Sea Anemones: Tide-Pool Predators
By Sherry Shahan • Photos by author
I am a photojournalist. My job is to write
stories by putting words and photographs
together.
Today’s assignment is to take pictures of
strawberry sea anemones (uh-NEM-uhneez). To find them, I put on high-topped
rubber boots and wade in tide pools along
the coast of California.
Twice each day, tide pools appear along
seacoasts as the pull of the moon’s gravity
makes the sea level fall and rise.
The author visits a tide pool on the
High-water times are called “high tides.”
coast of California. The long lens on her
Many kinds of sea creatures move into the
camera works like a microscope. She uses
it to take big pictures of small creatures.
shallow waters during high tides.
Periods when the water is low are called “low tides.”
At these times, much more of the shore is exposed to the
air. At the end high tide, when the water retreats, some
water is trapped among the rocks, forming pools. In these
tide pools, I find delicate creatures, such as sea stars,
ocean-going snails called abalones (a-buh-LOW-neez),
and sea anemones.
Strawberry Anemones
As you might guess from its name, the strawberry
anemone is as bright as the sweet fruit and is speckled
Tide pools often have sea stars
with white dots. But it’s an animal, not a plant.
(on the left), sea anemones (on
Sea anemones are related to jellyfish. Both of these
the right), and abalones (in
creatures are called invertebrates because they don't have
between, covered with
backbones.
barnacles).
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
Assignment completed: This
strawberry anemone was later
because they look like flowers, with their tentacles
photographed by the author.
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 A giant green anemone sits underwater,
stings.
waiting to use its tentacles to capture
But the green anemone’s stinging cells do not hurt
prey.
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.
This sea anemone has covered
itself with seashells and pebbles
The water seeping over the tops of my boots lets
to protect itself from the sun until
me know the tide has started to return. Soon the
the tide covers it with water again.
exposed rocks will be covered with lapping
waves as the sea pushes its way toward high tide.
I didn’t find any strawberry anemones today. But that’s OK. The tide pool will be back
again.