As a Lithodid crab,
this species has no uropods
and the abdomen is folded against the underside of the thorax.
Its 5th walking legs are reduced. Oedignathus
inermis has a thick, soft abdomen which is not tightly
the thorax (photo).
The first (basal) segment
of the abdomen has calcified plates, as do the two terminal
inermis has chelipeds
very unequal in size (the right cheliped
is largest) and the dactyl
is shorter than the "palm" of the propodus.
is sharp but has no spines (photo).
are rounded (not heavily flattened). The chelipeds
have large granular tubercles
but no spines on the upper surface. The large cheliped
has violet to gray or blue tubercles
and a smooth tan to white tip to the claw with a spoonlike hollow where
contact one another. The shall cheliped
has small, sharp granules and setae.
The walking legs have sharp granules, setae,
and dark brown and white spots (photo).
margins of legs 2-4 have some setae,
and small spines but no large spines. Note, however, that there are
spines on the anterior margins of leg 1 (the chelipeds).
to 3 cm long and 2.5 cm wide in males, 2 cm wide in females; wider
than anteriorly, brown with scales on the dorsal surface. It
white-centered orange granules and dark brown spots, but these colors
be masked by mud. May have white on the sternum.
few if any setae
on the body.
Common name(s): Paxillose crab, Granular claw crab,
inermis, Hapalogaster brandti, Oedignathus gilli
inermis from Sares
Head. Found intertidally in a sea cave
|(Photo by: Dave Cowles,
How to Distinguish from
Of the Lithodid crabs with soft abdomens, Placetron
wosnessenskii has a much thinner abdomen and has
scales on the
and legs. Acantholithodes
has large spines on the rostrum. Hapalogaster
mertensii and H.
have strongly flattened cephalothorax
and legs and have spines on the upper surface of their chelipeds.
AK to Monterey, CA; eastern Russia, Japan, Korea. Mostly on
coast. Rarely seen in the San Juan islands and is said to not
occur in Puget Sound; rare in California.
to 15 m
Under encrusting coralline
algae, under Mytilus
californianus mussels or Anthopleura
xanthogrammica anemones, in crevices, and in
crabs are often found in pairs, and may be in such a tightly secluded
that they appear to be trapped. They feed by straining
the water with their third maxillipeds.
Captive individuals also catch worms and small crustaceans with their
claw and crush mussels with the large claw. Predators include
and Carlton, 1975
and Snook, 1955
et al., 1980
and O'Clair, 1998
General Notes and
abundances, unusual behaviors:
The abdomen of this species is thick and soft. The basal
and the two distal segments have some calcified plates, which are not
in this view.
One claw is much larger than the other. The "palm" of the chela
on the large claw is longer than the dactyl.
The upper surface of the chelipeds
is covered with prominent, granular tubercles
but with no obvious spines.
is short. The carapace
has orange-red tubercles
with a white spot in the middle.
The walking legs have setae and granules but no spines.
Authors and Editors of Page:
Dave Cowles (2007): Created original page
CSS coding for page developed by Jonathan Cowles (2007)