{{Short description|Family of ray-finned fishes}} {{Automatic taxobox | image = Atlantic threadfin ( Polydactylus octonemus ).jpg | image_caption = Atlantic threadfin, ''Polydactylus octonemus'' | taxon = Polynemidae | authority = Rafinesque, 1815<ref name = VDLEF>{{cite journal | author1 = Richard van der Laan | author2 = William N. Eschmeyer | author3 = Ronald Fricke | name-list-style = amp |year=2014 | title = Family-group names of Recent fishes | url = https://biotaxa.org/Zootaxa/article/view/zootaxa.3882.1.1/10480 | journal = Zootaxa | volume = 3882 | issue =2 | pages = 001–230| doi = 10.11646/zootaxa.3882.1.1 | pmid = 25543675 | doi-access = free }}</ref> | subdivision_ranks = Genera | subdivision = See text }}
'''Threadfins''' are silvery grey ray-finned fish of the family '''Polynemidae'''. Found in tropical to subtropical waters throughout the world, the threadfin family contains nine genera and about 40 species.<ref name = Nelson5errata>{{cite web | url = https://81a86d48-a-62cb3a1a-s-sites.googlegroups.com/site/fotw5th/Inserts%20for%20pp.%20437-441%20in%20FotW5.pdf?attachauth=ANoY7cru1eiQxyWX8FftCgaTlRq9uD0uYDI1EC32O0iAg-exxLlJoV0tig3JxqIskoE9lDff-FZQgh-HnL2SjOMJcBU3obkvnrkdEJJK-81gj_tCcLedWnb6FgxKVLIY_TGKddKHUVwBuXDEv_JTYPh-mLSQcdVoFfVTHyK-UfvJzknKcwPrwv1Emc1ecKU8OkALrUr6PX_CEHQIjheLBwZ3EwOb7kqz8iSpmirHBGnnbtpJx1aiszU%3D&attredirects=0 | title = Inserts for pages 437–441 | access-date = 13 April 2020 | publisher = John Wiley & Sons Limited}}</ref> A distantly related species sometimes known by the name threadfin, ''Scyris indica'', is properly the Indian threadfish (family Carangidae).
Ranging in length from {{convert|11|cm|in|abbr=on|round=0.5}} in the dwarf threadfin (''Parapolynemus verekeri'') to {{convert|2|m|ft|abbr=on}} in fourfinger threadfin (''Eleutheronema tetradactylum'') and giant African threadfin (''Polydactylus quadrifilis''), threadfins are both important to commercial fisheries as a food fish, and popular among anglers. Their habit of forming large schools makes the threadfins a reliable and economic catch.
==Description== Their bodies are elongated and fusiform, with spinous and soft dorsal fins widely separated. Their tail fins are large and deeply forked, indicating speed and agility. The mouth is large and inferior; a blunt snout projects far ahead. The jaws and palate possess bands of villiform (fibrous) teeth. Their most distinguishing feature is their pectoral fins: they are composed of two distinct sections, the lower of which consists of three to seven long, thread-like independent rays. ''Polynemus'' species may have up to 15 of these modified rays.
[[Image:sixfinger threadfin school.jpg|thumb|left|200px| ''Filistriatus sexfilis'' or ''moi'' (sixfinger threadfins),<ref>{{FishBase |genus=Polydactylus |species=sexfilis |id= |month=August |year=2019 }}</ref> were reserved for Hawaiian royalty or the aliʻi<!--ali'i-->.<ref name=krisnawati&umemoto/>]]
In some species, such as the royal threadfin (''Pentanemus quinquarius''), the thread-like rays may extend well past the tail fin. This feature explains both the common name threadfin and the family name Polynemidae, from the Greek ''poly'' meaning "many" and ''nema'' meaning "filament." Similar species, such as the mullets (family Mugilidae) and milkfish (family Chanidae), can be easily distinguished from threadfins by their lack of filamentous pectoral rays.
==Distribution and habitat== Threadfins frequent open, shallow water in areas with muddy, sandy, or silty bottoms; they are rarely seen at reefs. Their pectoral rays are thought to serve as tactile structures, helping to find prey within the sediments. Noted for being euryhaline, threadfins can tolerate a wide range of salinity levels. This attribute allows threadfins to enter estuaries and even rivers. They feed primarily on crustaceans and smaller fish.
==Reproduction== Presumed to be pelagic spawners, threadfins probably release many tiny, buoyant eggs into the water column, which then become part of the plankton. The eggs float freely with the currents until hatching.
