Sealife guideThe red sea urchinMesocentrotus franciscanus
Last updated on 09/30/2025 at 11:08 PM
Taxonomy
Description
The red sea urchin is the largest sea urchin species and can reach a diameter of about 7 inches in the largest specimens. Its body is dark red to black in color with large, lighter red spines.
Geographic range
The red sea urchin is found on the eastern side of the Pacific ocean, along the west coast of North America down to the tip of Baja California, Mexico.
Habitat
The red sea urchin mainly lives in the rocky parts of the shoreline, also called the intertidal zone and down to depths of about 525 feet.
Diet
The red sea urchin is an herbivore and feeds mainly on kelp, which is why it is often found in kelp forests.
Reproduction
After the eggs are released into the seawater and fertilized, larvae hatch and drift freely before settling on the seafloor and developing into young juvenile sea urchins.
Did you know ?
By feeding on
giant kelp, the red sea urchin plays an important role in the development of giant kelp forests and in shaping the structure of the entire ecosystem.
Discover also

Blue spiny starfish
(Coscinasterias tenuispina)

Giant basket star
(Astrophyton muricatum)

Green Brittle Star
(Ophiarachna incrassata)

Hatpin sea urchin
(Centrostephanus longispinus)

Red cushion sea star
(Oreaster reticulatus)

Red striped sea cucumber
(Thelenota rubralineata)

Spiny starfish
(Marthasterias glacialis)

Stony sea urchin
(Paracentrotus lividus)
The marine species from eastern Pacific ocean

Bat sea star
(Patiria miniata)

California spiny lobster
(Panulirus interruptus)

Giant kelp
(Macrocystis pyrifera)

Gorgona guitarfish
(Pseudobatos prahli)

Leopard shark
(Triakis semifasciata)

Mexican hogfish
(Bodianus diplotaenia)

Mosshead warbonnet
(Chirolophis nugator)
Our latestUpdates

Saturday, November 15th 2025
Batz island
Located in the English Channel off the northern coast of Brittany, just a few kilometers from the town of Roscoff, Batz island is a true little haven of peace where you can enjoy its wild landscapes, unspoiled beaches and historical heritage.

Friday, November 7th 2025
The common sea fan
The common sea fan, is a type of soft coral found in the warm, shallow waters of the Caribbean and the western Atlantic ocean. It grows in wide, fan-shaped forms that sway gently with the ocean currents, helping it catch tiny food particles drifting by. Its beautiful purple branches are covered by a thin living tissue that hosts tiny algae, which provide much of the coral's energy through sunlight.

Thursday, October 30th 2025
The leopard blenny
The leopard blenny is a small reef fish from the Indo-Pacific ocean. It is easily recognized by its spotted coloration, which resembles that of a leopard. It lives on shallow coral reefs, feeds mainly on algae and polyps and skillfully camouflages among the corals to avoid predators.
Photo of the Day

Poulpe commun
(Octopus vulgaris)