Sea Urchin In Foot

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The small, reddish or purplish urchins of the genus Arbacia, such as A. punctulata, the common urchin from Cape Cod to the West Indies, are familiar subjects in embryology; a female may release several million eggs at a time. In the West Indies, sea eggs—the ovaries of Tripneustes ventricosus—are eaten raw or fried; in the Mediterranean region, frutta di mare is the egg mass of Paracentrotus lividus (the best known rock borer) and other Paracentrotus species; and, on the U.S. Pacific coast, the eggs of the giant purple (or red) urchin (Strongylocentrotus franciscanus) are similarly considered a delicacy. The slightly smaller S. purpuratus, of the same region, is known to excavate holes in steel pilings. See also cake urchin; heart urchin.

sea urchin

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sea urchin – Children’s Encyclopedia (Ages 8-11)
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sea urchin

sea urchin, any of about 950 living species of spiny marine invertebrate animals (class Echinoidea, phylum Echinodermata) with a globular body and a radial arrangement of organs, shown by five bands of pores running from mouth to anus over the test (internal skeleton). The pores accommodate tube feet, which are slender, extensible, and often sucker-tipped. From nodules on the test arise long, movable spines and pedicellariae (pincerlike organs); these structures may have poison glands. The mouth, on the underside of the body, has a complex dental apparatus called Aristotle’s lantern, which also may be venomous. The teeth of Aristotle’s lantern are typically extruded to scrape algae and other food from rocks, and some urchins can excavate hiding places in coral or rock—even in steel. Sea urchins live on the ocean floor, usually on hard surfaces, and use the tube feet or spines to move about. In addition, a few carnivorous species have been described.

The largest urchin (known from a single specimen) is Sperostoma giganteum of deep waters off Japan. Hatpin urchins, such as Centrostephanus longispinus of the Mediterranean and eastern Atlantic, Diadema (formerly Centrechinus) setosum of the Indo-Pacific, and D. antillarum of Florida and the West Indies, have toxic spines up to 30 centimetres (12 inches) long. The slate-pencil urchin (Heterocentrotus mammillatus) of the Indo-Pacific has 12-cm spines that may be 1 cm thick—stout enough to be used for writing. Lytechinus variegatus, a pale-greenish urchin of the southeastern coast of the United States and the Caribbean, and the large, short-spined Psammechinus (sometimes Echinus) miliaris of Iceland, Europe, and western Africa use their tube feet to hold up bits of seaweed or shell as a shield against sunlight in shallow water.

The small, reddish or purplish urchins of the genus Arbacia, such as A. punctulata, the common urchin from Cape Cod to the West Indies, are familiar subjects in embryology; a female may release several million eggs at a time. In the West Indies, sea eggs—the ovaries of Tripneustes ventricosus—are eaten raw or fried; in the Mediterranean region, frutta di mare is the egg mass of Paracentrotus lividus (the best known rock borer) and other Paracentrotus species; and, on the U.S. Pacific coast, the eggs of the giant purple (or red) urchin (Strongylocentrotus franciscanus) are similarly considered a delicacy. The slightly smaller S. purpuratus, of the same region, is known to excavate holes in steel pilings. See also cake urchin; heart urchin.

The Editors of Encyclopaedia Britannica This article was most recently revised and updated by Adam Augustyn.

To Remove Sea Urchin Spines From Your Feet

Jay DiMartino is a writer and a former competitive surfer who spent more than a decade competing on the famed North Shore of Oahu.

Removing Sea Urchin Spines

Here are tips on how to remove sea urchin spines from your feet if you ever find yourself in such an unfortunate state.

Soak in hot water—Alleviate the pain and soften the needles by soaking the afflicted area in hot water.
Settle down with a pair of tweezers—Try to pick out as many of the pieces as you can with a knife, needle or, preferably, tweezers. The biggest problem is that sea urchin spines often break off under the skin, so be very careful when plucking out the spines.
Soak in vinegar—Urban legend has it that human urine, or pee, will treat both jellyfish stings and sea urchin spines, but peeing on the afflicted area does not actually work. Try using distilled white vinegar instead. Soak the area in pure vinegar (a solution of hot water and vinegar will work as well), which will soften the spines. The urchin spines will either dissolve under the skin or lift to the surface. Continue to soak the affected area until the spines are gone.
Rinse with soap and water—When all of the spines are gone, avoid infection by rinsing the afflicted area with soap and clean water.
Let a doctor remove any remaining spines—If there are any spines that you cannot remove or are too painful to remove, you should make an appointment with a doctor, who can remove the spines with more refined tools.

Why Sea Urchins Attack

Actually, sea urchins don’t really attack humans. They aren’t aggressive creatures, and they tend to be slow-moving. Stings are usually the result of an accidental brush between a human and a sea urchin.

The sea urchin’s spines are its way of defending itself when it feels threatened. There are many types of sea urchins with spines that differ in sharpness and length. Some species’ spines are filled with venom, while others are not. But even without venom, the spines are an effective and painful defensive tool.

Some sea urchin species have another painful tool to protect themselves called pedicellarines, tiny, claw-like structures that can grab your skin and inject a painful poison.

Don’t take a brush with a sea urchin lightly. In addition to infection, you could suffer more severe consequences if venom builds up in your system. Uncommon but possible effects are fainting, muscle spasms, and difficulty breathing. Left untreated in enough quantity, the venom could be fatal.