Echinoderms

Echinoderms: The most common Echinoderms are the star fish.

Characteristics:

-Most echinoderms exhibit pentamerous radial symmetry. Animals with this type of symmetry can be divided into five equal parts from a central axis.

Two features are unique to echinoderms:

One is their system of Tube feet, a series of suction disks used in locomotion and getting food. Tube feet are powered by a unique system of water-pumping tubes.

The other is their endoskeleton, or internal skeleton. The endoskeleton protects and supports the organism's soft tissues. It also provides a place to which muscles can attach. The endoskeleton is made of calcium compounds that form plates just below the epidermis. A number of spiny projections extend from these plates through the epidermis. Different spines are modified for different functions in the various classes of echinoderms.

The name echinoderm means " spiny skin."

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Development:

-During development, echinoderms go through a bipinnaria larva stage. The bipinnaria is a bilaterally symmetrical. This suggests that echinoderms evolved from an ancestor with bilateral symmetry. The bipinnaria larva differs structurally from the trochophore larva of mollusks.

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Digestion:

-Most starfish are carnivores. Food is taken into the mouth, located on the starfish's lower surface. From the mouth, food goes through the esophagus to the stomach, where digestion takes place. Many starfish can push the stomach outside of their body to surround a food organism. Digestive enzymes are produced by digestive glands in each arm. Undigested wastes are eliminated through the anus on the starfish's upper surface. �

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Reproduction:

-Reproduction in starfish is usually sexual. Males and females generally shed egg and sperm cells into the water. Starfish also have remarkable powers of regeneration. If a starfish is broken into pieces, many of the pieces will regenerate. For example, a severed arm will regenerate the entire animal as long as the arm has part of the central disk attached to it. A few species of starfish reproduce asexually by shedding arms.

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Examples of some Star Fish!�

Cushion Star

� � 1.)The cushion star is a thick-bodied species of starfish with short legs. 2.)It ranges in color from brown to orange, red, and yellow. 3.)Its hard shell is covered with raised knobby spines. 4.)This starfish is grows to a diameter of 10 inches, and is found on the sandy bottoms in the Atlantic watersfrom South Carolina to Florida. 5.)Its hard shell makes it a popular species among shell collectors. �

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Sunflower Starfish

1.)The sunflower star is among the larger of the starfish species. 2.)With its 24 arms, it can reach a diameter of over 2 feet! 3.)The color of this starfish can range from purple to red, pink, brown, orange, and yellow. 4.)It is common along the Pacific coast and can be found along the rocky sea bottoms from Alaska to southern California.

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Pacific Starfish

� 1.)This brightly-colored starfish is a common species found along the western coast of the United States and Canada. 2.)It can range in color from red to orange, yellow, and purple. 3.)This starfish grows to a diameter of about 8 inches, and is found under rocks where it feeds on small sponges and algae.

�Short Spined Starfish

1.)The short spined starfish is a coldwater species found in the northern waters from the Arctic to Cape Hatteras. 2.)They can be seen in a wide range of colors from orange to red, purple, yellow, and white. Dark red varieties are sometimes known as blood stars. 3.)They can be found scavenging along the rocky sea bottom.

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Orange Starfish

1.) This colorful orange and red starfish is one of the most common species. 2.)Aquarium hobbyists find the orange starfish quit popular due to the colorful markings and docile nature. 3.)This starfish grows to about 4 inches in diameter. � 4.)It is commonly found in the Indian ocean near Indonesia where is feeds on small sponges and algae.

For More Info:

http://mbgnet.mobot.org/salt/animals/echinod.htm

http://www.kidport.com/RefLib/Science/Animals/Echinoderms.htm

Other kinds of invertebrates�

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