Green Sea Urchin Test (also known as the Shore Urchin or Common Urchin)
Kingdom: Animalia, Phylum: Echinodermata, Class: Echinoidea, Order: Camarodonta, Family: Strongylocentrotidae, Genus: Strongylocentrotus, Species: S. droebachiensis · Strongylocentrotidae (Sea Urchin family) · Echinoid Test (not a true shell, but an endoskeleton of a marine invertebrate); Shape: Globose/Discoidal
Species
Strongylocentrotus droebachiensis (Likely, 85% confidence based on tubercle density and shape)
Shell Type
Echinoid Test (not a true shell, but an endoskeleton of a marine invertebrate); Shape: Globose/Discoidal
Family
Strongylocentrotidae (Sea Urchin family)
Size
Approximately 1.5 - 2 inches in diameter. This is a sub-adult size; adults typically reach 3 to 4 inches.
Color & Pattern
Naturally dull white to off-white with subtle greenish or tan hints near the apical disc. The test appears sun-bleached, as living specimens are vibrant green or olive. The pattern consists of five radiating ambital sections defined by rows of small circular bumps (tubercles).
Rarity
Common (frequently found washed up on northern beaches after storms, though usually in fragments).
Habitat
Typically found in the intertidal and subtidal zones up to 1,000 meters deep. Prefers rocky substrates, kelp forests, and cold water environments.
Geographic Range
Circumpolar; found in the North Atlantic and North Pacific, ranging from the Arctic down to New Jersey in the US and to the UK in Europe.
Description
A lightweight, fragile globose dome known as a test. The surface is adorned with numerous small mamillated tubercles where spines were once attached. It features five distinct segments in a pentamerous symmetry. The central hole visible is the apical system where the madreporite and gonopores are located.
Key Features
Pentamerous (five-part) radial symmetry; small, numerous primary tubercles; circular shape; high-domed profile compared to sand dollars; central apical opening.
Collector Value
Low to Moderate ($2 - $10 USD). While common, finding a whole, unbroken test on the beach is a highlight for casual collectors. Larger, perfectly preserved specimens with original green coloration are more desirable.
Condition Notes
Good condition. The test is intact and not crushed, which is rare for beach-found urchins. It shows significant sun-bleaching (loss of green pigment) and all spines have been naturally removed by wave action. Collectibility Grade: Fine.
Interesting Facts
The living animal moves using tube feet and a complex set of five teeth called 'Aristotle's Lantern.' They are known for 'grazing' on kelp forests and can create 'urchin barrens' if their population is not checked by predators like sea otters or lobsters.
Ecological Role
Primary consumer/herbivore. They play a critical role in controlling algae growth but can be destructive to kelp ecosystems if overpopulated. They are a vital food source for birds, crabs, and sea stars.
Similar Species
Psammechinus miliaris (Green Sea Urchin of Europe) which is smaller with a flatter profile, and Strongylocentrotus purpuratus (Purple Urchin) which has a deeper, more vibrant purple test.
Beach Finding Tips
Search the high-tide line after a heavy storm. Look in sheltered rocky coves or within piles of washed-up kelp (wrack lines) where the light tests often get caught.