Description: The most distinctive
feature of large lithodid crab is the fact that when it pulls its legs
under itself and folds its claws across its front, as it often does, a
large notch on the carpus
of its chelipeds
combined with a smaller notch on the carpus
of leg 2 lie beside each other, creating a prominent tubelike opening presumably
used for breathing. Other features include the fact that its abdomen
is completely calcified and its legs are not markedly longer than the carapace.
with sharp spines and has no pronounced depression on the posterodorsal
surface. It is rounded posterolaterally and does not resemble an
equilateral triangle, and it has no lateral extensions which cover its
legs when viewed from above. The sides of the walking legs are smooth
and fit together tightly when folded, while the dorsal surfaces have tubercles
and spines (photo). The merus
of the chelipeds
has lateral extensions on its inner dorsal margin, and the carpus
curve upward and cover the mouth when they are folded against the body.
The largest cheliped
(usually the right) has large, blunt white teeth on the cutting surface,
while the small chela
has small sharp teeth. The rostrum
is a sharp upturned spine with more spines near the base (photo),
somewhat like that of Rhinolithodes
wosnessenskii. Color is red-brown or tan with purplish
and white areas. The chelae
are tan and mottled red, with white on the dorsal side and orange or red
fingers and white tips. Carapace
width to 18.5 cm or larger. Maximum size in males is larger than
that for females.
Lopholithodes foraminatus (Stimpson,
Common name(s): Box crab, Brown box crab, Puget Sound box crab, Oregon
caught by Joe Watson of Campbell River BC at 110-130 m depth in a crab
trap near Twin Island in the Strait of Georgia, Canada. This is a
large male. The distinctive foramen
created by the legs can be seen to the left, between the base of the chela
and the next leg, lined with smooth purple and white cuticle.
|(Photo by: Will Duguid,
University of Victoria)
How to Distinguish from Similar Species:
The tubelike passage (foramen) through the folded legs provides certain
mandtii looks similar but it is more brightly colored and has
blunt bumps (tubercles)
rather than bumps with spines on its carapace. Rhinolithodes
wosnessenskii and Phyllolithodes
papillosus have a deep posterodorsal depression in their carapace. Oedignathus
inermis has a soft abdomen.
Geographical Range: Kodiak, Alaska
to San Diego, CA
Depth Range: Low intertidal to 547
m. Usually deep. In the Oregon offshore fishery they are mostly
caught at 128-165 m depth.
Habitat: Soft bottoms deeper than
18 m, or on rocky faces overlooking soft bottoms.
Biology/Natural History: This species
is said to feed by scooping up sediment with its claws, and also to feed
on the clams it digs up. Will Duguid reports that in the laboratory
adults of this species are strongly attracted to and feed on brittle stars.
They may also feed on urchins such as Strongylocentrotus
droebachiensis. It is thought that octopus may be
its main predator. It may bury itself in the sediment, except that
the front with the foramen is exposed for breathing. The abdomen
has knobby plates and Flora
and Fairbanks say it is also partly soft and not held very tightly
against the thorax
(this seems to conflict with other accounts). An intermittent open
coast fishery for this species exists off Oregon.
This species is said to occur in large aggregations of mixed males
and females on soft bottoms. Molting within an aggregation seems
to be synchronous, but not synchronized with that of other aggregations.
Eggs and larvae of snailfish, especially Careproctus
melanurus, the blacktail snailfish, are often found among the gill
filaments of these crabs. These may occur in large numbers and even
may contribute to collapse of the gills, but usually they do not seem to
cause any harm.
Off British Columbia this species has a biennial (two-year) cycle for
brooding. Females molt and breed during mid-summer, then brooded
their eggs and larvae for 18 months before releasing them as zoeae
the second winter or early spring (Feb-April) after breeding. Much
of this long brooding period was due to the fact that the brooded eggs
underwent a 12-month diapause in the gastrula stage. The females
released the larvae gradually, averaging a period of 69 days. Brooding
females have a mean carapace
length of 8.9 cm (width 10.7 cm) and a minimum carapace
length of 7.5 cm (width 8.8 cm). Females which have been brooding
for a number of months and post-breeding females often have extensive overgrowth
of polychaete tubeworms, hydrozoans, and small bivalves. The distal
legs and much of the underside has a black stain not seen on males or pre-incubation
females (Duguid and Page, 2011).
and Fairbanks 1966
Gotshall and Laurent, 1979
and Snook, 1955
Duguid, William D.P. and Louise R. Page, 2011.
