Sea Urchin Embryology Back to Contents page       SUMMARY:
Interesting information about the sea urchin.   There are no
fresh water echinoderms. This may be why people most often
associate the sea with sea urchins and starfish, more than any
other organisms. Echinoderms are a very successful group, first
showing up in the fossil record some 600,000,000+ years ago.
Though at their peak there were as many as 20,000 species there
are still a respectable 6,000 species today. They occur at all
depths and in all climates. See Classification Tree  We will be
primarily concerned with the sea urchins, 700 species, as this
is the organism we use in our work. What they lack in species,
they make up for in numbers. It is thought that the primary
macroscopic organism on the deep sea floor is the sea urchin.
Fossil sea urchins from Pat Antonio's collection, Pacific Grove,
CA.   Sea urchins live only in the ocean and cannot survive in
fresh water. They are found from the intertidal to the deep
ocean. The species that we ar