Sea Urchin Sea urchin, any of about 950 living species of spiny marine invertebrate animals (class Echinoidea, phylum Echinodermata) with a globular body and a radial arrangement of organs, shown by five bands of pores running from mouth to anus over the test (internal skeleton). The pores accommodate tube feet, which are slender, extensible, and often sucker-tipped. From nodules on the test arise long, movable spines and pedi cellariae (pincer like organs); these structures may have poison…

The rare, spectacular and unique sea urchins seen in this image represent only a fraction of those displayed at the Sea Urchin Science Centre and Gallery in Sydney, Australia. The centre is the only one of its kind in the World, and it is open to the public. Seen here are tests - the internal skeleton - of the Class Echinoidea, commonly referred to as 'regular urchins'. Which one's your favourite?

Sea urchins are social sea creatures.

Sea Urchin

The little sea urchin on top is quite unusual. It was discovered by a research vessel near New Caledonia at a depth of 1000 ft.