Aggregating Anemone
Anthopleura elegantissima

Physical Description

  • A tube-shaped body crowned with tentacle, attached permanently to a hard surface
  • A green body with white tentacles that are pink-tipped
  • Tube about 2.5 inch diameter, tentacles about 3.5 inch diameter
  • When exposed to air, the anemone will close up completely and cover itself with broken shells and sand that provide camouflage and prevent it from drying out

Range

  • Alaska to Baja California, Mexico

Habitat

  • Rocky shores and tidepools
  • Intertidal zone to about 60 foot depth

Diet

  • They eat plankton like copepods, isopods, amphipods
  • They eat falling mussels, acorn barnacles, small crabs, chitons, and small fishes

Predators

  • Nudibranchs (that disable the stinging nematocyst cells)
  • Leather star, wentletrap snail, sea stars and fishes

Interesting Facts

  • A microalgae (zoochlorallae) and a dinoflagellate (zooxanthellae) live inside the anemone’s tissues and photosynthesize, or use the energy of the sun, to provide food and energy for the anemone. In turn, the anemone gives them shelter. The anemone also bends towards the sun to give them optimal sunlight. 
  • Their tentacles have stinging cells called nematocysts that paralyze their prey and defend them from predators. 
  • They can reproduce by spawning or by binary fission, where they create whole colonies of genetically identical anemones! 
  • When one group of genetically identical clones encounters another, they will battle for territory by stinging each other. In the end, they often leave a large neutral zone. 

Sources: Monterey Bay Aquarium; University of Puget Sound; California Diving News; Walla Walla University; Californiatidepools.com

Photo: Mark Royer

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