Download Echinoderm Classes Asteroidea – Sea Stars

http://photography.nationalgeographic.com/staticfiles/NGS/Shared/StaticFiles/Photography/Images/Content/sea-star-pair-758303-sw.jpg
Riley Galton
Echinoderm Classes
Asteroidea – Sea Stars:
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Multiple arms radiating from
central disk
Tube feet on bottom
http://photography.nationalgeographic.com/staticfiles/
Ophiuroidea – Brittle Stars:
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Distinct central disk with snake like arms
Tube feet lack suckers
http://environment.nationalgeographic.com/staticfiles/
Riley Galton
Echinoderm Classes
Echinoidea – Sea Urchins and Sand Dollars:
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No arms, but 5 rows of tube feet
Have muscles that can move
spines
www.emiliogrossi.com/images/Photo
graphyiles/
Crinoidea – Feather Stars
and Sea Lilies
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Flexible arms used in
suspension feeding
Haven’t changed in 500 million
years
http://environment.nationalgeographic.com/staticfiles/
http://lh6.ggpht.com
http://image44.webshots.com
Riley Galton
Echinoderm Classes
Holothuroidea – Sea Cucumbers
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Reduced endoskeleton
Five rows of tube feet
http://www.sfu.ca/~fankbone/v/xyloplax.jpg
Concentricycloidea – Sea Daisies
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Only two known species
Disk shaped, less than 1cm in diameter
http://blog.case.edu/case-news/2008/03/06/seacucumber.jpg
Riley Galton
Echinoderm Sensory
Structures
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Eyespots on the ends of ambulacra are
sensitive to light
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Pedicellariae (jaw like skeletal structures used to keep
organisms from settling on skin), tube feet, and spines
are sensitive to touch
http://www.ucmp.berkeley.edu/echinodermata/echinomm.html
Riley Galton
Echinoderm Reproduction
Sexual:
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•
http://www.biolbull.org/content/vol204/issue3/images/medium/cov
erfig.gif
Eggs and sperm are released into the
water where they are fertilized
Larvae are planktonic
Internal fertilization has been observed
in certain species of sea stars, brittle
stars, and sea cucumbers
Asexual:
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Echinoderms can regenerate body
parts and organs
Asexual reproduction can occur
(though not by will) if the echinoderm is
torn with enough of the body on each
part
http://www.oceaninn.com/guides/echino.htm
http://www.starfish.ch/Fotos/echinoderms
Julia Heunis
Body Cavity (Coelom)
PRESENT!
 Coelom = A fluid-filled cavity between body wall and gut;
lined by mesoderm
 Two parts:
Perivisceral coelom – large, fluid-filled cavity where major
organs, digestive tube and sex organs, are suspended
Water Vascular System - network of hydraulic canals unique
to echinoderms that branches into extensions (tube feet)
which function in locomotion, feeding and gas exchange
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http://www.colin.edu/science/awashington/syllabi/General%20Zoology%20Terminology.htm
http://biology.kenyon.edu/courses/biol112/Biol112WebPage/Syllabus/Topics/Week%207/Resources/coelom.GIF
http://www.britannica.com/EBchecked/topic/452108/perivisceral-coelom
http://www.und.nodak.edu/instruct/jvaughan/b151/VOCAB_vertebrates.html
Julia Heunis
Body Symmetry
http://tbn2.google.com/images?q=tbn:KrJSbsj0l4ImqM:http://
photos.tobinhosting.com/d/117553-2/sea%2Burchins.jpg
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evolved from animals with bilateral
symmetry
adult echinoderms possess radial
symmetry
All echinoderms exhibit fivefold radial
symmetry in portions of their body at some
stage of life (5 parts around central axis),
even if they have secondary bilateral
symmetry
For the most part…
LARVAE ~ bilateral
ADULTS ~ radial
http://en.wikipedia.org/
wiki/Echinoderm
Julia Heunis
Excretory System
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NO true excretory
system!
