Echinoderms

Section 29.1

Animal Classification

Animals

Invertebrates

Vertebrates

SpongesCnidariansWormsMollusksArthropodsEnchinoderms

Ectotherms(cold-blooded)

Endotherms(warm-blooded)

FishesAmphibiansReptiles

BirdsMammals

Echinoderms

What is an Echinoderm?

Echinoderm (Greek word) “echinos” – spiny “derma” – skin

Rays – long, tapering arms that are covered with short, rounded spines

What is an Echinoderm?

Pedicellariae (PEH dih sih LAHR ee ee) – modified spines into pincerlike appendages

Echinoderms have radial symmetry

Water Vascular System

Water vascular system – a hydraulic system that operates under water pressure

Water enters and leaves the water vascular system of a sea star through the madreporite

Water Vascular System

Madreporite (mah druh POHR ite) – a sievelike, disk-shaped opening on the upper surface of an echinoderm’s body

Water Vascular System

Tube feet – hollow, thin-walled tubes that end in a suction cup

Tube feet look somewhat like miniature droppers

Water Vascular System

Ampulla – the round, muscular structure works like the bulb of a dropper

Tube feet also function in gas exchange and excretion

Varied Nutrition

Sea stars are carnivorous and prey on worms and clams

Brittle stars and sea cucumbers feed on dead and decaying matter that drifts down to the ocean floor

Simple Nervous System

Echinoderms have no head or brain, but they do have a central nerve ring

Each radial nerve branches into a nerve net that provides sensory information to the animal

Simple Nervous System

Sea stars have eyespots located at the tip of each arm

Diversity of Echinoderms

Sea stars Most species of sea stars have five rays, but

some can have up to 40 rays

http://www.youtube.com/watch?v=A100m5EpfFI

Sea Stars

Diversity of Echinoderms

Brittle stars Brittle stars are extremely fragile This adaptation helps the brittle star to distract a

predator

Diversity of Echinoderms

Sea urchins Globe-shaped Do not have rays Look like pin cushions

Sand dollars Disk-shaped Do not have rays A living sand dollar is

covered with hair-like spines

http://www.youtube.com/watch?v=3uwOURjneWQ

Sand Dollars

Diversity of Echinoderms

Sea cucumbers When threatened, they may expel their organs

(intestines) through the anus The organs may rupture and is regenerated in a

few weeks

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

Sea Cucumbers