Green Sea Urchin

Author:  Martina Sarra

Scientific Name:  Strongylocentrotus droebachiensis

Size Range:the average adult size is 50 mm (2 in), but it has been recorded at a diameter of 87 mm (3.4 in).

Identifying Features   The Green Sea Urchin can appear dull green, yellow-green or, generally, greenish-brown: light green at base of the spines and lighter toward the tip; vertical rows of tube feet usually appear as dark bands and the test is usually purple to violet rather than green.

The brittle “shell”, or test, is comparatively small, low but not flat, reaching a width of 8 cm; the short blunt spines crowd close together and are 1 to 5 cm long.  The outer epidermis is made up of a single layer of ciliated cells equipped with tiny moveable hairs (cilia) which cover all external parts including all the appendages (spines and pedicellariae).  These help take food towards the mouth as well as sweep waste away from the urchin.

A nerve network is situated beneath the epidermis but outside the test. Each spine and pedicellaria has a nerve ring around the base with branches travelling up the length.

Habitat:  A widespread Arctic and northern boreal species; from the Arctic Ocean to Washington and the Sea of Japan in the Pacific, and from Hudson Bay, Greenland, Iceland, northern Europe to Chesapeake Bay, USA, Scotland and the western part of Baltic Sea in the Atlantic.  Adults live in cold climates in water temperatures from 0 to 15 degrees Celsius and are found on rocky or gravel shorelines from the intertidal zones to about 1200 meters (about 4000 ft) deep.

This creature uses its strong Aristotele’s lantern (special teeth structure) to burrow into rock/ sand-stone, and then can widen its home with the spines. They can leave their hole to find food and then return, but sometimes it creates a hole that gets bigger as it gets deeper. The Strongylocentrotus droebachiensis is a euryhaline species, and can survive in waters of low salinity. This allows it to flourish in the south Puget Sound.

Food  Sea urchins feed primarily on fixed algae and depends on season and locality, but also on small gastropods, barnacles, dead fish, diatoms, and detritus. They use their sense of smell to locate food, detecting chemicals given off by their prey.  Most of the animals they eat are attached to the substrate, like sea squirts, hydroids and sponges. The pedicellariae are also able to paralyze small animals and larvae, or grab the hairs of some crustaceans, allowing the urchin to capture live food. In the fall we often see large kelps covered with sea urchins munching away on their tissues. They use their spines and tube feet to grab pieces of the algae then manoeuvre them down to the jaws that protrude through the mouth at regular intervals to tear off smaller pieces. The digestive tract is the most obvious organ in the interior of the test and supports an astonishing assortment of ciliated protozoans, most of which seem to be commensals feeding on bacteria in the gut. From the mouth, it passes through the lantern as the pharynx. It emerges from the top as the esophagus and forms a short loop. Then it becomes the small intestine, it doubles back on itself and expands into the large intestine, exiting at the anus. The sharp tips of the five jaws that make up a structure called Aristotele’s lantern chop the food into tiny fragments which can be swallowed and digested for whatever nutritional value they have.

Predators   Despite their protective spines, some predators routinely prey on sea urchins. Vertebrates that eat sea urchins include Sea Otters, crows, gulls, Wolf-eels and other large fish. Sea stars and crabs are the main invertebrate predators. Sea urchins use their spines and pedicellariae to defend themselves. The pedicellariae react when something foreign touches the surface of the urchin. They can be aggressive or defensive.

Of all the predators humans are probably the most devastating. People in many parts of the world (Mediterranean, Peru, Ecuador, Japan) consider the sea urchin’s ripe gonads a delicacy. The Green Urchin is known to be eaten by the Native peoples of New Brunswick from archaeological remains.

Life cycle:   Sea urchins are dioecious, meaning they either contain male or female reproductive organs: they contain five gonads tucked under the test, protected by genital place. Sea urchins all release their ripe individuals shed eggs or sperm directly into the water column at the same time to ensure fertilization.

