1. RESPIRATORY SYSTEM Dermal Branchiae
Soft Bumps on the body that absorb oxygen from the water. These are projections from the coelom and covered by a thin layer of epidermis.
So…
They take oxygen via diffusion and very simple gills.

2. Digestive System Eversion!
Some Echinoderms, like the Asteroidea (stars), can evert their stomach and begin external digestion.

3. Digestive System Long, coiled intestine (sea urchins/sea cucumber) -
Small mouth (+ evertable stomach) –

4. Nervous System
Basic Nerve Net similar to radially symmetric organisms
Oscelli –
Regeneration (like Porifera) – arms can regenerate.
If more than 1/5 of the central disk is present, sometimes a new organism can regenerate.
Sea Cucumbers (holothuroidea) – can regenerate internal organs (defense mechanism – puke up your guts!
Sea Urchins (spines, pedicellariae, and tube feet) – class Echinoidea
WHY the

5. Echinoderm Classes! Asteroidea Ophiuroidea Echinoidea
Asteroidea - Five arms (usually) (______________________), organs equally divided into the five arms.
Ambulacral Grooves lined with __________________
Predatory.
Ophiuroidea
Ophiuroidea – brittle stars; long arms; no SUCTION on tube feet; LONGER arms for better movement; organs in central disk
Echinoidea
Echinoidea – Sea Urchins
Locomotion – SPINES ARE MOVABLE!
Some spines are venomous! (like cnidarians!)
10 plates alternate between ambulacral grooves (tube feet) and spines
Aristotle’s Lantern – complex arrangement of muscles and chitinous teeth

6. Echinoderm Classes! (cont)
Holuthuroidea
Wormlike…
So… WHY are they in the phylum Echinodermata?
Maintain their pentamerism…
Imagine an urchin on its side and elongated!
The five segments are divided by microscopic endoderm protruding from the skin.
Some, however – the more advanced SC, show a transition to bilateralism.
Body plan sort of like a …

7. Echinoderm Reproduction
Diecious –
Aggregation during reproductive season – often triggered by echinodermitation
Sexual – External (similar to many) –
Brood eggs – Starfish carry in special pouches (NEW)
Asexual – fission – separate themselves or triggered by trauma