Editing Japanese spider crab

{{Short description|Species of crab}}
{{Speciesbox
| image = Macrocheira kaempferi.jpg
| image2 = Spider Crab (19066404505).jpg
| genus = Macrocheira
| species = kaempferi
| authority = ([[Coenraad Jacob Temminck|Temminck]], 1836)
| synonyms =
* ''Maja kaempferi'' <small>Temminck, 1836</small>
* ''Inachus kaempferi'' <small>(Temminck, 1836)</small>
* ''Kaempferia kaempferi'' <small>(Temminck, 1836)</small>
| synonyms_ref = &nbsp;<ref name="Ng"/>
}}

The '''Japanese giant spider crab''' ('''''Macrocheira kaempferi''''') is a [[species]] of [[Marine biology|marine]] [[crab]] and is the biggest one that lives in the waters around [[Japan]]. At around 3.7 meters, it has the largest leg-span of any [[arthropod]]. The Japanese name for this species is ''taka-ashi-gani'', (Japanese: タカアシガニ), literally translating to "tall legs crab". It goes through three main larval stages along with a prezoeal stage to grow to its great size.<ref name=":0" /> 

The genus ''Macrocheira'' contains multiple species. Two fossil species of this genus have been found: ''M. ginzanensis'' and ''M. yabei'', both from the [[Miocene]] of Japan.<ref name="MSIP" /><ref name="Mees" /> Its diverse taxonomic history is an important part of what these creatures are and how they evolved to be what they are today. They are sought by [[crab fisheries]], and are considered a [[Japanese cuisine|delicacy]] in Japan. To prevent overexploitation from harming the species, conservation efforts have been put in place to protect them and their population from overfishing.<ref name=":1" /> 

The Japanese giant spider crab is similar in appearance to the much smaller [[Maja squinado|European  spider crab]] ''(Maja squinado)'', though the latter, while within the same superfamily, belongs to a different family: the [[Majidae]].

==Description==
[[File:Spider crab at manila ocean park.jpg|thumb|left|A Japanese spider crab at the [[Manila Ocean Park]], the Philippines]]

The Japanese spider crab has the greatest leg span of any known arthropod, reaching up to {{convert|3.7|m|ft|1|abbr=on}} from claw to claw.<ref name=McClain>{{Cite journal|last1=McClain|first1=Craig R.|last2=Balk|first2=Meghan A.|last3=Benfield|first3=Mark C.|last4=Branch|first4=Trevor A.|last5=Chen|first5=Catherine|last6=Cosgrove|first6=James|last7=Dove|first7=Alistair D.M.|last8=Gaskins|first8=Lindsay C.|last9=Helm|first9=Rebecca R.|date=2015-01-13|title=Sizing ocean giants: patterns of intraspecific size variation in marine megafauna|journal=PeerJ|language=en|volume=3|pages=e715|doi=10.7717/peerj.715|issn=2167-8359|pmc=4304853|pmid=25649000 |doi-access=free }}</ref> The body may grow to {{convert|40|cm|0|abbr=on}} in [[carapace]] width and the whole crab can weigh up to {{convert|19|kg|abbr=on}}<ref>{{cite book |title=International Wildlife Encyclopedia |url=https://archive.org/details/internationalwil20burt0 |url-access=registration |chapter=Spider crab |author=Maurice Burton |author2=Robert Burton |name-list-style=amp |edition=3rd |publisher=[[Marshall Cavendish]] |year=2002 |isbn=978-0-7614-7266-7 |pages=2475–2476}}</ref>—second in mass only to the [[American lobster]] among all living arthropod species. The males have the longer [[cheliped]]s;<ref name="Mees"/> females have much shorter chelipeds, which are shorter than the following pair of legs.<ref name="MSIP"/> 