In temperate regions most spawning takes place in the spring and summer, and some sea urchins brood their young.

Once fertilized, the gamete grows via mitosis and eventually becomes a larva capable of simple swimming called an echinoplutes. The metamorphosis is hugely complex. At the end of the process the sea urchin settles down to a benthic life.

In the San Juan Islands individuals can be ripe from January to June with a peak in spawning from March to April. Eggs are usually 155-160 micrometer in diameter. At 9-10°C the embryo reaches the plates stage in five days and metamorphoses into a juvenile urchin in 9 or 10 weeks. The test reaches a diameter of one centimetre in about a year. All these values can vary depending on temperature and food supply.

Conservation Status:  The green sea urchins and its habitat are not in any way threatened by the environment.  However, if green sea urchins were to be reduced in population, there would be mass amounts of kelp that would cause the water to be congested. This situation does not allow boats to pass through the water.


Bannister, D., D. Campbell. 1985. The Encyclopedia of Aquatic Life.

Kozloff, E. (1993). Seashore life of the northern Pacific coast: An illustrated guide to Northern California, Oregon, Washington, and British Columbia. Seattle, Washington: University of Washington Press.

Lamb, A. and Hanby, B. P. (2005). Marine Life of the Pacific Northwest: A photographic encyclopedia of invertebrates, seaweeds and selected fishes. Harbour.

Lambert, P. and C. Austin, W. (2007). Brittle Stars: Sea Urchins and Feather Stars of British Columbia, southeast Alaska and Puget Sound. Royal BC Museum.

Snively, G. (1978). Exploring the Seashore in British Columbia, Washington and Oregon: A guide to shorebirds and intertidal plants and animals. Gordon Soules Book Publishers.

Valiela, I. 1995. Marine Ecological Processes.


Striped Sun Star

Author: Kaylan Guidon

Scientific name: Solaster stimpsoni     

Size range: 50 cm (20 inches) across

Photos by D. Young taken at Race Rocks, Victoria, BC

Identifying features:  This species can be identified by the dark blue to blue-purple stripes that radiate from the centre to the tips of the arms. The base colour of the top surface varies from red-orange to a orange-yellow. The stripes may be difficult to see in darker specimens.  The top surface has distinct papillae and the underside of the arms have two rows of tube feet.  They generally have 10 arms.

Habitat and Life History:  This sea star can be found intertidally to subtidal and is mostly found on rocky bottoms. This species of sea star is found from the Bering Sea down the Pacific Northwest to Southern California.  Similar to other sun stars the Striped Sun Star is a carnivore and feeds mostly on sea cucumbers as well as sea pens, sea squirts and lampshells.  The main predator of this sun star is it’s close cousin the Morning Sunflower Star (Solaster dawsoni).


Lamb, A. and Hanby, B.P. (2005).  Marine Life of the Pacific Northwest: A photographic encyclopedia of invertebrates, seaweeds and selected fishes. Madeira Park, BC: Harbour Publishing.

Lambert, P. (2000).   Solaster stimpsoni Verrill, 1880.  Retrieved November 26, 2018 from

McDaniel, N. (2011). A Field Guide to Sea Stars of the Pacific Northwest. Madeira Park, BC: Harbour Publishing

Author:  Rose Desi-Seulean

Arctic Cookie Star

Common Names: Arctic Cookie Star

Scientific Name: Ceramaster arcticus

Size Range: 11cm (4.2in) across

Identifying Features:  The Arctic Cookie Star is typically pink with darker red accents in color. The arms and disc is bordered by large marginal plates. The Arctic Cookie Star is pentagonal, rigid and its arboreal (top) surface is usually covered with small flat-topped plates.

Habitat:  Most Arctic Cookie Stars tend to live close to shore, typically interdial to 186m (620 ft.).  They can be found around the Aleutian Islands (Attu) and anywhere from Alaska to the Strait of Juan de Fuca, south of British Columbia and into Washington State.

