Discorsopagurus schmitti (Stevens,
1925)
Common name(s): Tubeworm
hermit
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Synonyms:
Pylopagurus schmitti,
Orthopagurus schmitti |
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Phylum Arthropoda
Subphylum Crustacea
Class Malacostraca
Subclass Eumalacostraca
Superorder Eucarida
Order Decapoda
Suborder Pleocyemata
Infraorder
Anomura
Superfamily Paguroidea
Family
Paguridae |
Discorsopagurus schmitti from 15 m
depth, Coffin Rocks.
Animal is in a tubeworm tube that is heavily overgrown with a white
colonial
tunicate. Leg span in photo approximately 1 cm. |
(Photo by: Dave Cowles,
August 2005) |
Description:
This small hermit crab has
an abdomen that is not coiled (photo) and symmetrical uropods
(photo).
The palm (propodus)
of the right chela
is little if any wider where the dactyl
and palm join than it is at the proximal end. The right chela
is
only slightly larger than the left (photo).
The legs have reddish-brown bands. The right and left halves
of the
telson are not separated by a groove (photo).
Carapace length up to 6 mm.
How to Distinguish from
Similar Species:
The palm of the right chela of Orthopagurus minimus
is wider at
the origin of the dactyl than it is at the base, and it is usually
found
in the shells of scaphopods (tusk shells). Its right claw is
much
larger than the left and it holds it straight out in front of itself
while
walking.
Geographical Range:
Sitka Sound, AK
to Puget Sound; Japan
Depth Range:
Mostly subtidal; low
intertidal to 220 m
Habitat:
In tubes of serpulid or sabellarid
tubeworms (usually Sabellaria cementarium or Serpula
vermicularis), rarely in snail shells.
Inland waters and
open coast.
Biology/Natural History:
Females usually
live in attached tubes, and males in broken-off tubes. Can
filter
feed using both the third maxillipeds and the antennae, plus catches
small
pieces of drift material.
References:
Dichotomous Keys:
Coffin,
1952 (as Orthopagurus schmitti)
Hart,
1982
Kozloff
1987, 1996
Wicksten
2009
General References:
Jensen,
1995
Kozloff,
1993
Scientific Articles:
Web sites:
General Notes and
Observations: Locations, abundances,
unusual behaviors:
This view shows the entire tube and tunicate the hermit crab is
carrying.
The total mass is so large that the hermit crab can barely crawl
along.
Photo by Dave Cowles, August 2005
Animal out of the tube. Note the straight abdomen, the many
setae
on the body, and the star-shaped pleopods. Note also the two
small
rear walking legs.
Total length about 2 to 2.5 cm.
In this ventral view of the thorax one can see the relative sizes of
the right and left chelae, the three long first walking legs and the
two
short rear walking legs, and the abundant setae.
In this ventral view of the abdomen one can see the star-shaped
pleopods
on the left side, the symmetrical uropods, and the telson which does
not
have a median groove.
I am guessing that this is a female, and that the star-shaped
pleopods
are for holding eggs. Although the animal was in a
technically movable
tube, it was so heavily overgrown that the animal could barely crawl.
Another individual, collected at about 130 m depth from the channel
between Lopez and San Juan Islands, is living in a tubeworm tube which
is encrusted with stones and tiny barnacles. Photo by Dave
Cowles,
July 2012
A closeup of the same individual.
Authors and Editors of Page:
Dave Cowles (2005): Created original page
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