Download - Phylum Echinodermata

Phylum EchinodermataPhylum Echinodermata

EchinodermsEchinoderms

• Sea StarsSea Stars

• Sea UrchinsSea Urchins

• Sand DollarsSand Dollars

• Sea CucumbersSea Cucumbers


• ““Spiny SkinSpiny Skin””

• 7,000 species7,000 species

• Marine EnvironmentsMarine Environments– Shallow and deep watersShallow and deep waters

• Vary in sizeVary in size– From 1cm to 1m (3feet)From 1cm to 1m (3feet)

• Often brilliantly coloredOften brilliantly colored

EchinodermsEchinoderms• Radial SymmetryRadial Symmetry

– Like Like cnidarians and ctenophorescnidarians and ctenophores

• Lack Lack cephalizationcephalization

• Larvae are Larvae are bilaterallybilaterally symmetrical symmetrical

Sea StarSea Star Sea UrchinSea UrchinBrittle StarBrittle Star


• Echinoderms are Echinoderms are deuterostomesdeuterostomes, which , which makes them different from all of the other makes them different from all of the other invertebrates invertebrates

• Deuterostomes are coelomates whose Deuterostomes are coelomates whose 1.1. embryos have radial cleavageembryos have radial cleavage2.2. anus forms near the blastoporeanus forms near the blastopore3.3. mesoderm arises from outpockets of the mesoderm arises from outpockets of the

endodermendoderm

Echinoderms Have:Echinoderms Have:

• PentaPentaradialradial symmetry symmetry– the body parts extend from the center along five spokesthe body parts extend from the center along five spokes

• An An endoskeletonendoskeleton composed of calcium carbonate plates composed of calcium carbonate plates

• Many small, movable extensions of the water-vascular Many small, movable extensions of the water-vascular system called system called tubetube feetfeet, , which aid in which aid in – MovementMovement– FeedingFeeding– RespirationRespiration– ExcretionExcretion

Echinoderm ClassificationEchinoderm Classification

• CLASSES:CLASSES:

– CrinoideaCrinoidea ( (kri-NOID-ee-uhkri-NOID-ee-uh))– AsteroideaAsteroidea ( (AS-tuh-ROID-ee-uhAS-tuh-ROID-ee-uh))– OphiuroideaOphiuroidea ( (OH-fee-yoor-OID-ee-uhOH-fee-yoor-OID-ee-uh))– EchinoideaEchinoidea ( (EK-uh-NOID-ee-uhEK-uh-NOID-ee-uh))– HolothuroideaHolothuroidea ( (HOH-loh-thuh-ROID-ee-uhHOH-loh-thuh-ROID-ee-uh))

Class CrinoideaClass Crinoidea

• ““lily-like”lily-like”

• Examples: sea lilies, feather starsExamples: sea lilies, feather stars– Five arms extend from the body and branch to Five arms extend from the body and branch to

form many more armsform many more arms– Tube feet Tube feet gas exchange gas exchange– Cilia on arms direct food to the mouthCilia on arms direct food to the mouth– Mouth faces upMouth faces up

Class OphiuroideaClass Ophiuroidea

• ““snake-tail”snake-tail”

• Examples: basket stars and brittle starsExamples: basket stars and brittle stars– Long, narrow arms help them move quicklyLong, narrow arms help them move quickly

• Can break and regenerate easilyCan break and regenerate easily

– Live on the ocean’s floorLive on the ocean’s floor– Either rake in food with arms or trap it with Either rake in food with arms or trap it with

their tube feet or mucus between their spinestheir tube feet or mucus between their spines

Class EchinoideaClass Echinoidea

• ““spinelike,”spinelike,”

• Examples: sea urchins, sand dollarsExamples: sea urchins, sand dollars– Test –compact, rigid endoskeletonTest –compact, rigid endoskeleton– Urchins:Urchins:

• Five teeth + their muscles = Aristotle’s LanternFive teeth + their muscles = Aristotle’s Lantern• Spines can be sharp and contain venomSpines can be sharp and contain venom

– Sand dollars:Sand dollars:• Burrows into the sandBurrows into the sand• Use spines for locomotion and burrowingUse spines for locomotion and burrowing

Aristotle’s LanternAristotle’s Lantern

Class HolothuroideaClass Holothuroidea

• “water polyp”

• Examples: sea cucumbers– Soft bodies because the particles that make

up their endoskeleton are small– Use tentacles to bring food to the mouth

Sea CucumbersSea Cucumbers

• Eviscerate their gut as a means of self defense

Class AsteroideaClass Asteroidea

• “starlike”

• Examples: sea stars– Live in coastal waters around the world– Prey on oysters, clams, and other foods

humans eat

Structure and FunctionStructure and Function

• Sea stars typically have 5 arms, but in some species, there may be as many as 2424

• Two rows of tube feet run along the underside of each arm


• On sea stars and sea urchins, pedicellariaepedicellariae, or little pincers, help keep the body surface free of foreign objects, including algae and small animals that might damage its soft tissues


• Gas exchange and waste excretion take Gas exchange and waste excretion take place by diffusion through the place by diffusion through the skinskin gillsgills, ,


• Primitive nervous systemPrimitive nervous system

• No head = no brainNo head = no brain

• The nervous system consists mainly of a The nervous system consists mainly of a nervenerve ringring that circles the mouth and a that circles the mouth and a radialradial nervenerve that runs from the nerve ring that runs from the nerve ring along the length of each armalong the length of each arm

• Together, they coordinate the movements Together, they coordinate the movements of the tube feetof the tube feet


• Sea stars also have a nervenerve netnet near the body surface that controls the movements of the spines, pedicellariae, and skin gills.

• Eyespot on each arm responds to light

• Tube feet respond to touch and chemicals

Water-Vascular SystemWater-Vascular SystemMadreporiteMadreporite-water enters through this small pore

Stone canalStone canal -connects madreporite and ring canal

Radial canalRadial canal -extends down each arm and carries water to hundreds of hollow tube feet---has valves to ensure one way flow

Feeding and DigestionFeeding and Digestion

• Most echinoderms are carnivores.• A sea star captures a clam and attaches to both

shells with its tube feet, eventually tiring the clam’s muscles. Once the shell is opened every so slightly, the sea star ejects a portion of its stomach into the clam to digest the tissue.

• The sea star ejects a portion of its stomach when it feeds.

• Waste is expelled through anus on aboral surface.

ReproductionReproduction

• Most echinoderms are dioecious.

• Fertilization occurs externally after the organisms spawn.

• A free-swimming larva called a bipinnaria results and eventually develops into an adult.

• As long as a portion of the central ring remains intact, a sea star can regenerateregenerate.

RegenerationRegeneration

Which Class?

AsteroideaAsteroidea

OphiuroideaOphiuroidea HolothuroideaHolothuroidea

EchinoideaEchinoidea

CrinoideaCrinoidea

Download - Phylum Echinodermata

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