Food:  Arctic Cookie Stars prey upon various species of sponges including the Peachball Sponge (Suberites montiniger). They also eat shellfish, mussels and mollusks.

Predators:  Sunfish, sea turtles, manta rays, sharks and larger starfish are a big threat to the Arctic Cookie Star. Humans also are a big threat to most sea life whether it’s a souvenir they steal from the beach, an oil spill or just simply littering, we are definitely harming the Arctic Cookie Star.

Life Cycle:  Like most sea stars, the Arctic Cookie Star reproduces through external fertilization. Sperm is first produced in the testes of the males and eggs are produced in the ovaries of the females; Cookie Stars are not hermaphrodites. Both gametes are shed in open water, where fertilization takes place. The larvae, which have bilateral symmetry, swim around for sometime and then swim to the ocean bottom where they develop into adults that have radial symmetry.

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Marine Biology

Author:  Yunfei Gong

Common name: Vermillion star

Scientific name: Mediaster aequalis

Size range: 5 inches

Identifying features

Mediaster aequalis is one of the smallest sea stars ranging in size from three to seven inches. It is a red, 5 armed (rarely,4 to 6 armed specimens) star with a distinctive round texture on its surface. This sea star is named because of its bright color. It is vermillion aborally and more orange on the oral side.


Mediaster aequalis is found along the west coast of North America, ranging from Alaska to California. It is found on many types of beaches at very low tides, particularly on negative tide. The Vermillion Sea Star is common in shallow subtidal waters down to about 160m depth. It is often found on rocks shell, sand, gravel, pebbles and mud.

Food (prey)

The Vermillion Sea Star eats a variety of living prey such as sponges, brachiopods, worms, bryozoans, tunicates and the Ptilosarcus gurneyi. It also scavenges dead animals and consumes detritus. Similar to other sea stars, they flip their stomachs out through their mouth and onto the prey they are eating. After selecting enzymes onto its prey and digesting it externally, it pulls its stomach back into its body again.


Sea stars do not have many predators because their outer skin is quite tough. But they do have some predators such as sharks, sea otters and other large fish and sea birds. They can curve their arms and turn into a ball to protect themselves. They also have the ability to regrow their arms if they are eaten by predators.

Life cycle

Sea stars can reproduce in both sexual and asexual ways. Vermillion Sea Stars reach sexual maturity within four years. As sea stars the males and females are in separate individuals. The eggs which are 1 to1.2mm are bright opaqe orange.

Photos by Yunfei Gong

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Stiff-Footed Sea Cucumber    

Author:  Haley Singleton and Sekoya Wellings
Scientific name: Eupentacta quinquesemita
Size range: Can grow up to 10 cm (4 inches) long

Identifying Features: 

The Stiff-Footed Sea Cucumber is white to cream coloured with eight large, yellow tentacles and two smaller ones which are used to collect food. This sea cucumber has tube-like feet covering its whole body. The size of the cucumber can vary from 4 cm to 10 cm long and its body wall is poisonous to certain types of fish.

This creature can be found under and between rocks along the coasts from Alaska to California. They are often found living in shallow rocky areas and underneath docks.  They are also commonly found along the underside and edges of floating docks.

With its mucous covered tentacles, the Stiff-Footed Sea Cucumber is a filter feeder that collects small particles such as plankton and small decaying organic matter for food.  It generally does this by holding its tentacles in the current and filtering out food items that stick to the “tree” of tentacles.  It then takes each tentacle (which is a modified tube foot) places it into its mouth and takes the food off of it.  It then withdraws the tentacle and places it back in the current.

The main predator of these sea cucumbers is the sea star Solaster stimpsoni.

Life Cycle:
Sea cucumbers are either male or female and they reproduce by releasing sperm and eggs into the ocean water. Spawning occurs in the spring and the egg, embryos and larvae are greenish in colour. The egg is inserted into a pouch on the adult’s body where it develops and eventually hatches from the pouch as a baby sea cucumber.

