Phylum Echinodermata

1.Echinodermata = “spiny skin” 2.Examples: Sea Star, Sea Urchin, Sea Cucumber, and sand dollars. A. Radial symmetry- body parts repeat around the center of the body. 1. No front or back 2. Do have a top (dorsal) and bottom (ventral). B. Internal skeleton made of stiff plates of calcium carbonate, called ossicles, which are found on the skin of the echinoderm. C. Network of tubes & appendages D. Bipinnaria – Larvae of echinoderms

2. Water vascular system A. Network of fluid filled canals that transport water throughout the echinoderms boy creating a powerful suction for movement, opening up mollusk and gripping surfaces. B. Connected to tube feet C. Used for: 1. feeding 2. movement 3. respiration 4. excretion

D. Madreporite – small pores on the dorsal surface where water enters. It is attached to the stone canal, that is attached to the ring canal. E. Stone Canal – short tube attached the madreporite to the ring canal..

F. Ring canal – ring in the center of the sea stars body that attaches to the radial canals. G. Radial Canal – extends from the ring canal to the end of each arm which carries water to hundreds of tube feet.

F. Tube Feet – end of the radial canal. Much like a suction cup that has a sucker on the end and muscles, With water, suckers and muscles, a hydraulic system is created, creating enormous force for walking and opening clams. G. Ampulla – a bulblike sac found on each end of a tube foot where water is forced in and out.

TUBE FEET

Starfish eating muscle

3. Feeding A. Oral side is where the mouth is located. 1). There are many methods of feeding, we will concentrate on the sea star only. a. The sea star wraps it’s arms around a mollusk, opens it’s shell slightly using it’s enormous force from it’s water vascular system.

b. Once slightly opened, the stomach of the seastar inverts and drops down into the soft body parts of the mollusk breaking down and digesting it’s soft body parts. (the stomach is still attached to the sea star). c. When finished it will pull it’s stomach back into it’s central cavity.

4. Nervous system A. No brain but has nerve cells. (nerve ring) and radial nerves. B. Sensory cells – taste and smell. C. Eyespots – detect light. D. Statocysts – which way is up.

9. Classes A. Asteroidea 1. ex. Sea stars 2. 5 or more arms a. with tube feet 3. carnivores

Crown of thorns sea star Unlike most other sea stars that have five arms, the crown-of-thorns has 12 to 19 arms. This star can grow to 20 inches (50 cm) in diameter. It is the only sea star that is venomous, and devourers coral reefs while it moves along them. They are extrememly destructive, and are a huge problem for marine life.

4. Ability to regenerate an arm as long as some or part of the central cavity is present.

B. Ophiuroidea 1. ex. Brittle stars, basket stars 2. long thin, flexible arms 3. nocturnal

Sea Stars

C. Echinoidea 1. ex. Sand dollars and sea urchins 2. nocturnal

D. Holothuriodea 1. ex. Sea cucumbers 2. detritus feeders

E. Crinoidea 1. ex. Sea lilies 2. most ancient members of the phylum