Apart from its large size, the Japanese spider crab differs from other crabs in a number of ways. The first [[pleopod]]s of males are unusually twisted, and the [[crustacean larvae|larvae]] appear primitive.<ref name="Ng">{{cite journal|journal=[[Raffles Bulletin of Zoology]] |year=2008 |volume=17 |pages=1–286 |title=Systema Brachyurorum: Part I. An annotated checklist of extant Brachyuran crabs of the world |author=Peter K. L. Ng |author2=Danièle Guinot |author3=Peter J. F. Davie |name-list-style=amp |url=http://rmbr.nus.edu.sg/rbz/biblio/s17/s17rbz.pdf |url-status=dead |archive-url=https://web.archive.org/web/20110606061453/http://rmbr.nus.edu.sg/rbz/biblio/s17/s17rbz.pdf |archive-date=2011-06-06 }}</ref> The crab is orange with white spots along the legs.<ref name="oregoncoastaq">{{cite web |url=http://www.aquarium.org/JapaneseSpiderCrabs.asp |title=Japanese Spider Crabs Arrive at Aquarium |work=Oregon Coast Aquarium |access-date=March 29, 2010}}</ref> It is reported to have a gentle disposition despite its ferocious appearance.<ref name="oregoncoastaq"/> The Japanese Spider Crab also has a unique molting behavior that occurs for about 100 minutes, in which the crab loses its mobility and starts molting its carapace rear and ends with molting its walking legs.<ref>{{Cite journal|last=Okamoto|first=Kazutoshi|date=5 January 2009|title=Molting behavior of the giant spider crab, Macrocheira kaempferi in captivity|url=http://fish-exp.pref.shizuoka.jp/03research/bull_pdf/43/43_67-70.pdf|journal=Bulletin of Shizuoka Prefectural Research Institute of Fishery|issue=43|pages=67–70}}</ref> 
[[File:タカアシガニ (Macrocheira kaempferi) (15257827710).jpg|thumb|At Sunpiazza Aquarium in [[Sapporo]], [[Japan]]]]
The Japanese spider crab has an armored exoskeleton that helps protect it from larger predators such as [[octopus]]es, but also uses camouflage. The crab's bumpy carapace blends into the rocky ocean floor. To further the deception, a spider crab adorns its shell with sponges and other animals.<ref>{{cite web|url=http://www.tnaqua.org/our-animals/invertebrates/giant-japanese-spider-crab|title=Giant Japanese Spider Crab – Tennessee Aquarium|first=Tennessee|last=Aquarium|website=www.tnaqua.org|access-date=6 April 2018|archive-date=11 July 2017|archive-url=https://web.archive.org/web/20170711184529/http://www.tnaqua.org/our-animals/invertebrates/giant-japanese-spider-crab|url-status=dead}}</ref> The way in which a spider crab is able to pick up and cover itself with such organisms is by following a specific routine behavior. Upon picking up the object with the crab's slender chelipeds, the chelae are used to twist and tear off the organism, such as a worm tube or sponge, from the substrate on which it currently resides.<ref name=":3">{{Cite journal|last=Wicksten|first=Mary K.|date=1993|title=A Review and a Model of Decorating Behavior in Spider Crabs (Decapoda, Brachyura, Majidae)|journal=Crustaceana|volume=64|issue=3|pages=314–325|doi=10.1163/156854093X00667|jstor=20104855|bibcode=1993Crust..64..314W |issn=0011-216X}}</ref> Once the material is picked up, it is brought to the crab's mouthparts to specifically orient and shape it before it is attached to the exoskeleton. Then, through mechanical adhesion and secretions, the materials attach to the crab, and are able to regenerate, and colonize on the crab.<ref name=":3" />

Unlike other species of crab, such as the Chilean crab ''[[Acanthonyx|Acanthonyx petiveri]]'', the Japanese spider crab does not specifically look for matching colors to blend into its environment; it simply camouflages in a way that disguises its entire structure.<ref name=":3" /> This is most likely because Japanese spider crabs are nocturnally active, so instead of trying to disguise themselves when catching prey, they are actually just trying to avoid predators at night.<ref name=":3" />

==Distribution and habitat==
[[File:Japanese Spider Crab Monterey Bay Aquarium.jpg|thumb|Rear view of a Japanese spider crab at [[Monterey Bay Aquarium]]]]