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Six Rayed Sea Star

By Anna Chhina

Common Name: Six Rayed Sea Star

Scientific Name: Leptasterias hexactis

Size Range: 5-9 cm (aprox. 2″)

Identifying Features: The Six Rayed Sea Star is often green, black, brown, red, and sometimes a more mottled color.  It is often overlooked by beachcombers because of its size since it only grows to about nine cm and is a fairly drab and mottled green color that often blends into the rocks.  Although there are flashier six-rayed stars of orange and yellow, they usually have a distinctive dark pattern.  The central disk is of a moderate-size with six arms.  The spines on the upper surface are dense and mushroom-like.  The Leptasterias hexactis is very similar to Leptasterias pusilla but can be set apart by its larger, flatter spines,  thicker arms, and darker molted coloring.

Habitat: The Six Rayed Sea Star range from British Columbia to southern Californias.  They are quite numerous in the middle of intertidal zones of rocky shores.  They typically move around on the top of rocks at nighttime after hiding under them during the day. They can often be found sheltered under rocks or algae at very low tides.  Locally the six-rayed sea star is found on either rocky or sandy intertidal beaches near eelgrass beds. Under each of its six arms or legs are hundreds of small tube feet, each of which is equipped with an individual suction cup.  It uses these small tube feet to get around and the suction cups to attach itself to a rock when the environment starts to get stormy.

Food: The six rayed sea star eats small gastropods such as snails and slugs.  It also eats limpets, mussels, chitons, barnacles, sea cucumbers, and a few other species, sometimes including dead animals.

Predators: The predators of the Six Rayed Sea Star are sea and shorebirds such as gulls or cormorants, herons, and even sometimes otters. Often people will collect sea stars especially the showier ones and in some places will occasionally eat them too.

Life Cycle: Leptasterias hexactis reproduces sexually.  Mature females (at least 2 years old) produces yellow, yolky eggs that stick together in a mass after fertilization.  These are kept under the disk of the female.  She will keep the eggs and larvae in brood clusters around her mouth area until the larvae reach adult form and are ready to hatch as miniature sea stars after 6 to 8 weeks.  Because of this, brooding females cannot completely flatten themselves against the surface of rocks and are anchored only by their outermost tube feet.  Unfortunately, they can often become dislodged by the waves, causing them to lose their eggs. The presence of the eggs blocks the female’s mouth and she will not feed while brooding, even if there the food is available.  The development of the embryos is direct and Six Rayed Sea Star young tend to reach full maturity within about 2 years.  While most sea star females release their eggs into the surrounding tide and the young must fend for themselves as soon as they’re fertilized, the Six-Rayed Sea Star mothers are far more nurturing.  They brood their young until they’re sure the babies are properly prepared to live on their own. The female forms a kind of tent over them for up to two months during the brooding, at which time she cleans, feeds and tends to them.


Melissa McFadden, Created original page, edited by Hans Helmstetler, December 2002, Dave Cowles… – retrieved January 15 2010

Nicholas Read, Vancouver Sun, Urban Critter: Six rayed sea star, July 4 2009…. -retrieved January 19 2010

Students of Lester B Person College, and Joaquin Puga, December 2001

Illustration by Anna Chhina

Photographs by D. Young

Sand Dollar

Author:  Molly Simpson and Emma Troost

Common Name: Sand Dollar

Scientific Name: Dendraster excentricus

Size Range: Up to 10cm in diameter

Identifying Features

Sand dollars have no front, back, head or tail; instead they have a bottom (oral side) and a top (aboral side). They are round disc-shaped creatures that have a diameter generally about 10cm when fully grown. When living, sand dollars are dark purple/black in colour but after death they turn a creamy white. On their aboral side there is a symmetrical design that resembles a flower with five petals. The shell, called a test, is penetrated by small brown spines that give it a velvety look and enable movement.


