Scleroplax granulata Rathbun, 1897 

Common name(s): Burrow pea crab

Synonyms: Scleroplax granulatus Scleroplax granulata
Phylum Arthropoda
Subphylum Crustacea 
Class Malacostraca
Subclass Eumalacostraca
Superorder Eucarida
Order Decapoda
Suborder Pleocyemata
Section Brachyrhyncha

Scleroplax granulata from a tubeworm burrow in Padilla Bay.  Background ruler scale is cm and mm.  Carapace dimensions for this male are 12 mm wide by 8 mm long.
(Photo by: Dave Cowles, June 2009)
Description:  This pea crab has a hardened carapace less than 1.5x as wide as long, smooth or finely granulated.  The borders of the carapace are smoothly curved.  Legs 3 and 4 do not have long hairs, and the dactyls of the walking legs are not strongly curved.  The males of this species have very large, thick claws for a pea crab, with a thick propodus and a short, curved, toothed dactyl (photo).  The claws of immature individuals and of females are much smaller and slender, with nearly equal fingers, small cutting teeth, and sharp tips.  The cornea of the eye is red (photo).  Carapace width of females to 12.9 mm, males slightly smaller.  The third walking leg is the longest.

How to Distinguish from Similar Species:  Mature males and females ofFabia subquadrata have long hairs on legs 3 and 4, plus the dactyls of the walking legs are strongly curved.  Most other pea crabs have a carapace at least 1.5x as wide as long.

Geographical Range:  Porcher Island, British Columbia, Canada to Ensenada, Baja California, Mexico

Depth Range:  Mid intertidal to 55 m

Habitat:  Commensal in burrows of mudflat hosts such as Neotrypaea californiensis,  style="font-style: italic;">Upogebia pugettensis, and the fat inkeeper worm Urechis caupo.  Johnson and Snook say that the females of this species live in mussels and other bivalves.

Biology/Natural History:  Feeds on detritus.  Also filter feeds with its maxillipeds.  More than one crab may be commensal in the same burrow.  The bryozoan Triticella elongata sometimes grows on the crab.  In central CA, mature females are most abundant February to April but may be found from January to August.



Dichotomous Keys:
  Carlton, 2007
  Coffin, 1952
  Flora and Fairbanks, 1966
  Kozloff 1987, 1996
  Wicksten, 2009

General References:
   Hart, 1982
  Jensen, 1995
  Johnson and Snook, 1955
  Lamb and Hanby, 2005
  McConnaughey and McConnaughey, 1985
  Niesen, 1994
  Niesen, 1997
  Ricketts et al., 1985

Scientific Articles:

Web sites:

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

Eye and Claw

This closeup of the face and claw of the male shows the red cornea of the eye and the thick propodus and curved dactyl of the cheliped.

Authors and Editors of Page:
Dave Cowles (2009):  Created original page
CSS coding for page developed by Jonathan Cowles (2007)