+
Means = spiny skin
Examples: Sea Stars, Sea urchins, Sea cucumbers,
Sand dollars, Sea Biscuits
Sea stars
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Sun star
Basket Star
Brittle Star
Crown of Thorns
picture of Patrick here
Sea stars
Sea Urchins
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Sand dollars
Sand dollars
Sea Biscuit
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Sea Cucumbers
1. Body Structure
A.
B.
Eucoelomate (true coelom w/ peritoneum)
Similarities to Chordates
1. Deuterostome Embryonic development (mouth
develops second) *
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*(NOTE: all animals covered before echinos. are
protostomes i.e. mouth develops first)
2. Endoskeleton
a. thin layer of skin on top
b. made of ossicles (hard bony plates) &
spines
c. f(x) = support, protect
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C.
Water vascular system
1.
Series of connected canals filled with water
2.
Water flow pattern:
madreporite (water intake) ►stone canal ►ring
canal ►radial canal ►lateral canal ►ampullae
& tube feet
2.
Level of Organization –
Organ system
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3.
Symmetry
Adults - Radial
(Sea stars mostly pentaradial)
Free swimming Larvae – bilateral
4.
Habitat
Marine
5.
Feeding
a. Complete digestive tract
(most complete so far ……..)
b. Two Stomachs + pyloric caecum
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c. Feeding Patterns
i. Carnivores – sea stars
ii. Scavengers – sea cucumbers
iii. Herbivores – sea urchins
iv. Filter feeders – brittle stars
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d. Hydraulic feeding : sea star eats bivalve
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o
o
o
o
o
Tube feet inserted between shells
Bivalve adductor muscles tire, it opens
Sea star everts stomach into bivalve
Enzymes released to digest prey
Stomach absorbs dissolved bivalve
Sea star retracts stomach
★ No dorsal, ventral, anterior or posterior
Mouth & Tube feet = oral side
Anus (anal pore) & madreporite = aboral side
6. Respiration
★ diffusion across skin gills, + water vascular system
7. Circulatory System
WVS
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8. Excretion
WVS + diffusion across skin gills
9. Response
ƒ No head, no cephalization
ƒ Central ring of nerves around mouth
ƒ Nerve branches in each arm
10. Locomotion – WVS
Process = ★water into ampullae,
pushes tube feet down
★water out of ampullae pulls
tube feet up
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11. Reproduction
ƒ Most dioecious
ƒ Fertilization external
ƒ Regeneration – one arm & part of central disk
makes a new sea star
(A problem for bivalve farmers!)
12. Ecological Roles
ƒ Predators
ƒ Coral eaters – crown of thorns sea star
ƒ Food – urchin eggs (sushi), sea cucumbers
ƒ Medical research
– regeneration studies
– embryology (sea star eggs are very large)
embryology similar to chordates
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1.
Class Ophiuroidea – e.g. brittle stars
a. Arms are slender & sharply set off from
central disk
b. Move quickly (may throw down an arm and flee)
(autotomy)
c. Scavengers & filter feeders
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2. Class Echinoidea – e.g. sea urchin, sand dollar,
sea biscuit
a. No arms
b. Central “shell” is fused ossicles = test
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c. Sharp (or stone) spines
3.
Class Holothuroidea e.g. sea cucumbers
a. Elongated cylindrical body
b. Reduced ossicles
c. Tube feet modified into oral tentacles for feeding,
Mucus traps food, detritus feeders
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4.
Class Asteroidea e.g. sea stars
a. Mostly predators
b. Eat plankton or bivalves
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