Transcript Chapter 38 - echinoderms

Ch. 38 – Echinoderms
 Phylum: Echinodermata
Sea stars, sand dollars, brittle stars, & sea
cucumbers
Marine
Usually 5 arms  pentaradial
No circulatory, respiratory, or excretory systems
Water-vascular system
Tube feet that aid in movement
Video
Video
Most invertebrates
have an
exoskeleton to support them .
Echinoderms have an
endoskeleton, which is a skeleton
within the body.
This is why echinoderms are
thought to be closer related to
vertebrates.
5 Classes of Echinoderms
1. Ophiuroidea  brittle stars &
basket stars
2. Crinoidea  sea lilies & feather
stars
3. Holothuroidea  sea cucumbers
4. Echinoidea  sand dollars & sea
urchins
5. Asteroidea  starfish & sea stars
Class: Ophiuroidea
Brittle stars
Gets it name brittle because its has
long, thin arms and are constantly
breaking off and regenerating.
Pg 783
Class: Crinoidea
Sea lilies & feather stars
Sessile
Pg. 782
Class: Holothuroidea
Sea cucumber
Soft body
If threatened the sea cucumber may eject
their organs out of their body at the
predator – called eviscerate. They then
regenerate their organs.
Video- http://www.youtube.com/watch?v=aCxKFc3XtJs
Pg. 784
Class: Echinoidea
Sand dollars & sea urchins
They have an Aristotle’s lantern,
which is a jaw-like structure for
grinding their food.
Sea urchins have long spines with
sometimes venom for protection
Sand dollars are about the size of
a silver dollar.
Class: Asteroidea (sea star)
Body Structure (external)
Aboral surface  Madreporite is located
(top side)
Oral surface  mouth is located (bottom
side)
Ossicles  calcium spines
Pedicellarie  tiny little pinchers that clean
the body surface so debris doesn’t collect.
Video
Water- Vascular System
Used to create movement
Enters the madreporite  stone
canal  ring canal  5 radial
canals lateral canal  the tube
feet (100s of tube feet), have
ampulla (air sacs), that act like a
pipette and release the water with
pressure. Pg. 786
Body Systems
No circulatory, respiratory, or
excretory systems.
Each arm has an eyespot at the end,
which senses light and touch.
Digestion  They have digestive
glands. Their tube feet are strong
enough to open clams & mussels.
Reproduction  Each arm of the
sea star has 2 gonads that produce
eggs and sperm cells. They are
hermaphrodites.
Sea stars can regenerate lost
parts. A new sea star can
regenerate from a segment of an
arm as long as it has part of the
ring canal attached.