Phylum Echinodermata

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Phylum Echinodermata
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Phylum Echinodermata
About 7,000 species Strictly marine, mostly
benthic. Typical deuterostomes.
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Phylum Echinodermata
Class Crinoidea (sea lilies)
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Phylum Echinodermata
Class Crinoidea
Class Asteroidea (sea stars)
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Phylum Echinodermata
Class Crinoidea
Class Asteroidea
Class Ophiuroidea (brittle stars and basket stars)
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Phylum Echinodermata
Class Crinoidea
Class Asteroidea
Class Ophiuroidea
Class Echinoidea (sea urchins and sand dollars)
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Phylum Echinodermata
Class Crinoidea
Class Asteroidea
Class Ophiuroidea
Class Echinoidea
Class Holothuroidea (sea cucumbers)
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What do Echinoderms look like?
Pentamerous radial symmetry. Oral and aboral
surfaces. Oral surface has ambulacral grooves
associated with tubefeet called podia.
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What do Echinoderms look like?
Oral and aboral surfaces.
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What do Echinoderms look like?
Arms (ambulacra) numbered with reference to the
madreporite. Ambulacrum opposite is A then
proceed couterclockwise. Ambulara C and D are the
bivium, A B and E are the trivium.
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What do Echinoderms look like?
Body wall
Epidermis covers entire body. Endoskeleton of
ossicles with tubefeet and dermal branchia
protruding through and spines and pedicellaria on
outside.
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What do Echinoderms look like?
Body wall
Ossicles can be fused into a test (urchins and
sand dollars). Ossicles spread apart in
cucumbers. Ossicles intermediate and variable in
seastars. Muscle fibers beneath ossicles.
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What do Echinoderms look like?
Body wall
Tubercles and moveable spines on skeletal plates
of echinoids. Small muscles attach spines to test.
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What do Echinoderms look like?
Body wall
Pedicellaria in echinoids and asreroids. Respond
to external stimuli independent of nervous
system. Keep debris and larvae from settling,
protection, hold on to material for camouflage.
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What do Echinoderms look like?
Water vascular system
Fluid-filled canals for internal transport and
locomotion. Fluid similar to sewater but has
coelomcytes and organic molecules. Moved through
system with cilia.
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What do Echinoderms look like?
Water vascular system
Asteroidea Madreporite on aboral surface.
Grooved with ciliated epidermis. May allow
seawater into vascular system. Ampulla under
madreporite connected to water vascular system
and hemal system. Stone canal connects ampulla to
rest of system. Connects to ring canal. Ring
canal leads to radial canals in each arm. Also
has Polian vessicles (maintain internal pressure)
and Tiedemanns bodies (produce coelomcytes).
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What do Echinoderms look like?
Water vascular system
Radial canals lead to lateral canals which pass
through pores in the skeletal plates and end in
tube feet.
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What do Echinoderms look like?
Water vascular system
Tube feet move by combination of muscles and
hydraulics. Valve at lateral canal that shuts and
isolates the tubefoot. Ampulla contracts and
pushes fluid into the tubefoot to extend it.
Sucker pressed on substratum and sticks with
adhesive secretions. Longitudinal muscles
contract to raise middle of sucker to create a
vacuum. Also shortens podium, forcing water back
into ampulla. For release, longitudinal muscles
relax, ampulla contracts and water forced back
into podium. Suction released.
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What do Echinoderms look like?
Water vascular system
Ophiuroids Madreporite on oral surface. Tudefeet
dont have suckers. Flexible used for feeding.
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What do Echinoderms look like?
Water vascular system
Echinoids Madreporite on special plate around
aboral pole. Podia pass through holes in
ambulacral plates
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How do Echinoderms support themselves and move?
Support
Calcareous endoskeleton with different degrees of
calcification. Holothuroids have very muscular
body walls.
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How do Echinoderms support themselves and move?
Movement
Crinoids walk on the tips of their arms. Some
swim.
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How do Echinoderms support themselves and move?
Movement
Ophiuroids use flexible arms for crawling.
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How do Echinoderms support themselves and move?