Japanese spider crabs are mostly found off the southern coasts of the Japanese island of [[Honshū]], from [[Tokyo Bay]] to [[Kagoshima Prefecture]]. Outlying populations have been found in [[Iwate Prefecture]] and off [[Su-ao, Yilan|Su-ao]] in [[Taiwan]].<ref name="MSIP">{{cite web |url=http://species-identification.org/species.php?species_group=crabs_of_japan&menuentry=soorten&id=857&tab=beschrijving |title=''Macrocheira kaempferi'' |work=Crabs of Japan |publisher=Marine Species Identification Portal |access-date=March 29, 2010 |archive-date=October 4, 2017 |archive-url=https://web.archive.org/web/20171004084920/http://species-identification.org/species.php?species_group=crabs_of_japan&menuentry=soorten&id=857&tab=beschrijving |url-status=dead }}</ref> Adults are found at depths between {{convert|50|and|600|m|abbr=on}}.<ref name="MSIP"/> They like to inhabit vents and holes in the deeper parts of the ocean.<ref name=georgiaaqua>{{cite web|title=Japanese Spider Crab|url=http://animalguide.georgiaaquarium.org/home/galleries/cold-water-quest/gallery-animals/japanese-spider-crab|publisher=Georgia Aquarium|access-date=6 June 2013|archive-url=https://web.archive.org/web/20131004215226/http://animalguide.georgiaaquarium.org/home/galleries/cold-water-quest/gallery-animals/japanese-spider-crab|archive-date=4 October 2013|url-status=dead}}</ref> The temperature preference of adults is unknown, but the species is regular at a depth of {{convert|300|m|ft|abbr=}} in [[Suruga Bay]], where the water generally is about {{convert|10|C|F|abbr=on}}.<ref name=AZA>{{cite web|url=https://www.aza.org/uploadedFiles/Animal_Care_and_Management/Husbandry,_Health,_and_Welfare/Husbandry_and_Animal_Care/Japanese%20Spider%20Crab%20Care%20Manual.pdf |title=Japanese Spider Crab Care Manual |work=AZA Aquatic Invertebrate Taxon Advisory Group |publisher=Silver Spring, MD: Association of Zoos and Aquariums |date=2014 |access-date=23 February 2016 |url-status=dead |archive-url=https://web.archive.org/web/20150908002036/https://www.aza.org/uploadedFiles/Animal_Care_and_Management/Husbandry%2C_Health%2C_and_Welfare/Husbandry_and_Animal_Care/Japanese%20Spider%20Crab%20Care%20Manual.pdf |archive-date= 8 September 2015 }}</ref> Based on results from [[public aquarium|public aquaria]], Japanese spider crabs tolerate temperatures between {{cvt|6|and|16|C|F}}, but are typically maintained at {{convert|10|-|13|C|F|abbr=on}}.<ref name=AZA/>

The Japanese spider crab is an omnivore, consuming both plant-matter and animals. It also sometimes acts as a scavenger, consuming dead/decaying fish. Some have been known to scrape the ocean floor for plants and algae, while others pry open the shells of mollusks and small marine invertibraes.<ref name="oregoncoastaq" /><ref name="georgiaaqua" />

==Lifecycle==
[[File:Japanese-spidercrab.jpg|thumb|Japanese spider crabs at [[Osaka Aquarium Kaiyukan]], [[Japan]]]]
Female crabs carry the fertilized eggs attached to their abdominal appendages until they hatch into tiny planktonic larvae.<ref name="georgiaaqua"/> They can lay up to 1.5 million eggs per season, and these eggs hatch in 10 days on average.<ref name=":1">{{Cite web|url=https://animaldiversity.org/accounts/Macrocheira_kaempferi/|title=Macrocheira kaempferi|last=Riebel|first=William|website=Animal Diversity Web|language=en|access-date=2020-03-09}}</ref> Once hatched, these larvae undergo four stages of development before they mature into adulthood.<ref name=":0">{{Cite journal|last1=Clark|first1=Paul F.|last2=Webber|first2=W. Richard|date=October 1991|title=A redescription of Macrocheira kaempferi (Temminck, 1836) zoeas with a discussion of the classification of the Majoidea Samouelle, 1819 (Crustacea: Brachyura)|journal=Journal of Natural History|language=en|volume=25|issue=5|pages=1259–1279|doi=10.1080/00222939100770781|bibcode=1991JNatH..25.1259C |issn=0022-2933}}</ref> 

