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GREEN SEA URCHINS
STRONGYLOCENTROTUS DROEBACHIENSIS
CLEAR RESIN ENCAPSULATION

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LIFE AT THE EDGE

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KINGDOM : Animalia

PHYLUM : Echinodermata

SUBPHYLUM : Echinozoa

CLASS : Echinoidea

SUBCLASS : Euechinoidea

ORDER : Echinoida

FAMILY : Strongylocentrotidae

SPECIES : S. Droebachiensis

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Gastropods & bivalves of Philippines

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GREEN SEA URCHINS
STRONGYLOCENTROTUS DROEBACHIENSIS

Green sea urchins have a circumpolar distribution, ranging into the Arctic regions of both the Atlantic and Pacific Oceans. It is found on the east coast of North America as far south as Cape Cod and in deeper waters to New Jersey, while its distribution ranges southwards to Puget Sound, Washington on the west coast.

They live mostly in shallow waters, with a preference for rocky bottom in areas that are not subject to extreme wave action, but they have been found at depths of more than 1,000 metres. They tend to move around more frequently than their relative, the red sea urchin, and it is believed they may migrate on a seasonal basis. Green sea urchins are fished commercially for their roe, the majority of which is exported to Asia.

These urchins are radially symmetrical and its diameter is not more than twice its thickness. It has spines that are crowded, short and rather fine. The test may be 8.3 cm wide with the spines reaching around 2.5 cm. Key characteristics for these urchins are jaws that lack lateral teeth, an anus situated outside the apical system, radial symmetry, and more than three pore plates per ambulacral plate. The ridges on the spines have rounded surfaces and periodic sculpturings (these somewhat fan-shaped)

In both sheltered and exposed kelp beds and rocky areas, located in the low intertidal zone and subtidal zone to 1,200 meters in the Atlantic Ocean. These urchins range from Alaska to the Puget Sound. They may also be found on the Atlantic coast and in Europe. This and S. pallidus are the only species of urchin in the Puget Sound area that are also found in the NW Pacific off Russia (Bazhin, 1998). Bazhin also says that the species is sometimes found but is not common in many areas of the Arctic Ocean so it should not necessarily be considered a circumpolar species.

S. droebachiensis feed on large algae such as bull kelp, green algae, and laminarians. They also scrape diatoms and coralline algae off rocks. They are harvested commercially for their roe, which is a delicacy in Japan. In the Gulf of Maine, males at widely separated populations seem to be release sperm at similar times, suggesting that they are responding to a widespread environmental signal. Spawning was most intense during full and new moon .

To successfully recruit, juveniles must survive until metamorphosis is complete. Initially metamorphosis is marked by a rapid transformation from the larval body form to the juvenile form. The juvenile rudiment everts from the vestibule and larval tissues are absorbed. Although metamorphosis appears to take only minutes, the juvenile gut does not function for several days. During this time juveniles cannot eat and must live off maternal reserves or food acquired during larval life.

Predation, dislodgement, physical conditions, and disease probably influence the success of juveniles after settlement. Several studies have documented predation on juvenile echinoids. On the western Atlantic coast, juveniles of Strongylocentrotus droebachiensis are consumed by rock crabs, lobsters, sculpins...

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