Ptilosarcus gurneyi (Gray, 1860)

Common name(s): Orange sea pen, fleshy sea pen, sea feather

  Ptilosarcus quadrangulare
  Leioptilus quadrangulare
  Leioptilus guerneyi
  Ptilosarcus quadrangularis
Phylum Cnidaria
 Class Anthozoa
  Subclass Alcyonaria (Octocorallia)
   Order Pennatulacea
     Suborder Subselliflorae 
      Family Pennatulidae
(Ptilosarcus gurneyi from Rosario Bay.  Approximate length 25 cm)
(Photo by: Dave Cowles August 2004)
Description:  A sea pen with a fleshy lower part of stalk (lower left in the picture above), which is buried in the sediment.  Upper part of central stalk (rachis) has a hard central support.  Branches are thick and fleshy with small polyps along the edges.  Usually yellow or orange, often large (up to 1/2 meter).  Has great powers to expand or contract.

How to Distinguish from Similar Species: There are no similar species near Rosario.

Geographical Range: Gulf of Alaska to southern California

Depth Range:  Shallow subtidal to 70 m

Habitat: Sand and mud bottoms

Biology/Natural History: The entire central part (rachis) is said to be one large polyp.  Smaller, inconspicuous polyps open into it and pump water in an out as needed for expansion or contraction.  Produces a strong greenish luminescence when disturbed.  Preyed upon by several nudibranchs, including Hermissenda crassicornis, Armina californica, and Tritonia festiva, and of the seastars Dermasterias imbricata, Pycnopodia helianthoides, Mediaster aequalis, Hippasteria phrygiana, and Crossaster papposusThe sea pens may rapidly burrow into the sediment when contacted by a predator.  Although they do not appear to burrow when exposed only to seawater which contained a predatory seastar, they were more likely to burrow after contacting a predatory seastar if they had already been exposed to its smell.  This species responds to different predators differently.

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Dichotomous Keys:
Kozloff 1987, 1996
Flora and Fairbanks, 1966

General References:
Gotshall and Laurent, 1979
Kozloff, 1993

Scientific Articles:
Weightman, Janice O.  and David J. Arsenault, 2002.   Predator classification by the sea pen Ptilosarcus gurneyi (Cnidaria): role of waterborne chemical cues and physical contact with predatory sea stars.  Can. J. Zool./Rev. Can. Zool. 80(1): 185-190 (2002)

General Notes and Observations:  Locations, abundances, unusual behaviors:

In our experience this species is usually found in quieter water such as behind Whidbey Island.  Years ago there was a small colony in Rosario bay.  The colony disappeared and no individuals were seen for 5-10 years.  In the 1980's some students working on a project harvested some individuals from behind Whidbey Island.  After the project they returned them to Rosario Bay.  Since that time the species has been becoming more abundant in the bay again.

In my experience, if this species is not placed into sand or mud in the aquarium, it usually has a problem with its lower stalk which becomes hyperinflated.

A short video of this species can be found at:

Another photo.  Note that the polyps are arranged in flaplike rows on the plume.  Photo by Dave Cowles, July 2005

This closeup shows the individual polyps lining the rows.  A small majid crab has climbed aboard, and may be nipping at the polyps, though the crab's activity did not stimulate Ptilosarcus to close.

Buds seem to be growing off 3 of the laminae on the right side of the plume of this individual.  Does Ptilosarcus do any budding for reproduction?
Photo by Dave Cowles, July 2005

Armina californica feeding on Ptilosarcus
This Ptilosarcus is being fed on by the nudibranch Armina californica. Below is a view of a Ptilosarcus after active feeding by Armina. The shaft is the rachis.
Ptilosarcus eaten by Armina

In Burrows Bay
I photographed this individual at 50 ft depth in Burrows Bay. Photo by Dave Cowles 2019

Authors and Editors of Page:
Dave Cowles (2005):  Created original page