Transcript Phylum Echinodermata

Phylum Echinodermata
1. Echinodermata = “spiny skin”
2. Examples: Sea Star, Sea Urchin, Sea Cucumber,
and sand dollars.
A. Radial symmetry- body parts repeat around the
center of the body.
1. No front or back
2. Do have a top (dorsal) and bottom (ventral).
B. Internal skeleton made of stiff plates of calcium
carbonate, called ossicles, which are found on the
skin of the echinoderm.
C. Network of tubes & appendages
D. Bipinnaria – Larvae of echinoderms
2. Water vascular system
A. Network of fluid filled canals that transport
water throughout the echinoderms boy creating
a powerful suction for movement, opening up
mollusk and gripping surfaces.
B. Connected to tube feet
C. Used for:
1. feeding
2. movement
3. respiration
4. excretion
• D. Madreporite – small pores
on the dorsal surface where
water enters. It is attached to
the stone canal, that is
attached to the ring canal.
• E. Stone Canal – short tube
attached the madreporite to
the ring canal.
•.
• F. Ring canal – ring in the
center of the sea stars body
that attaches to the radial
canals.
• G. Radial Canal – extends
from the ring canal to the end
of each arm which carries
water to hundreds of tube feet.
• F. Tube Feet – end of the radial
canal. Much like a suction cup
that has a sucker on the end and
muscles, With water, suckers and
muscles, a hydraulic system is
created, creating enormous force
for walking and opening clams.
• G. Ampulla – a bulblike sac
found on each end of a tube foot
where water is forced in and out.
TUBE FEET
Starfish eating muscle
3. Feeding
A. Oral side is where the mouth is
located.
1). There are many methods of
feeding, we will concentrate on the
sea star only.
a. The sea star wraps it’s arms
around a mollusk, opens it’s shell
slightly using it’s enormous force from
it’s water vascular system.
b. Once slightly opened, the
stomach of the seastar inverts
and drops down into the soft
body parts of the mollusk
breaking down and digesting
it’s soft body parts. (the
stomach is still attached to the
sea star).
c. When finished it will
pull it’s stomach back into it’s
central cavity.
4. Nervous system
A. No brain but has nerve
cells. (nerve ring) and radial
nerves.
B. Sensory cells – taste and
smell.
C. Eyespots – detect light.
D. Statocysts – which way is
up.
9. Classes
A. Asteroidea
1. ex. Sea stars
2. 5 or more arms
a. with tube feet
3. carnivores
Crown of thorns
sea star
Unlike most other sea stars that have five arms, the
crown-of-thorns has 12 to 19 arms. This star can grow to
20 inches (50 cm) in diameter. It is the only sea star that
is venomous, and devourers coral reefs while it moves
along them. They are extrememly destructive, and are a
huge problem for marine life.
4. Ability to regenerate an arm as long
as some or part of the central cavity is
present.
B. Ophiuroidea
1. ex. Brittle stars, basket stars
2. long thin, flexible arms
3. nocturnal
Sea Stars
C. Echinoidea
1. ex. Sand dollars and sea urchins
2. nocturnal
D. Holothuriodea
1. ex. Sea cucumbers
2. detritus feeders
E. Crinoidea
1. ex. Sea lilies
2. most ancient members of the phylum