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

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

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

Sea Urchins

They belong to the Class Echinoidea, one of the five classes of the phylum Echinodermata

Others include sea cucumbers, crinoids, starfish and brittlestars

Phylum Echinodermata

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

Class Echinoidea

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

Larval Forms

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

Tube Feet