Aggregating anemones, elegant flowerlike animals, have a tube-shaped body crowned with tentacles. Two types of microscopic algae live in the anemones' tissues and give them their green color—anemones without algae are white. The algae supply food to the anemones, and the anemones bend toward or away from the light to provide the algae with the proper amount of light needed for photosynthesis.
Anemones are voracious feeders that eat almost anything. Stinging cells (nematocysts) on their tentacles paralyze small prey animals. Anemones can even ingest small crabs and then spew out the shells.
Because aggregating anemones can rapidly clone themselves, they’re abundant on the rocky shore. If they’re buried by drifting sand, they can survive for more than three months. Oil spills or oil from storm drains, however, can destroy anemone habitats—and it can take two years or more for habitats to recover from such catastrophes. If you go tidepooling, be careful not to walk on or disturb anemones or other tide pool creatures.
Although they live side by side, clonemates from different groups are enemies. Warrior anemones with knoblike swellings packed with large stinging cells border each group. If a warrior comes in contact with an enemy warrior, they exchange a barrage of poison darts, causing injury to both. The warriors withdraw, leaving behind a “demilitarized zone.”
Anemones exposed to air retract their tentacles and shrink in size. Sticky bumps on their bodies collect sand and bits of shells, which provide camouflage and prevent them from drying out. Remember to watch your step when tidepooling—more than one tired tidepooler has sat down on a rock for a short rest, only to discover she’s sitting on a wet and squishy anemone.
Aggregating anemones live on rocks in tide pools and crevices, either alone or in dense masses. Each mass is a group of clones that are genetically identical and of the same sex. To clone themselves, anemones split in half—literally tearing themselves apart (asexual reproduction). Asexual reproduction spreads new animals rapidly over rocks. Aggregating anemones also reproduce sexually by broadcasting eggs and sperm. Sexual reproduction results in new combinations of genes, and larvae that establish new colonies in other locations.