. • Most species produce pelagicplanktonic larvae which feed on plankton. These larvae are bilaterally symmetrical, unlike their parents. • Echinoderms can regenerate arms, limbs, spines, and intestines. • “Some brittle stars and sea stars can reproduce asexually by breaking a ray or arm or by deliberately splitting the body in half. Each half then becomes a whole new animal.”

  6. Classes: • 1) Class: Asteroidea--Starfish or Sea Stars (Six-rayed Starfish)— *Sea stars have fairly developed senses of smell, touch, and taste. *Can Respond to light (eyespots) *They normally eat small prey whole, but they have to “extrude their stomachs to digest larger prey outside their bodies. “ *Sometimes, sea stars will use their tube feet to help pry open bivalves, and then they will slip their stomachs in between the two shells. • (2) Class: Ophiuroidea--Brittle Stars*Found in all oceans (but mainly in the tropics). *The group includes about 2000 species, with different colors. *Eat decaying matter and microscopic organisms. • (3) Class: Echinoidea--(*) Sea Urchins *They move by using short to long, movable spines. *“Between their spines are small, pincerlike organs called pedicellariae which they use to clean and defend themselves. “ *The pedicellariae also contain a powerful toxin. • (4) Class: Crinoidea--Feather Stars*Will swim if disturbed. • (5) Class: Holothuroidea--Sea Cucumbers

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