Green Sea Urchin Test (Sea Urchin Shell)
Phylum: Echinodermata, Class: Echinoidea, Order: Echinoida, Family: Strongylocentrotidae, Genus: Strongylocentrotus, Species: Strongylocentrotus droebachiensis · Strongylocentrotidae (Strongylocentrotid urchins) · Echinoid test (endoskeleton, often collected as a shell)
Species
Strongylocentrotus droebachiensis
Shell Type
Echinoid test (endoskeleton, often collected as a shell)
Family
Strongylocentrotidae (Strongylocentrotid urchins)
Size
Approximately 2 to 3 inches in diameter, which is typical for an adult of this species, ranging generally from 1.5 to 3.5 inches.
Color & Pattern
Pale greenish-yellow to off-white base color due to being a weathered test (shell) without spines or skin. The surface features numerous prominent tubercles where spines were once attached, arranged in distinct ambulacral and interambulacral plates.
Rarity
Common in appropriate cold-water rocky coastal environments, though intact tests washed ashore can be fragile and require some searching to find undamaged.
Habitat
Found in shallow marine waters, rocky subtidal zones, kelp forests, and tide pools, typically ranging from the low intertidal zone down to depths of several hundred feet.
Geographic Range
Circumpolar distribution in cold northern waters, including the North Atlantic (south to New Jersey in the west and the English Channel in the east) and the North Pacific.
Description
This specimen is the calcareous endoskeleton, or 'test', of a sea urchin. It features a nearly spherical, slightly flattened globular shape with a central opening (peristome) visible. The surface is intricately patterned with vertical rows of tubercles and microscopic pore pairs through which the urchin's tube feet once extended. The texture is chalky yet rigid, composed of fused plates that once held moveable spines.
Key Features
Spherical to slightly flattened globular test, prominent rows of primary and secondary tubercles, distinct ambulacral and interambulacral plates, and a prominent central aperture.
Collector Value
Low to moderate commercial value, often sold in shell shops and coastal gift stores, but highly valued by beachcombers and nature crafters as a decorative natural specimen.
Condition Notes
Good condition for a beach-combed or naturally cleaned test. All spines and soft tissues have weathered away, exposing the fragile porous calcareous shell. Some minor wear on the tubercles is visible, but the structural integrity of the test remains largely intact.
Interesting Facts
When alive, sea urchins are covered in sharp, moving spines and hundreds of tiny tube feet used for locomotion, feeding, and anchoring. They graze heavily on kelp and algae, sometimes creating 'urchin barrens' if predator populations decline.
Ecological Role
Plays a vital role as a primary herbivore in kelp forest ecosystems, controlling algae growth. They serve as an important food source for sea otters, large fish, crabs, and seabirds. Populations are regulated by natural predators.
Similar Species
Purple Sea Urchin (Strongylocentrotus purpuratus) which tends to have a more intense purple hue, and various species of heart urchins or cake urchins which are distinctly flattened or heart-shaped.
Beach Finding Tips
Look along rocky northern beaches, tide pools, and kelp-strewn shorelines, especially after heavy storms or rough wave action that dislodges urchins from subtidal rocky reefs.