Phylum Echinodermata

Phylum Echinodermata (spiny skin)• Sea stars, sea urchins, sea cucumbers• Pentamerous radial symmetry • Oral/aboral sides (anus), no brains• Endoskeleton• Water vascular system that extends to muscular

tube feet (madreporite pulls in H2O)• Tube feet end w/ sucker for attachment,

movement and receiving stimuli

Sea Stars/Starfish• Five arms from a central disk usually• 100’s tube feet in ambulacral grooves, slow

moving, gas exchange• Endoskeleton made of interconnected CaCO3 plates

for flexibility• Spines like mini-pincers (pedicellariae)

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

Nervous System• Nerve net similar to cnidarians (no brain)– Coordinates movement of tube feet and spines

• More complex behavior– Rightning of body– http://www.youtube.com/watch?v=44iw5FvYb7s

Feeding and Digestion• If prey is bigger than mouth, flip stomach

outwards and release digestive enzymes• Prey on bivalves, gastropods, barnacles

Reproduction (Sexual)

• Timed spawning (Sexual)• Larvae are bilaterally symmetrical

Reproduction (Asexual)• Can separate central disk or body into two

pieces (sea stars, brittle stars, sea cucumber)• Regeneration- ability to grow lost or damaged

body parts – Needs part of central disk in most cases

Sunflower star• Up to 24 arms• Moves at 1m/min• 15,000 tube feet!

Brittle Stars• 5 arms, longer, flexible, sharply demarcated

from central disk• Tube feet without suckers• Lack anus

Feather Stars

Crown of Thorns Starfish

• Menace to coral reefs• One of the poisonous varieties of echinoderm

Sea Urchins• Round, rigid endoskeleton (test), movable spines,

pincers, tube feet along body• Mouth on bottom (Aristotle’s lantern), anus on top• Feed on seaweeds, detritus• Sand dollars have flat bodies, short spines– Deposit feeders

http://imageshack.us/

Sea Cucumbers• No spines, no test (calcareous spicules only)• Elongated body plan• 5 rows tube feet extending from mouthanus• Deposit feeders- feeds on organic matter• Burrow often

• Defense: discharge sticky, sometimes toxic, substance. Some expel organs from mouth/anus to distract (evisceration)

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