Biennial reproduction with embryonic diapause in Lopholithodes foraminatus
(Anomura: Lithodidae) from British Columbia waters. Invertebrate
Biology 131:1 pp. 68-82.
Kato, S., 1992. Box Crab. p. 192 in
W.S. Leet, C.M. Dewees, and C.W. Haugen (eds). California's living
marine resources and their utilization. Sea Grant Extension, University
of California, Davis, CA
Parrish, R.H., 1972. Symbiosis in the blacktail
snailfish, Careproctus melanurus, and the box crab, Lopholithodes foraminatus.
California Fish and Game 58(8): 239-240
Peden, A.E. and C.A. Corbett, 1972. Commensalism
between a liparid fish, Careproctus sp. and the lithodid box crab, Lopholithodes
foraminatus. Canadian Journal of Zoology 51: 555-556
General Notes and Observations: Locations,
abundances, unusual behaviors:
This species is said to have previously been often found in the Puget
Sound/Straits of Juan de Fuca region by SCUBA divers at depths below 15-18
m but it is now rarely seen. I have not seen one near the Rosario
Beach Marine Laboratory but the station museum has a large specimen captured
years ago. This species is apparently more common below SCUBA depths so
it may by near our station but found deeper than we dive.
This photo of an adult is by Will Duguid
In this closeup of the face the small spinelike rostrum
can be seen. Other features include the spine-tipped tubercles
on the dorsal carapace
and on the dorsal surfaces of the legs and chelae.
Note that in Anomuran crabs the second antennae are based lateral to
the eyes, as can be seen here.
Photo by Will Duguid.
of adult males and females differ in several ways.
This is the abdomen
of a female, which is shown above, is broader than that of a male and is
The plates on the left side of the female abdomen
(to the right above) are larger than those on the left.
The right side of the female abdomen
also has a row of small marginal plates but the left side does not.
The female also has pleopods
on her abdomen,
which cannot be seen without pulling the abdomen away from the thorax.
of a male is not as broad and is more triangular. It has a small
row of marginal plates on both sides.
The adult male has no pleopods.
Photo by Will Duguid
This photo helps illustrate why these crabs are called box crabs.
When disturbed they fold their legs and abdomen
and hold them tightly against the body so that they are like a tight
box or ball. The crabs on the left side of the seat are
upright while those to the right are upside-down.
Photo by Will Duguid
This front view of a dried specimen shows the distinct openings for
respiratory excurrent flow formed by the front legs when they are folded
in front of the face. This, no doubt, is the reason for the 'foraminatus'
in the species name. Photo by Dave Cowles, August 2016
This live individual was photographed in the Seaside,
OR aquarium. Photo by Dave Cowles, August 2017
||This is the glaucothoe stage. By this stage the young crab has
a well-developed abdomen with pleopods.
It can swim with the pleopods.
|This crab is an instar III juvenile (3 molts past the glaucothoe stage).
At this stage it no longer has the pleopods
it had as a glaucothoe, and it walks rather than swims.
||This young crab is an instar VI juvenile (six molts past the glaucothoe
|Lithodid crabs such as Lopholithodes
foraminatus pass through the nauplius
stage before hatching from the egg. A nauplius
has only 3 appendages, which will become the first and second antennae
and the mandibles
(jaws) in the adult, but during the nauplius
stage they are paddle-like. The crab hatches from the egg as the
first of four zoea
larva stages (instars). Zoea
larvae swim through the plankton but they do it using some extra thoracic
appendages which they grew during the molt, called maxillipeds.
After the zoea
stages comes one glaucothoe stage, called a postlarva. The glaucothoe
swims using pleopod
appendages which have appeared on its abdomen during its molt. This
is similar to the way a shrimp swims. The glaucothoe molts through
several juvenile stages which resemble an adult (they walk rather than
swim) but are much smaller. Interestingly, in the molt from glaucothoe
to juvenile the young crab loses its pleopod
appendages. After several juvenile stages the crab becomes a sexually
mature adult. In adults of this species the males have no pleopods
but the females re-form pleopods
which are used to carry the eggs. These photos are of lab-raised
individuals by Will Duguid.
Authors and Editors of Page:
Dave Cowles (2008): Created original page
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