INTRO TO

ECHINODERMS P1, 5

Phylum Echinodermata

• Means “spiny skinned”

• Members called echinoderms

5 Main Classes

• Asteroidea sea stars

• Echinoidea sea urchins & sand dollars

• Ophiuroidea brittle stars

• Crinoidea sea lilies & feather stars

• Holothuroidea sea cucumbers

Key Characteristics

• Lack segmentation no

cephalothorax or abdomen

• Radial symmetry (usu. 5-part)

• Has central point of body

• All similar structures regularly

arranged around it

• Internal skeleton called

endoskeleton

SEA STARS P1, 5

Sea Star Anatomy

Jonathan Bird’s Blue World – Sea Stars

• https://www.youtube.com/watch?v=vxbW4W_nM

Zs

• Please write in your notes:

• Northern Sea star

• Basket star

• Crown-of-thorns sea star

• Giant Pacific sun star

• Blue Linckia sea star

• For each sea star, jot down the behavior/life

activity described by Jonathan Bird

Adaptations in the Sea Star

Survival & Protection

• Often lose an arm in struggles can regenerate

• Spiny covering provides support & protection

Respiration & Circulation

• Breathe t/ skin & tube feet

• Skin gills on dorsal side, tube feet on ventral side

• O2 diffuses into fluid-filled space called coelom

• Ciliated cells circulate oxygenated fluid around body

• Open circulatory system

Adaptations in the Sea Star (cont’d)

Feeding & Locomotion

• Use tube feet for movement & food-getting

• Suction disks cling to surfaces

• Feed primarily on bivalves • Pull on shells in opposite direction w/ tube feet

• Adductor muscles get tired & bivalve opens

• Push stomach into shell & digest prey externally w/ enzymes

• Water vascular system allows for locomotion • Sieve plate stone canal ring canal radial canals tube

feet

• Ampullae of tube feet contracts tube feet extends

• Tube feet contracts water forced back into ampullae creates suction

Adaptations in the Sea Star (cont’d)

Reproduction & Regeneration

• Separate sexes, but must examine internally to

identify

• Gonads located in each arm near central disk

• Sperm & eggs shed into water

• External fertilization, external development

• Asexual reproduction t/ regeneration

• If arm torn off, whole new sea star can grow from

severed arm if part of central disk is present

Zombie Sea Stars video

• https://www.youtube.com/watch?v=KrfcglOmBYw

SEA URCHINS & SAND

DOLLARS P1, 5

Sea Urchins

• Class Echinoidea

• Movable spines attached

to endoskeleton

• Use spines & tube feet to

move

• Endoskeleton formed by

fused bony plates (CaCO3)

• Inhabit intertidal & subtidal

zones along rocky coasts

• Scrape algae off rocks w/

five-toothed mouth

structure called Aristotle’s

lantern

Long-spined sea urchin

Purple & green sea urchin

Rock-boring urchin

Life Cycle of the Sea Urchin

• Male & female can’t tell gender

externally

• External fertilization, external

development

• Larvae part of plankton

community until settle on seafloor

Army of Sea Urchins

• https://www.youtube.com/watch?v=D3W4OCnHyCs

Sand Dollars & Sea Biscuits

• Sand dollars have short spines covering skin

• Use to burrow in sand

• Feed by catching plankton & organic debris in sticky strings beneath spines

• Flat endoskeleton (CaCO3) remains often collected by people

• Sea biscuits are more rounded w/ longer spines

• Inhabits sandy seafloors around coral reefs

• Eats organic debris & algae

BRITTLE STARS P1, 5

Brittle Stars

• Class Ophiuroidea

• Most abundant of echinoderms

• Nocturnal, bottom-dwelling animals hide under rock during day

• Live in intertidal zone (arctic to tropics)

• Subgroup called basket stars • Live on deep ocean floor

• Distinct flattened central disk

Locomotion & Food-Getting

• Do NOT use tube feet

for movement have

muscles in arms

• Multiple feeding

methods:

• Use arms to gather

organic debris

• Capture live

invertebrates

• Filter-feed using sticky

strands

• Capture suspended food

bits w/ tube feet

SEA LILIES & FEATHER

STARS P1, 5

Sea Lilies & Feather Stars

• Class Crinoidea

• Members called crinoids

• Most ancient group of echinoderms

• Body composed of dozens of feathery

arms perched atop jointed stalk

• Generally limited ability to move

• Sea lilies sessile

• Feather stars crawl along coral reefs &

swim by flapping arms

• Filter feed by waving arms & capturing

zooplankton w/ tube feet

• Also do NOT use tube feet for

locomotion

Feather Star Videos

Feather Star Swimming

https://www.youtube.com/watch?v=rRej1VKDgcE

Feather Star Feeding

https://www.youtube.com/watch?v=3mz0jNyHkJ0

Sea Urchin Consumes Feather Star

https://www.youtube.com/watch?v=LNbT-VhoWXs

SEA CUCUMBERS P1, 5

Sea Cucumbers

• Class Holothuroidea

• Soft, oblong body lacks

arms, but has tube feet

arranged in 5 rows

• Lost endoskeleton & spines

only small bony pieces

in skin

• Live on sandy & rocky

seafloors in intertidal &

subtidal zones

• Most abundant at great

depths

Life Activities

• Use sticky, branching tentacles (modified tube feet) to trap

microscopic organisms

• Located around mouth

• Can extend & retract

• 5 rows of tube feet help it move slowly & trap food

particles in sand

• One-way digestive tract

• Breathe t/ anus

• Water goes in gas exchange occurs inside coelom across

membranes of respiratory tree

• Can release digestive organs when disturbed

• Predator eats decoy later regenerates lost organs

Sea Cucumber Videos

Sea Cucumber Fights With Guts

https://www.youtube.com/watch?v=wXf_YodWw40

Most Extreme

https://www.youtube.com/watch?v=vsLBOkYLLeI

Pearlfish Hides Inside a Sea Cucumber

https://www.youtube.com/watch?v=giA16BoH_no