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

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.

Oral and aboral surfaces. What do Echinoderms look like?

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.

Body wall What do Echinoderms look like? Epidermis covers entire body. Endoskeleton of ossicles with tubefeet and dermal branchia protruding through and 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 asreroids. Respond to external stimuli independent of nervous system. Keep debris and larvae from settling, protection, hold on to material for camouflage.

Water vascular system What do Echinoderms look like? Fluid-filled canals for internal transport and locomotion. Fluid similar to sewater but has coelomcytes and organic molecules. 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. Also has Polian vessicles (maintain internal pressure) and Tiedemann s bodies (produce coelomcytes).

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 Ophiuroids: Madreporite on oral surface. Tudefeet don t have suckers. Flexible used for feeding. What do Echinoderms look like? 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? Support Calcareous endoskeleton with different degrees of calcification. Holothuroids have very muscular body walls.

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.

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.

Crinoids How do Echinoderms feed and digest? Filter feed with oral side up and arms and pinnules outstretched. Food particles brought to mouth via cilia in ambulacral grooves. Mouth opens to short esophagus, to long intestine, to anus.

Asteroids How do Echinoderms feed and digest? Most are predators and scavengers. Eversible portion of stomach (cardiac stomach) extruded onto or into prey.

Asteroids How do Echinoderms feed and digest? Mouth ---> cardiac stomach ---> pyloric stomach ---> pyloric ducts ---> pyloric cecae ---> intestine ---> anus

Ophiuroids How do Echinoderms feed and digest? Predators, scavengers, filter feeders, deposit feeders. Food collected and passed along podia and spines to mouth. Digestive system reduced with no anus.

Echinoids How do Echinoderms feed and digest? 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.

Echinoids How do Echinoderms feed and digest? Digestive mouth system ---> esophagus out of Aristotle s lantern ---> long intestines ---> rectum ---> anus.

Holothuroids How do Echinoderms feed and digest? 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.

Holothuroids How do Echinoderms feed and digest? Cuverian tubules - blind sticky tubes at base of respiratory tree. Entangle predators. Evisceration.

Circulation How do Echinoderms maintain homeostasis? 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.

Gas exchange How do Echinoderms maintain homeostasis? Across podia and dermal gills (dermal branchia). Countercurrent exchange.

Gas exchange How do Echinoderms maintain homeostasis? Ophiuroids have ten invaginations in the body wall called bursae. Water circulated by cilia.

Gas exchange How do Echinoderms maintain homeostasis? Holothuroids have respiratory trees. Water is actively pumped by muscular hind end. Gases picked up by coelom and hemal system.

Osmoregulation How do Echinoderms maintain homeostasis? 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. Ophiopluteus of brittle star Echinopluteus of urchin. Aricularia of sea cucumber