Sand dollars live in the Pacific, Atlantic, and Arctic oceans.  They live in the sand in the intertidal zone, around 90m deep. They live in groups, called beds, of varying sizes with as many as 625 in one square yard of sand. They prefer sheltered bays, sandy lagoons, or otherwise the shallow water of the open ocean. Generally you will find sand dollars along the North American east coast, or in British Columbia, Siberia or Japan.


Sand dollars eat algae, fragments of organic material, crustacean larvae, diatoms, copepods, and detritus. In calm waters, sand dollars use a method called suspension feeding to eat. In suspension feeding, they position themselves so that one edge of their test is buried in the sand and one is sticking up so that the hole on their oral side (their mouth) is right above the sand and they can catch food sitting or moving on the bottom. Sand dollars have 5 teeth set up in a symmetrical pattern in a structure called an Aristotle’s lantern. It can take them 15 minutes to chew their food and up to 2 days to digest it. They have spines which enable movement. The spines have fine hair like cilia on them that are coated with mucus and bring smaller food to the mouth.  They also have tube feet, which are small suction cup like tentacles about as small as their spines. They use these tube feet to help them move around and bring larger food to their mouth.


Sand dollars, being slow, have many predators, including snails. Their main predators are: the large pink sea star, the Starry Flounder, the California Sheep Head, sea gulls, crabs, otters, and octopuses. To protect themselves they dig into the sand where they won’t be found by any of their predators.

Life Cycle

Sand dollars live anywhere from 8-13 years; you can tell how old they are by the growth rings on their test. When spring begins the mating cycles begins too. Once the salinity and temperature of the water is just right the females release their eggs and the males release their sperm. Once sperm and egg meet they immediately develop into larvae via cell division. After a month of floating the larvae settle into the sand and start growing a test to become adults.

How to find and preserve a sand dollar test: The best time to find sand dollars is after a large storm when they wash ashore and die, leaving a white shell, called a test, behind. To prevent them from stinking put them in a diluted bleach solution and let them sit for about 15 minutes. Afterwards rinse them off, let them dry, and you have a beautiful white sand dollar test!  Live ones should of course be left in the ocean.

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Red Sea Urchin

By Victoria Cholak

Common name: Red Sea Urchin

Scientific name: Strongylocentrotus franciscanus

Size range: Its test can be up to 17 cm (6½ inches) wide and its spines up to 7.6 cm (3 inches) long

Identifying Features: Like all sea urchins, the Red Sea Urchin has a round circular body and a protective shell, called a test, that is made of calcium carbonate, minerals and proteins. The Red Sea Urchin’s test can be up to 6½ inches (7.6 cm) wide and ranges in colours from red to purple. The test has tubercles where the short and long spines attach.  The spines tend to be lighter than the test and can be up to 3 inches (7.6 cm) long. Sea urchins in general, have tiny holes in their tests where their tube feet come through.

Habitat:  Red Sea Urchins can be found on both rocky shorelines where there is a lot of wave action and on quite shores. They live in the low intertidal zone to 91 meters deep.  In the Pacific Northwest you would more likely find the Green and Purple Sea Urchins in the low intertidal area than the larger Red Sea Urchin; they are generally found in deeper water.

Food: All sea urchins eat seaweed. The Red Sea Urchins prefer to eat kelp (brown seaweed) and red seaweed, however in our aquarium they have been observed eating a diversity of things including Eel Grass (Zostera marina). On one occasion a Bay Pipefish (Syngnathus leptorhynchus) was captured by the tube feet of our Red Sea Urchin and eventually eaten.  Sea Urchins use their tube feet to pass the food that they find into their jaws, where their 5 teeth (aristotles lantern) chew the food as they take it into their mouth and digestive tract.

Predators:  The hard test and spines give the Red Sea Urchin some protection from its predators but they aren’t venomous.  The main predators of this species include sea stars, sea otters, octopus, crabs, and wolf eels. In Japan, people eat the Red Sea Urchin’s reproductive organs as a delicacy.

