Class Echinoidea
Subclass Euechinoidea
Order Echinoida
Order Clypeasteroida
Subclass Euechinoidea
Order Echinoida
Strongylocentrotus purpuratus (Stimpson, 1857)
Phylum Echinodermata, Class Echinoidea, Subcl. Euechinoidea, Order Echinoida, Family Strongylocentrotidae
Purple sea urchin; test 5 cm diameter (10 cm max), spines short (usually < half diameter of test). Small juveniles often white.
Common on rocky substrate, in crevices & other sheltered microhabitats inaccessible to sea otters. Herbivorous with a strong preference for giant kelp.
Geogr. Range: Alaska to Baja
Synonyms:
Similar species: Mesocentrotus franciscanus is larger, redder and has longer spines relative to test
Image: Stylaster (hydrocoral), Corynactis (bottom cntr.& rt.), Diplosoma (lower left)
Mesocentrotus franciscanus (A. Agassiz, 1863)
Phylum Echinodermata, Class Echinoidea, Subcl. Euechinoidea, Order Echinoida, Family Strongylocentrotidae
Red sea urchin; test to 10 cm diameter or more. Spines long (usually > half diameter of test).
Moderately common in Monterey region, in crevices where sea otters cannot reach them. Herbivorous with preference for giant kelp.
Geogr. Range: Alaska to Baja
Synonyms: Strongylocentrotus franciscanus
Similar species: juvenile Strongylocentrotus purpuratus is smaller with shorter spines.
Lytechinus pictus (Verrill, 1867)
Phylum Echinodermata, Class Echinoidea, Subcl. Euechinoidea, Order Camarodonta, Family Toxopneustidae
Light-colored sea urchin; test to 4 cm diameter. Spines shorter than M. franciscanus. Test white to yellowish or purple-gray, with irregular dark purple blotches.
Uncommon; appeared in Monterey region at shallow depths ~2012. Herbivorous; consumes a variety of smaller seaweeds.
Geogr. Range: Santa Rosa Island to Baja
Synonyms: Lytechinus anamesus
Similar species: juvenile Strongylocentrotus purpuratus may also be white-ish, but lack irregular dark blotches on test.
Order Clypeasteroida
Dendraster excentricus (Eschscholtz, 1831)
Phylum Echinodermata, Class Echinoidea, Subcl. Euechinoidea, Order Clypeasteroida, Family Dendrasteridae
Sand dollar; test oval & flat, 7 cm diameter; dark gray, brown, or purplish, covered with short club-tipped spines. Dead skeleton (pictured) white with distinctive petaloid pattern where respiratory tube feet project.
Common, in dense aggregations on sand with moderate to strong water motion. Diet of particulate detritus, unattached drift algae & small motile prey such as larvae & copepods.
Geogr. Range: Alaska to Baja
Synonyms:
Similar species: