{{Short description|Species of crab}} {{Speciesbox | image = Helice tridens (Kohnoura).jpg | genus = Helice | species = tridens | authority = (De Haan, 1835)&nbsp;<ref>{{cite web |url=http://www.marinespecies.eu/species.php?species_group=crabs_of_japan&menuentry=soorten&id=1739&tab=beschrijving |title=''Helice tridens'' |work=Crabs of Japan |accessdate=January 31, 2009}}</ref> | synonyms_ref = &nbsp;<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=P. K. L. Ng, D. Guinot & P. J. F. Davie |url=http://rmbr.nus.edu.sg/rbz/biblio/s17/s17rbz.pdf |url-status=dead |archiveurl=https://web.archive.org/web/20110606061453/http://rmbr.nus.edu.sg/rbz/biblio/s17/s17rbz.pdf |archivedate=2011-06-06 }}</ref> | synonyms = *''Ocypode tridens'' <small>De Haan, 1835</small> *''Cyclograpsus latreillii'' <small>H. Milne-Edwards, 1837</small> *''Helice latreillei'' <small>H. Milne-Edwards, 1837</small> }}

'''''Helice tridens''''' is a species of crab which lives on mudflats around the coasts of Japan and the Korean Peninsula.<ref>{{cite journal |journal=Zoological Studies |url=http://zoolstud.sinica.edu.tw/Journals/47.1/114.pdf |title=Taxonomy, phylogeny, and biogeography of the endemic mudflat crab ''Helice''/''Chasmagnathus'' complex (Crustacea: Brachyura: Varunidae) from East Asia |author1=Hsi-Te Shih |author2=Hiroshi Suzuki |name-list-style=amp |volume=47 |issue=1 |pages=114–125 |year=2008 |access-date=2010-03-27 |archive-date=2017-08-09 |archive-url=https://web.archive.org/web/20170809075913/http://zoolstud.sinica.edu.tw/Journals/47.1/114.pdf |url-status=dead }}</ref>

==Ecology== It is semi-terrestrial, returning to the sea to spawn.<ref name="Hayama">{{cite book |chapter=Rapid range expansion of the feral raccoon (''Procyon lotor'') in Kanagawa Prefecture, Japan, and its impact on native organisms |author1=Hisayo Hayama, Masato Kaneda |author2=Mayuh Tabata |name-list-style=amp |pages=196–199 |editor1=F. Koike |editor2=M. N. Clout |editor3=M. Kawamichi |editor4=M. De Poorter |editor5=K. Iwatsuki |title=Assessment and Control of Biological Invasion Risks |publisher=Shoukadoh Book Sellers, Kyoto, Japan and IUCN, Gland, Switzerland |year=2006 |url=http://vege1.kan.ynu.ac.jp/isp/pdf/Hayama_et_al.pdf |access-date=2009-01-31 |archive-url=https://web.archive.org/web/20110722080721/http://vege1.kan.ynu.ac.jp/isp/pdf/Hayama_et_al.pdf |archive-date=2011-07-22 |url-status=dead }}</ref> The species appears to be adversely affected by the presence of raccoons (''Procyon lotor''), an invasive predator.<ref name="Hayama"/> ''H. tridens'' has a salinity requirement which lies between those of two other estuarine crabs in Japan, ''Helicana japonica'' and ''Chiromantes dehaani''.<ref>{{cite journal |journal=Tohoku Journal of Agricultural Research |volume=44 |issue=1–4 |year=1994 |title=Difference of salinity requirements among the three estuarine crab species, ''Chiromantes dehaani'', ''Helice tridens'' and ''H. japonica'' (Brachyura: Grapsidae) |author1=Bambang Irawan |author2=Akihiro Kijima |name-list-style=amp |url=http://ir.library.tohoku.ac.jp/re/bitstream/10097/29948/1/KJ00000715049.pdf |access-date=2009-01-31 |archive-url=https://web.archive.org/web/20120602075333/http://ir.library.tohoku.ac.jp/re/bitstream/10097/29948/1/KJ00000715049.pdf |archive-date=2012-06-02 |url-status=dead }}</ref>

Smaller individuals shelter in burrows in reed marshes, apparently in order to avoid cannibalism; this may also be the reason for the migration of larger individuals to brackish water lagoons in summer, when the crabs exceed their carrying capacity.<ref>{{cite journal |title=Wandering behaviour of the mud-crab ''Helice tridens'' related to evasion of cannibalism |author1=Yasushi Kurihara, Katsuhiro Sekimoto |author2=Masahide Miyata |name-list-style=amp |url=https://www.int-res.com/articles/meps/49/m049p041.pdf |volume=49 |pages=41–50 |year=1988 |journal=Marine Ecology Progress Series |doi=10.3354/meps049041|doi-access=free |bibcode=1988MEPS...49...41K }}</ref>

==Taxonomy== ''Helice tridens'' was first described by Wilhem de Haan in an 1835 volume of ''Fauna Japonica'', as ''Ocypode tridens''.<ref>{{cite book |chapter-url=http://edb.kulib.kyoto-u.ac.jp/exhibit/b04/image/01/b04s0137.html |title=Fauna Japonica |author=Wilhem de Haan |author-link=Wilhem de Haan |editor=Philipp Franz von Siebold |editor-link=Philipp Franz von Siebold |year=1835 |chapter=''Ocypode (Helice) tridens'' sp. nov. |page=57 |access-date=2009-01-31 |archive-date=2011-07-25 |archive-url=https://web.archive.org/web/20110725014805/http://edb.kulib.kyoto-u.ac.jp/exhibit/b04/image/01/b04s0137.html |url-status=dead }}</ref> The former subspecies ''H. t. wuana'' and ''H. t. sheni'' are now recognised as a separate species, ''Helicana wuana''.<ref name="Ng"/>

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

==External links== {{Portal|Crustaceans}} *{{Commons category-inline|Helice tridens|''Helice tridens''}}

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Category:Grapsoidea Category:Crustaceans of Japan Category:Crustaceans of Korea Category:Crustaceans described in 1835 Category:Taxa named by Wilhem de Haan Category:Korean seafood