The first, or prezoeal, stage lasts only a matter of minutes, with most molting within 15 minutes to enter the first zoeal stage.<ref>{{Cite journal|last=Okamoto|first=Kazutoshi|date=1995|title=Prezoeal Stage of Giant Spider Crab ''Macrocheira kaempferi'' (Crustacea, Decapoda, Majidae) |url=https://www.jstage.jst.go.jp/article/fishsci1994/61/1/61_1_161/_article |journal=Fisheries Science |language=en|volume=61|issue=1|pages=161–162|doi=10.2331/fishsci.61.161|issn=0919-9268|doi-access=free|bibcode=1995FisSc..61..161O }}</ref> It looks very different from its parents at this stage, with a small, transparent body. 
[[File:Giant Japanese Spider Crab, Shedd Aquarium, Chicago.webmhd.webm|thumb|A Japanese spider crab at [[Shedd Aquarium]], Chicago, US]]
''M. kaempferi'' undergoes two zoeal stages and a megalopa stage before it reaches adulthood.<ref name=":0" /> Each of these stages is influenced greatly by temperature, both in terms of survival and stage length. The optimum rearing temperature for all larval stages is thought to be between 15 and 18&nbsp;°C, with survival temperatures ranging from {{cvt|11|to|20|°C}}.<ref name="Okamoto" /> At these temperatures, the zoeal stages can last 7 to 18 days, with the megalopa stage lasting 25 to 45 days.<ref name="Okamoto" /> Colder water is associated with longer durations in each stage. 

During the larval stages, ''M. kaempferi'' is found near the surface, as the planktonic forms drift with ocean currents.<ref name="Okamoto" /> This surface water ranges between 12 and 15&nbsp;°C during the hatching season (January to March).<ref name="ADW">{{cite web|url=http://animaldiversity.org/accounts/Macrocheira_kaempferi/|title=''Macrocheira kaempferi'' |author=Riebel, W.|year=2011|publisher=Animal Diversity Web|access-date=3 June 2017}}</ref> This is much warmer than the waters at depths below {{cvt|200|m|0}}, where adults are found, with waters steadily around {{cvt|10|°C}}. Optimal temperatures have a 70% survival through the first zoeal stage, which is greatly reduced to a 30% survival in the second zoeal and megalopa stages.<ref name="Okamoto" />

==Taxonomic history==
[[File:Japanese spider crab.jpg|thumb|This crab specimen from the American Museum of Natural History measures {{convert|3.8|m|ft}} across its outstretched legs.]]
The Japanese spider crab was [[species description|originally described]] by Western science in 1836 by [[Coenraad Jacob Temminck]] under the name ''Maja kaempferi'', based on material from [[Philipp Franz von Siebold]] collected near the artificial island [[Dejima]].<ref name="NArt">{{cite web|url=http://www.naturalart.be/Mainpages/Articles/JGSC.htm|title=The Japanese Giant Spider Crab – ''Macrocheira kaempferi'' – Taka-ahi-gani|publisher=Natural Art|url-status=dead|archive-url=https://web.archive.org/web/20110823172329/http://www.naturalart.be/Mainpages/Articles/JGSC.htm|archive-date=August 23, 2011|access-date=March 29, 2010}}</ref> The [[specific name (zoology)|specific epithet]] commemorates [[Engelbert Kaempfer]], a German naturalist who lived in Japan from 1690 to 1692 and wrote about the country's [[natural history]].<ref>{{cite web |url=http://www.tmbl.gu.se/libdb/taxon/personetymol/petymol.k.html |title=Engelberg Kaempfer |work=Biographical Etymology of Marine Organism Names |author=Hans G. Hansson |publisher=[[University of Gothenburg|Göteborgs Universitet]] |access-date=March 29, 2010 |archive-date=January 28, 2015 |archive-url=https://web.archive.org/web/20150128114215/http://www.tmbl.gu.se/libdb/taxon/personetymol/petymol.k.html |url-status=dead }}</ref> It was moved to the genus ''[[Inachus (crab)|Inachus]]'' by [[Wilhem de Haan]] in 1839, but placed in a new subgenus, ''Macrocheira''. That subgenus was raised to the [[taxonomic rank|rank]] of the genus in 1886 by [[Edward J. Miers]].<ref name="Ng"/> Placed in the family [[Inachidae]], ''M. kaempferi'' does not fit cleanly into that group, and it may be necessary to erect a new family just for the genus ''Macrocheira''.<ref name="Ng"/> Four species of the genus ''Macrocheira'' are known from [[fossil]]s:<ref name="Grave">{{cite journal|journal=[[Raffles Bulletin of Zoology]] |year=2009 |volume=Suppl. 21 |pages=1–109 |title=A classification of living and fossil genera of decapod crustaceans |first1=Sammy |last1=De Grave |first2=N. Dean |last2=Pentcheff |first3=Shane T. |last3=Ahyong |url=http://rmbr.nus.edu.sg/rbz/biblio/s21/s21rbz1-109.pdf |display-authors=etal |url-status=dead |archive-url=https://web.archive.org/web/20110606064728/http://rmbr.nus.edu.sg/rbz/biblio/s21/s21rbz1-109.pdf |archive-date=2011-06-06 }}</ref><ref name=FWMacrocheira>[https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=22528 ''Macrocheira''] at [[Fossilworks]].org</ref>

