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Sea Urchins and Sand Dollars: Echinoidea

Physical Characteristics, Behavior And Reproduction, Sea Urchins, Sand Dollars, And People, Long-spined Sea Urchin (diadema Savignyi): Species AccountsGEOGRAPHIC RANGE, HABITAT, DIET, CONSERVATION STATUS

LONG-SPINED SEA URCHIN (Diadema savignyi): SPECIES ACCOUNTS
PEA URCHIN (Echinocyamus pusillus): SPECIES ACCOUNTS
WESTERN SAND DOLLAR (Dendraster excentricus): SPECIES ACCOUNTS
SIX KEYHOLE SAND DOLLAR (Leodia sexiesperforata): SPECIES ACCOUNTS
TUXEDO PINCUSHION URCHIN (Mespilia globulus): SPECIES ACCOUNTS

Sea urchins and sand dollars live all over the world.

Sea urchins live on wave-exposed rocks, in crevices within rocks, in rock pools, on coral reefs, in sandy lagoons, in sea grass beds, and in kelp forests. Sand dollars live in sand and coarse gravel.


Some sea urchins eat only algae, sea grass, and seaweed. Algae (AL-jee) are plantlike growths that live in water and have no true roots, stems, or leaves. Others also eat small animals and waste particles. Sand dollars eat diatoms and plant particles that accumulate in sand. Diatoms (DYE-uh-tahms) are a type of algae that have a shell.

The World Conservation Union (IUCN) lists one species of sea urchins and sand dollars as Low Risk/Near Threatened, or at risk of becoming threatened with extinction in the future.

Additional topics

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