King crab



King crabs are decapod crustaceans in the family Lithodidae that are chiefly found in cold seas. 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 crab ancestors within the Paguridae, which may explain the asymmetry still found in the adult forms. This ancestry is supported by several anatomical peculiarities which are present only in king crabs and hermit crabs. Although some doubt still exists about this hypothesis, king crabs are the most widely quoted example of carcinisation among the Decapoda. 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 superfamily Paguroidea into a separate superfamily, Lithodoidea. 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. In 2023, king crabs were folded back into Paguroidea, with Lithodoidea being considered superseded.

Species
, 137 species of king crab (one extinct) are known in 15 genera. These are split across its two subfamilies – Hapalogastrinae and Lithodinae – and include:

Hapalogastrinae

 * Acantholithodes
 * Acantholithodes hispidus
 * Dermaturus
 * Dermaturus mandtii
 * Hapalogaster
 * Hapalogaster cavicauda
 * Hapalogaster dentata
 * Hapalogaster grebnitzkii
 * Hapalogaster mertensii
 * Oedignathus
 * Oedignathus inermis
 * Placetron
 * Placetron wosnessenskii

Lithodinae

 * Cryptolithodes Brandt, 1848
 * Cryptolithodes expansus Miers, 1879
 * Cryptolithodes sitchensis Brandt, 1853 – umbrella crab
 * Cryptolithodes typicus Brandt, 1848 – butterfly crab
 * Echidnocerus Brandt, 1848
 * Echidnocerus cibarius White, 1842 – Puget Sound king crab
 * Echidnocerus foraminatus Stimpson, 1859 – brown box crab
 * Glyptolithodes Faxon, 1895
 * Glyptolithodes cristatipes (Faxon, 1893)
 * Lithodes Latreille, 1806
 * Lithodes aequispinus Benedict, 1895 – golden king crab or brown king crab
 * Lithodes ahyongi Takeda, 2018
 * Lithodes aotearoa Ahyong, 2010
 * Lithodes australiensis Ahyong, 2010
 * Lithodes ceramensis Takeda & Nagai, 2004
 * Lithodes chaddertoni Ahyong, 2010
 * Lithodes confundens Macpherson, 1988
 * Lithodes couesi Benedict, 1895 – scarlet king crab
 * Lithodes ferox Filhol, 1885
 * Lithodes formosae Ahyong & Chan, 2010
 * Lithodes galapagensis Hall & Thatje, 2009
 * Lithodes jessica Ahyong, 2010
 * Lithodes longispina Sakai, 1971
 * Lithodes macquariae Ahyong, 2010
 * Lithodes maja (Linnaeus, 1758) – Norway king crab or trollkrabbe
 * Lithodes mamillifer Macpherson, 1988d
 * Lithodes manningi Macpherson, 1988
 * Lithodes megacantha Macpherson, 1991
 * Lithodes murrayi Henderson, 1888
 * Lithodes nintokuae Sakai, 1976
 * Lithodes panamensis Faxon, 1893
 * Lithodes paulayi Macpherson & Chan, 2008
 * Lithodes rachelae Ahyong, 2010
 * Lithodes richeri Macpherson, 1990
 * Lithodes robertsoni Ahyong, 2010
 * Lithodes santolla (Molina, 1782) – Chilean centolla or Chilean king crab
 * Lithodes turkayi Macpherson, 1988
 * Lithodes turritus Ortmann, 1892
 * Lithodes unicornis Macpherson, 1984
 * Lithodes wiracocha Haig, 1974
 * Neolithodes A. Milne-Edwards & Bouvier, 1894
 * Neolithodes agassizii (Smith, 1882)
 * Neolithodes asperrimus Barnard, 1947
 * Neolithodes brodiei Dawson & Yaldwyn, 1970
 * Neolithodes bronwynae Ahyong, 2010
 * Neolithodes capensis Stebbing, 1905
 * Neolithodes diomedeae (Benedict, 1895)
 * Neolithodes duhameli Macpherson, 2004
 * Neolithodes flindersi Ahyong, 2010
 * Neolithodes grimaldii (A. Milne-Edwards & Bouvier, 1894)
 * Neolithodes indicus Padate, Cubelio & Takeda, 2020
 * Neolithodes nipponensis Sakai, 1971
 * Neolithodes vinogradovi Macpherson, 1988
 * Neolithodes yaldwyni Ahyong & Dawson, 2006
 * Paralithodes Brandt, 1848
 * Paralithodes brevipes (H. Milne-Edwards & Lucas, 1841)
 * Paralithodes californiensis (Benedict, 1895) – California king crab
 * Paralithodes camtschaticus (Tilesius, 1815) – red king crab
 * Paralithodes platypus (Brandt, 1850) – blue king crab
 * Paralithodes rathbuni (Benedict, 1895)
 * Paralomis White, 1856
 * Paralomis aculeata Henderson, 1888
 * Paralomis africana Macpherson, 1982
 * Paralomis alcockiana Hall & Thatje, 2009
 * Paralomis alis Ahyong, 2020
