Discorsopagurus schmitti (Stevens, 1925)

Common name(s):  Tubeworm hermit

Synonyms:  Pylopagurus schmitti, Orthopagurus schmitti
Phylum Arthropoda
 Subphylum Crustacea
  Class Malacostraca
   Subclass Eumalacostraca
    Superorder Eucarida
     Order Decapoda
      Suborder Pleocyemata
       Infraorder Anomura
        Superfamily Paguroidea
         Family Paguridae
Discorsopagurus schmitti from 15 m depth, Coffin Rocks.  Animal is in a tubeworm tube that is heavily overgrown with a white colonial tunicate.  Leg span in photo approximately 1 cm.
(Photo by: Dave Cowles, August 2005)
Description:  This small hermit crab has an abdomen that is not coiled (photo) and symmetrical uropods (photo).  The palm (propodus) of the right chela is little if any wider where the dactyl and palm join than it is at the proximal end.  The right chela is only slightly larger than the left (photo).  The legs have reddish-brown bands.  The right and left halves of the telson are not separated by a groove (photo).  Carapace length up to 6 mm.

How to Distinguish from Similar Species:  The palm of the right chela of Orthopagurus minimus is wider at the origin of the dactyl than it is at the base, and it is usually found in the shells of scaphopods (tusk shells).  Its right claw is much larger than the left and it holds it straight out in front of itself while walking.

Geographical Range:  Sitka Sound, AK to Puget Sound; Japan

Depth Range:  Mostly subtidal; low intertidal to 220 m

Habitat:  In tubes of serpulid or sabellarid tubeworms (usually Sabellaria cementarium or Serpula vermicularis), rarely in snail shells.  Inland waters and open coast.

Biology/Natural History:  Females usually live in attached tubes, and males in broken-off tubes.  Can filter feed using both the third maxillipeds and the antennae, plus catches small pieces of drift material.



 
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References:

Dichotomous Keys:
  Coffin, 1952 (as Orthopagurus schmitti)
  Hart, 1982
  Kozloff 1987, 1996
  Wicksten 2009

General References:
  Jensen, 1995
  Kozloff, 1993
 

Scientific Articles:
 

Web sites:
 



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


This view shows the entire tube and tunicate the hermit crab is carrying.  The total mass is so large that the hermit crab can barely crawl along.  Photo by Dave Cowles, August 2005



Animal out of the tube.  Note the straight abdomen, the many setae on the body, and the star-shaped pleopods.  Note also the two small rear walking legs.
Total length about 2 to 2.5 cm.



In this ventral view of the thorax one can see the relative sizes of the right and left chelae, the three long first walking legs and the two short rear walking legs, and the abundant setae.



In this ventral view of the abdomen one can see the star-shaped pleopods on the left side, the symmetrical uropods, and the telson which does not have a median groove.

I am guessing that this is a female, and that the star-shaped pleopods are for holding eggs.  Although the animal was in a technically movable tube, it was so heavily overgrown that the animal could barely crawl.


Another individual, collected at about 130 m depth from the channel between Lopez and San Juan Islands, is living in a tubeworm tube which is encrusted with stones and tiny barnacles.  Photo by Dave Cowles, July 2012


A closeup of the same individual.



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