King crabs are
decapodcrustaceans in the
familyLithodidae that are chiefly found in cold seas.[2] Because of their large size and the taste of their meat, many
species are widely caught and sold as food with the most common being the
red king crab (Paralithodes camtschaticus).
King crabs are not true
crabs, and are generally thought to be derived from
hermit crabancestors within the
Paguridae, which may explain the
asymmetry still found in the adult forms.[3] This ancestry is supported by several anatomical peculiarities which are present only in king crabs and hermit crabs.[4] Although some doubt still exists about this hypothesis, king crabs are the most widely quoted example of
carcinisation among the
Decapoda.[4] The evidence for this explanation comes from the asymmetry of the king crab's
abdomen, which is thought to reflect the asymmetry of hermit crabs, which must fit into a spiral shell.
Taxonomic controversy
In 2007, the king crabs were moved from their classification among the hermit crabs in the
superfamilyPaguroidea into a separate superfamily, Lithodoidea.[1] This was not without controversy, as there is widespread consensus in the scientific community that king crabs are derived from hermit crabs and closely related to
pagurid hermit crabs; therefore, a separate superfamily in the classification poorly reflected the
phylogenetic relationship of this taxon.[4][5] In 2023, king crabs were folded back into Paguroidea, with Lithodoidea being considered superseded.[2]
Species
As of April 2024[update], 137 species of king crab (one extinct) are known in 15
genera.[6][2][7] These are split across its two subfamilies – Hapalogastrinae and Lithodinae – and include:
Glyptolithodes is found chiefly in the
Southern Hemisphere, but extending as far north as
California, although all its closest relatives live in the
Northern Hemisphere. Its single species, G. cristatipes, was originally placed in the genus Rhinolithodes.
Paralithodes
Red (P. camtschaticus) and blue (P. platypus) king crabs are some of the most important fisheries in Alaska. However, populations have fluctuated in the past 25 years, and some areas are currently closed due to overfishing. The two species are similar in size, shape and life history.[9][10][11] Habitat is the main factor separating the range of blue and red king crabs in the
Bering Sea.[12] Red king crabs prefer shallow, muddy or sandy habitats in Bristol Bay and Norton Sound,[12][13] while blue king crabs prefer the deeper areas made up of cobble, gravel and rock that occur around the
Pribilof,
St. Matthew,[14][15]St. Lawrence, and
Diomede Islands.
Red king crabs have an 11-month brood cycle in their first reproductive year and a 12-month cycle thereafter.[11] Both red and blue king crabs have planktotrophic larvae that undergo 4 zoeal stages in the water column and a non-feeding intermediate
glaucothoe stage which seeks appropriate habitat on the sea floor.
The red king crab, Paralithodes camtschaticus, is a very large species, sometimes reaching a carapace width of 11 in (28 cm) and a leg span of 6 ft (1.8 m). Its natural range is the Bering Sea around the
Kamchatka Peninsula area, between the
Aleutian Islands and
St. Lawrence Island. It can also be found in the
Barents Sea and the European
Arctic, where it was intentionally introduced and has now become a pest.[16][17] By 2022 they had spread to the
North Sea, becoming both a lucrative new stock to British fisheries, and an
invasive species.[18]
The blue king crab, Paralithodes platypus, lives near
St. Matthew Island, the
Pribilof Islands, and the
Diomede Islands, Alaska, and there are populations along the coasts of Japan and Russia.[15] Blue king crabs from the Pribilof Islands are the largest of all the king crabs, sometimes exceeding 18
lb (8
kg) in weight.[19]
Symbiosis
Juveniles of species of king crabs, including Neolithodes diomedeae, use a species (Scotoplanes Sp. A) of
sea cucumber (often known as “sea pigs”) as
hosts and can be found on top of and under Scotoplanes. The Scotoplanes reduce the risk of predation for the N. diomedeae, while the Scotoplanes are not harmed from being hosts, which supports the consensus that the two organisms have a
commensal relationship.[20]
Parasites
Some species of king crab, including those of the genera Lithodes, Neolithodes, Paralithodes, and likely Echidnocerus, act as
hosts to some
parasitic species of
careproctus fish.[21] The careproctus lays eggs in the gill chamber of the king crab which serves as a well-protected and aerated area for the eggs to reside until they hatch. On occasion king crabs have been found to be host to the eggs of multiple species of careproctus simultaneously.[citation needed]
^
abcKeiler, Jonas; Richter, Stefan; Wirkner, Christian S. (2013-03-19). "Evolutionary morphology of the hemolymph vascular system in hermit and king crabs (Crustacea: Decapoda: Anomala)". Journal of Morphology. 274 (7): 759–778.
doi:
10.1002/jmor.20133.
PMID23508935.
S2CID24458262.
^Klitin, A.K.; Nizyaev, S.A. (1999). "The distribution and life strategies of some commercially important Far Eastern lithodid crabs in the Kuril Islands". Biologiya Morya. 25 (3). Vladivostok: 221–228.
ISSN1063-0740.
^Soong, Joyce; Kohler, Tom (October 2005).
Norton Sound winter Red King Crab studies(PDF) (Report). Fisheries Data Series. Alaska Department of Fish and Game. No. 05-48.
Archived(PDF) from the original on 2017-01-26.
^
abVining, Ivan; Blau, S. Forrest; Pengilly, Doug (October 27–30, 1999). "Evaluating changes in spatial distribution of Blue King Crab near St. Matthew Island". In Kruse, Gordon H.; Bez, Nicolas; Booth, Anthony; Dorn, Martin W.; Hills, Sue; Lipcius, Romuald N.; et al. (eds.). Spatial Processes and Management of Marine Populations. Symposium on Spatial Processes and Management of Marine Populations. University of Alaska Sea Grant College Program (published 2001). pp. 327–348.
ISBN978-1-56612-068-5. Report No. AK-SG-01-02.
Archived(PDF) from the original on 2019-01-10.
^Barry, James P.; Taylor, Josi R.; Kuhnz, Linda A.; DeVogelaere, Andrew P. (2016-10-15). "Symbiosis between the holothurian Scotoplanes sp. A and the lithodid crab Neolithodes diomedeae on a featureless bathyal sediment plain". Marine Ecology. 38 (2): e12396.
doi:
10.1111/maec.12396.
eISSN1439-0485.