Echinoderms

Characteristics of Echinoderms

Echinoderms are invertebrates

They have radial symmetry

They have an internal skeleton called an endoskeleton

They have a system of fluid-filled tubes called a water vascular system

THINK! – What does echinoderm mean? “Spiny Skinned”

Movement An echinoderm has an internal system of tiny fluid-filled

tubes.

Portions of these tubes can squeeze together forcing water into structures called tube feet.

The tube feet stick out from the echinoderm’s underside and when filled with water act like suction cups.

This allows the echinoderm to grip the surface of an object and move along slowly.

Video Clip - Echinoderms in a Minute! Check out how they move!

Activity: Color Coding a Sea Star

Stomach anus

Digestive glandsRingCanal

WaterVascular System

Tube feet

Use the following key Anus

Stomach

Digestive Glands

Ring Canal

Water Vascular System

Tube Feet

Spines

Spines

Sea Stars

Predators that eat mollusks, crabs, and other echinoderms

A sea star will grasp a clam with all 5 arms and force its stomach out. Digestive juices then break down the clam’s tissue so the sea star can eat.

Brittle Stars

It has long, slender arms with flexible joints.

Brittle stars do not have suction cups.

They move by waving each of their long arms in a snake-like motion against the ocean floor.

Sea Urchins

They have no arms

Movable spines cover their body

To move, bands of tube feet extend out between the spines

They eat their food (seaweed) with 5 teethlike structures protruding from their mouth

Sea Cucumbers

They look like cucumbers

Underneath their leather-like skin their bodies are soft, flexible, and muscular

They use their tube feet to crawl

It uses tentacles around its mouth to feed

Echinoderms Video Clip

Watch this clip closely to see how the tube feet work in movement!