Stomphia didemon Siebert, 1973 

Common name(s): Orange anemone.  Swimming anemone.  Apple anemone.
Synonyms: Actinostola sp.
Phylum Cnidaria
 Class Anthozoa
   Subclass Zoantharia
    Order Actiniaria
     Family Actinostolidae
Stomphia didemon, about 3.5 cm diameter and 4 cm tall.  Captured by otter trawl at about 90 m depth from San Juan Channel
Photo by: Dave Cowles July 2001
Description:  This subtidal anemone has no acontia, no tubercles on the column wall (see picture), usually a cream or orange color, tentacles orange and sometimes banded but with no white spots at their bases.  The column is often more than 5 cm high and can stretch to much higher than it is wide.  Sometimes the anemone has darker orange or red blotches or streaks (picture).  The anemone has at least 160 tentacles in individuals of over 5 cm column height.

How to Distinguish from Similar Species: Stomphia coccinea has a whitish column with red or orange-red streaks, is not usually more than 3 cm high, and usually is found on horse mussel (Modiolus modiolus) shells.  Stomphia sp. has less than 130 tentacles on individuals 5 cm or more tall, and its color is a uniform reddish beige.

Geographical Range:  Web sources indicate that it can be found at least in Alaska, British Columbia, and Washington State.

Depth Range:  The Monterey Bay Aquarium reports that this species lives from 60-180 m depth (http://www.mbayaq.org/efc/living_species/default.asp?hOri=0&hab=9&inhab=495)

Habitat:  In the San Juan channel specimens are often captured from sand/gravel bottoms at about 80-100 m depths.  They usually come up not attached to anything, though they will readily attach to a solid object in an aquarium.  Perhaps this is because they have a swimming response to predators.

Biology/Natural History:  Little is known.  This is a recently described species.  The spincter of Stomphia species in general is strong enough that the upper part of the body can cover the tentacles (the tentacles can be retracted completely inside).  This species, as well as a relative Stomphia coccinea, are known to detach from the bottom and swim away from predators such as the leather star, Dermasterias imbricata.  S. coccinea is found in northern boreal waters of the Atlantic and Pacific.  Another relative, S. selaginella, inhabits McMurdo Sound in Antarctica.
On one web site (http://www.bbc.co.uk/nature/animals/features/292feature1.shtml), the BBC reports on S. didemon: "When approached by a predatory leather star, this anemone, Stomphia didemon, became highly agitated. It elongated and swayed from side to side. Then, bending low, it brushed its tentacles over the leather star. Finally, this normally sedentary animal inflated a muscular cone at its base to lever itself free from its moorings and danced away in the water column."
The species is said to eat small crustaceans.


 
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References:


Dichotomous Keys:

Kozloff, 1987

General References:
 
 

Web References:
http://www.underwater-photos.com/pw046.html (a photo and short note on S. coccinea)
http://www.ups.edu/faculty/jkelliott/escape.htm (photos and description of S. didemon escaping from the leather star)
 

Scientific Articles:

Dalby, J. Jr., J. K. Elliott, and D. M. Ross. 1988. The swimming response of the actinian Stomphia didemon to certain asteroids: distributional and phylogenetic implications. Can. J. Zool. 66: 2484-2491.
 


General Notes and Observations:  Locations, abundances, unusual behaviors, etc.:
We have usually caught this species by otter trawl in the San Juan Channel north of San Juan Island, using the Friday Harbor Marine Lab vessel


Stomphia didemon's column wall.  This species has no tubercles or acontia on the wall.  A few bits of debris may be present but they appear to be just loosely attached by mucus.


Another individual.  Captured 100 m depth, San Juan Channel.  Photo by Dave Cowles, July 2000


A view of the oral disk.  Photo by Dave Cowles, July 2000


This individual from 100 m, San Juan Channel, is perched on a shell.


The tentacles end with a small pore.


An unusually pale individual.
 


Authors and Editors of Page:
Dave Cowles (2004):  Created original page