Phylum Echinodermata
Spiny Skin Echinodermata 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
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 Asteroidea Class Ophiuroidea (brittle stars and basket stars) Phylum Echinodermata
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.
Body wall 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.
Water vascular system What do Echinoderms look like? Fluid-filled canals for internal transport and locomotion. Moved through system with cilia.
Water vascular system What do Echinoderms look like? 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
Water vascular system What do Echinoderms look like? 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.
Water vascular system What do Echinoderms look like? 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.
Water vascular system What do Echinoderms look like? 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.
Water vascular system What do Echinoderms look like? 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. Sand dollars use spines to burrow in sand. Cucumbers crawl on podia of trivium or by muscular action of the body wall.