Sea Pens



Upper: A group of Ptilosarcus gurneyi at Possession Point beach, Whidbey Island, 50 feet, California, Eastern Pacific Ocean, 19 August 2009, Sandy slope. Photographer: Jan Kocian.

Lower: One dying Sea Pen washed ashore after storm. Armstrong Beach, On shore, Queensland, Australia, Coral Sea, 10 February 2010, Length: Approx 10 cm. Photographer: Sharyn Reen.

Sea pens are cnidarians or coelenterates, related to sea anemones, corals and jellyfish. Each 'animal' is a colony, with a fleshy anchor which sticks down into the mud or sand, and an upper 'feather-like part with layers of flaps which can expand out into the water. At the edge of the flaps are a row of polyps, which look like small sea anemones. They live offshore in sheltered bays, feeding on small organisms in the water. Some species are eaten by arminid nudibranchs. See messages attached to the Armina californica for many examples, in particular message #23276.

See also message #23267 for photos of Armina semperi feeding, and close-up photos of the sea pen polyps.

Authorship details
Rudman, W.B., 2010 (March 9) Sea Pens. [In] Sea Slug Forum. Australian Museum, Sydney. Available from

Related messages

  1. Re: Sea pens [2]
    From: Leanne and David Atkinson, March 15, 2010
  2. Re: Sea pens [1]
    From: Leanne and David Atkinson, March 15, 2010
  3. Armstrong Beach, Queensland. What is it?
    From: Sharyn Reen, February 22, 2010
  4. Sea Pens from Western Australia
    From: Beth Turnbull, July 25, 2006

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