Zoology
Phylum Echinodermata
I. Intro to Echinoderms
A. Name means  “sharp spines”
B. Radial symmetry
1. able to cut in half
equally
2. Usually 5 segments
-can be more
C. Regeneration
1. Ability to grow back
D. Pedicellariae – tiny spines
E. Mainly marine
F. Bottom dwellers
II. Class Holothuroidea
A. Facts
1. Common Ex:
a. Sea cucumber
2. Shaped like
vegetable
3. Deep ocean dwellers
a. Philippine Trench
(10540 m)
4. Bottom Grazers
B. Special Anatomy of Sea Cucumber
1. Mouth
a. 10-30 tentacles
2. Body
a. 5 rows of tube feet
b. Respiratory Tree (lung)
c. Some contain toxins
III. Class Crinoidea
A. Facts
1. Ex: sea lilies, feather stars
2. Body  calyx
a. Tegmen – leathery skin; contains
calcareous plates
3. Calyx + arms  crown
4. Mostly sessile
5. Separate sexes (males and females)
6. Tentacles  some poisonous
IV. Class Asteroidea
A. Facts
1. Ex: sea stars + starfish
2. found along shorelines + rocky
areas
3. Brightly colored
4. Found world wide
B. External Anatomy (Ventral Side)
1. Central Disc – circular center of
starfish
2. Arms – usually 5
3. Mouth – ventral side – central
disc
4. Ambulacral Groove – runs
lengthwise of arm toward the mouth
5. Tube Feet – found inside
ambulacral groove
6. Spines – cover starfish
1.
Central Disc
3. Mouth
2. Ambulacral
Groove
6. Tube Feet
4 + 5. Arm/Spines
C. External Anatomy (Dorsal Side)
1. Madreporite – Water intake valve
2. Anus – removes waste
-inconspicuous
3. Pedicellarie – tiny jaws around base of
spine
-used to keep surface free
-protection
-aid in catching food
4. Eyespot
-senses motion (black/white)
-found at end of arm
Madreporite
D. Internal Anatomy
1. Canals (Locomotion) – connected
to madreporite
a. Stone Canal – transfers water
from madreporite to ring canal
b. Ring Canal – transfers water to
radial canal
c. Radial Canal – transfers water to
lateral canal
d. Lateral Canal – transfers water
to tube feet
e. Ampulla – muscular sac that
pushes water out causing
locomotion
Madreporite
Stone Canal
Tube Feet
/Ampulla
Ring Canal
Radial Canal
Lateral Canal
2. Digestive System
a. Stomach
-Cardiac – ventral
*can be everted (pushed out)
-Pyloric – dorsal
*completes digestion
b. Intestine…anus
c. Feed on…
-clams, oysters, mussels, fish
*How do they get inside of a clam?*
3. Nervous System
a. Nerve Plexus – acts as brain
b. Nerve ring – runs around the
central disc
c. Radial nerve – runs to each
arm
d. Sensitive to touch, light,
chemicals, and temp
4. Reproductive System
a. Separate Sexes
b. External fertilization