1. Phylum Echinodermata “spiny” “skin”

3. Major Classes of Echinoderms
ECHINOIDEA: Includes the sea urchins and sand dollars
ASTEROIDEA: includes the sea stars

4. OPHIUROIDEA: includes the brittle stars
(below: a fossilized brittle star)
HOLOTHUROIDEA: includes the sea cucumbers

5. CRINOIDEA: includes the sea lilies and feather stars

6. Unifying Characteristics
Coelomate and radially symmetrical
Body is usually 5 rayed (pentaradial)
Have a calcareous skeleton
Composed of calcium carbonate
Possess a water vascular system used for gas exchange, feeding and locomotion

7. Unifying Characteristics
Complete digestive system
Open/reduced circulatory system (no heart) with a central ring and vessels
Simple radial nervous system (no brain)

8. Unifying Characteristics
Reproductive system consists of gonads which take up a significant amount of space in the body cavity
Sexual reproduction with fertilization outside body (most)
Have ciliated, free-swimming larvae
Abundant on most sea coasts especially on rocky shores

9. Echinoderm Larvae

10. Defense systems of Echinoderms
Spines are observed on many echinoderms and can be soft or hard and sharp. Their presence deters predators
Pedicellariae are pincer-like structures that protrude from the body surface between the spines
They keep the body surface clear of encrusting organisms
Echinoderms also camouflage with their natural color into their environment

11. Ecological Roles of Echinoderms
Starfish and brittle stars prevent the growth of algal mats on coral reefs
Part of the food chain, larvae produce food for other creatures
The death of echinoderms often is followed by an increase in seaweed growth and destruction of reefs

12. Ecological Roles
Sea urchin grazing reduces the rate of colonization of bare rock
Burrowing of sand dollars and sea cucumbers depletes the sea floor of nutrients and encourages deeper penetration which increases levels of oxygen and ecological tiering
Sea urchins bore into rocks releasing nutrients
Sea cucumbers provide habitats for parasites
Echinoderms feed on dead and decaying organisms

13. Cool Echinoderm Facts
Sea stars are capable of regeneration of body parts as long as part of the central disk remains
The gonads of Sea urchins and cucumbers are considered a delicacy in SE Asia
Sea cucumbers will eviscerate (shoot out parts of their internal organs) when they sense extreme danger (the organs then re-grow)
Sea urchins can replace spines that are damaged or lost