Strongylocentrotus droebachiensis

Strongylocentrotus droebachiensis inhabits colder temperatures of mostly northern oceans. Green sea urchins are found in coastal areas of Alaska to Washington, the western part of the Baltic Sea, on the coast of Korea, as well as in almost every other type of major marine habitats. (Hubbell, 1999; Smith, 2000)

Green sea urchins live primarily in areas with cold waters mainly in the northern hemisphere. Green sea urchins prefer living in rocky, or gravel areas, but they are mostly found in sandy, sea floor bottoms. Adults live in cold climates in water temperatures from 0 to 15 degrees Celsius. Green sea urchins are found between intertidal zones to about 1200 meters. The rate at which urchins take in or remove oxygen does not depend on water temperature.

The green sea urchin is one of the only urchins that has expanded into an environment of brackish water such as the Baltic Sea. (Banister and Campbell, 1985; Grzimek, 1972; Roessler, 1977; Smith, 2000)

Strongylocentrotus droebachiensis acquire their common name, "green sea urchin" from the green outer shell. All sea urchins have an exoskeleton made of calcitic plates rooted into their skin. The solid exoskeleton, or the test, is composed of several plates that are tightly bound together. The mouth is located in the center of the peristomial membrane. This membrane is composed of a flexible collogenous skin that is tough and serves as a type of lip-like structure. Teeth are found in the mouth to help tear off food to eat. Another structure that is commonly found with almost all sea urchins is the pedicellaria, tiny stalked valves used to keep the surface of the sea urchin clean by removing small particles it encounters. Sea urchins have spines and tubes that serve roles in acquiring food, protection and respiration. The tube-feet on the sea urchins are a type of suction discs that allow them to adhere onto other organisms or substances. They have also have an internal skeleton called the stereom.

Green sea urchins are very small, compact animals that usually do not exceed a length of 8 cm. The average size for a green sea urchin is about 7.8 cm. The larval forms are bilaterally symmetric. After metamorphosis they measure about 0.5 mm and are radially symmetric. The sexes are monomorphic. (Banister and Campbell, 1985; Grzimek, 1972; Smith, 2000; Thurman and Webber, 1984)

Because they are such small animals, green sea urchins are vulnerable to predators. The spines that are located around its outer skeleton help protect them from predators such as lobsters, crabs, flatfish, wolffish, sea gulls, and others. The urchins also help protect other animals, such as small fish, from their predators by allowing these animals to seek shelter between their spines.

Strongylocentrotus droebachiensis usually come out at night to seek food. The green sea urchins hide until sunset and then search the area for food, mainly algae and kelp. If by chance light does hit these urchins, they begin to pulse sending out brilliant reds and blues until the light has been taken away from them.

Generally, the process of movement among sea urchins is by using their spines, which have muscles attached to it as well as a ball and socket joint. Sea urchins are not only able to move across sea grounds, but they can also climb rocks using their tube-feet. The tube-feet are also used for gas exchange. (Banister and Campbell, 1985; Grzimek, 1972; Roessler, 1977; Smith, 2000)

Green sea urchins feed on a wide variety of organisms, ranging from marine worms to sponges. However, this specific urchin particularly feed on a type of kelp known as Laminaria. Green sea urchins also eat bull kelp and green algae. Often, green sea urchins scrape the surface of rocks using their "Aristotle's lantern," or masticatory apparatus, in search of diatoms as well as algae. Whenever an urchin is injured, the other urchins immediately move away, but they return within a short time span to eat it. (Friedrich, 1969; Grzimek, 1972; Hubbell, 1999; Smith, 2000; Valiela, 1995)

There are no known adverse effects of green sea urchins on humans.

This species is harvested for its roe, which is considered a delicacy in Japan.

At this point, 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 congestion does not allow boats to pass through the water. Therefore, it is important to preserve populations of this species. (Valiela, 1995)