This porcelain crab has
of unequal size and with tubercles
and few to many setae
on the cheliped surface. Its telson
has 5 plates (picture) and the
anterior margin (Carlton:
inner margin) of the carpus
of the cheliped
is a broad, nearly triangular lobe (picture).
width to 19 mm. Color dull brown, often mottled with gray.
Pachycheles rudis Stimpson,
Common name(s): Lumpy
crab, Thick-clawed porcelain
|Pachycheles rudis male, found
minus tide under rock with
female, Sares Head. Carapace width 1.4 cm.
|(Photo by: Dave
June 26, 2005)
How to Distinguish
Similar Species: Petrolisthes
species have flat, smooth chelae.
pubescens has 7 plates on the telson,
a thick covering of setae
on the chelae, and the carpus
of the cheliped
has 3-4 uneven, serrated teeth on the anterior (Carlton: inner) margin.
Alaska to Bajia
Magdalena, Baja California
Depth Range: Low
intertidal to 29 m; mostly
intertidal in Puget Sound
rocky areas, especially on semiprotected
coasts. May be in abandoned holes of boring clams, kelp
empty barnacle shells, eelgrass roots, mussel clumps, pilings.
Are often found
in male-female pairs in holes, which they may grow too large to escape
from. The larger claw may be either the right or the
Males and females are of similar size.
chamber of this crab is sometimes parasitized by the bopyrid
isopod Aporobopyrus muguensis. This
reduces fecundity by about
Porcellanid crabs are filter feeders.
and Fairbanks, 1966
and Carlton, 1975
and Brusca, 1978
and Snook, 1955
et al., 1980
Floy E., 1972. The larval development of northern
Porcellanidae (Decapoda: Anomura) I. Pachycheles
Holmes in comparison to Pachycheles rudis
Bulletin 142: 57-70
Rodriguez, Irene Teresa, Gonzalo Hernández, Isabel
Juan A. Bolaños, and Darryl L. Felder, 2004. Larval
of Pachycheles serratus (Decapoda: Anomura:
laboratory conditions, with notes on the larvae of the genus.
of Crustacean Biology 24(2): 291-308
Van Wyk, P.M., 1982. Inhibition of the growth
of the porcellanid crab Pachycheles rudis by the
muguensis. Parasitology 85: 459-473
General Notes and
Observations: Locations, abundances,
I found a pair on Sares Head June 23, 2005, in a hole at
width was 1.4 cm. The female was carrying eggs. I
find this species on Sares Head.
Male Pachycheles rudis, showing the broad,
anterior margin of the carpus
of the cheliped. Carlton says it is the inner margin of the carpus
which has the triangular lobe.
A female showing the triangular lobed margin of the carpus
of the cheliped.
The telson of this species has 5 plates.
This female is carrying eggs. Note also that this
is largest, while the left one of the male above is largest.
by Dave Cowles June 25, 2005.
|This gravid female was found
low intertidal rock
at Sares Head in June, 2010. Carapace
width 1.4 cm. Notice that she has far more setae
on her chelipeds
and legs than the two individuals above have. She is carrying
light orange eggs but they do not protrude out from the edges of her
In this female the right chela
is largest. Note the long antennae characteristic of
|This closeup photo of the back portion of her
shows the small 5th leg folded up over her back, which is
of many Anomurans. The much larger left 4th leg is extending
||This closeup of her underside shows the
which along with the telson
form a tailfan at the end of her abdomen, plus the long, fine setae
which help hold her eggs in place. The abdomen is folded
thorax and the bases of the thoracic walking legs (pereopods)
can be seen to the sides and the maxillipeds
at the top.
Authors and Editors of Page:
Dave Cowles (2005): Created original