Description: The carapace of Pagurus
hirsutiusculus has setae
but no spines, and only the shield
is calcified (photo). The shield
is about as wide or wider than it is long. The carpus
of the right cheliped
is wider than it is long and is not strongly flattened (photo).
of legs 2 and 3 is not twisted. It does not have longitudinal blue
or white stripes, but does have some red stripes (photo).
The dorsal surface of the left chela
does not have a prominent ridge or crest, nor a concavity near the midline.
The ventral surface of the merus of the right cheliped
has one prominent tubercle,
but it is often obscured by the abundant setae
(photo). The chelae
do not have stout spines but have closely spaced tubercles,
granules, and setae
(photo). The ventral side of the
of the right cheliped
is not greatly swollen. The long second antennae are mainly green,
with yellow or white bands or spots (photo).
The legs are greenish brown with many setae
(photo), and legs 2 and 3 have white
or bluish bands at the articulation of the propodus
(photo), and usually a blue dot at the upper end
of the propodus
(may also have a blue dot on the dactyl)
(photo). Overall color olive green,
brown, or black Carapace
length to 19 mm.
Pagurus hirsutiusculus (Dana, 1851)
Common name(s): Hairy hermit crab
Pagurus (Eupagurus) mertensi,
Bernhardus hirsutiusculus, Eupagurus hirsutiusculus, Pagurus (Trigonocheirus)
hirsutiusculus, Eupagurus mertensi
|Pagurus hirsutiusculus from the Rosario area
|(Photo by: Dave Cowles, August 2005)
How to Distinguish from Similar Species: Pagurus
hemphilli is mostly similar but has orange-red antennae. Of the
very common intertidal species, P.
granosimanus has olive-green legs with small blue dots. P.
samuelis has a bright blue dactyl
on legs 2 and 3 instead of just a blue band, plus it occurs mainly on the
open coast. P. caurinus
is often mistaken for a small P. hirsutiusculus, but P.
caurinus has spines on its chelae
and its 2nd antennae are reddish brown without spots.
Geographical Range: Pribilof Islands, Alaska
to Monterey, CA; Siberia, Japan; smaller and less hairy south of Puget
Sound, and even more so south of Monterey Bay. Common in San Francisco
Depth Range: Intertidal to 110 m
Habitat: Intertidal tide pools and under
rocks and algae, more abundant in protected water.
This species is
less resistant to emersion than is P.
granosimanus, but it is more tolerant of brackish water.
Many occupy small, light shells which they cannot completely retract into.
They will also abandon their shell more readily than do some other species,
such as P. granosimanus
(photo), sometimes even when they are berried
(carrying eggs (photo). They seem to
have definite shell preferences, but these may be different in different
places. Favorites include Nucella
spp, and Olivella
biplicata shells. Diet is mainly detritus, though they will
eat live prey opportunistically. It is known to feed on hatchlings
emarginata, which lay and attach their eggs in the low intertidal.
Predators include sculpins. Females become ovigerous in late fall
and carry a total of about 5 broods through spring and summer. Parasites
include the parasitic barnacles Peltogaster paguri and Peltogastrella
gracilis and the bopyrid isopod Pseudione giardi.
and Fairbanks, 1966
and Carlton, 1975
and Brusca, 1978
and Snook, 1955
et al., 1980
and O'Clair, 1998
et al., 1985
General Notes and Observations: Locations, abundances,
Although Pagurus hirsutiusculus is often the most common intertidal
hermit crab in this region, we find few of these on Sares Head. Perhaps
this is because P. hirsutiusculus is most common in the mid-intertidal
and Sares Head has few tide pools except in the very low intertidal.
There are plenty of rocks they could hide beneath, though. They are
much more common on the protected side of Fidalgo Island, around rocks
in Padilla Bay.
Another individual from Sares Head.
of P. hirsutiusculus has setae
but no spines. The front part (shield),
which is the only part which is calcified, is about as wide as it is long.
In this photo the
of the carapace
is to the top right, behind the eyestalks.
In this view of the chelae,
legs, and second antennae, one can see the setae
which cover the chelae
and legs, the larger right chela
which is characteristic of Pagurus,
and the fact that the carpus
of the right chela
is slightly longer than wide and it is not flattened. The antennae
are green with white bands.
of legs 2 and 3 are not twisted, and there is a white (or blue) band at
the junction of the propodus
surface of the right merus
(center of photo) has one prominent
but it is largely obscured by the abundant setae.
This individual jumped out of its shell which was stuck. That
makes it easy to see the abundant body and leg setae.
Photo by Dave Cowles July 2008
This female readily crawled out of her shell even though she is "berried"
(carrying eggs under her abdomen).
Photo by Dave Cowles at Kalaloch Beach #4, July 2009
The eyes of Pagurus hirsutiusculus generally seem to have a
dark crescent-shaped band in them, as can be seen in this closeup dorsal
view of the head.
Photo by Dave Cowles July 2008
This individual has both white bands and blue spots on the legs.
Photo by Dave Cowles, July 2010
|Occasionally individuals are encountered with barnacles
growing on them. The individual on the left above is carrying a shell
but has a strong encrustation of barnacles on its carapace
and on several legs. The individual on the right was encountered
running around without a shell and has a very heavy growth of barnacles
on its carapace and several on its legs. The barnacles appear to
be so large that it would be difficult for either of these individuals
to find a shell large enough that they could withdraw into, though the
left individual can at least tuck its abdomen into its shell. Both
were found in tidepools at Beach #4, Kalaloch, WA. Photos by Dave
Cowles, July 2012.
This juvenile, which apparently hitched a ride on something else into
my classroom tank, is small and has few hairy setae
on the legs yet but already is developing the white bands on the distal
ends of the propodus
of the walking legs and the blue spot on the proximal end. It has
selected a Littorina
scutulata shell, 8 mm long, for its home. Photo by Dave
Cowles, August 2016.
Authors and Editors of Page:
Dave Cowles (2005): Created original page