Life Cycle: Red Sea Urchins fertilize in water column. After a period the fertilized eggs develop into larvae. It takes 6 to 8 weeks for the larvae to develop into juvenile sea urchins. Adult urchins can live up to be 7 to 10 years old.

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Authors: Emma Grigg & Nastja Kharine

Common Name: Purple Sea Urchin.

Scientific Name: Strongylocentrotus purpuratus

Size range: up to 15 cm (6 inches) across.

Identifying Features:  As in its name, the Purple Sea Urchin is purple but it can also be a purplish green colour. The Purple Sea Urchin is a medium sized sea urchin compared to its relatives the Green and Red Sea Urchin, measuring up to 15 centimeters across. It has a circular body covered in heavy spines. These spines cover the entire crust-like body acting as protective armor.

Habitat: Purple Sea Urchins are found from the coast of Alaska to the north of Mexico. They live in water up to about 160cm (63inches) deep on rocky coastlines. They use their spines to dig holes in pebbles, sand and rock to create a protective groove. These grooves are their homes and they shelter the urchins from crashing waves. Purple sea urchins like living with their friends and family, so you can usually find them in groups.

Food: The Purple Sea Urchin eats mostly algae. It has teeth that help it pull algae off rocks. They are also known to eat plankton, kelp, periwinkles, barnacles, mussels, dead fish and sea sponges.

Predators: Many things eat Purple Sea Urchins, even though they have huge spines. Crabs, sunflower stars, snails, sea otters, some birds, fish and people like Purple Sea Urchins on their menus.

Life Cycle: Purple Sea Urchins usually live up to 30 years or longer. They breed around January to March every year. The female sea urchins can produce up to twenty million eggs in one year. When the female sea urchins lay their eggs, the young urchins start off as larvae. It takes a few months for the larvae to develop into small baby sea urchins. It takes 2-5 years before a new sea urchin can reproduce.

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Leather Star

Author: Meaghan Claughton
Photos by D. Young

Scientific name: Dermasterias imbricata

Size: Up to 30cm

Identifying Features  The Leather Star (also commonly called the ‘Garlic Star’) is a five-legged echinoderm. The Leather Star often has light blue skin with reddish scales, and when rubbed smells faintly of garlic.

Habitat    Dermasterias imbricata is found from the central coast of Alaska to northern Mexico. They generally live among the rocks in low intertidal zones, but can be found up to 300ft deep.

A Leather Star at low tide at Prevost Island, British Columbia.

Food/Prey    Leather Stars often feed on anemones, but will also consume sea cucumbers, sea urchins, sponges, chitons, and fish eggs. Sea stars feed by attaching to its prey using tube feet on the bottom of its arms. It uses its arms to pry open the victim’s shell, just wide enough so the sea star can squeeze its stomach into the shell. The sea star’s stomach comes out through its mouth, and once inside it’s prey’s shell, digests it, and retracts the stomach back into its mouth, leaving an empty shell. One has been observed feeding on the Stiff-Footed Sea Cucumber (Eupentacta quinquesemita) in our class aquarium.

Predators   Starfish do not have many predators, as their outer skin is quite hard, but manta rays, sharks, other large fish, and even certain types of snails will eat them. Larger sea stars are also a threat. The leather star uses its garlic-like odor to ward of enemies, and like many sea stars, has sensitive skin that can detect chemical changes in the water.

Life Cycle   Sea stars can reproduce sexually and asexually. They reproduce asexually by dividing their bodies and regenerating missing parts. The decapitated starfish limb can grow into a new sea star, so long as a part of the central body portion is attached. In sexual reproduction, a sea star’s eggs are externally fertilized by a male sea star’s spermatozoa. The fertilized eggs develop into swimming larvae categorized into two groups: Bipinnaria and Brachiolaria. These larvae use cilia to move and eventually settle to the ground when growing into adults. When developing into a fully grown sea star, the larva’s left side will become its oral structures, facing the ground, and its right side will become it’s back.

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