Download Phylum Echinodermata

Phylum Echinodermata
Phylum Echinodermata
About 7,000 species
Strictly marine, mostly benthic.
Typical deuterostomes.
Phylum Echinodermata
Class Crinoidea (sea lilies)
Phylum Echinodermata
Class Crinoidea
Class Asteroidea (sea stars)
Phylum Echinodermata
Class Crinoidea
Class Asteroidea
Class Ophiuroidea (brittle stars and
basket stars)
Phylum Echinodermata
Class Crinoidea
Class Asteroidea
Class Ophiuroidea
Class Echinoidea (sea urchins and
sand dollars)
Phylum Echinodermata
Class Crinoidea
Class Asteroidea
Class Ophiuroidea
Class Echinoidea
Class Holothuroidea (sea cucumbers)
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.
Ambulara C and D are the bivium, A B
and E are the trivium.
What do Echinoderms look like?
Body wall
Epidermis covers entire body.
Endoskeleton of ossicles with
tubefeet and dermal branchia
protruding through and spines and
pedicellaria on outside.
What do Echinoderms look like?
Body wall
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.
What do Echinoderms look like?
Body wall
Tubercles and moveable spines on
skeletal plates of echinoids.
Small muscles attach spines to test.
What do Echinoderms look like?
Water vascular system
Fluid-filled canals for internal
transport and locomotion.
Fluid similar to sewater but has
coelomcytes and organic
molecules.
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. Also has Polian vessicles
(maintain internal pressure) and Tiedemann’s bodies (produce
coelomcytes).
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?
Support
Calcareous endoskeleton with different degrees of calcification.
Holothuroids have very muscular body walls.
How do Echinoderms support themselves and move?
Movement
How do Echinoderms support themselves and move?
Movement
Sand dollars use spines to burrow in sand.
Cucumbers crawl on podia of trivium or by
muscular action of the body wall.
How do Echinoderms support themselves and move?
Nervous system
Decentralized without cerebral ganglia.
Relatively simple receptors: chemoreceptors, statocysts, touch.
Some brittle stars have sclerites that act as tiny lenses across their
dorsal surface and work together as one giant lens.
How do Echinoderms feed and digest?
s
How do Echinoderms feed and digest?
Asteroids
Most are predators and scavengers. Eversible portion of stomach
(cardiac stomach) extruded onto or into prey.
How do Echinoderms feed and digest?
Asteroids
Mouth ---> cardiac stomach ---> pyloric stomach ---> pyloric ducts
---> pyloric cecae ---> intestine ---> anus
How do Echinoderms feed and digest?
How do Echinoderms feed and digest?
Echinoids
Herbivores, suspension feeders, detritovores. Urchins have Aristotle’s lantern. Hard plates and muscles that
control protraction of five teeth.
Teeth scrape algae off rocks and take
bites of macroalgae. Can excavate
holes in rocks.
How do Echinoderms feed and digest?
Echinoids
Digestive mouth system ---> esophagus out of Aristotle’s lantern --->
long intestines ---> rectum ---> anus.
How do Echinoderms feed and digest?
Holothuroids
Suspension and deposit feeders.
Extend mucus-covered buccal tentacles into water. Tentacles are
pushed into mouth one at a time.
Mouth ---> esophagus ---> long intestines ---> rectum ---> anus.
How do Echinoderms feed and digest?
Holothuroids
Cuverian tubules - blind sticky tubes at base of respiratory tree.
Entangle predators.
Evisceration.
How do Echinoderms maintain homeostasis?
Circulation
Internal transport by coeloms, water vascular system, and hemal
systems.
Hemal system - array of canals and spaces enclosed within coelomic
channels called perihemal sinuses. Parallels water vascular system.
Probably helps distribute respiratory gases and nutrients.
How do Echinoderms maintain homeostasis?
Gas exchange
Across podia and dermal gills (dermal
branchia).
Countercurrent exchange.
How do Echinoderms maintain homeostasis?
Gas exchange
How do Echinoderms maintain homeostasis?
Gas exchange
Holothuroids have respiratory trees. Water is actively pumped
by muscular hind end. Gases picked up by coelom and
hemal system.
How do Echinoderms maintain homeostasis?
Osmoregulation
Osmoconformers.
Waste is usually ammonia lost across podia and dermal
branchia.
How do Echinoderms reproduce and develop?
Asexual reproduction
Most capable of regenerating lost parts. Holothuroids
regenerate intestines and respiratory trees.
Asteroids and ophiuroids regenerate lost arms and suckers.
How do Echinoderms reproduce and develop?
Sexual reproduction
Most gonochoristic.
Gonads housed in genital sinuses. In classes with multiple
gonads, each has own gonopore in an interambulacral area.
How do Echinoderms reproduce and develop?
Sexual reproduction
Free spawning with indirect development to brooding with
direct development.
How do Echinoderms reproduce and develop?
Sexual reproduction
Isolecithal egg with small amount of yolk.
Radial holoblastic cleavage ---> coeloblastula --->
coelogastrula by invagination ---> blastopore becomes anus
---> coelom formation by enterocoely ---> embryo becomes
bilaterally symmetrical and develops into a larva.
Vitellaria of crinoid
Bipinnaria and brachiolaria of seastars
How do Echinoderms reproduce and develop?
Sexual reproduction
Isolecithal egg with small amount of yolk.
Radial holoblastic cleavage ---> coeloblastula --->
coelogastrula by invagination ---> blastopore becomes anus
---> coelom formation by enterocoely ---> embryo becomes
bilaterally symmetrical and develops into a larva.
Echinopluteus
of urchin.
Aricularia of
sea cucumber