Echinoderms
IN: 137
I. General Characteristics
1. Phylum Echinodermata- “spiny skinned”
2. Have bumpy exoskeletons covered with spiny
skin (made from calcium carbonate)
3. Radial symmetry – enables them to sense food
and predators from all sides
I.General Characteristics
4. Circulation
-Water vascular system transports oxygen,
food, & wastes thru body.
5. Respiration – filter oxygen from the water thru
tube feet or skin or gills
6. Nervous System
a. no brain, has a nerve ring
b. Eyespots – detect light & touch
7. Reproduction –
a.
b.
Sexual- separate sexes & external fertilization
Asexual- regeneration
II. Water Vascular System – provides waterpressure to
operate the tube feet, regulate locomotion, excretion, gas
exchange, & capture food
1. Madreporite – disc shaped opening in the body where
water enters & exits
2. Stone Canal-tube that attaches madreporite to ring
canal
3. Ring Canal – connects madreporite to radial canals in
rays
4. Radial Canals – in arms, connect to tube feet
5. Ampullae/Tube feet – Bulb shaped tip attached to
hollow tubes with suction cups on the end,sensitive to
touch, used to move, hold prey, & open shells
II. Types of Echinoderms
A. Starfish
1. Most have 5 rays (arms)
2. eyespots on the ends of rays
3. Regenerate arms if central
disc not damaged
4. Strict carnivores
Star fish Digestion
- stomach pushes out of mouth, over food
- enzymes digest food and stomach
absorbs it
- stomach goes back into starfish
Fig. 28-23 Anatomy of a Starfish
Eyespot
Endoskeletal plates
Anus
Stomach
Digestive glands
Ring canal
Radial canal
Madreporite
Reproductive glands
Tube foot
Sucker
B. Brittle Stars
1. Similar to a starfish
2. Filter feeders
3. Slender, flexible rays
Ventral
Dorsal
C. Sea Urchins & Sand Dollars
1. Globes or disk shaped, no rays
2. Sea urchins –wedge themselves in rock
crevices, herbivores
3. Sand dollars – flat, covered with spines
when alive, burrow in sand
Sand Dollar with Spines
dorsal
ventral
Sea Urchin with spines & without
Endoskeleton
D. Sea Cucumbers
1. Slug-like bodies with leathery skin &
tentacles around the head, tube feet to
move
2. When threatened can expel internal
organs for predators to eat – regenerates
E. Sea Lilies and Feather Stars
1. Filter feeders with long,
feathery arms
2. Oldest class of echinoderms
3. Sessile
1. Echinoderm means
a. Soft-bodied
b. Jointed leg
c. Spiny skin
2. The advantage to radial symmetry is
a. There is a distinct head region with a brain.
b. They can sense predators/prey from all directions.
c. They can move very quickly.
3. What is the bulb shaped object at the top of the tube foot called?
a. Madreporite
b. Ampullae
c. Stone canal
4. What is the structure labeled B- it is used for movement.
a. Madreporite
b. Tube foot
c. mouth
5. What do starfish do when they are disturbed?
a. Release an ink cloud to distract predator.
b. Bite predator with radula and beak.
c. Shoot spines at predator.
d. Release a ray/arm which it will regenerate later.
A.