Significance to humans

Some echinoids are commercially valuable. In the United States, for example, red sea urchin, Strongylocentrotus francis-canus, purple sea urchin, S. purpuratus, and green urchin, S. droebachiensis, are harvested for their roe. In Japan, urchin eggs and their reproductive organs are eaten as a delicacy. In European waters, overexploitation of Paracentrotus lividus has resulted in habitat destruction and decline in population numbers. In areas where predators of urchins have been over-fished, urchin numbers can explode, causing devastating impacts to the marine community. In the Caribbean, for example, urchins have been responsible for 90% of the bioerosion of coral reefs. Ironically, their efficiency at consuming unwanted algae and detritus has made them popular animals for aquariums.

The sea urchin, Diadema, is perhaps the most well known for its long spines that easily puncture human skin, leaving deep and painful wounds. The spine tips easily break off under the skin and are almost impossible to remove.

Urchins' dried and empty tests are a familiar component of strandlines on beaches and provide a valuable commodity for souvenir hunters.

Sandollar Images Illustration

1. Rock boring urchin (Echinostrephus aciculatus); 2. Sea biscuit (Plagiobrissus grandis); 3. Slate-pencil urchin (Eucidaris tribuloides); 4. Six keyhole sand dollar (Leodia sexiesperforata); 5. Heart urchin (Abatus cordatus); 6. Western sand dollar (Dendraster excentricus). (Illustration by Bruce Worden)

Sea Urchin Wounds

1. Long-spined sea urchin (Diadema savignyi); 2. West Indian sea egg (Lytechinus variegatus); 3. Tuxedo pincushion (Mespilia globulus)', 4. Short-spined sea urchin (Anthocidaris crassispina); 5. Magnificent urchin (Astropyga magnifica); 6. Pea urchin (Echinocyamus pusillus). (Illustration by Bruce Worden)

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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