Tag Archive: sea urchins

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

Genus/species: Strongylocentrotus purpuratus

GENERAL CHARACTERISTIC: Round body with radially symmetrical test, (shell), covered with large spines 0.5 cm (2 in) in diameter, rarely to 10 cm (4 in). Test and spines are pale green (young) to purple (adults). Also covering the test or shell, are tube feet and pedicellariae (pincers). The long
suckered tube feet visible above the spines are used for locomotion and capture of food, which is then passed along to the mouth. The oral side of the urchin, on which the mouth is located, faces the substrate (down). Sexes are not physically distinguishable from one another (monomorphic).

DISTRIBUTION/HABITAT: British Columbia to Baja California in the lower intertidal to 160 m (525 ft) depth. Rounded burrows in rock that have been scoured out by the present or previous urchin using its teeth (Aristotle’s lantern) and spines, a strategy that protects from predators and surge.  Subtidal purple urchins live, often in large numbers, on the substrate among kelp holdfasts.


DIET IN THE WILD: Herbivore/Detritivore. Uses calcite (CaCO3) teeth (Aristotle’s lantern) to feed on kelp, other algae, diatoms and scavenge on dead animals. These urchins prefer the giant brown kelp Macrocystis and can destroy entire forests of kelp which are commercially important for fisheries. Algin a product from kelp is also used in the manufacturing of plastics, paints and as a thickening agent in foods such as gravy and pudding.

REPRODUCTION: Sexually mature during their second year. Sexes are separate, although hermaphrodites occur. Broadcast spawning deposits sperm or eggs into the sea where random fertilization occurs. Pluteus larvae hatch, drift and settle. Growth after metamorphosis is slow.

PREDATORS: Preyed upon by seastars such as the sunflower star and cancer crab species as well as fish such as the California sheepshead, shorebirds and sea otters. Sheephead blow over sea urchins and nibble at the oral side where the spines are shortest. When approached by most sea stars, the urchin allows the potential predator to get close, then uses its pincers to attack the sea star’s tube feet. Most sea star species will beat a hasty retreat; however, the sunflower star is too big and fast; the urchin cannot escape and is swallowed whole! Average lifespan 20 years but can live to more than 30 years.

CONSERVATION: CITES; no special status

REMARKS: Purple pigments from this urchin lodge in the bones and teeth of sea otters, turning the otter’s skeleton and teeth purple.

In the wild, they protect themselves from predation, drying out, and damage from the sun’s UV light by covering themselves with seaweed or shells.

Sea urchin is commonly used in sushi and is considered a delicacy Japan. The primary urchin harvesting company in California sends 75% of the harvest to Japan.


RockyReefcluster, Abalone and urchins, Rocky Coast Main Exhibit, Tidepool


California Academy of Sciences Docent Water is Life Guide 2015

eol  http://eol.org/pages/598175/details

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Kingdom: Animalia
Phylum: Echinodermata
Class: Echinoidea (Sea urchins)
Subclass: Cidaroidea
Order: Cidaroida
Family: Cidaridae

Genus/species: Eucidaris tribuloides

GENERAL CHARACTERISTICS: Brown body with thick spines in all directions. 

Slate Pencil UrchinIMG_1479

DISTRIBUTION/HABITAT: North Carolina through Brazil, Caribbean, Bahamas, Florida. Found in coral reef crevices, in turtle grass beds, or under rocks and rubble in back reef lagoon areas. Depth to 800 m (usually 50 m). 



Slate Pencil UrchinIMG_1478

DIET IN THE WILD: Nocturnal omnivore: algae and small invertebrates such as sea squirts and sponges.

Slate Pencil UrchinIMG_0664

REMARKS: The spines of pencil urchins, unlike other urchin groups, are not covered with epidermis. They are, however, often covered with algae and epizoans that provide excellent camouflage. Spines are also covered with barbs that can inflict serious pain to a predator. Seek shelter in rocky crevices by day, using the thick spines to maintain a protected position.


Encyclopedia of life eol.org/pages/600976/details

Smithsonian Tropical Research Institute 


Animal Diversity Web animaldiversity.ummz.umich.edu/accounts/Eucidaris_tribulo…

Ron’s flickr https://www.flickr.com/photos/cas_docents/4330820247/in/set-72157608501343477

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Caribbean  PR36

Kingdom: Animalia
Phylum: Echinodermata
Class: Echinoidea
Order: Diadematoida
Family: Diadematidae

Genus/species: Diadema setosum

GENERAL CHARACTERISTICS:  Usually black but some or all of them can be grey or white. Very long, black spines are up to 30 cm (1.1 inches). Orange-red ring around anal cone at the center of its dorsal surface is distinctive. Weight 35 gm (1.25 oz) to 80 gm (2.8 oz).  Adult test to 9 cm (3.5 inches) diameter with a distinct pattern of iridophores, usually with 5 white dots.  Height to around 40 mm (1.5 inches) high. 


DISTRIBUTION/HABITAT: Red Sea, east Africa to western Pacific (Philippines) in low tide areas to 20 m (66 ft) on rubble and seagrasses. Often abundant in shallow water areas that have been recently disturbed. Also in lagoons and on coral and rocky reefs.


DIET IN THE WILD: Herbivore. Hides during the day, and emerges at night to feed on algae, plankton, and waste material. Its feeding habits help keep the reef free from coral-smothering algae; however, too many of these algal-eating machines can actually threaten a reef, scraping away living coral as they devour algae and leaving little food for other herbivores.

CONSERVATION: IUCN Red List ; not evaluated.

REMARKS: Uses hundreds of flexible, tube feet to move around, eat and breathe.

The venom is mild and causes swelling and pain, and gradually diffuses over several hours. Tiny hooked barbs often require surgical removal.

Commensal with a number of species, including various shrimps and fishes.


Sea-grass shallows PR03a


Encyclopedia of Life  eol.org/pages/2942801/details

Archive www.arkive.org/long-spined-sea-urchin/diadema-setosum/

WordPress Shortlink  http://wp.me/p1DZ4b-Qv

flickr http://www.flickr.com/photos/cas_docents/sets/72157608501343477/with/4333507132/

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


Ron’s flickr https://www.flickr.com/photos/cas_docents/6063267260/in/set-72157608501343477/

Walla Walla University www.wallawalla.edu/academics/departments/biology/rosario/…

Oregon State University fishbull.noaa.gov/1014/19ebertf.pdf

University of Michigan Animal Diversity  Web.http://animaldiversity.ummz.umich.edu/accounts/Strongylocentrotus_franciscanus/

Ron’s WordPress shortlink  https://fishoncomputer.wordpress.com/wp-admin/post-new.php

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