Phylum: Echinodermata
Class: Echinoidea
Order: Echinoida
Family: Strongylocentrotidae

Genus/species: Strongylocentrotus franciscanus

GENERAL CHARACTERISTICS: Largest urchin found in the Pacific Northwest. Color of spines varies–may be red, brick-red, pink, purple, or even maroon. Tube feet are dark, often wine red. The largest recorded test diameters approaching 19 cm (7.5 inches). Spines up to 7 cm (2.75 inches) long. (deters predators and facilitates movement).

(Strongylocentrotus purpuratus is smaller and a strong purple color. )

Strongylocentrotus franciscanus6063267260_280398b0bb_o

DISTRIBUTION/HABITAT: N. Japan and Alaska to Isla Cedros, Baja California. Found in very low intertidal on open, coastal rocky substrates; more abundant subtidally to 90 m deep. Juveniles often shelter among the rigid outer spines of adults.

Strongylocentrotus franciscanus3750941637_8fa3f8704a_o

DIET IN THE WILD: Herbivorous upon red and brown algae; preference is for the giant brown kelp Macrocystis. Their grazing can cause “barren grounds” in which no algae remain.

Strongylocentrotus franciscanus8519677227_2871028244_k

REPRODUCTION: Broadcast spawners. Fertilized eggs develop into planktonic larvae, known as echinoplutei, which go through a number of stages of development over 6-10 weeks then settle to substrate.

MORTALITY: Can live more than 100 years. A favored treat of sea otters. Other predators include the sunflower star Pycnopodia helianthoides, leather star Dermasterias imbricata, red rock crab Cancer productus, spiny lobster Panulirus interruptus and sheepshead fish. Starfish may swallow red sea urchins whole or split the animals open along their vertical axis.


REMARKS: Raw gonads (uni) are considered gastronomic delicacies by some people. Removal of sea urchins promotes growth of kelp and thus improves habitat for many other species, including rockfish juveniles .

Small urchins (less than 5 cm test diameter) often hide under the adults.

Have been known to bore holes into metal pier pilings.

Tube feet of red sea urchins are chemo-receptive, allowing them to detect food sources and predators.

They may reabsorb their own tissues if no other source of energy is present. (“Red Sea Urchins”, 2013; Kato and Schroeter, 1985)

LOCATION California Rocky Coast


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