Main opening of a
sponge used only to
EXPEL WASTE
Anus leads directly from
stomach/digestive tract
Anus = top
mouth = bottom
universe-review.ca
Olivia Heunis
http://universe-review.ca/I10-82-starfish.jpg
Julia Heunis
Skeletal Type
Echinodermata: “Spiny Skinned”
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DO NOT possess an exoskeleton
a thin outermost skin covers a mesodermal
endoskeleton made of tiny calcified plates and
spines - forms rigid support contained within
tissues of the organism
Skeleton composed of skeletal plates called
ossicles
Ossicles = small bones
In some species, such as the sea urchin, plates
of the skeleton are locked together to form a
rigid structure.
most sea stars and brittle stars can flex their
‘arms’ = skeleton has gaps, flexible plate
junctures
http://ebiomedia.com/prod/BOechinoderms.html
http://en.wikipedia.org/wiki/File:Sanc0521.jpg
Julia Heunis
Other Unique Features
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Echinoderms can REGENERATE
ex: sea cucumbers can eject a portion of
gut in response to predators and
regenerate when safe
Water vascular system (described earlier)
is unique to echinoderms; varies water
pressure to control tube feet
Crinoids and some brittle stars = passive
filter-feeders, absorbing suspended
particles from passing water
sea urchins = grazers
http://www.starfish.ch/reef/echinoderms.html
sea cucumbers = deposit feeders
starfish = active hunters
Julia Heunis
More Unique Features
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Autonomy = The spontaneous
self amputation of an
appendage when the organism
is injured or under attack. The
autotomized part is usually
regenerated.
“arms” → multiples of 5; some
have more because of
regeneration
mutable collagenous tissue ~
connect ossicles; can maintain
different positions without
much effort
http://www.starfish.ch/reef/echinoderms.html
David Lin
Nervous System
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Decentralized
central nerve ring surrounds gut, connect
radial nerves.
Radial nerves run under each arm, coordinate
movement, etc.
Do not have “brains,” but some have ganglia
along radial nerves
http://www.tolweb.org/Echinodermata
David Lin
Digestive System
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Complete digestive system
(tubular gut), mouth to anus.
(bottom to top)
Crinoidia: filter-feed, use cilia
Asteroidea: Cardiac (evert),
pyloric stomach, digestive glands
Urchins: “Aristotle’s lantern”
(masticatory apparatus)
Holothurians: suspension/deposit
feeders, use tentacles.
http://www.experiencefestival.com/a/Sea_star__Internal_Anatomy/id/2099728
http://userwww.sfsu.edu/~biol240/labs/lab_17hydrostatics
k/pages/echinoderm.html
David Lin
Locomotion/Musculature
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Utilize water vascular
system and tube feet
Water in from
madreporite, pumped into
ampulla by radial canal
Ampulla contracts, water
to podia
Podia contracts, water to
ampulla
– Podia bend, shorten
allows movement
(vacuum and suction)
http://animaldiversity.ummz.umich.edu/site/resources/biodidac/basicechino.jpg/mediu
m.jpg
http://userwww.sfsu.edu/~biol240/labs/lab_17hydrostaticsk/pages/echinoderm.html
David Lin
Gas Exchange
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Asteroids, crinoids: dermal
gills (thin epidermis)
Urchins: infolds of body wall
(bursae) opening to outside
Sand dollars: modified podia
on top (petaloids) which are
thin-walled and flaplike.
Holothurians: highly branched
hindgut called "respiratory
tree"
http://faculty.vassar.edu/mehaffey/academic/animalstructure/outlines/echinode
rmata.html
David Lin
Circulatory System
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Mostly in perivisceral
coelom, enhanced by
water vascular system
and hemal system.
– Hemal system: series
of canals and spaces
mostly in coelomic
channels. Fluid
movement by cilia.
Used to distribute
nutrients. No
respiratory system.
http://faculty.vassar.edu/mehaffey/academic/animalstructure/outlines/
echinodermata.html
http://www.dailygalaxy.com/photos/uncategorized/urchins_1.jpg
Quiz
1.
2.
3.
4.
Echinodermata have ________ symmetry as
larvae, but display ________ symmetry as adults.
What allows Echinoderms to function in locomotion,
feeding and gas exchange?
Sea stars can grow new arms and sea cucumbers
can replace their gut after ejecting them. What
feature of echinoderms does this demonstrate?
Name the stomachs of a sea star. Functions?
Answers
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Bilateral, radial
Water vascular
system
Regeneration
Cardiac, pyloric;
evert and enzymes,
further digestion