Sea Anemones: Tide-Pool Predators
By Sherry Shahan • Photos by author
As you might guess from its name, the strawberry anemone is as bright as the sweet fruit and is speckled with white dots. But it’s an animal, not a plant.
Sea anemones are related to jellyfish. Both of these creatures are called invertebrates because they don't have backbones. The bodies of anemones and jellyfish are made mostly of water and are shaped like hollow sacks, so they’re soft and squishy. Anemones and most jellyfish have tentacles with stinging cells. But here’s a difference: Jellyfish are free swimmers. But each sea anemone uses a suckerlike disk to attach itself to a solid foundation, usually a rock. Crabs often attach sea anemones to their backs. The anemones give the crabs camouflage and protection. Sea anemones are easy to find in the shallow water because they look like flowers, with their tentacles stretched out like petals to catch their prey. But anemones vary a lot, too. In my search for strawberry anemones, I wade through a shallow pool of trapped water. I spot a giant green anemone. With bluish-green tentacles fanned out, it’s the size of a saucer. Stinging Cells
I’m careful when I brush my finger over an anemone’s sticky tentacles. The stickiness is caused by tiny stinging cells called nematocysts (NEM-uh-tuh-sists) lining the sides of the tentacles. Each nematocyst contains a barbed, threadlike tube. When something touches the capsule, it explodes and shoots out its tiny, harpoonlike tube. Usually, many nematocysts are triggered at the same time, shooting many barbs into whatever brushes past. In some types of anemones, the nematocysts inject poison—both to catch their prey and to protect the anemone from other predators. Some of these anemones can deliver painful, poisonous stings. But the green anemone’s stinging cells do not hurt people. So even when many of the cells stick their barbs into my finger, it doesn’t hurt. It just makes the tentacle feel sticky. The green anemone preys on crabs, shrimp, snails, and other small animals that crawl or swim by. Once an anemone captures a meaty morsel, it pulls the prey toward its slitlike mouth. On a recent visit, I saw a green anemone swallow a shore crab. Then I watched as it spit out bits of crab shell. Tumbling Anemones
Still searching for strawberry anemones, I see a green anemone creep along the tide-pool floor. To move, an anemone releases its sucker disk, then does a slow “somersault,” using its tentacles to flip over. Sea anemones don’t lay eggs or bear young. Instead, they split in two. These parts also divide. In time, the rocks may be covered by a blanket of anemones. Other anemones stay hidden. A narrow channel leads me to a ledge that sticks up out of the water. Using my macro lens—which is like having a microscope on the end of a camera—I focus on the shaded area under the rocky lip. Hidden from harsh sunlight and wave action, a colony of club-tipped anemones thrive. They are only one inch high and are topped with a flared crown of bright pink tentacles. The water seeping over the tops of my boots lets me know the tide has started to return. Soon the exposed rocks will be covered with lapping waves as the sea pushes its way toward high tide. The Intertidal Zone
Littoral Zone Animal Printouts
The intertidal area (also called the littoral zone) is where the land and sea meet, between the high and low tide zones. This complex marine ecosystem is found along coastlines worldwide. It is rich in nutrients and oxygen and is home to a variety of organisms.
An Inhospitable, Changing Environment:
Much of this inhospitable environment is washed by the tides each day, so organisms that live here are adapted to huge daily changes in moisture, temperature, turbulence (from the water), and salinity. * Moisture: The littoral zone is covered with salt water at high tides, and it is exposed to the air at low tides; the height of the tide exposes...
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