This grapsid crab is different
from all other grapsids because of the transverse
lines on its carapace
and the two teeth (rather than 3) on the anterolateral
margin of its carapace.
to 4.8 cm wide in males, 4.1 cm in females.
Common name(s): Lined shore
striped shore crab
Brachyura (true crabs)
|Pachygrapsus crassipes from
Beach, CA. Carapace
width about 3 cm.
|(Photo by: Dave
How to Distinguish
oregonensis have three teeth on the anterolateral
margin of the carapace,
plus do not have the transverse
lines on the carapace.
Isla de Santa Margarita, Baja California, + Gulf of California, Japan,
Korea (it may have been introduced to Asia)
Depth Range: High
and mid intertidal
under rocks, in tidepools
and mussel beds. Sometimes in clay burrows, especially in San
This crab can be
very abundant in its range. It is the most semi-terrestrial
shore crabs, living highest in the intertidal. Forages in and
of the water, active during the day. They spend at least half
time out of water but return periodically to pools to moisten their
They are osmoregulators, and can withstand hypo- and hyperosmotic
It feeds on films of algae and diatoms, which it scrapes off the rocks
with the tips of its chelae.
May also eat small green algae Ulva and Enteromorpha,
algae Fucus, and red Endocladia,
Grateloupia. Occasionally eats dead
animals or small intertidal
invertebrates, and has especially been noted eating limpets.
include gulls, raccoons, anemones, and fish. Ovigerous
females are found from March to September in central California; peak
is in June and July.
In central Japan this species can be parasitized by any
sacculinid barnacles, Sacculina confragosa, S.
or S. yatsui (Tsuchida et al., 2006).
and Carlton, 1975
and Rokop, 1985
et al., 1980
Paola C., Henry S. Carson, Geoffrey S. Cook, F. Joel Fodrie, Bonnie J.
Becker, Claudio DiBacco, and Lisa A. Levin, 2012.
connectivity? An empirical, multi-species approach.
and Comparative Biology 52:4 pp. 511-524
A. D., Dunbar, S.G., and Boskovic, D. 2010. Temporal
fatty acids in Pachygrapsus
from Southern California. Journal of Crustacean Biology. 30(2): 257 –
Kohei, Jorgen Lutzen, and Mutsumi Nishida, 2006.
infection by Sacculina parasites (Cirripedia:
of an intertidal grapsoid crab. J. Crustacean Biology 26:4
General Notes and
Observations: Locations, abundances,
Note: This grapsid crab likes to pinch, and
readily draw blood!
It is more likely to do so than are the Hemigrapsus
Another individual, at Little Corona del Mar, CA. Photo by
Cowles March 2005
The underside of this male shows the lack of spots on the chela,
the two anterolateral
teeth on the carapace
behind the eye, and the setae
on the legs.
Photo by Dave Cowles, Little Corona del Mar, March 2005
|In July 2007 we found the
on Cape Flattery. It is clearly recognizable as a female Pachygrapsus
crassipes though it is hundreds of miles north of its
Photos were taken by Tyler Shelton
|The two views above clearly
lines on the carapace
and the purplish red and greenish barred color characteristic of Pachygrapsus
|There are no purple spots on the propodus of the chelae
and there are abundant setae
on the legs. Both of these characteristics distinguish this
has only 2 anterolateral
teeth (characteristic of Pachygrapsus) instead of
the 3 characteristic
|Although this crab species is
seldom found north of central Oregon, in July 2020 I found this
individual at Cape Alava, WA. Photos by Dave Cowles
|This species seems to be
colonizing the Cape Alava region. In 2001 my students and I walked the
coast from Cape Alava south to Sand Point and encountered around half a dozen Pachygrapsus crassipes
individuals along the way, including this one. The crab was so feisty
that I couldn't even get a photo of it without holding it firmly in
place. We found the crabs all along the rocky beach to nearly as far south as Sand Point. Photo by Dave Cowles
Authors and Editors of
Dave Cowles (2005): Created original page