*''Macrocheira'' sp. – Pliocene [[Takanabe Formation]], Japan
*''M. ginzanensis'' – Miocene [[Ginzan Formation]], Japan
*''M. yabei'' – Miocene [[Yonekawa Formation]], Japan
*''M. teglandi'' – Oligocene, east of [[Twin River]], [[Washington (state)|Washington]], United States

However, some evidence indicates that the genus ''Macrocheira'' does come from this family in some way due to its anatomical arrangements. This genus is similar in anatomical arrangement to the genus ''Oncinopus'', seeming to preserve the earliest stage of anatomical evolution in the family Inachidae. The genus ''Onicinopus'' has a semi-hardened body, which allows the basal segment of the antennae, which articulates with the head capsule, to move. The antennulae which are segmented appendages between and below the eye stalks are connected. Like ''Oncinopus'', the genus ''Macrocheira'' also has a seven-segmented abdomen and a basal segment of antennae that is mobile. ''Macrocheira'' also has orbital parts, the eye socket and features around it, that are similar to differentiated genera. Another differentiating feature is the supraorbital eave. It is part of the orbital region above the eyestalks. It projects laterally and becomes part of the spine. From the anatomical observations of this genus and others in the family Inachidae, ''Macrochiera'' was placed in the family Inachidae, descending from the genus ''Oncinpus'' and from it descending the genera ''Oreconia'', ''Parapleisticantha'', and ''Pleistincantha''.<ref name=":2">{{Cite journal|last=Sakai|first=K.|date=1987|title=Tune Sakai (1903-1986)|journal=Crustaceana|volume=53|issue=2|pages=205–209|doi=10.1163/156854087X00826|jstor=20104298|bibcode=1987Crust..53..205S |issn=0011-216X}}</ref>

==Anatomy==
{{Verify|section|date=November 2024}}
[[File:Oceanário de Lisboa 2018 (23).jpg|thumb|In the [[Lisbon Oceanarium]], [[Portugal]]]]
''M. kaempferi'' is a giant crab with a pear-shaped carapace that is 350&nbsp;mm (13.7 in) when measured on the median line. Its surface is covered in small spike-like projections or tubercles. The spine of an adult giant crab is short and curves outward at the tip. The spines in young giant crabs, though, are long compared to their carapaces, along with an uncurved spine. It has been discovered that as the crab matures, the carapaces remain the same size, however its legs will continue to grow past maturity. This proportionality explains, as in other decapod crustaceans, that spine size decreases as specimens grow older. As mentioned in the taxonomic section, this genus contains the family's primitive feature of a movable antenna at the basal segment, but "the development of a spine at the posterior angle of the supraocular eave, and the presence of intercalated spine and antennulary septum seem to attribute a rather high position to this genus." Lastly, differences are seen between the sexes. Adult males have very long front legs where the claws are located, but they are still shorter than the ambulatory legs of females, located in the back of the carapace.<ref name=":2"/>

