Transcript Echinoderms

Slide 1
Phylum Echinodermata
“Spiny Skin”
Sea stars, sand dollars, sea urchins,
feather stars, brittle stars, sea lilies,
sea cucumbers and sea daisies.
Slide 2
Major Characteristics of
Echinoderms
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Marine Invertebrates
Endoskeleton
Pentaradial Symmetry
Coelom
Water Vascular System
Deuterostome Development
Slide 3
Endoskeleton
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A large number of calcium-rich
plates, called ossicles make the
body of the echinoderm.
The skin covers the ossicles, but
may be worn away or have spines
protruding through it.
Used for muscle attachment and
protection.
Slide 4
Pentaradial Symmetry
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5 part radial symmetry as adults.
Larvae often have bilateral
symmetry.
The number of arms may vary, but
are most often in multiples of 5.
Slide 5
Coelom
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A true coelom acts as a simple
circulatory and respiratory system.
Skin gills are also useful for
respiration and getting rid of waste.
Skin gills greatly increase the
surface area for gas exchange with
the sea water.
Slide 6
Water Vascular System
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A system of water-filled canals
connected to thousands of tube feet.
In many species, the tube feet extend
out of the ossicles and have little
suckers at the tip.
Useful for locomotion, feeding, gas
exchange, and even excretion.
Slide 7
Water Vascular System:
Path of water traveling through the water vascular
system.
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Water enters through the
Madeporite or Sieve Plate.
Travels down the stone canal . . .
Around the ring canal . . .
Out the radial canals . . .
To the ampulla of the tube feet.
Slide 8
Tube Feet
Ampulla
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Tube Foot
Tube feet are a
little like droppers.
When the ampulla
squeeze, water
exits the foot.
When the ampulla
are full of water,
there is suction at
the bottom of the
foot.
Slide 9
Regeneration
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Starfish do not have
a head or brain.
The central disc
contains a ring of
nerves.
If part of the central disc is
present, regeneration can
occur.
Slide 10
Errors in Regeneration
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Sometimes,
errors can occur.
A starfish may not
regrow an arm,
and have only 4
or fewer.
A starfish may
regrow multiple
arms and have 6
or more!
Slide 11
Diversity in Echinoderms:
Class Ophiurodea
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Brittle stars and sea baskets make
up this largest class of
echinoderms.
Some are predators, but most live
on the ocean floor and feed on food
from sediment or are filter feeders.
oceanexplorer.noaa.gov
www.scubacentro.com
Slide 12
Diversity in Echinoderms:
Class Crinoidea
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Sea lilies and feather stars are the
most ancient and primitive of the
living echinoderms.
The mouth is on the upper instead
of lower surface.
Most sea lilies and feather stars are
sessile filter feeders.
www.childrensmuseum.org
tackettproductions.com
Slide 13
Diversity in Echinoderms:
Class Echinodea
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Sea urchins and sand dollars do
not have distinct arms, but do
display pentaradial symmetry.
Sea urchin spines are used for
protection, and may contain a
venom that causes a severe
burning sensation.
Sand dollars live in sandy coastal
waters.
www.humboldt.edu
www.users.zetnet.co.uk
Slide 14
Diversity in Echinoderms:
Class Holothuroidea
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Sea cucumbers have very small,
unfused ossicles, so their body feels
soft, with a tough, leathery exterior.
Their tube feet are modified into sticky
tentacles that trap plankton. The sea
cucumber draws the tentacles into the
mouth to feed.
Sea cucumbers can eject sticky
threads from it’s anus to trap potential
attackers.
www.afsc.noaa.gov
Slide 15
Diversity in Echinoderms:
Class Asteroidea
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Sea stars (a.k.a. starfish) are the most wellknown. They are carnivores and often predators!
A crown-of-thorns can eat 65 feet of coral polyps
in one hour! Over time it could destroy an entire
reef ecosystem.
Sea stars have eyespots at the end of each arm
to detect light and tiny tentacles to respond to
touch.
Many sea stars have pinchers called pedicellarie
which contain their own muscles and nerves and
snap at anything that touches them! This
prevents organisms from attaching to the surface.
Slide 16
Feeding in Sea Stars
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Feed on mollusks, worms, and other
slow-moving animals.
Tube feet grasp onto 2 halves of a clam
shell and pulls until it opens.
Turns stomach inside out, and begins
digesting the clam right in its shell!
Returns stomach in through mouth to
finish digestion.
Solid waste exits through the mouth.
Slide 17
Reproduction in Sea Stars
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Separate sexes, with 2 gonads in
each arm.
External fertilization and
development.
Regeneration can occur if part of
the central disc is present.
Slide 18
Other Info You Should Know:
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Oxygen is obtained and waste is excreted
through the skin gills and diffusion across
tube feet.
Nervous control:
– Nerve ring and nerve cord coordinate nerve
messages.
– Tube feet respond to touch.
– Eyespots at the end of each arm respond to
light.
– Small tentacles on each arm respond to touch.
Slide 19
Ecological Importance of
Echinoderms
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Beautiful - tourism
Chemical signals
for regeneration
studied for human
applications.
Sea urchin
fertilization is
dependent on
water quality - it’s
a monitor!
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Sea stars eat
many mollusks,
can destroy clam
beds.
Sea stars also eat
coral, could
destroy reef
ecosystem.