 * Paralomis anamerae Macpherson, 1988
 * Paralomis arae Macpherson, 2001
 * Paralomis arethusa Macpherson, 1994
 * Paralomis aspera Faxon, 1893
 * Paralomis birsteini Macpherson, 1988
 * Paralomis bouvieri Hansen, 1908
 * Paralomis ceres Macpherson, 1989
 * Paralomis chilensis Andrade, 1980
 * Paralomis cristata Takeda & Ohta, 1979
 * Paralomis cristulata Macpherson, 1988
 * Paralomis cubensis Chace, 1939
 * Paralomis danida Takeda & Bussarawit, 2007
 * Paralomis dawsoni Macpherson, 2001
 * Paralomis debodeorum Feldmann, 1998 †
 * Paralomis diomedeae (Faxon, 1893)
 * Paralomis dofleini Balss, 1911
 * Paralomis echidna Ahyong, 2010
 * Paralomis elongata Spiridonov, Türkay, Arntz & Thatje, 2006
 * Paralomis erinacea Macpherson, 1988
 * Paralomis formosa Henderson, 1888
 * Paralomis gowlettholmes Ahyong, 2010
 * Paralomis granulosa (Hombron & Jacquinot, 1846)
 * Paralomis grossmani Macpherson, 1988
 * Paralomis haigae Eldredge, 1976
 * Paralomis hirtella de Saint Laurent & Macpherson, 1997
 * Paralomis histrix (De Haan, 1849)
 * Paralomis hystrixoides Sakai, 1980
 * Paralomis inca Haig, 1974
 * Paralomis indica Alcock & Anderson, 1899
 * Paralomis investigatoris Alcock & Anderson, 1899
 * Paralomis jamsteci Takeda & Hashimoto, 1990
 * Paralomis japonicus Balss, 1911
 * Paralomis kyushupalauensis Takeda, 1985
 * Paralomis longidactylus Birstein & Vinogradov, 1972
 * Paralomis longipes Faxon, 1893
 * Paralomis macphersoni Muñoz & García-Isarch, 2013
 * Paralomis makarovi Hall & Thatje, 2009
 * Paralomis manningi Williams, Smith & Baco, 2000
 * Paralomis medipacifica Takeda, 1974
 * Paralomis mendagnai Macpherson, 2003
 * Paralomis microps Filhol, 1884
 * Paralomis multispina (Benedict, 1895)
 * Paralomis nivosa Hall & Thatje, 2009
 * Paralomis ochthodes Macpherson, 1988
 * Paralomis odawarai (Sakai, 1980)
 * Paralomis okitoriensis Takeda, 2019
 * Paralomis otsuae Wilson, 1990
 * Paralomis pacifica Sakai, 1978
 * Paralomis papillata (Benedict, 1895)
 * Paralomis papua Ahyong, 2020
 * Paralomis pectinata Macpherson, 1988
 * Paralomis phrixa Macpherson, 1992
 * Paralomis poorei Ahyong, 2010
 * Paralomis roeleveldae Kensley, 1981
 * Paralomis seagranti Eldredge, 1976
 * Paralomis serrata Macpherson, 1988
 * Paralomis sonne Guzmán, 2009
 * Paralomis spectabilis Hansen, 1908
 * Paralomis spinosissima Birstein & Vinogradov, 1972
 * Paralomis staplesi Ahyong, 2010
 * Paralomis stella Macpherson, 1988
 * Paralomis stevensi Ahyong & Dawson, 2006
 * Paralomis taylorae Ahyong, 2010
 * Paralomis truncatispinosa Takeda & Miyake, 1980
 * Paralomis tuberipes Macpherson, 1988
 * Paralomis verrilli (Benedict, 1895)
 * Paralomis webberi Ahyong, 2010
 * Paralomis zealandica Dawson & Yaldwyn, 1971
 * Phyllolithodes Brandt, 1848
 * Phyllolithodes papillosus Brandt, 1848 – flatspine triangle crab
 * Rhinolithodes Brandt, 1848
 * Rhinolithodes wosnessenskii Brandt, 1848 – rhinoceros crab
 * Sculptolithodes Makarov, 1934
 * Sculptolithodes derjugini Makarov, 1934

Glyptolithodes
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. Habitat is the main factor separating the range of blue and red king crabs in the Bering Sea. Red king crabs prefer shallow, muddy or sandy habitats in Bristol Bay and Norton Sound, while blue king crabs prefer the deeper areas made up of cobble, gravel and rock that occur around the Pribilof, St. Matthew, 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. 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.



Paralithodes camtschaticus
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. By 2022 they had spread to the North Sea, becoming both a lucrative new stock to British fisheries, and an invasive species.

Paralithodes platypus
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. Blue king crabs from the Pribilof Islands are the largest of all the king crabs, sometimes exceeding 18 lb (8 kg) in weight.

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.

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. 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.