==Fishery and conservation==
[[File:茹でガニ.jpg|alt=See caption|thumb|Boiled Japanese spider crab legs in Japan]]
Temminck, in his original description, noted that the crab was known to the Japanese for the serious injuries it can cause with its strong claws.<ref name="Mees">{{cite journal |url=http://www.repository.naturalis.nl/document/149787 |title=Over het belang van Temminck's "Discours Préliminaire" voor de zoologische nomenclatuur |author=G. F. Mees |journal=[[Zoologische Mededelingen]] |volume=35 |issue=15 |pages=205–227 |year=1957 |trans-title=On the importance of Temminck's "Discours Préliminaire" for zoological nomenclature |quote=on dit, que ce Crustacé est redouté des habitants par les , qu'il est en état de faire au moyen de ses fortes serres <!-- "it is said that this crustacean is known to the Japanese for the serious injuries it can cause with its strong claws" -->|language=nl}}</ref> The Japanese spider crab is "occasionally collected for food",<ref>{{cite book |series=FAO Species Identification Guide for Fishery Purposes |title=The Living Marine Resources of the Western Central Pacific. Volume 2: Cephalopods, crustaceans, holothurians and sharks |editor=Kent E. Carpenter |editor2=Volker H. Niem |name-list-style=amp |publisher=[[Food and Agriculture Organization]] |year=1998 |isbn=92-5-104052-4 |pages=1136–1137 |chapter=Majidae |chapter-url=ftp://ftp.fao.org/docrep/fao/009/w7192e/w7192e33.pdf }}</ref> and even considered a delicacy in many parts of Japan and other areas in the region.<ref name="georgiaaqua"/><ref name=tenauq>{{cite web|title=Giant Japanese Spider Crab|url=http://www.tnaqua.org/OurAnimals/Invertebrates/GiantJapaneseSpiderCrab.aspx|publisher=The [[Tennessee Aquarium]]|access-date=5 June 2013|archive-date=11 November 2013|archive-url=https://web.archive.org/web/20131111151934/http://www.tnaqua.org/OurAnimals/Invertebrates/GiantJapaneseSpiderCrab.aspx|url-status=dead}}</ref> In total, {{convert|24.7|t|lb}} were collected in 1976, but fell to only {{convert|3.2|t|lb}} in 1985.<ref name="Okamoto">{{cite journal|title=Influence of temperature on survival and growth of larvae of the giant spider crab ''Macrocheira kaempferi'' (Crustacea, Decapoda, Majidae) |author=Kazutoshi Okamoto |year=1993 |journal=[[Nippon Suisan Gakkaishi]] |volume=59 |issue=3 |pages=419–424 |doi=10.2331/suisan.59.419 |doi-access=free }}</ref> The [[crab fisheries|fishery]] is centred on [[Suruga Bay]]. The crabs are typically caught using small trawling nets.<ref name="tenauq" /> The population has decreased in number due to [[overfishing]], forcing fishermen into exploring deeper waters to catch them. The average size caught by fishermen is a legspan of {{convert|1.0|-|1.2|m|abbr=on}}.<ref name="NArt" /> Populations of this species of crab have diminished over recent years and many efforts are being made to protect them.<ref name="tenauq" /> One of the primary methods of recovery of the species being used is restocking artificially cultured juvenile crabs in fisheries.<ref name="Okamoto" /> Additionally, laws have been put into place in Japan that prohibit fishermen from harvesting spider crabs from January through April, during their typical mating season when they are in shallower waters and more vulnerable to being caught.<ref name="tenauq" /> This protection method seeks to keep natural populations growing, and enables time for juvenile spider crabs to go through the early stages of their lifecycle.<ref name="tenauq" />

==See also==
*[[Largest and heaviest animals#Arthropods (Arthropoda)|Largest arthropods]]
*[[King crab]]
*[[Red king crab]]

==References==
{{Reflist|32em}}

==External links==
*{{Commons category-inline|Macrocheira kaempferi|''Macrocheira kaempferi''}}
*{{Wikispecies-inline|Macrocheira kaempferi|''Macrocheira kaempferi''}}

{{Taxonbar|from=Q273655}}
{{Portal bar|Crustaceans|Marine life|Japan}}

[[Category:Majoidea]]
[[Category:Crustaceans of Japan]]
[[Category:Crustaceans described in 1836]]
[[Category:Taxa named by Coenraad Jacob Temminck]]
[[Category:Articles containing video clips]]