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.

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

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

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

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

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 …

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