Kingdom Animalia
Subkingdom Eumetazoa
Bilateria
Phylum Echinodermata
Professor Andrea Garrison
Biology 3A
Illustrations ©2014 Cengage Learning unless otherwise
noted
Text ©2014 A. Garrison
Echinoderms, Vertebrates
& Related Phyla
• Deuterostomes
– Radial, indeterminate
cleavage
– Enterocoelous coelom
– Blastopore develops into
anus, archenteron cuts
through to form mouth
Echinodermata
2
Phylum Echinodermata
• Sea stars, sea urchins,
sea cucumbers, brittle
stars, crinoids (echinos =
spiny; derma = skin)
• Marine
• Far more abundant in
fossil record than today
• Bottom-dwellers
– Slow moving
• Secondary radial
symmetry
– Usually pentamerous
– Develop from bilateral
larvae
– Oral/aboral axis
Echinodermata
3
Phylum Echinodermata
• No head or brain
– Some sensory structures
• Tactile
• Chemosensory
• Photoreceptors
• Nervous system simple
– Ring around gut
– Radial nerves
• Calcium Carbonate
endoskeleton
– Covered by epidermis
– Plates with spines or
spicules in dermis
Echinodermata
4
Phylum Echinodermata
• Coelomate
• Open circulatory system
– Not well-developed
• Water vascular system
– Separate compartment of
coelom
– Fluid-filled channels
– Hydraulic system
• Podia sit in ambulacral groove
– Respiration
– Locomotion
– Sensory
– Opens to outside through
madreporite on aboral surface
– Unique to echinoderms
Echinodermata
5
Phylum Echinodermata
• Water vascular system
– Podia sit in ambulacral
grooves
Echinodermata—photo by A. Garrison
6
Phylum Echinodermata
• Most with complete
digestive system
• No excretory organs
• Most dioecious
• Reproduction
– Sexual
• External fertilization
• Free-swimming larvae
– Asexual
• Regenerate from broken
pieces
Echinodermata
7
Phylum Echinodermata
• 6 living classes
– Asteroidea
– Ophiuroidea
– Echinoidea
– Holothuroidea
– Crinoidea
– Concentricycloidea
• Uncommon, sunken wood in deep sea
Echinodermata
8
Class Asteroidea
• Sea stars (asteroeides =
starlike)
• Intertidal to 10,000m deep
• Central disk with ventral
mouth surrounded by arms
(usually 5, may be >25)
• Feed on invertebrates and
small fish
• Climb over prey, evert
cardiac stomach
– Extracellular digestion
Echinodermata; top photo by Alain Feulvarch, http://commons.wikimedia.org/wiki/File:Starfish,_Mauritius.jpg,
http://creativecommons.org/licenses/by/2.0/deed.en; bottom photo by Brocken Inaglory,
9
http://commons.wikimedia.org/wiki/File:Sun_flower_sea_star_in_tide_pools.jpg; http://creativecommons.org/licenses/by-sa/3.0/deed.en
Class Asteroidea
• Endoskeleton
– Ossicles not fused
• Flexibility
– Spines protrude from
ossicles
– Pincher-like pedicellariae
at base of spines remove
debris from aboral
surface
Echinodermata; photo by Philippe Bourjon,
http://commons.wikimedia.org/wiki/File:P%C3%A9dicellaires_d%27_Acanthaster_Planci.JPG,
http://creativecommons.org/licenses/by/3.0/deed.en
10
Class Asteroidea
• Podia sit in open
ambulacral groove
Echinodermata; photo by Mokele, http://commons.wikimedia.org/wiki/File:Starfish_%281%29.jpg,
http://creativecommons.org/licenses/by/3.0/deed.en
11
Class Ophiuroidea
• Brittle stars (ophioneos =
snakelike)
• Intertidal to 10,000m
deep
• Central disk with ventral
mouth surrounded by
skinny arms
• Move quickly
• Arms break easily
– Escape prey
• Feed on small prey,
plankton or detritus
Echinodermata
12
Class Echinoidea
• Sea urchins, sand
dollars (ekhinos =
porcupine)
• Urchins voracious
eaters
– Destroy kelp
forests
Echinodermata
13
Class Echinoidea
• Ossicles fused into
solid tests
• Moveable spines
extend from test
– Some with poison
glands
• Urchins
– 5 rows of podia
extended through
test
– Mouth on oral
surface, anus and
gonopores on aboral
surface
Echinodermata; photo by Janek Pfeifer, http://commons.wikimedia.org/wiki/File:Seeigel-Saugfuesse%28Galicien2005%29.jpg,
14
http://creativecommons.org/licenses/by-sa/3.0/deed.en
Class Echinoidea
• Sand dollars
– Oral-aborally flattened
– 5 regions of podia on
aboral surface
Echinodermata; top photo by John Tracy,
http://commons.wikimedia.org/wiki/File:Live_Sand_Dollar_trying_to_bury_itself_in_beach_sand.jpg,
http://creativecommons.org/licenses/by/2.0/deed.en; bottom photo by Wildcat Dunny,
http://commons.wikimedia.org/wiki/File:Sand_dollar_test.jpg, http://creativecommons.org/licenses/by/2.0/deed.en
15
Class Holothuroidea
• Sea cucumbers
(holothourion = water
polyp)
• Soft body with spicules in
dermis
• Radial symmetry from
mouth end
• 5 rows of podia run
length of body
• Tentacles around mouth
are modified podia
Echinodermata
16
Class Holothuroidea
• Sea cucumbers
(holothourion = water
polyp)
• Soft body with spicules in
dermis
• Radial symmetry from
mouth end
• 5 rows of podia run
length of body
• Tentacles around mouth
are modified podia
Echinodermata; Livingstone ©BIODIDAC; http://creativecommons.org/licenses/by-nc/4.0/legalcode
17
Class Crinoidea
• Sea lilies and feather stars
(krinon = lily)
• Mostly extinct
• Many deep water forms
• Oral surface is up
• Branched arms coated
with podia and mucus
– Trap tiny organisms
• Sea lilies sessile on stalk
• Feather stars swim or
crawl
Echinodermata; photo by Alexander Vasenin; http://commons.wikimedia.org/wiki/File:Crinoid_on_the_reef_of_Batu_Moncho_Island.JPG,
http://creativecommons.org/licenses/by-sa/3.0/deed.en; bottom photo by Previewh,
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http://commons.wikimedia.org/wiki/File:Feather_Star_1.jpg, http://creativecommons.org/licenses/by-sa/2.0/deed.en