Echinoidea - Sea Urchins
Though probably visible during normal low tides, exploring
further into the crevices of the rocks of the tide pools, you
are likely to find sea urchins. The living urchin is like a pin
cushion covered with red, purple or green spines which are movable
on a socket like base. These spines provide the creature with
a protective coating as well as a means of transportation. Despite
the spines, most California sea urchins can be picked up and
held if done correctly.
Up to 3" wide, it digs holes n the rocks for protection
against the waves. this burrowing is accomplished by a motion
of the test - skeleton - and spines while the animals clings
with its tube feet to the rock. Spines are quickly worn away
by this abrasive contact but they are being constantly renewed
by growth. The purple sea urchin primarily feeds on seaweed,
which is chewed by the five toothed jaw known as Aristotle's
Lantern, located on the underneath or "oral" side of
the creature. Young purple sea urchins are green and due to their
size require more thorough searching to be seen.
Purple Sea Urchin - Strongylocentrotus purpuratus
Red Sea Urchin - Strongylocentrotus franciscanus
The red sea urchin can also be found in these tide pools.
These spines are longer than the purple sea variety and the red
sea urchin does not show these same boring tendencies. If touched
with a sharp object, the spines will immediately bend toward
it as if an effort to keep it away from the test.