2. Echinoderms
• a slow-moving or sessile marine
deuterostome with a water vascular system
and, in adults, radial anatomy
• 6000 species, all marine
3. Living Echinoderms are divided
into six classes...
• 1- Asteroidea: sea stars aka starfish
• - star shaped body with multiple arms; mouth
directed to substrate
4. Classes, continued
• 2- Ophiuroidea: brittle stars
• - Distinct central disk; long, flexible arms;
tube feet lack suckers
5. Classes, continued
•3 - Echinoidea: sea urchins and sand dollars
• - Roughly spherical or disk-shaped; no arms;
five rows of tube feet enable slow movement;
mouth ringed by complex, jaw-like structure
6. Classes, continued
• 4 - Crinoidea: sea lilies and feather stars
• - Feathered arms surrounding upward-pointing
mouth
7. Classes, continued
•5 - Holothuroidea: sea cucumbers
• - Cucumber-shaped body; five rows of tube feet;
additional tube feet modified
8. Classes, continued
•6 - Concentricycloidea : sea daises
• - Disk-shaped body ringed with small spines;
incomplete digestive system; live on submerged
wood
9. Physical Description
• adult forms have radial symmetry
• larvae are bilateral
• varied skeletal and muscular arrangement
• water vascular system
• Respiration
• gills on the skin
10. Reproduction
• there are 2 sexes
except:
o asteroids&echinoids -
multiple gonads in arms
o crinoids - lack distinct
gonads
o holothurians - single
gonad
• gametes are released
into water
11. Characteristics
•Behavior
• most are immobile
• water vascular system originally for food
collection but now evolved for locomotion
• Communication
• non-central nervous system: movement is
sense from all sides
• Development
• deuterostomes: anus forms first, then mouth
12. Food
• Crinoidea
• sit with arms out and collect passing food
• Asteroidea
• predators or scavengers; everts stomach
and secretes digestive enzymes on prey;
suspenson feeders, too
• Ophuroidea
• imcomplete digestive system; predators,
deposit feeders, and scavengers
13. Food, cont.
• Echinoidea
• suspension feeders,
herbivores, detritivores,
predators
• Holothuroidea
• suspension or deposit
feeders; use digestive
organs in response to threat
• group of hard plates that
retract and grasp like teeth
14. Execretion
• amoeboid cells carry wastes out of the body
15. Predation
• most vulnerable in larval stage
• asteriods:
o anti-predator adaptation
• holothurians
o discharge, sticky tubules called Cuvierian tubules
17. Starfish
• Digestion and Excretion:
• - mouth is located on underside of the body
• - Has a digestive tract
• Reproduction:
• - each arm contains two gonads and releases
gametes into surrounding water
• - fragmentation
• Symmetry:
• - pentamerous symmetry
18.
19. Feather Stars
• Class: Crinoidea
•Circulatory System:
• - Water-vascular system and tube feet
• - do not use tube feet for locomotion
• Nervous System:
•- Has small sensory cells throughout their skin
•- Central nervous ring around the mouth,
arms, and base
20. Feather Stars
• Digestion and Excretion:
• - Captures particles or plankton
• - Has a digestive tract
• Reproduction:
• - releases sperm and egg into surrounding
water
• Symmetry:
• - radial symmetry
21.
22. Sea Urchin
• Class: Echinoidea
• Circulatory System:
• - Water-vascular system and tube feet
• Nervous System:
• - no true brain
• - Central nervous ring around the mouth
23. Sea Urchin
• Digestion and Excretion:
•- Has a mouth containing teeth, jaw, and
tongue like structure
• - Has a digestive tract
• Reproduction:
• - releases sperm and egg into surrounding
water
• Symmetry:
• - radial symmetry
