Characteristics of Echinoderms One of the strangest and most unusual phylum in the animal kingdom Echinoderms are deuterostomes which is a trait they share with chordates vertebrates All of the other invertebrates we learned about so far have been protostomes ID: 599279
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Slide1
Chapter 14, EchinodermsSlide2
Characteristics of Echinoderms
One of the
strangest
and
most unusual group of animals
in the animal kingdom.
Echinoderms are
deuterostomes
, which is a trait they share with chordates (vertebrates).
All of the other invertebrates we learned about so far have been protostomes.
No cephalization or brain
, very
few sensory organs
or
nervous system tissues.Slide3
Characteristics of Echinoderms
Echinoderms have an
endoskeleton
made up of dermal
calcareous
ossicles
.
A
water-vascular system
that controls
tentacle-like projections
called
tube feet.
Development begins with a free-swimming,
bilaterally symmetrical larva (called
bipinnaria
)
, and a
metamorphosis
into a
radially symmetrical
adult.Slide4
Development and SymmetrySlide5
The Water-Vascular System
Echinoderms have a unique
system of canals and tube feet
that make up their
w
ater-vascular system.
The
primary functions
of the
water-vascular system
are
locomotion
and
feeding
.
The
water-vascular system
also
plays a role
in
respiration
and
excretion
.Slide6
The Water-Vascular System
The water-vascular system
enters the body through a small opening
called the
madreporite
.
The
madreporite
leads to a canal
called the
stone canal
. The
stone canal leads to a ring around the mouth
called the
ring canal
.
The
ring canal branches off
into
radial canals,
and the
radial canals branch off
into
lateral canals
. The
lateral canals lead to muscular sacs
called
ampulla
, which eventually lead to the
podia or tube feet.Slide7
The Water-Vascular SystemSlide8
Class Asteroidea (Sea Stars)
Sea stars or starfish typically have
five arms
which is called
pentaradial
symmetry
Mouth
is on the
oral side
. The side that is opposite of the mouth is the
aboral
side.
Ambulacral
grooves
radiate out along the arms from the mouth, on the oral side.
Tube feet
(also called
podia
) stick out from the
ambulacral
grooves.
Radial nerves
run the length of the grooves.Slide9
General Anatomy of an EchinodermSlide10
Feeding and Digestive System
Sea stars typically have
two stomachs.
A
larger
and lower
cardiac stomach
and the
smaller
upper
pyloric stomach.
Sea stars are
opportunistic carnivores
.
They feed on
mollusks, crustaceans, fish,
polychaetes
and
other echinoderms.
They
hunt by grabbing their prey with their tube feet
. Then they
evert
their stomach
(turn it inside out) and
secrete digestive enzymes.Slide11
Sea Star Eating
A
n AnchovySlide12
Sea Star Reproduction
Separate
s
exes
in
most species
.
Sea stars
can
also
regenerate lost parts.
Sea stars
can also deliberately detach part of their own bodies
and
cast off an arm near its base
. A feature referred to as
autotomy
.
If a detached arm retains at least one fifth of the central disc
(main body), the arm can
regenerate an entirely new sea star.Slide13
Sea Star RegenerationSlide14
Class
Ophiuroidea
(Brittle Stars)
Arms of brittle stars
are
more slender
than species in class
Asteroidea
.
Tube feet
are
used for feeding
, but
not for locomotion
like the sea stars.
Locomotion for brittle stars
is accomplished by
movement of their arms.
The
madreporite
is located on the
oral surface
.
No anus
, so
waste is expelled out the mouth
.Slide15
Brittle StarsSlide16
Class
Ophiuroidea
(Brittle Stars)
Because the arms are so slender,
all of the major organs are in the central disc
(body).
The
water-vascular system, nervous system, and reproduction
is very
similar
to the members of class
Asteroidea
.
Sexes are usually separate
, and brittle stars can undergo
regeneration
and
autotomy
just like the sea stars.Slide17
Brittle StarsSlide18
Class
Echinoidea
(Sea Urchins and Sand Dollars)
Members of class
Echinoidea
have
a compact body or shell
called a
Test.
Echinoids
lack arms
, but
their test is still divided into five parts
like the sea star's and the brittle star's.
Inside a sea urchin's test
is a
coiled digestive system
and
a complex chewing mechanism
called an
Aristotle's lantern.
The
Aristotle's lantern
is
used for chewing food
, and it
has teeth
that are
controlled by
retractor
and
protractor muscles
.Slide19
Class
Echinoidea
(Sea Urchins and Sand Dollars)
Sand Dollar
Sea UrchinSlide20
Sea Urchin AnatomySlide21
Class
Holothuroidea
(Sea Cucumbers)
Sea cucumbers are
elongate
and have 10-30
oral tentacles
(modified tube feet)
around the mouth
.
Strangely,
although there appears to be an anterior end, cephalization and a brain are completely absent
.
Respiration
occurs by way of a
network of tubes and branches
called the
respiratory tree.
When threatened
, they
can discharge long, sticky, toxic substances
called
Cuvierian
tubules.Slide22
Sea CucumbersSlide23
Cuvierian
TubulesSlide24
Sea Cucumber AnatomySlide25
Class Crinoidea
(Sea Lilies and Feather Stars)
Their
bodies are attached
to the
ocean floor
for at least a
part of their life.
The
calyx
(body) of a
sea lily
is
attached
to a
stalk
on the
aboral
side
.
The
stalk
attaches to the ground surface.
Five flexible arms
with
many lateral branching
pinnules
arranged like
barbs on a feather
.
Feather stars resemble sea lilies
, except they are
without a stalk.Slide26
Sea Lily AnatomySlide27
Sea Lilies and Feather StarsSlide28
Echinoderms