General Characteristics Spiny skinned

Lack segmentation

Radial symmetry

Water vascular system

• All marine

• Test made of calcium plates with

protruding spines

• Bilateral, free-swimming larva to sessile

adult

• Adults have pentaradial

(5 part) symmetry

• Separate sexes

Capable of extensive regeneration

• Ventral surface called the oral surface &

where mouth is located

• Dorsal surface known as aboral surface

& where anus is located

• Have a nervous system, but no head or

brain in adults

• No circulatory, respiratory, or excretory

systems

• Have a network of water-filled canals

called the water vascular system to

help move & feed

• Tube feet on the underside of arms

help in moving & feeding

• One-way digestive system consists

of mouth with oral spines, gut, &

anus

Class Asteroidea – sea stars

C. Ophiuroidea – brittle stars

C. Echinoidea – sea urchins/sand dollar

C. Crinoidea – sea lily/feather star

C. Holothuroidea – sea cucumber

Echinoderm Classification

C. Asteroidea – starfish or sea stars

• Usually along shorelines

• Come in a variety of colors

• Prey on bivalve mollusks such as

clams & oysters

• Have 5 arms that can be regenerated

• Arms project from the central disk

•Have pedicellariae or tiny, forcep-like

structures surrounding their spines to help

clean the body surface

• Reproduce sexually & asexually

• Have external fertilization

• Females produce up to 200,000,000

eggs per season

Examples:

Atlantic Sea star: east coast

Bat Star : west coast

Sun Star: 15 to 20 arms, Pacific coast

Crown of Thorns: up to 80 cm, 4-5cm

spines, Great Barrier Reef

Class Crinoidea - sea lilies &

feather stars

FEATHER STAR

SEA LILY

• Have a long stalk with branching arms

that attach them to rocks & the

ocean bottom

• Can detach & move around

• May have 5 to 200 arms with sticky

tube feet to help capture food (filter

feeders) & take in oxygen

• Common in areas with strong currents

& usually nocturnal feeders

Class Ophiuroidea – brittle stars

• Largest class of echinoderms

• Live on the ocean bottom beneath

stones, in crevices, or in holes

• Have long, narrow arms

• Arms readily break off & regenerate

• Move faster than starfish

• Feed by raking in food with arms or

trapping it with its tube feet

Class Echinoidea – sea urchins &

sand dollars

• Internal organs enclosed by

endoskeleton or test made of fused

skeletal plates

• Body shaped like a sphere (sea urchin)

or a flattened disk (sand dollar)

• Lack arms

• Bodies covered with movable spines

• Have a jaw-like, crushing structure

called Aristotle's lantern to grind food

Sea Urchins:

* Spherical shape

* Live on ocean bottom

* Scrape algae to feed

* Long, barbed spines make venom

for protection

Sand Dollars:

* Flattened body

* Live in sand along coastlines

* Shallow burrowers

* Have short spines

Class Holothuroideasea cucumbers

• Lack arms

• Shaped like a pickle or cucumber

• Live on ocean bottoms (hide) in caves

during the day

• Have a soft body with a tough, leathery

outer skin

• Five rows of tube feet run lengthwise

on the aboral surface of the body

• Have a fringe of tentacles (modified

tube feet) surrounding the mouth to

sweep in food &

•water

• Tentacles have sticky

ends to collect

plankton

•Show bilateral symmetry

•Can eject parts of their internal organs

(evisceration) to scare predators;

regenerate these structures in days

The Giant California Sea Cucumber (up to 40cm)