Introduction to the characteristics and members of Phylum Echinodermata (sea stars, sea urchins, sand dollars, brittle stars).

1. Phylum
Echinodermata
(Echinoderms)
Cassandra Miller
INST 4400

2. Roots:
•Echin – means “spiny” or “prickly”
(the echidna is also known
as the “spiny anteater”)
•Derm – means “skin”
(dermatitis is inflammation of the skin,
a dermatologist is a skin doctor)

3. Echinoderms have spiny skin.

4. Examples:
•Sea urchins
•Sand dollars
•Sea cucumbers
•Sea stars* and brittle stars
*Preferred over the term “star fish”
since these creatures are NOT fish.

5. Additional Characteristics:
• Invertebrates (no backbone)
• Internal skeleton (calcium carbonate)
• Water vascular system (instead of blood)
• “Tube feet” (work like suction cups)
• Radial symmetry
• Appendages usually in multiples of 5

6. Regeneration:
• Some echinoderms have the ability to
regrow lost body parts.

7. Anatomy:
• No anterior or posterior end.
• No cephalization.
• The side containing the mouth is
called the oral surface.
• The aboral surface is directly opposite
of the oral surface.

9. Feeding:
• Sea urchins scrape algae from rocks.
• Sea lilies catch prey with tube feet.
• Sea stars can pry open clams.

10. Reproduction
• Sexual reproduction (involves 2 parents)
• External fertilization
• Sperm and egg are released into open
water, where fertilization occurs.
• Larvae swim to the ocean bottom
and develop into adults.

11. References:
• Diagram on Slide #8:
e-Learning Session. (n.d.). e-Learning Session. Retrieved from
http://www.mhhe.com/biosci/genbio/maderbiology7/student/
olc/chap35-outline.mhtml.
• All other images:
Explore and Discover. (n.d.). ARKive. Retrieved from
http://www.arkive.org.
• Information:
Miller, K., & Levine, J. (2006). Biology. Prentice Hall.