King crab
Template:Short description Template:Automatic taxobox
King crabs or stone crabs are marine decapod crustaceans of the family LithodidaeTemplate:Efn that are chiefly found in deep waters and are adapted to cold environments.Template:Sfn<ref name="Hall & Thatje 2009">Template:Cite journal</ref> They are composed of two subfamilies: Lithodinae, which tend to inhabit deep waters, are globally distributed, and comprise the majority of the family's species diversity;<ref name="Hall & Thatje 2009" /><ref name="Noever & Glenner 2017" /> and Hapalogastrinae, which are endemic to the North Pacific and inhabit exclusively shallow waters.<ref name="Hall & Thatje 2009" /> King crabs superficially resemble true crabs but are generally understood to be closest to the pagurid hermit crabs.Template:Sfn<ref name="Noever & Glenner 2017">Template:Cite journal</ref><ref name="Ahyong 2010"/> This placement of king crabs among the hermit crabs is supported by several anatomical peculiarities which are present only in king crabs and hermit crabs, making them a prominent example of carcinisation among decapods.<ref name="Keiler">Template:Cite journal</ref> Several species of king crabs, especially in Alaskan and southern South American waters, are targeted by commercial fisheries and have been subject to overfishing.Template:Sfn<ref name="Dvoretsky & Dvoretsky 2017">Template:Cite journal</ref><ref name="Klaus et al. 2004"/>
TaxonomyEdit
The phylogeny of king crabs as hermit crabs who underwent secondary calcification and left their shell has been suspected since the late 1800s.<ref name="Noever & Glenner 2017" /> They are believed to have originated during the Early Miocene in shallow North Pacific waters, where most king crab genera – including all Hapalogastrinae – are distributed and where they exhibit a high amount of morphological diversity.<ref name="Noever & Glenner 2017" /><ref name="Karasawa et al. 2017">Template:Cite journal</ref>
In 2007, the king crabs were moved from their classification among the hermit crabs in the superfamily Paguroidea into a separate superfamily, Lithodoidea.<ref name="Grave" /> 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.<ref name="Keiler" /><ref>Template:Cite journal</ref> In 2023, king crabs were folded back into Paguroidea, with Lithodoidea being considered superseded.Template:Sfn The king crab's relationship to other hermit crabs as well as the family's internal phylogeny can be seen in the following two cladograms:<ref name="Noever & Glenner 2017"/><ref name="Wolfe 2019">Template:Cite journal</ref> Template:Anomura cladogram Template:Lithodidae cladogram
Template:As of, there are 15 known genera of king crabs across two subfamilies.<ref name="WoRMS">Template:Cite WoRMS</ref>Template:Sfn<ref>Template:Cite journal</ref> These include:<ref name="WoRMS" />
HapalogastrinaeEdit
LithodinaeEdit
DescriptionEdit
King crabs are a morphologically diverse group, distinctive among hermit crabs for their superficial similarity to true crabs.<ref name="Noever & Glenner 2017" /><ref name="Ahyong 2010">Template:Cite book</ref> They have five pairs of legs, called pereopods:Template:Efn the first – frontmost – set are chelipeds whose right side is generally noticeably more robust than the left; the second, third, and fourth are walking legs tipped with sharp dactyli; and the fifth, used for cleaning, are very small and generally sit inside the branchial chamber.<ref name="Ahyong 2010"/> On their underside, they have a short abdomen – composed of plates – which is asymmetrical in females.<ref name="Ahyong 2010" /> This abdomen (sometimes called a pleon)<ref name="Noever & Glenner 2017" /> is folded against the underside of the cephalothorax and is composed of six segments – called somites or pleonites – and a telson.<ref name="Ahyong 2010" />Template:SfnTemplate:Efn In Hapalogastrinae, this abdomen is soft, while it is hard and calcified in members of Lithodinae.<ref name="Noever & Glenner 2017" /> Lithodids lack any sort of uropod seen in some decapods.<ref name="Ahyong 2010"/>
DistributionEdit
King crabs are typically found in deep waters, especially in polar and subpolar regions and near hydrothermal vents and cold seeps.Template:Sfn Members of Lithodinae can be found in all five of the world's oceans, namely the Pacific,Template:Sfn Atlantic,Template:Sfn Indian,<ref>Template:Cite journal</ref> Southern,Template:Sfn and Arctic,<ref>Template:Cite journal</ref> while members of Hapalogastrinae are only found in the North Pacific.<ref name="Hall & Thatje 2009"/> Members of Hapalogastrinae exhibit a tolerance for higher temperatures than Lithodinae; whereas Lithodinae tend to live exclusively in deep waters or – less commonly – high-latitude shallow waters, Hapalogastrinae are found only in shallow waters (<Template:Convert).<ref name="Hall & Thatje 2009"/> At the deepest, members of the Lithodinae genera Paralomis, Neolithodes, and Lithodes have been found at depths of Template:Convert, Template:Convert, and Template:Convert, respectively.Template:Sfn
FisheriesEdit
Because of their large size, the taste of their meat, and their status as a delicacy, some species of king crabs are caught and sold as food.<ref name="Cocito et al. 2024">Template:Cite journal</ref><ref name="Klaus et al. 2004"/><ref name="Dvoretsky & Dvoretsky 2017"/> Red (Paralithodes camtschaticus) and blue (Paralithodes platypus) king crabs are heavily targeted by commercial fisheries in Alaska and have been for several decades. However, populations have fluctuated in the past 25 years, and some areas are currently closed due to overfishing.<ref name="Jensen">Template:Cite journal</ref><ref>Template:Cite journal</ref><ref name="Stevens">Template:Cite journal</ref><ref name="NPFRC2005">Template:Cite report</ref> Alaskan fisheries additionally target the golden king crab (Lithodes aequispinus).<ref name="Olson et al. 2018">Template:Cite journal</ref> In South America, both the southern king crab (Lithodes santolla) and several species of Paralomis are targeted by commercial fisheries,<ref name="Cocito et al. 2024"/>Template:Sfn and as a result, the population of L. santolla has seen a dramatic decline.<ref name="Klaus et al. 2004">Template:Cite journal</ref>
Symbionts and parasitesEdit
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.<ref>Template:Cite journal</ref> Endosymbiotic microorganisms of the order Eccrinida have been found in Paralithodes camtschaticus and Lithodes maja, living in their hindgut between molts.<ref name="Pavlova 2018">Template:Cite journal</ref>
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.<ref name="Gardner et al. 2016">Template:Cite journal</ref> 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.<ref name="Gardner et al. 2016" /> On occasion king crabs have been found to be host to the eggs of multiple species of careproctus simultaneously.<ref name="Gardner et al. 2016" /> King crabs are additionally parasitized by rhizocephalan genus Briarosaccus, a type of barnacle.<ref name="Noever 2017">Template:Cite thesis</ref> The barnacle irreversibly sterilizes the crab, and over 50% of some king crab populations are affected.<ref name="Noever 2017" />