| Shark Egg Cases |
Exhibit
Gallery: Sharks: Pacific Northwest
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Sharks bear their young in dramatically different ways. Some sharks package their young in leathery egg cases, then abandon them at sea. Nourished by their yolk-filled egg sacs, the young sharks, called pups, develop on their own. After several months, one edge of the case comes apart and the tiny sharks emerge, alive and swimming.
Occasionally egg cases wash up on beaches before the sharks inside can hatch. Beachcombers may know the pillow—shaped cases as "mermaid's purses." Swell shark egg cases come with strings attached—long, wiry tendrils at the corners that catch on rocks and seaweed. These tendrils anchor the egg cases to the bottom and help prevent them from washing up on shore.
While some sharks cast their egg cases adrift, other mothers brood the developing embryos inside their bodies, then give birth to live offspring. Compared to bony fishes, many of which produce thousands of offspring each year, sharks bear relatively few young—usually fewer than a hundred, and in some species, only one or two. |
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