Pachycerianthus fimbriatus McMurrich, 1910 Common name(s): Tubedwelling anemone
Synonyms: Pachycerianthus torreyi, P. plicatulus
Phylum Cnidaria  Class Anthozoa  Subclass Ceriantipatharia  Order Ceriantharia  Family Cerianthidae
	Pachycerianthus fimbriatus photographed at Monterey Bay Aquarium.  Tentacle spread is approximately 30 cm.
	(Photo by:  Dave Cowles, August 2010)

Description: This anemone-like species lives in a slippery black tube that they secrete.  It has two rings of slender, translucent brownish, purplish-black, orange, or light colored tentacles.  The inner ring may be held over the mouth while the outer ring is extended further.  Animal length to 35 cm.  Tube up to about 2.5 cm diameter and may be more than a meter long.

How to Distinguish from Similar Species: This is the only member of this Subclass in our area.  Other members of the subclass include black corals

Geographical Range: Southern Alaska to Isla San Martin, Baja California

Depth Range: Rarely intertidal, mostly subtidal to at least 54 m

Habitat: Very soft mud such as bays and harbors.  Sometimes in sand.

Biology/Natural History:  This anemone-like cerianthid lives in a soft, black, slimy tube that may extend a meter or farther into the sediment.  The tube extends slightly above the sediment and is made of a secretion of nematocyst-like organelles called ptychocysts.  The cerianthid quickly withdraws into the tube when disturbed, and may leave a star-shaped track in the mud around the tube entrance with its tentacles when it withdraws.  Predators include the nudibranch Dendronotus iris, which may be drawn into the tube and continue feeding when the cerianthid withdraws. Dendronotus iris attaches its eggs to the tube of the cerianthid, which appears to be its principal prey.  Feeding by the nudibranch usually does not kill the cerianthid.  The aboral end of the cerianthid is pointed and adapted to digging.  Cerianthids differ from anemones in several ways, such as having an aboral anal pore.  Cerianthids have unusually rapidly-conducting nervous systems for Anthozoans.  Some cerianthids have fluorescent tentacles (in some other animal phyla fluorescent pigments have been shown to help defend against ultraviolet radiation).

References:

General References:
  Gotshall, 1994
  Harbo, 1999
  Hinton, 1987 (as P. estuari)
  Lamb and Hanby, 2005
  Morris et al., 1980
  Niesen, 1994
  Niesen, 1997
  Ricketts et al., 1985

Scientific Articles:

Web sites:

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

I have not observed this species near Rosario, where bottoms are sandy or rocky.  It may be found in quieter, muddier bays.

More individuals, showing the variety of tentacle colors.  Sometimes the tentacles are banded.  Photo by Dave Cowles at Monterey Bay Aquarium, August 2010.

Rosario Invertebrates web site provided courtesy of Walla Walla University