Pagurus hirsutiusculus (Dana, 1851)
Common name(s): Hairy hermit crab
|Synonyms: 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 Bay.
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
Many occupy small, light shells which they cannot completely retract
They will also abandon their shell more readily than do some other
such as P.
(photo), sometimes even
when they are berried
(carrying eggs (photo).
They seem to
have definite shell preferences, but these may be different in
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
emarginata, which lay and attach their eggs in the
Predators include sculpins. Females become ovigerous in late
and carry a total of about 5 broods through spring and
include the parasitic barnacles Peltogaster paguri
gracilis and the bopyrid isopod Pseudione giardi.
|Main Page||Alphabetic Index||Systematic Index||Glossary|
Brusca and Brusca, 1978
Johnson and Snook, 1955
Morris et al., 1980
O'Clair and O'Clair, 1998
Ricketts et al., 1985
Although Pagurus hirsutiusculus is often
the most common intertidal
hermit crab, we find few of these on Sares Head. Perhaps this
because P. hirsutiusculus is most common in the
Sares Head has few tide pools except in the very low
There are plenty of rocks they could hide beneath, though.
Another individual from Sares Head.
The carapace 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
shield 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 spots.
The dactyls of legs 2 and 3 are not twisted, and there is a white (or blue) band at the junction of the propodus and dactyl.
The ventral surface of the right merus (center of photo) has one prominent tubercle 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.|