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The Echinoderms
Phylum Echinodermata
Echinoderms
 Marine
 Sea
stars
 Brittle stars
 Sea urchins
 Sea
cucumbers
 Sea lilies
Brittle Star
Sea Urchin
 Aristotle’s
Lantern – chewing mechanism
attached to teeth - circular
Sea Cucumber
Sea Lily
 Found
in all oceans/at all depths
 Most common animal in extreme depths
 11,000 m – Philippine Trench
 No
parasitic/mostly symbiotic
 Many other animals live on and in
echinoderms
 Algae/protozoa/ctenophores/snails/clams
fish etc.
 Particle feeders/predators
 Scavengers/browsers/deposit or filter
feeders
 Very
unusual group of animals
 Confusing to scientist even today
 Name is derived from their external spines
 2 Sub phyla/6 classes
 Fossil record dates back to the Cambrian
period
Subphylum Pelmatozoa
 Stalk
animal
 Connected to a substrate
 Class Crinoidea – lily form
 Sea lilies
 Feather stars
Subphylum Eleutherozoa
animal – not bound
 Class
 Concentricycloidea- sea daisies – center
form
 Asteroidea- sea stars ( star fish) – star
form
 Free
brittle stars – snake form
 Echinoidea- sea urchins – hedgehog form
 Holothuroidea- sea cucumbers – sea
cucumber from
 Ophiuroidea-
Unusual Characteristics
moving – Radial Symmetry
 Mirror image more than 1 plane
 Bilateral larva- Radial Adults – results in
90% reorientation of body axis
 Very complex internal – Radial symmetry
 Coelom has been transformed into a water
vascular system (system of tubes and
ducts) that uses hydraulic power
 Free
 Hydraulic
power is used to operate tube
feet – small muscular fluid filled tubes
 Food gathering/locomotion
 Endoskeleton of dermal ossicles – can
fuse together to form plate of armor
 Ambulacral area –mouth to tip of each arm
 Miniature jawlike pinsers(pedicellariae)
can have poison glands(little foot)
Echinoderms
 Echinoderms/chordates
have common
ancestor
 Evolutionary history very unknown/has
made them different from any other animal
 Deuterostome -pattern of development –
anus forms first – they have this in
common with vertebrates
 Protostome – all other invertebrates –
mouth forms first
Characteristics
 Nonmetameric
body
 Radial symmetry
 5 or more radiating
areas
 No cephalization –
no head or brain
 Tactile/photo/chemo
 statysts
 Nervous
system
has circumforal
ring and radial
nerves
 2 or 3 systems of
rings at different
levels
 Complete digestive
system – usually
coiled
characteristics
 Madreporite
or
sieve plate takes
water in to water
vascular system
–
dermal branchiae,
tube feet,
respiratory tree
 Excretory organs
absent
 Cannot
osmoregulate
 No brackish water
capabilities
 Respiration
Reproduction
 Sexes
usually
separate
 Some
hermaphroditic
 Multiple gonads
 Ducts release
gametes
 Fertilization is
usually external
 Egg
develops into
free swimming
larva
 Bilateral symmetry
Regeneration
 Sea
stars can regenerate lost limbs
 Can take months to regenerate
 Also possess autonomy- can self
amputate injured piece of arm or part
 Some species can regenerate a new sea
star from a lost arm if it contains part of the
central disc