==Cuisine==
Threadfin has been used to create crab stick.
==Mariculture== In Hawaii, sixfinger threadfins are the subject of commercial open-ocean cage mariculture.<ref>{{Cite journal|url=https://www.int-res.com/abstracts/meps/v371/p65-72/|doi = 10.3354/meps07675|title = Partial recovery of infaunal communities during a fallow period at an open-ocean aquaculture|year = 2008|last1 = Lin|first1 = DT|last2 = Bailey-Brock|first2 = JH|journal = Marine Ecology Progress Series|volume = 371|pages = 65–72|bibcode = 2008MEPS..371...65L|doi-access = free}}</ref><ref>{{Cite journal|url=https://www.int-res.com/abstracts/meps/v307/p175-185/|doi=10.3354/meps307175|title=Temporal changes in the polychaete infaunal community surrounding a Hawaiian mariculture operation|year=2006|last1=Lee|first1=HW|last2=Bailey-Brock|first2=JH|last3=McGurr|first3=MM|journal=Marine Ecology Progress Series|volume=307|pages=175–185|bibcode=2006MEPS..307..175L|doi-access=free}}</ref>
==Genera and species== [[File:Eleutheronema tetradactylum(Shaw, 1804).jpg|thumb|Fourfinger threadfin (''Eleutheronema tetradactylum'')]] [[File:Filimanus heptadactyla.png|thumb|Sevenfinger threadfin (''Filimanus heptadactyla'')]] [[File:Elegant paradiseus fish Polynemus multifilis.jpg|thumb|Elegant paradise fish (''Polynemus multifilis'')]]
The family includes 43 species in nine<ref name=":0">{{Cite journal |last1=Girard |first1=Matthew G. |last2=Chovanec |first2=Kevin R. |date=2025-09-30 |title=Unlocking the genomic potential of historical and formalin-fixed specimens: phylogenetic insights from museum-preserved threadfin fishes (Teleostei: Polynemidae) |url=https://peerj.com/articles/20029 |journal=PeerJ |language=en |volume=13 |article-number=e20029 |doi=10.7717/peerj.20029 |doi-access=free |issn=2167-8359}}</ref> genera:
* Genus ''Eleutheronema'' ** ''Eleutheronema rhadinum'' <small>(Jordan & Evermann, 1902)</small> (East Asian fourfinger threadfin) ** ''Eleutheronema tetradactylum'' <small>(Shaw, 1804)</small> (Fourfinger threadfin) ** ''Eleutheronema tridactylum'' <small>(Bleeker, 1849)</small> (Threefinger threadfin) * Genus ''Filimanus'' ** ''Filimanus heptadactyla'' <small>(Cuvier, 1829)</small> (Sevenfinger threadfin) ** ''Filimanus hexanema'' <small>(Cuvier 1829)</small> (Javanese threadfin) ** ''Filimanus perplexa'' <small>Feltes 1991</small> (Splendid threadfin) ** ''Filimanus sealei'' <small>(Jordan & Richardson, 1910)</small> (Eightfinger threadfin) ** ''Filimanus similis'' <small>Feltes 1991</small> (Indian sevenfinger threadfin) ** ''Filimanus xanthonema'' <small>(Valenciennes, 1831)</small> (Yellowthread threadfin) * Genus ''Filistriatus''<ref name=":0" /> ** ''Filistriatus bifurcus'' (<small>Motomura, Kimura & Iwatsuki, 2001)</small> (Slender fivefinger threadfin) ** ''Filistriatus plebeius'' <small>(Broussonet, 1782)</small> (Striped threadfin) ** ''Filistriatus sexfilis'' <small>(Valenciennes, 1831)</small> (Sixfinger threadfin) ** ''Filistriatus siamensis'' (<small>Motomura, Iwatsuki & Yoshino, 2001)</small> (Largemouth striped threadfin) * Genus ''Galeoides'' ** ''Galeoides decadactylus'' <small>(Bloch, 1795)</small> (Lesser African threadfin) * Genus ''Leptomelanosoma'' ** ''Leptomelanosoma indicum'' <small>(Shaw, 1804)</small> (Indian threadfin) ** ''Leptomelanosoma longipes'' (<small>Motomura, Okamoto & Iwatsuki, 2001)</small> (Long-limb threadfin) * Genus ''Parapolynemus'' ** ''Parapolynemus verekeri'' <small>(Saville-Kent, 1889)</small> (Dwarf paradise fish) * Genus ''Pentanemus'' ** ''Pentanemus quinquarius'' <small>(Linnaeus, 1758)</small> (Royal threadfin) * Genus ''Polydactylus'' (likely not monophyletic<ref>{{Cite journal|last1=Girard|first1=Matthew G.