View
279
Download
4
Category
Preview:
Citation preview
Phylum Echinodermata
Echinodermata • “Spiny Skin”
• Radially symmetrical in five ways (pentamerous)
Echinodermata • No head, right or left side, or top or bottom, so
we refer to the “oral surface” (mouth side) and the “aboral surface” (side without a mouth)
Echinodermata • Complete digestive tract
• Coelom
• Endoskeleton
• Water vascular system
• Tube feet
Echinodermata
Examples of Echinoderms • Sea Stars
Examples of Echinoderms • Brittle Stars
Examples of Echinoderms • Urchins
Examples of Echinoderms • Sand Dollars
Examples of Echinoderms • Sea cucumbers
Phylum Echinodermata
About 7,000 species Strictly marine, mostly benthic.
Phylum Echinodermata
Class Crinoidea (sea lilies)
Phylum Echinodermata
Class Crinoidea
Class Asteroidea (sea stars)
Phylum Echinodermata
Class Crinoidea
Class Ophiuroidea (brittle stars and basket stars)
Class Asteroidea
Phylum Echinodermata
Class Crinoidea
Class Echinoidea (sea urchins and sand dollars)
Class Ophiuroidea
Class Asteroidea
Phylum Echinodermata
Class Crinoidea
Class Holothuroidea (sea cucumbers)
Class Echinoidea Class Ophiuroidea
Class Asteroidea
What do Echinoderms look like?
Pentamerous radial symmetry. Oral and aboral surfaces. Oral surface has ambulacral grooves associated
with tubefeet called podia.
What do Echinoderms look like?
Oral and aboral surfaces.
What do Echinoderms look like?
Arms (ambulacra) numbered with reference to the madreporite. Ambulacrum opposite is A then proceed couterclockwise.
What do Echinoderms look like?
Epidermis covers entire body. Endoskeleton of ossicles with
tubefeet, spines and pedicellaria on outside.
Body wall
What do Echinoderms look like?
Ossicles can be fused into a test (urchins and sand dollars). Ossicles spread apart in cucumbers. Ossicles intermediate and variable in seastars. Muscle fibers beneath ossicles.
Body wall
What do Echinoderms look like?
Tubercles and moveable spines on skeletal plates of echinoids.
Small muscles attach spines to test.
Body wall
What do Echinoderms look like?
Pedicellaria in echinoids and asteroids. Respond to external stimuli independent of
nervous system. Keep debris and larvae from settling, protection,
hold on to material for camouflage, capture prey.
Body wall
What do Echinoderms look like?
Water vascular system
Fluid-filled canals for internal transport and locomotion.
Moved through system with cilia.
What do Echinoderms look like?
Water vascular system
Asteroidea: Madreporite on aboral surface. Grooved with ciliated epidermis. May
allow seawater into vascular system. Ampulla under madreporite connected to water vascular system and
hemal system. Stone canal connects ampulla to rest of system. Connects to ring canal. Ring canal leads to radial canals in each arm
What do Echinoderms look like?
Water vascular system
Radial canals lead to lateral canals which pass through pores in the skeletal plates and end in tube feet.
Each tube foot has an ampulla on top
and a suckered muscular podium on bottom.
Tube feet used for locomotion, prey capture, adherence to substratum.
Terminal tubefeet are chemosensory.
What do Echinoderms look like?
Water vascular system
Tube feet move by combination of muscles and hydraulics.
Valve at lateral canal that shuts and isolates the tubefoot.
Ampulla contracts and pushes fluid into the tubefoot to extend it.
Sucker pressed on substratum and sticks with adhesive secretions. Longitudinal muscles contract to raise middle of sucker to create a
vacuum. Also shortens podium, forcing water back into ampulla. For release, longitudinal muscles relax, ampulla contracts and water
forced back into podium. Suction released.
What do Echinoderms look like?
Water vascular system
Ophiuroids: Madreporite on oral surface. Tudefeet don’t have suckers.
Flexible used for feeding.
Crinoids: Water vascular system entirely
coelomic fluid. No madreporite, many stony canals.
Radial canals extend up each arm. Suckerless podia on branches called
pinnules.
What do Echinoderms look like?
Water vascular system
Echinoids: Madreporite on special plate around
aboral pole. Podia pass through holes in
ambulacral plates
Holothuroids: Madreporite internal and open to
coelom. Three rows of tube feet (trivium) on
“ventral” surface, two rows (bivium) on “dorsal” surface.
How do Echinoderms support themselves and move?
Movement
Crinoids walk on the tips of their arms. Some swim.
Asteroids crawl with tube feet.
How do Echinoderms support themselves and move?
Movement
Ophiuroids use flexible arms for crawling.
Urchins use tube feet and moveable spines.
Cucumbers crawl on podia of trivium or by muscular action of the body wall.
Sand dollars use spines to burrow in sand.
Recommended