Phylum Echinodermata
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“Spine skin”
Marine (or estuarine)
Water vascular system
Pentaradial symmetry
Echinodermata
• 6500 species living
• 13,000 from fossils
• Classes: Crinoidea, Stelleroidea,
Echinoidea, Holothuroidea
Water vascular system
•Fluid-filled canals
that lead to tube
feet
•Sea star:
madreporite, stone
canal, ring canal,
radial canal,
ampulla, tube feet
Water vascular system
•Tiedemann’s body:
•Contains
phagocytes; remove
foreign matter such
as bacteria from
incoming seawater
Water vascular system
Ambulacral ossicles
support ampullae and
tube feet
Contraction of ampulla
moves fluid to tube feet
Muscles in tube feet for
retracting
http://www.youtube.com/watch?v=
HPhAGyDceLo
Water vascular system
•Cilia on inner
surface of tube feet
circulate water
•Gas exchange
•Fluid similar to
seawater; contains
coelomocytes,
proteins, K ions
Class Crinoidea
• Lily-like
• Feather stars and sea lilies
• Oldest of living echinoderms
Class Crinoidea
•Feeding, repro
structures at top of
stalk
•Complete digestive
system in calyx:
mouth – intestine,
anus
•http://www.youtube.com/wat
ch?v=s1xfRc4SDsw
Class Crinoidea
• Arms have ambulacral
groove with mucussecreting glands
adjacent.
• Food particles stick in
mucus, flicked to the
ambulacral groove,
then mouth
Class Stelleroidea
• Armed echinoderms
• Brittle stars, sea stars
Brittle stars and
basket stars
•~ 2100 described
•Joints allow flexibility
•Tube feet present
•Sensitive to light – oral
surface
•http://www.youtube.com/watch?v=
mj8ZYysrmxU
Brittle stars and
basket stars
• Tube feet
through small
holes
• Digestive
system mostly in
disc – no anus
• Bursal slits for
water exchange
Brittle stars and basket
stars
• Deposit feeders,
suspension feeders,
carnivores,
scavengers
• Many are nocturnal
• Many live in
associations
Sea stars
• ~ 1600 species
• Arms not as distinct from disc as in brittle
stars
• Move slowly with tube feet
• Tube feet move individually
Figure 20_06
Sea stars
• Digestion: lower cardiac stomach digests
food
• Upper pyloric stomach for secreting
enzymes and absorption
Pedicellariae: stalked or sessile
Figure 20_09
Concentricycloids – sea daisies
• Recently (1986) discovered echinoderms
• > 1000 m New Zealand, Bahamas
– Tube feet arrangement different
Class Echinoidea:
spine-like
• Sea urchins, sand dollars
• < 1000 species
Class Echinoidea:
spine-like
• Ossicles form
test
• Complex system
of ossicles and
muscles for
grazing =
Aristotle’s lantern
•Spines attach to
skeleton – ball and
socket joint
•Toxins
•Ossicles flat and
joined = inflexible
Class Echinoidea:
spine-like
• Tube feet in 5
double rows of
plate
• Pedicellariae –
globular forms
have toxin
• Feeding and
digestion:
• Aristotle’s lantern
• Teeth protruded
to scrape algae
or consume food
• Species w/o
lantern usually
detritivores
• Mouth –
esophagus –
intestine – anus
• WVS
• http://www.youtube.co
m/watch?v=D3W4OCn
HyCs
• Class Holothuroidea: sea cucumbers
• ~ 1200 species
• Ossicles
microscopic
• Multiple shapes
• Tube feet modified into
tentacles around mouth
• Mostly deposit-feeders,
few filter-feeders
• Digestion system:
elongated
• Mouth – esophagus –
stomach – intestine –
cloaca – anus
• WVS – madreporite in
coelomic cavity = no
outside connection
• Respiratory tree:
connects to cloaca –
water supply
• Expulsion of internal
organs
• Echinoderm repro +
development:
• Some are asexual
• Most are dioecious
• Multiple gonads, gametes
into seawater = external
fert
• Distinctive ciliated
larval form in each
class
• Free-swimming,
planktonic
• Metamorphosis into
adult
• Echinoderm NS
• No brain
• 3 nerve networks
• Ectoneural = ring
around esophagus:
receives sensory
input
• Echinoderm NS
• Hyponeural =
circumoral nerve:
motor function
• Entoneural =
associated with
aboral end,
neurons from stalk
down arms