Strongylocentrotus droebachiensis
| Green sea urchin | |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Echinodermata |
| Class: | Echinoidea |
| Subclass: | Euechinoidea |
| Order: | Echinoida |
| Family: | Strongylocentrotidae |
| Genus: | Strongylocentrotus |
| Species: | S. droebachiensis |
| Binomial name | |
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Strongylocentrotus droebachiensis (O. F. Müller, 1776) |
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| Strongylocentrotus droebachiensis range | |
Strongylocentrotus droebachiensis is commonly known as the green sea urchin because of its characteristic green color. It is commonly found in northern waters all around the world including both the Pacific and Atlantic Oceans to a northerly latitude of 81 degrees and as far south as the Puget Sound (Washington State) and England. The average adult size is around 50 mm (2 in), but it has been recorded at a diameter of 87 mm (3.4 in). The green sea urchin prefers to eat seaweeds but will eat other organisms. They are eaten by a variety of predators, including sea stars, crabs, large fish, mammals, birds, and humans.
Strongylocentrotus droebachiensis is found on rocky substratum in the intertidal and up to depths of 1,150 meters (3,770 ft). It uses its strong Aristotle's lantern to burrow into rock, and then can widen its home with the spines. Usually, this sea urchin can leave its hole to find food and then return, but sometimes it creates a hole that gets bigger as it gets deeper, so that the opening is too small for S. droebachiensis to get out. S. droebachiensis is a euryhaline species, and can survive in waters of low salinity. This allows it to flourish in the south Puget Sound. Acclimation and size are important factors as larger individuals have a lower surface area to volume ratio and can handle the increased osmotic tension.
Strongylocentrotus droebachiensis is in the shape of a slightly flattened globe (dorsoventrally). The oral side rests against the substratum and the aboral side (the side with the anus) is in the opposite direction. It has pentameric symmetry, which is visible in the five paired rows of podia (tube feet) that run from the anus to the mouth. The size is calculated as the diameter of the test (the body not including the spines). This is a relatively fast growing sea urchin, and its age is generally calculable based on its size: one year for every 10 mm.
The spines of Strongylocentrotus droebachiensis are used for defense and locomotion and are not considered poisonous. The spines attach to small tubercles on the test where they are held in place by muscles creating a ball and socket joint. They are round, tapering to a point, with ridges around the outside in a fan-like design made of calcium carbonate. Usually, the longest spines are around the peripheral edge of the animal. If broken, the spines will regenerate, and if completely torn off, the tubercle will be reabsorbed to fit the slowly growing spine.
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Wikipedia