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

Echinoderm Taxonomy

Frank Fish 2010

= 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

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Aboral and oralview of a seastar

1. Madreporite2. Mouth3. Ambulacral

Groove

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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

Close up of pyloric caeca of Asterias

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

Sea Urchin Internal Anatomy

Photomicrographs of sea urchinlarval stage

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

Dorsal view

Ventral viewshowingmodificationinto a sole.

Sea Cucumber External Anatomy

Holothuroid Internal Anatomy

Class Concentricycloidea

= sea daisiesHighly modified armless seastarDiscovered in 1986Deep sea >1000m on woodLess than 1cm in diameterResembles jelly medusaDouble ring of water vascularsystem