Bi 212: Lecture 6 Phylum Echinodermata. Phylum Echinodermata: Spiny-skinned.
Phylum Echinodermata -...
Transcript of Phylum Echinodermata -...
Echinoderm Characteristics=spiny /hedgehog skinMarine or brackishPentamerous symmetry= 1. 5-pt symmetry o calciumcarbonate 2. balanceEndoskeleton = mesodermSize moderate to largeMost free movingDeuterostome (primitive)Coelomocytes
Echinoderm BauplanNo definitive headOral versus aboral
1. SkeletonDermalPlates/ossicles that vary in shape:
a) massive/linked b) hinged/pliable c) sculpted/individual
Ambulacra/interambulacraArising features: a) spines
b) pedicellariae
Echinoderm BauplanSpinesDefense, may contain toxins
PedicellariaeDefense, cleaning
2. CoelomEnterocoelic, general, hemocoel,WVS
Schematic and photographs of echinoderm tube feet
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1. Ampulla 4. Tube foot2. Lateral canal 5. Sucker3. Body wall
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3. Water Vascular System
Feeding and Digestion1. Suspension FeedersCrinoids =Pinnules & ciliary mucous
Holothurians = SclerodactylaDendritic/palpate tentacles
AsteroidsSupplemental to diet only
OphiuroidsMucous net or extension of arms
Feeding and Digestion2. Deposit FeedersHolothurians = LeptosynaptaTentacles sweep surfaces
3. CarnivoresAsteroidsTubefeet and stomach
OphiuroidsCoil arms around foodOften capture prey in groupshttp://www.youtube.com/watch?v=xwWsow4gsfo
4. Grazers = Echinoids
5. DOM = Concentricycloids
Excretion/Circulation/RespirationNo specialized organCoelomocytes= phagocytize particlesAccessory structures:papulae, podia, bursa,respiratory tree
No closed circulationCoelom, WVS, Hemalsystem
Podia, gills, papulaeSpecialized structures:Respiratory tree (H)Bursa (O)
Locomotion and Nervous SystemPodia = tubefeetSmooth muscles
Non-centralized NS3 nervous networks:Ectopleural - circumoral,sensoryHyponeural - deep oral,motor function, motor fibers& gangliaEntoneural - aboral,reduced in most classes,absent in holothuroids,important in crinoids
Sense Organs1. PhotoreceptorsTubefeetEyespots at tip of armsCup ocelli
2. ChemoreceptorsBuccal tentaclesOral tubefeet
3. TouchReceptors
Reproduction/ Development
Most dieciousVariable number of gonads:Echinoids (5), asteroids (10),holothurians (1)Deuterostome cleavage
Complex metamorphosis= bilateral -> pentamerousSome with direct development =large yolky eggs
= sea lilies (flower likeappearance)
Most primitive1. StalkedPermanently attachedCup-shaped calyx withextending armsFlexible stalk2. UnstalkedComatulidsCirri, not stalk
Class Crinoidea
"snake-tail form” = brittlestars, basket starslargest and most successfularms break off easily =regenerationmobile, writhing, serpent-likemotionmouth = five moveable platesteeth = modified spinessac-like stomach in the centraldisc bursae = brood chamber,gas exchange
Class Ophiuroidea
Sea stars or starfishflattened and flexible bodyvarying number (often 5) armsor raysnon distinct central discoral surface faces thesubstrate"top side" = aboral surface =anus
Class Asteroidea
Schematic and photograph of the dyeinjected sea star watervascular system
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1. Madreporite 4. Radial canal2. Stone canal 5. Ampullae 3. Ring canal 6. Tube feet
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Schematic and slide of a cross sectionthrough a sea star arm
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1. Coelom 4. Pyloric cecum 8. Radial nerve2. Dermal ossicle 5. Spine 9. Tube foot3. Dermal branchia 6. Radial canal 10. Sucker
7. Pedicellaria
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Schematic and photo of thedigestive system of Asterias rubens(aboral surface removed).
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1. Anus2. Pyloric stomach3. Cardiac stomach (beneath pyloric stomach)4. Pyloric caeca (digestive glands)
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Close-up of pyloric and cardiac stomachof Asterias rubens
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1. Pyloric stomach 3. Connection between pyloric2. Cardiac stomach stomach and pyloric glands
Schematic and photo of thereproductive system of Asterias
(stomachs and pyloric ceca removed)
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1. Paired gonads2. Ambulacral groove
Bipinnaria Brachiolaria
1. Ciliated bands usedfor feeding andlocomotion
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2. Adhesive arms3. Ciliated arms
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Photomicrographs of starfish larvalstages
Class Echinoidea= sea urchins, heart urchins,sand dollars
Globular, ovalSuckered podia0.5-38 cm body size
Close-up of urchin skin
Strongylocentrotusdroebachiensis, thegreen sea urchin
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31. Spines2. Pedicellariae3. Tube feet
Mouth = centrally located oral (flattened) sideFive teeth protrude, chewing apparatus = Aristotle’sLantern. consists of calcareous plates and muscles
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1. Teeth2. Lips3. Gills4. Spines
soft-bodiedtiny ossicles embedded inleatheryorally-aborally elongatedcyclindrical bodytentacles surrounding themouth = modified tube feetinternal, highly branchedrespiratory trees attachedto the cloacahttp://www.youtube.com/watch?v=lKWSLg5PDiU
Class Holothuroidea