Clade Deuterostomia
Phylum Echinodermata
Phylum Hemichordata
Phylum Chordata
Protostomes vs. Deuterostomes
• Zygote cleaves to become blastula and then forms
gastrula. The blastopore of the gastrula can become
either the mouth or the anus of the organism
• Protostome- “first mouth” Blastopore becomes the
mouth. Ex-Annelids, Mollusks and arthropods
• Deuterostome- “second mouth” Blastopore
becomes anus.
Ex-echinoderms, hemichordates,chordates
Embryonic Development
• Protostome
– Blastopore becomes mouth
• Deuterostome
– Blastopore becomes anus
3
Coelomatestrue body
cavity lined
with
mesoderm
• EX: all other
animals
Phylum
Echinodermata
Phylum Echinodermata
• Includes starfish, sea urchins, sea cucumber & sand
dollars- all marine
• Successful for 500 my
• “Spiny-skinned”
• Pentaradial Symmetry
• Coelom, no segmentation
• endoskeleton
• Lack a centralized brain- have a
Nerve ring with radial and lateral
nerves -sense touch, light, temp,
water conditions
Ouch!
Phylum Echinodermata: Anatomy
• Bipinnaria larvae(bilaterally symm.)
• Water Vascular System:
-- Series of water-filled canals
-- Carries out functions including respiratory,
circulation, and movement.
-- Oxygen, food, & wastes are carried by the
water vascular system.
Phylum Echinodermata: Anatomy
• Water enters madreporite and flows through the
stone canal and then enters the circular ring canal.
• Water then is separated into five radial canals that
branch into double rows of bulblike structures
called ampullae, which are on each side of the
ambulacral ridge.
• The ampullae are connected to suckerlike
podia = tube foot
Water Vascular System
Phylum Echinodermata: Anatomy
• Have 5 sections or rays or arms
• Tube Feet:
-- Act like suction cups
-- Extend from the body
-- Used to “walk”, capture, and hold prey
*How a single tube
foot moves*
Tube Feet
Checkpoint
1. What does Echinodermata mean?
2. What are the basic characteristics of these
animals?
3. What type of symmetry do echinoderms
have?
4. What is the function of the water vascular
system?
5. What do echinoderms use to move?
6. What type of embryological development do
they have?
Class Asteroidea
Star Fish
Starfish: External Anatomy
• Typically have 5 armsrays thick and short
• Arms emerge from a central disc
• Have an endoskeleton of small calcareous
plates called ossicles
Starfish: External Anatomy
• From the ossicles project spines & tubercles that
are responsible for their spiny surface
Starfish: External Anatomy
• On the oral surface
-- Ambulacral (am-bu-la ‘kral) grooves: Radiate out
along the arms from the centrally located mouth
-- Tube feet project from the grooves
Ambulacral Groove
Starfish: External Anatomy
• On the oral surface
-- A large radial
nerve can be seen in the
center of each ambulacral groove between
the rows of tube feet.
-- Under the radial nerve is an extension of
the coelom and the radial canal of the
water-vascular system
Phylum Echinodermata: Anatomy
• They have two stomachs.
• One stomach is used for digestion, and the other
stomach can be extended outward to engulf and
digest prey.
1 - Ambulacral ossicles
and ampullae.
2 - Madreporite.
3 - Stone canal.
4 - Pyloric caecae.
5 - Rectal glands.
6 - Gonads.
Phylum Echinodermata: Anatomy
• Starfish push their stomach out once prey is caught.
-- Stomach pushes out of mouth to surround
prey (ex: clam)
-- Pours out enzymes
-- Digests clam in its own shell
-- Then it pulls its stomach and the partially digested
prey into its mouth.
Groups of Echinoderms
• Sea Stars or Starfish
-- Preys on bivalves
-- Regenerates arms
-- If pulled apart into pieces, each piece will
grow into a new animal, as long as it contains
a portion of the central part of the body.
Reproduction
• Starfish are capable of both sexual and
asexual reproduction.
• Individual starfish are male or female.
Fertilization takes place externally, both male
and female releasing their gametes into the
environment.
• Resulting fertilized embryos form part of the
zooplankton.
Reproduction
• The fertilized embryos that float as zooplankton are
known as deuterostomes.
• The deuterostomes then become a larva that are
bilateral symmetrical.
• As they grow, they then change to radial
symmetrical adults.
Class Echinoidea
Sea Urchins & Sand Dollars
Class Echinoidea
• Sea Urchin
-- Eat algae
-- Have calcium carbonate plates covered with
spines.
-- Can swivel spines
-- Many animals prey on sea urchins
-- Yes, people eat sea urchins
Call it “roe”
Sea
Urchins
• Sea urchins are one of the sea otters favorite
food.
• Sea otters keep sea urchin populations in
check. Without sea otters, the sea urchins can
devastate kelp forests which upsets the
ecosystem.
Sea Urchins
• On the oral surface of the sea urchin is a centrally
located mouth made up of five united calcium
carbonate teeth or jaws, with a fleshy tongue-like
structure within.
• The entire chewing organ is known as Aristotle's
lantern.
Sea Urchins
• Shell, which is also called the "test", is globular in
shape and covered with spines.
Sea Urchin
• The spines, which in some species are long and
sharp, serve to protect the urchin from predators
and aid in locomotion.
• The spines can inflict a painful wound on a human
who steps on one, but they are not seriously
dangerous, and it is not clear that the spines are
truly venomous
Sand Dollars
Class Echinoidea
• Sand Dollars
-- Flattened disk
-- Few animals eat/bother sand dollars.
-- Burrows into the sand.
-- Also called sea biscuits.
Class Holothuroidea
Sea Cucumbers
Class Holothuroidea
• Sea Cucumbers:
-- Look like warty moving pickles
- - arms or rays absent
- - tentacles around mouth
-- Benthic: Live on the ocean floor
Sea Cucumbers
Are little bull dozers
-- Eat detritus in sand
-- Suck up organic matter & remains of other
organisms.
-- Sea cucumbers extract oxygen from water in a
pair of 'respiratory trees' that branch off the cloaca
just inside the anus, so that they 'breathe' by
drawing water in through the anus and then
expelling it.
Sea Cucumber
Sea Cucumbers
• A variety of fish, most commonly pearl fish, have
evolved a Mutualistic symbiotic relationship with
sea cucumbers in which the pearl fish will live in sea
cucumber's cloaca (anus) using it for protection
from predation,
• The pearl fish’s waste provides a source of
food/nutrients to the sea cucumber
Class Holothuroidea
• More Sea Cucumber
-- When threatened, they spill their guts!
-- It takes 1 ½ to 5 weeks to re-grow their guts
-- The predator will eat the ejected guts, &
leaves the sea cucumber alone. It eventually
grows back the lost organs.
-- Yes, people eat them!
The End
Checkpoint
1. List the three classes of Echinoderms studied,
facts about each class, and the organisms that
belong to these classes.