Nervous system
Decentralized without cerebral ganglia. Relatively
simple receptors chemoreceptors, statocysts,
touch. Some brittle stars have sclerites that act
as tiny lenses across their dorsal surface and
work together as one giant lens.
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How do Echinoderms feed and digest?
Crinoids
Filter feed with oral side up and arms and
pinnules outstretched. Food particles brought to
mouth via cilia in ambulacral grooves.
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How do Echinoderms feed and digest?
Asteroids
Most are predators and scavengers. Eversible
portion of stomach (cardiac stomach) extruded
onto or into prey.
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How do Echinoderms feed and digest?
Asteroids
Mouth ---gt cardiac stomach ---gt pyloric stomach
---gt pyloric ducts ---gt pyloric cecae ---gt
intestine ---gt anus
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How do Echinoderms feed and digest?
Ophiuroids
Predators, scavengers, filter feeders, deposit
feeders. Food collected and passed along podia
and spines to mouth. Digestive system reduced
with no anus.
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How do Echinoderms feed and digest?
Echinoids
Herbivores, suspension feeders, detritovores.
Urchins have Aristotles lantern. Hard plates
and muscles that control protraction of five
teeth.
Teeth scrape algae off rocks and take bites of
macroalgae. Can excavate holes in rocks.
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How do Echinoderms feed and digest?
Echinoids
Digestive mouth system ---gt esophagus out of
Aristotles lantern ---gt long intestines ---gt
rectum ---gt anus.
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How do Echinoderms feed and digest?
Holothuroids
Suspension and deposit feeders. Extend
mucus-covered buccal tentacles into water.
Tentacles are pushed into mouth one at a
time. Mouth ---gt esophagus ---gt long intestines
---gt rectum ---gt anus.
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How do Echinoderms feed and digest?
Holothuroids
Cuverian tubules - blind sticky tubes at base of
respiratory tree. Entangle predators. Evisceratio
n.
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How do Echinoderms maintain homeostasis?
Circulation
Internal transport by coeloms, water vascular
system, and hemal systems. Hemal system - array
of canals and spaces enclosed within coelomic
channels called perihemal sinuses. Parallels
water vascular system. Probably helps distribute
respiratory gases and nutrients.
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How do Echinoderms maintain homeostasis?
Gas exchange
Across podia and dermal gills (dermal
branchia). Countercurrent exchange.
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How do Echinoderms maintain homeostasis?
Gas exchange
Ophiuroids have ten invaginations in the body
wall called bursae. Water circulated by cilia.
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How do Echinoderms maintain homeostasis?
Gas exchange
Holothuroids have respiratory trees. Water is
actively pumped by muscular hind end. Gases
picked up by coelom and hemal system.
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How do Echinoderms maintain homeostasis?
Osmoregulation
Osmoconformers. Waste is usually ammonia lost
across podia and dermal branchia.
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How do Echinoderms reproduce and develop?
Asexual reproduction
Most capable of regenerating lost parts.
Holothuroids regenerate intestines and
respiratory trees. Asteroids and ophiuroids
regenerate lost arms and suckers.
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How do Echinoderms reproduce and develop?
Sexual reproduction
Most gonochoristic. Gonads housed in genital
sinuses. In classes with multiple gonads, each
has own gonopore in an interambulacral area.
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How do Echinoderms reproduce and develop?
Sexual reproduction
Free spawning with indirect development to
brooding with direct development.
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How do Echinoderms reproduce and develop?
Sexual reproduction
Isolecithal egg with small amount of yolk. Radial
holoblastic cleavage ---gt coeloblastula ---gt
coelogastrula by invagination ---gt blastopore
becomes anus ---gt coelom formation by enterocoely
---gt embryo becomes bilaterally symmetrical and
develops into a larva.
Vitellaria of crinoid
Bipinnaria and brachiolaria of seastars
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How do Echinoderms reproduce and develop?
Sexual reproduction
Isolecithal egg with small amount of yolk. Radial
holoblastic cleavage ---gt coeloblastula ---gt
coelogastrula by invagination ---gt blastopore
becomes anus ---gt coelom formation by enterocoely
---gt embryo becomes bilaterally symmetrical and
develops into a larva.
Ophiopluteus of brittle star
Aricularia of sea cucumber
Echinopluteus of urchin.