1. By: Laura Hein, Jaeyoung Kim Period 3 Rall
ECHINODERMATA
By: Laura Hein, Jaeyoung Kim
Period 3
Rall

2. Phylum: Echinodermata
Classes:
Ophiuroidea: brittle stars
Asteroidea: Sea stars
Echinoidea:
sea urchins
sand dollars

3. Classes: cont. Crinoidea: sea lillies Holothuroidea: sea cucumbers

4. Laura Hein Body cavity (coelom)
-Echinoderms form their coeloms as outpocketings from the archenteron (embryonic gut),
-process=enterocoely.
-In most species, the coeloms are trimerous, and initially bilaterally symmetrical. -some coelom departments are similar and may reflect a common evolutionary ancestor within the phylum:
- left mesocoel gives rise to most or all of the water vascular system, and one or both somatocoels form the lining of the body cavity.
Laura Hein

5. Body Symmetry Radial (pentameral) Jaeyoung Kim
Jaeyoung Kim

6. Nervous System Decentralized nervous system
Radial nerves run under the ambulacra (legs)
Central nerve ring surrounds the gut
Eyespots that can detect light
No specialized sensory organs
and no definitive brain
The arrangement of the central nervous system of echinoderms is quite different from that in other deuterostomes.
Radial nerves run under each of the ambulacra, and contain the cell bodies of almost all
motor neurons and interneurons. A central nerve ring surrounds the gut, and is composed primarily of fiber
tracks connecting the radial nerves. No known echinoderm contains anything that could be called a brain,
although ganglia are present along the radial nerves in some echinoderms. Unlike most bilaterian phyla,
echinoderms lack any trace of cephalization, and have no specialized sense organs.
Sensory neurons are located primarily within the ectoderm of podia, and send axons to the radial nerves.
Jaeyoung Kim

7. Circulatory Structures
-A Echinoderm has water pumped through its body as part of its very simple circulation system
-no specific structures for the circulatory system
Hemal system of water pumps through the coelom.
Laura Hein

8. Digestive/Excretory System
Tubes grab onto food -> invert their stomach -> secrete/squirt juices (enzymes) that digest -> reabsorb digested food through mouth under the center -> wastes out the aboral anus
Jaeyoung Kim

9. Locomotion
Vascular system consist of a network of hydraulic canals branching into extensions called papullae (tube feet), which provides:
slow movement
feeding
and gas exchange
Tube feet uses hydraulics to create negative pressure which acts as a suction force.
Jaeyoung Kim

10. Laura Hein Skeletal type
-Biomineral matrix composed of calcium carbonate and several proteins
-calcite is composed of numerous tiny crystals lie on same crystal axis within an ossicle
-because of this, ossicles are sponge-like microstructures called stereom that is unique to that phylum
-Embryologically, echinoderm ossicles are a true endoskeleton, since they are produced by mesenchymal cells and are usually covered by epidermis
-However, they act more like an exoskeleton, lying just under the epidermis and enclosing most other tissues in a flexible but tough covering.
Laura Hein

11. Sensory Structures/Features
-rudimentary senses including:
-light sensitive eyespots
sensory tentacles (modified tube feet) at the tips of the arms
small patches of cells sensitive to chemicals or touch.
Starfish Tube Feet
Laura Hein

12. Reproductive System
Most are dioecious, with separate male and female individuals, but some are hermaphrodites.
Each arm contains two gonads, which release gametes through openings called gonoducts, located on the central body between the arms.
dioecious
Jaeyoung Kim

13. Unique Features Can regenerate lost limbs Jaeyoung Kim
Jaeyoung Kim

14. Quiz
1.Which of the following is not a sensory structure of the echinodermata
A) Light sensitive eyespots
b) Sensory tentacles (modified tube feet) at the tips of the arms
c) Small patches of cells sensitive to chemicals or touch.
d) Taste Buds
2. Which of these do not belong to the echinodermata phyla?
a) Starfish
b) Brittle Stars
c) Jelly Fish
d) Sea Cucumbers
3. What kind of circulatory system does the echinodermata possess?
a) No specific structures for the circulatory system
b) A system of capillaries running throughout the body
c) A heart with arteries, blood vessels, veins, and capillaries
d) A simple heart-like organ with no separate ventricles
4. Free Response: What are the steps to the digestive/excretory system of an echinodermata?

15. Answers
1. A
2. C
3. A
4. See slide 8.