PHYLUM

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PHYLUM ECHINODERMATA
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• General Information
• Echinoderm- spiny skin
• Have water vascular system
• Do not have true circulatory, respiratory, or
  excretory system
• Pentaradial symmetry- body parts arranged in
  fives or multiples of fives around an oral
  (mouth) and aboral (anus) surface.

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• Classification
• 1. Kingdom Animalia
• 2. Phylum Echinodermata
• 3a. Class Asteroidea
• 3b. Class Echinoidea
• 3c. Class Ophiuroidea
• 3d. Class Holothuroidea
• 3e. Class Crinoidea

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• IIIa. Class Asteroidea (sea stars)
• Structure/Support
• 1. Endoskeleton-
• a. calcium carbonate plates called
  ossicles.
• b. Spines- deter predators
• 2. Pedicellaria- pinchers for protection
• for keeping aboral
• surface clean of debris.

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Oral (ventral) surface
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Aboral (dorsal) surface
Central disk
Arm/Ray
Spine
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• Water Vascular System- movement, respiration,
  circulation, some excretion
• 1. Madreporite on aboral surface.
• 2. Stone canal
• 3. Ring canal
• 4. Ring canal has Polian vesicles attached that
  allow for storage of water.
• 5. 5 radial canals, one in each ray.
• 6. Water enters hundreds of bubble-like sacs
  called the ampulla which inflate.
• 7. Muscles are stimulated which contract
  ampulla and push water down a tube to the
  suction cup-like tube foot.
• 8. The tube foot attaches to a surface creating
  movement.

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Radial canal
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• Digestion/Feeding
• 1. Mouth is on oral surface (underneath)
• 2. Use rays tube feet to grasp prey (clams)
• 3. Opens shell 0.1mm, enuf to insert cardiac
  stomach.
• 4. The pyloric caeca (digestive glands) release
  digestive enzymes that begin to dissolve prey.
• 5. As the digestive enzymes work, the clam
  muscles weaken, making it easier to open.
• 6. Partially digested food is taken to the
  pyloric stomach where it is absorbed and
  nutrients are passed to the pyloric caeca which
  transport nutrients throughout.
• 7. Wastes leave thru the aboral surface thru
  anus.
• 8. This process can take up to 8 hours
  depending on size of clam!

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(No Transcript)
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D. Respiration/circulation 1. Tube feet 2.
Dermal gills- aboral surface 3. No blood or
circulatory system 4. Have vestigial hemal
system but function is unknown.
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• Excretion
• 1. Tiedemanns bodies- (in ring canal) filter
  water of debris
• 2. Amoebocytes- collect debris bodily wastes
  excrete thru dermal gills.

• Nervous/sensory system- chemicals light
• 1. Nerve ring around mouth
• 2. Radial nerves in each arm (coordinate tube
  feet)
• 3. Photosensitive eyespots at tip of each ray

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• Reproduction
• 1. Asexual- regeneration
• a. Can take up to a year
• b. Some broken arms can regenerate entire
  body if central disk is attached

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2. Sexual- dioecious a. Gonads (ovaries-red,
testes- white) in each ray b. External
fertilization c. Gametes released thru
gonopore at base of each arm d. Release
pheromones to induce gamete release among
other starfish in area for spawning. e.
Larvae (bipinnaria) live amongst plankton
until adult organs grow
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1. Central disc
2. Arm/ray
3. Madreporite
4. Ambulacral canal
5. Endoskeletal plates
6. Ampulla
7. Coelom
8. Anus
9. Cardiac stomach
10. Pyloric stomich
11. Pyloric caecum
12. gonad

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• IIIb. Class Echinoidea- sea urchins sand
  dollars
• Globe or disc shaped
• No rays
• Movable, hollow
• spines- may be
• venomous
• 4. Skeleton of 10
• ossicle plates

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• Digestion- chewing
• mouth called aristotles
• lantern
• Eat algae, coral,
• dead animals
• 7. Water vascular system, tube feet
• 8. Habitat- rocks, sand, mud,
  shallow water

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• IIIc. Class Ophiuroidea- brittle stars
• Long narrow arms
• Habitat- rocks, coral
• Predators scavengers
• Use arms tube feet in
• sweeping motion to collect
• prey which is then transferred to the mouth.

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• IIId. Class Holothuroidea- sea cucumbers
• No rays
• Elongate body
• Circumoral tentacles
• (surround mouth)
• 4. No spines or pedicellaria
• 5. earthworms of the sea- feed on detritus
  turn over ocean soil

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6. Digestion- food trapped in net-like tentacles
which are licked clean by mouth. 7.
Evisceration- eject mass of visceral organs when
disturbed. Confuses predator.
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• IIIe. Class Crinoidea- sea lilies feather
  stars
• Usually sessile
• Have fan-like appearance
• Filter feeders