Pagurus granosimanus (Stimpson, 1858)

Common name(s): Grainyhand hermit crab, Granular hermit crab

Synonyms:  Eupagurus granosimanus
Phylum Arthropoda
 Subphylum Crustacea 
  Class Malacostraca 
   Subclass Eumalacostraca 
    Superorder Eucarida 
     Order Decapoda 
      Suborder Pleocyemata
       Infraorder Anomura
        Superfamily Paguroidea 
         Family Paguridae
Pagurus granosimanus from Sares Head, in a Nucella lamellosa shell.
(Photo by: Dave Cowles July 2005)
Description:  This common intertidal hermit crab is most easily distinguished by the light blue raised dots on the chelipeds and walking legs, plus the unbanded orange or red antennae. The legs of young individuals may be yellow.  Carapace to 1.9 cm.

How to Distinguish from Similar Species:  Of the species common in the intertidal, no others have the blue dots all over the legs.  P. beringanus has red bands and red dots on the legs.  P. hirsutiusculus has no dots and hairy legs.  P. hemphilli has dark red legs with yellow spots, with a white dot at the end. P. samuelis is found only on the open coast and has red antennae and a blue band on the dactyls of legs 2 and 3.

Geographical Range:  Unalaska, Aleutian Islands, Alaska to Bahia de Todos Santos, Baja California.  Less abundant than P. samuelis in California and south.

Depth Range:  Low intertidal to 36 m

Habitat:  Rocky, cobbles, and among algae.

Biology/Natural History:  This species is often found in Tegula funebralis, Searlesia dira or Nucella lamellosa shells.  Small individuals live in Littorina shells.  It seems to prefer shells large enough that it can completely withdraw inside.  It lives lower in the intertidal than does P. hirsutiusculus but higher than P. beringanus.  This is said to be the smallest intertidal hermit crab to be found in Puget Sound, but I have not noticed it being particularly small.  Predators include the black prickleback, Xiphister atropurpureus.  The species is active mainly in the afternoon and night, and sometimes can be found in large aggregations on shallow sand bottoms.  They produce 3 broods per year in the Puget Sound area.  The females carry their eggs for about 55 days, and the planktonic zoea/megalops stages last about 70 days.

In Puget Sound this hermit is said to change shells more often than does P. hirsutiusculus, and holds onto its shells more tenaceously.  It is often able to evict P. hirsutiusculus from its shell and take it over.



 
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References:

Dichotomous Keys:
  Coffin, 1952
  Flora and Fairbanks, 1966
  Hart, 1982
  Kozloff 1987, 1996
  Smith and Carlton, 1975
  Wicksten, 2009
 

General References:
  Brusca and Brusca, 1978
  Jensen, 1995
  Johnson and Snook, 1955
  Kozloff, 1993
  Morris et al., 1980
  O'Clair and O'Clair, 1998
  Sept, 1999

Scientific Articles:
 

Web sites:
 



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

I find this hermit crab on Sares Head much more often than I find P. hirsutiusculus.
 


This species often chooses shells large enough to withdraw into entirely.  Photo by Dave Cowles, July 2005


The carpus of the right cheliped is longer than wide.  The merus has 2 prominent tubercles on its underside (colored light blue)  Photo by Dave Cowles, July 2005


Here Pagurus granosimanus is living in a Tegula funebralis shell.
Photo by Kirt Onthank, 2005
 
 



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