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EchinodermsEchinodermsOdyssey ExpeditionsOdyssey Expeditions

Jason Buchheim

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IntroductionIntroduction

• Entirely marine• Typically bottom

dwellers• Generally posses

pentamerous radial symmetry at some point in life cycle (most can be divided into five parts around a central axis)

• Internal skeleton composed of calcareous ossicles (small plates)

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Introduction

• Sexes are generally separate

• External fertilization• Planktonic development• Many have water

vascular system (hydraulic system) for food collection and locomotion.– Motion accomplished by

transmitting water pressure.

Water vascular system in blue

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ClassesClasses

• Class Asteroidea

• Class Ophiuroidea

• Class Echinoidea

• Class Holothuroidea

• Class Crinoidea

• Class Concentricycloidea

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Class AsteroideaClass Asteroidea

• Sea stars• 1,800 species• Typically have five

arms• Regeneration

capabilities (in some a new animal is formed)

• Mouth on bottom (centrally located)

• Anus on top

NOAA

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Class AsteroideaClass Asteroidea

• Carnivores, detritivores, opportunists, mud swallowers

• Some can invert stomachs out mouth to surround prey – Bivalve predators slide

stomach between valves and feed on the organism while outside the body

• Organs distributed in arms

Organs in arms

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Class AsteroideaClass Asteroidea

• Two to four rows of podia (tube feet) extend down each arm from the mouth– Used for prey capture and locomotion

• Podia extended by hydraulic pressure– Pressure generated by contraction of

bulblike ampulla

• In many, suckers are found on podia

• Arms can twist and bend allowing locomotion over varied terrain

Podia

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Class OphiuroideaClass Ophiuroidea

• Brittle and Basket Stars• Largest class (2,000 species)• Mouth is centrally located on

the underside of body• Highly mobile• Long thin arms• Organs in central disk not

arms• Podia typically not

responsible for locomotion• Use arms to push and pull

themselves along NOAA

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Class OphiuroideaClass Ophiuroidea

• Two distinct orders

• Order Ophiurae– Brittle Stars

• Order Euryalae– Basket Stars

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Order OphiuraeOrder Ophiurae

• Five arms generally heavily spined

• Calcareous plates (arm shields) on arm tops allow only lateral movement

• Arms break off easily• Generally hide in crevices

and under rocks during the day

• At night move into open to feed

• Feed on detritus and small animals

NOAA

NOAA

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Order EuryalaeOrder Euryalae

• Have five arms that continually divide into smaller branches

• Lack arm shields which enables full movement

• During day can be found curled into a ball clinging to gorgonians

• At night they stretch out their arms to filter out plankton that drifts over the reef

• Small spines and tube feet move food to mouth Jason Buchheim

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Class EchinoideaClass Echinoidea

• Sea urchins, sand dollars and heart urchins

• 1,000 species• Moveable spins cover

theses animals• No arms• Circular or oval • Globular or flattened• Some display secondary

bilateral symmetryJason Buchheim

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Class EchinoideaClass Echinoidea

• Ossicles are fused to create a solid structure called a test

• Two basic groups:– Regular Urchins (sea urchins)– Irregular Urchins (heart urchins, sand dollars,

sea biscuit)

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Regular Urchins

• Sea Urchins• Generally globular in

shape • Covered with long

moveable spines (some long and pointed some short and stubby)

• Anus on topJason Buchheim

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Regular UrchinsRegular Urchins

• Mouth centrally located on underside

• Scrape algae with their unique five teeth arrangement call Aristotle’s Lantern

• Important to the reef because of the algae control they provide.

Mouth

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Irregular UrchinsIrregular Urchins

• Heart urchins, sand dollars, and sea biscuits

• Evolved to specialize in burrowing

• Small moveable spines cover the body and are used for burrowing

• Two orders:– Order Spatangoida (heart

urchins)– Order Clypeasteroida (sand

dollars and sea biscuits)

USGS

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Order SpatangoidaOrder Spatangoida

• Heart urchins• Oval dome-like in shape• Feed on organic

materials in the substrate

• Mouth (lacks Aristotle’s Lantern) in front and anus in back

• Typically found buried in the substrate

• May be seen at night

NOAA

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Order ClypeasteroidaOrder Clypeasteroida

• Sand dollars and sea biscuits

• Flattened disk shape • Mouth centrally

located on the underside with Aristotle’s Lantern

• Anus found towards rear

• Live buried in the sand

USGS

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Class HolothuroideaClass Holothuroidea

• Sea cucumbers• Tubular in shape• 1,000 species• Mouth in front and anus in

rear• Most feed on organics

found in the sand that they consume

• Some filter feed

Odyssey Expeditions

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Class HolothuroideaClass Holothuroidea

• Tube feet cover the bottom surface

• If threatened can expel most of their guts

• Can regenerate these guts

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Class CrinoideaClass Crinoidea

• Feather stars (Crinoids)• Oldest echinoderms (living

fossils)• 600 species• Five arms that fork to give

ten or more• Look like feathers• Arms are sticky and sweep

water for food particles• Can regenerate arms

Jason Buchheim

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Class CrinoideaClass Crinoidea• Can move short

distances

• Some swim with arms

• Others walk on legs called cirri

Jason Buchheim

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ResourcesResources

• Barnes, Robert D. and Edward Ruppert. Invertebrate Zoology: Sixth Edition. Fort Worth: Saunders College Publishing, 1994

• Humann, Paul and Ned Deloach. Reef Creature Identification: Florida Caribbean Bahamas. Florida: New World Publications, Inc., 2003

• Kinsella, John, Drew Richardson and Bob Wohlers. Life on an Ocean Planet. California: Current Publishing Corp., 2006

• Taylor, Walter K. and Robert L. Wallace. Invertebrate Zoology: A Laboratory Manual Sixth Edition. New Jersey: Prentice Hall, 2002