Elassochirus tenuimanus (Dana, 1851)

Common name(s): Widehand hermit crab
Synonyms:  Bernhardus tenuimanus, Eupagurus tenuimanus, Pagurus tenuimanus
Phylum Arthropoda
 Subphylum Crustacea
  Class Malacostraca
   Subclass Eumalacostraca
    Superorder Eucarida
     Order Decapoda
      Suborder Pleocyemata
       Infraorder Anomura
        Superfamily Paguroidea
         Family Paguridae
Elassochirus tenuimanus from 12 m depth, Coffin Rocks, Bowman Bay.
(Photo by: Dave Cowles, July 2005)
Description:  In this large, mostly subtidal hermit crab, the right chela is larger than the left, and the carpus and propodus of the right chela are very wide and flattened. The carpus of the right cheliped is wider than it is long.  There are spines on the dorsal surface of the claws.  The first and 2nd walking legs have 3 dark stripes on the dorsal surface and a white stripe on the medial surface of the carpus, and rows of red spots on the propodus and dactyl (photo).  The cornea of the eye is inflated.  Color:  orange, brown, and white, with a purplish-blue on the upper walking legs.  Antennae are orange-brown.  Carapace length to about 4.2 cm.

How to Distinguish from Similar Species:  Elassochirus is the only hermit crab genus in this area has a large right cheliped that has a carpus that is wider than long. The other Elassochirus species, such as E. cavimanus and E. gilli, have a propodus to the right cheliped that is narrower than the carpus.

Geographical Range:  Bering sea and Aleutian Islands, Alaska to Washington; northwestern Pacific

Depth Range:  Intertidal (rarely) to 388 m

Habitat:  Around rocks, mud, sand, or shell bottoms, but usually near rocks

Biology/Natural History:  This species uses the large right claw to block the entrance to the shell when the animal retreats inside (photo).  When walking, the claw is bent beneath the body.  The hydroid Hydractina milleri often lives on the shells this hermit crab lives in.  Ovigerous females in Washington can be found from August to May.  Larvae hatch March to May.  Planktonic stages last several months.


 
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References:

Dichotomous Keys:
  Coffin, 1952 (as Pagurus tenuimanus)
  Hart, 1982
  Kozloff 1987, 1996
 

General References:

  Gotshall, 1994
  Harbo, 1999
  Jensen, 1995
  O'Clair and O'Clair, 1998

Scientific Articles:
 

Web sites:
 


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



The large, flattened right chela is used to seal the entrance of the shell when the animal withdraws inside.  Photo by Dave Cowles, July 2005



In this side view the color pattern on the walking legs can be seen:  The propodus and dactyl have rows of red spots.  The carpus has red stripes.  The merus has large areas of purplish-blue.



This individual is scavenging in an Enteroctopus dofleini midden.  Underwater photo by Jim Nestler, July 2005

x
Another individual photographed underwater by Kirt Onthank, July 2007.  It is living in a leafy hornmouth shell.
 

The following views of an individual out of its shell are for an individual of 9 mm carapace(rather, thorax) length trawled from 135 m depth in the San Juan Channel, 2018

Dorsal

Dorsal view


Eyescale furrow
Closeup of the deep eyescale furrows

right side

Right side.

legs 4-5

This is a photo of the left side of the rear thorax and abdomen of an individual out of its shell, showing the small legs 4-5. Photo by Dave Cowles, July 2018


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