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Anemones

Sea anemones thrive on a special partnership

 Giant GreenGreen sea anemones have single-celled algae living in their tissues. The algae probably have a relatively safe place to live, but the sea anemone may get a good portion of its food from the algae, as well as some camouflage. Anemones living in dark crevasses are paler green.

Similar to their jellyfish relatives, sea anemones use their tentacles to sting and retrieve prey. Small fish, open snails, and other intertidal animals are caught by the tentacles, pulled into the mouth, and eaten. An anemone with tentacles tucked insstyle=ide while underwater is probably eating; an anemone with tentacles tucked inside when out of the water is probably protecting its tentacles and mouth from drying and other damage.

Poking anemones may cause them to squirt out valuable water they need to stay hydrated during low tide, please observe gently.

Aggregating anemonesAggregating Anemone

The most commonly encountered sea anemone in Oregon’s tidepools, aggregating anemones may be overlooked because they’re small. Aggregating anemones also thrive high up in the intertidal and people often overlook them because the anemones are closed up when exposed during the low tide that draws people to the shore. Aggregating anemones are often packed closely together, making it more difficult to make out individual animals; the shell bits on the outside complete the camouflage.

Why are aggregating anemones sometimes packed tightly together? Anemones reproduce by shedding eggs and sperm into the water, or by budding, or by splitting in two—cloning: aggregating anemones are especially good at cloning. A cloning aggregating anemone starts by stretching into a long oval then a long figure 8, eventually dividing into two genetically identical individuals.

Look for the pink-tipped tentacles in an open aggregating anemone while you’re looking for cloning individuals and boundaries between clone colonies. If you're lucky, you may even see the acrorhagi, or specialized tentacles used by this anemone to warn off members of other clones.

More information

Description: Shaped overall like shallow bowls with ultra-thick bottoms attached to the substrate, sea anemones may look more like flowers than like animals—especially the ones that are green. Pointed “petals” around the top rim are stinger-armed tentacles that frame the central disc, the mouth of the animal. The floor of the central disc is smooth with a doughnut-shaped lump in the middle, while the outside of the body, below the tentacles, is usually a darker green and rough, and is often flecked with bits of shell. Many of the intertidal sea anemones you are likely to see in Oregon are olive to bright green (some species have splashes of other colors). Depending on species, age, and environment, some of our tidepool sea anemones can grow up to 10” across (about the size of a dinner plate!).

Taxonomy:

Kingdom Animalia  – Animal, animaux, animals
   Subkingdom Radiata 
      Phylum Cnidaria Hatschek, 1888 – cnidarians, coelenterates, cnidaires, coelentérés, água viva, anêmona, caravela, cnidario, coral, hidra
         Subphylum Anthozoa 
            Class Anthozoa Ehrenberg, 1834 – corals, flower animals, sea anemones, anémones de mer, coraux, água viva, anêmona, antozoário, caravela, corais, gorgônia
               Subclass Hexacorallia 
                  Order Actiniaria  – anemones, sea anemones, actinies, anémones
                     Suborder Nyantheae Carlgren, 1899
                        Infraorder Thenaria Carlgren, 1899
                           Family Actiniidae Rafinesque, 1815
                              Genus Anthopleura Duchassaing de Fonbressin and Michelotti, 1860

Common species:

  • Anthopleura xanthogrammica (Brandt, 1835) -- giant green anemone
  • Anthopleura elegantissima (Brandt, 1835) -- clonal anemone, aggregating anemone

Taxonomic information source: ITIS.gov