Lophopanopeus bellus subspecies bellus (Stimpson, 1860) 

Common name(s): Black-clawed crab, Black-clawed pebble crab, Northern black-clawed crab
Synonyms:  Xantheo bella, Lophoxanthus bellus
Phylum Arthropoda
 Subphylum Crustacea
  Class Malacostraca
   Subclass Eumalacostraca
    Superorder Eucarida
     Order Decapoda
      Suborder Pleocyemata
       Infraorder Brachyura
        Section Brachyrhyncha
         Family Xanthidae
Lophopanopeus bellus bellus from Swirl Rocks.  Carapace width approximately 3 cm.
(Photo by: Dave Cowles, July 2000)
Description:  The two subspecies of Lophopanopeus bellus are the only two crabs from Family Xanthidae in our region.  Xanthid crabs are true crabs which have no rostrum, have approximately trapezoidal to oval carapaces (wider in front) which are toothed at the anterolateral margins and have a notch between the wide-set eyes; the male also has only 4 segments to the abdomen plus the telson.  This species is commonly found in the intertidal, mainly under rocks.  Carapace color variable, from creamy white to brown to gray to reddish or purple.  The ends of its chelipeds are black (see picture), though the very tips may be white and the black is only on the "fingers" of the claw, not on the broad "hand" of the propodus.

How to Distinguish from Similar Species: Lophopanopeus bellus subspecies diegensis is subtidal in our area and has prominent tubercles on the carpus of the chelopeds, whereas subspecies bellus has a smooth carpus.  The cancrid crab Cancer oregonensis is of similar size and carapace shape, hides under rocks, and has black claw tips but the Cancer crabs have a more truly oval carapace and have 5 teeth between the eyes.

Geographical Range: Aleutian Islands, Alaska to San Luis Obispo County, CA; rare in southern part of the range.

Depth Range: Intertidal to 80 m

Habitat: Under rocks, especially on gravel, both in protected waters and on the open coast; and on kelp holdfasts.

Biology/Natural History: This species is onmivorous, and feeds on algae, small mollusks, and barnacles.  Sometimes captured individuals extend and lock their claws when handled.  Eggs are carried beginning in March and hatch from May to August in British Columbia.  Many females produce 2 broods per year, with 6,000 to 36,000 eggs per brood.  May be parisitized by a Rhizocephalan Sacculinid barnacle (At Sitka, Alaska perhaps 25% of the crabs are parasitized).  I have not found this high a percent parasitism in the Puget Sound area.  Fossils of this species have been found in Pleistocene deposits in Playa del Rey, southern California.  This species has 124 chromosomes (62 pairs).


 
Return to:
Main Page Alphabetic Index Systematic Index Glossary

References:

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

General References:
Brown and Rovetta, 1996
Harbo, 1999
Hinton, 1987
Jensen, 1995
Kozloff, 1993
McConnaughey and McConnaughey, 1986
Morris et al., 1980
Niesen, 1994
Niesen, 1997
O'Clair and O'Clair, 1998
Ricketts et al., 1985
Sept, 1999

Scientific Articles:
 


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


View of the egg mass of a berried female.  The numerous eggs of this species are so small and so dirty-looking that they can be mistaken for the Rhizocephalan Sacculinid barnacle identified as Loxothylacus panopaei, which when sexually mature erupts from the abdomen.  Observe carefully to see whether the crab is actually parasitized or simply carrying a dirty-looking egg mass.  Photo by Dave Cowles
Note:  More recent references seem to indicate that Loxothylacus panopaei is not found in the Pacific, so the parasitized crabs in California and Alaska must be parasitized by a different barnacle.

The carapace of this crab can be purple, as in this individual photographed at Orcas Island by Alexandra Tyler in July 2021:
Purple color

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