Lopholithodes foraminatus


Lopholithodes foraminatus (Stimpson, 1862) Common name(s): Box crab, Brown box crab, Puget Sound box crab, Oregon queen crab
Synonyms:
Phylum Arthropoda Subphylum Crustacea Class Malacostraca Subclass Eumalacostraca Superorder Eucarida Order Decapoda Suborder Pleocyemata Infraorder Anomura Family Lithodidae
	Lopholithodes foraminatus 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)

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. The carapace has tubercles 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 and propodus 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.

How to Distinguish from Similar Species: The tubelike passage through the folded legs provides certain identification. Lopholithodes 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 feeds 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 intrmittent 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).

References:

Dichotomous Keys:
Coffin, 1952
Flora and Fairbanks 1966
Kozloff 1987, 1996
Wicksten, 2009

General References:

Gotshall and Laurent, 1979
Harbo, 1999
Hart, 1982
Jensen, 1995
Johnson and Snook, 1955

Scientific Articles:

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

Web sites:

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.

The abdomens 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 asymmetrical.
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.

The abdomen 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

Folded into a box
This photo helps illustrate why these crabs are called box crabs. When disturbed they fold their legs and abdomen together
and hold them tightly against the body so that they are like a tight box or ball. The crabs on the left of the seat are
upright while those to the left are upside-down.
Photo by Will Duguid

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 stage).

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.

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	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 stage).
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.

Lopholithodes foraminatus (Stimpson, 1862)

Common name(s): Box crab, Brown box crab, Puget Sound box crab, Oregon queen crab

References: