Chapter 7Chapter 7

Phylum EchinodermataPhylum Echinodermata

Phylum EchinodermataPhylum Echinodermata• Characteristics:Characteristics:

– Name means “spiny skin" Name means “spiny skin" – EndoskeletonEndoskeleton– Water vascular system with tube feet important in Water vascular system with tube feet important in

feedingfeeding and locomotionand locomotion– Skin gills for respiration.Skin gills for respiration.– Radial symmetry in adults- larvae are bilaterally Radial symmetry in adults- larvae are bilaterally

symmetricalsymmetrical– Nervous system is decentralized- Nervous system is decentralized-

•No brain - this allows No brain - this allows anyany portion of the body to portion of the body to leadlead

– Can regenerate lost body partsCan regenerate lost body parts– All 7000 species exclusively marineAll 7000 species exclusively marine

Class AsteroideaClass Asteroidea•Sea starsSea stars

– Move with tube feetMove with tube feet– Have a central disc in center of body surrounded Have a central disc in center of body surrounded

by five arms (or multiples of 5 arms)by five arms (or multiples of 5 arms)– Internal organs extend through the entire body, Internal organs extend through the entire body,

including the armsincluding the arms– Calcium carbonate plates are loosely embedded Calcium carbonate plates are loosely embedded

in spiny skin making them slightly flexible in spiny skin making them slightly flexible – Carnivores that normally Carnivores that normally consume shellfish and

coral

Diagram of Sea StarDiagram of Sea Star

Class OphiuroideaClass Ophiuroidea• Brittle starsBrittle stars

– Like sea stars, they have a central Like sea stars, they have a central disc surrounded by armsdisc surrounded by arms

– Five arms seen in brittle stars are Five arms seen in brittle stars are thin and covered in numerous spinesthin and covered in numerous spines

– Internal organs are restricted to the Internal organs are restricted to the central disccentral disc

– The tube feet present in brittle stars The tube feet present in brittle stars are without suckers and used for are without suckers and used for feeding on detritus and small feeding on detritus and small animalsanimals

Class EchinoideaClass Echinoidea• Sea Urchins, Sea Biscuits, Sand DollarsSea Urchins, Sea Biscuits, Sand Dollars

– Elongated, movable spines much longer than Elongated, movable spines much longer than those sea in other groupsthose sea in other groups

– Rigid plates are fused into a solid structure called Rigid plates are fused into a solid structure called a a ““testtest””

– Move with tube feetMove with tube feet– Mouth on the bottom, anus on top of bodyMouth on the bottom, anus on top of body– Biting mouth for grazing – Aristotle’s lantern is the Biting mouth for grazing – Aristotle’s lantern is the

feeding structure of muscles and mouthpiecesfeeding structure of muscles and mouthpieces– Feed on detritus, encrusting organisms, algae or Feed on detritus, encrusting organisms, algae or

anything else they can scrape off surfacesanything else they can scrape off surfaces

Class EchinoideaClass Echinoidea

Class PelmatozoaClass Pelmatozoa• CrinoidsCrinoids

– feather stars and sea liliesfeather stars and sea lilies– 600 species are typically found in deep water600 species are typically found in deep water– Sea lilies live attached while feather stars are Sea lilies live attached while feather stars are

mobilemobile– 5 or more arms that branch out for suspension 5 or more arms that branch out for suspension

feeding feeding – Some use a mucous net to aid in food captureSome use a mucous net to aid in food capture

Class HolothuroideaClass Holothuroidea

• Sea cucumbersSea cucumbers– Five rows of two feet are restricted to one side, Five rows of two feet are restricted to one side,

where the animal lieswhere the animal lies– Plates found in the sea cucumbers are loosely Plates found in the sea cucumbers are loosely

embedded in the thick skinembedded in the thick skin– Deposit feeders or suspension feedersDeposit feeders or suspension feeders– Sea cucumbers have a interesting predator Sea cucumbers have a interesting predator

escape plan called evisceration, where they escape plan called evisceration, where they expel the internal organs; it is assumed this expel the internal organs; it is assumed this allows escape for the sea cucumber.allows escape for the sea cucumber.

– Since all echinoderms have regenerative Since all echinoderms have regenerative capabilities, these internal organs will grow capabilities, these internal organs will grow back.back.

Video about EchinodermsVideo about Echinoderms

• The Shape of LifeThe Shape of Life