1. Sea Urchins
Sea Urchins have radially symmetrical bodies divided into 5 equal parts
They move about using articulating spines and tube feet
Jawed tube feet called pedicellariae are employed for defense along with sometimes venomous spines

2. Sea Urchins Urchins feed upon algae, sponge, or detritus.
Tend to be found in structured habitats by day and move about the reef at night to feed
Their hard jaws and stout spines are capable of eroding coral or rock in some species
Urchin roe is a delicacy in Japan and supports a fishery in the North Pacific

3. Sea Urchins
Sea urchins are a group of marine invertebrates that today can be found in almost every major marine habitat - poles to the equator; intertidal zone to >5,000 meters
Around 800 extant species
Fossil record stretching back 450 million years to the Late Ordovician Period

4. Phylum Echinodermata
They belong to the Class Echinoidea, one of the five classes of the phylum Echinodermata
Others include sea cucumbers, crinoids, starfish and brittlestars

5. Class Echinoidea
All echinoderms have a skeleton composed of plates embedded in their skin (their skeleton is internal and called a test)
Plates in the test are arranged into 5 columns radiating from an (top) apical zone to the mouth – called pentaradiate

6. Larval Forms
Sea urchins have a very characteristic larval development, passing first through a bilateral planktonic larval stage
After several weeks this larva undergoes a metamorphosis which gives rise to the adult body form

7. Tube Feet
All echinoderms have tube-feet and in echinoids these play a very important role in feeding and respiration
Echinoids move by means of spines and climb and cling on to hard substrata by means of their tube-feet