|last2=Davis|first2=Matthew P.|last3=Baldwin|first3=Carole C.|last4=Dettaï|first4=Agnès|last5=Martin|first5=Rene P.|last6=Smith|first6=W. Leo|title=Molecular phylogeny of the threadfin fishes (Polynemidae) using ultraconserved elements|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/jfb.14997|journal=Journal of Fish Biology|year=2022|volume=100|issue=3|pages=793–810|language=en|doi=10.1111/jfb.14997|pmid=35137410|bibcode=2022JFBio.100..793G |s2cid=246678758|issn=1095-8649|url-access=subscription}}</ref>) ** ''Polydactylus approximans'' <small>(Lay & Bennett, 1839)</small> (Blue bobo) ** ''Polydactylus luparensis'' <small>Lim, Motomura & Gambang, 2010</small> (Sarawak giant threadfin) ** ''Polydactylus macrochir'' <small>(Günther, 1867)</small> (King threadfin) ** ''Polydactylus macrophthalmus'' <small>(Bleeker, 1858)</small> (River threadfin) ** ''Polydactylus malagasyensis'' <small>Motomura & Iwatsuki, 2001</small> (African blackspot threadfin) ** ''Polydactylus microstomus'' <small>(Bleeker, 1851)</small> (Smallmouth threadfin) ** ''Polydactylus mullani'' <small>(Hora, 1926)</small> (Arabian blackspot threadfin) ** ''Polydactylus multiradiatus'' <small>(Günther, 1860)</small> (Australian threadfin) ** ''Polydactylus nigripinnis'' <small>Munro, 1964</small> (Blackfin threadfin) ** ''Polydactylus octonemus'' <small>(Girard, 1858)</small> (Atlantic threadfin) ** ''Polydactylus oligodon'' <small>(Günther, 1860)</small> (Littlescale threadfin) ** ''Polydactylus opercularis'' <small>Seale & Bean, 1907</small> (Yellow bobo) ** ''Polydactylus persicus'' <small>Motomura & Iwatsuki, 2001</small> (Persian blackspot threadfin) ** ''Polydactylus quadrifilis'' <small>(Cuvier, 1829)</small> (Giant African threadfin) ** ''Polydactylus sextarius'' <small>(Bloch & Schneider, 1801)</small> (Blackspot threadfin) ** ''Polydactylus virginicus'' <small>(Linnaeus, 1758)</small> (Barbu) * Genus ''Polynemus'' ** ''Polynemus aquilonaris'' <small>Motomura, 2003</small> (Northern paradise fish) ** ''Polynemus bidentatus'' <small>Motomura & Tsukawaki, 2006</small> ** ''Polynemus dubius'' <small>Bleeker, 1854</small> (Eastern paradise fish) ** ''Polynemus hornadayi'' <small>Myers, 1936</small> (Hornaday's paradise fish) ** ''Polynemus kapuasensis'' <small>Motomura & van Oijen, 2003</small> (Kapuas elegant paradise fish) ** ''Polynemus melanochir'' <small>Valenciennes, 1831</small> (Blackhand paradise fish) ** ''Polynemus multifilis'' <small>Temminck & Schlegel, 1843</small> (Elegant paradise fish) ** ''Polynemus paradiseus'' <small>Linnaeus, 1758</small> (Paradise threadfin)
==Phylogeny== The following cladogram is from Girard & Chovanec (2025):<ref name=":0" />
{{Clade | style = font-size: 70&; line-height: 70% | label1 = '''Polynemidae''' | 1 = {{Clade sequential | 1 = ''"Polydactylus" quadrifilis'' | 2 = ''Pentanemus quinquarius'' | 3 = ''Galeoides decadactylus'' | 4 = {{Clade sequential | 1 = {{Clade sequential | 1 = ''Polydactylus opercularis'' | 2 = ''Polydactylus approximans'' | 3 = ''Polydactylus virginicus'' | 4 = ''Polydactylus octonemus'' | 5 = ''Polydactylus oligodon'' }} | 2 = {{Clade sequential | 1 = {{Clade sequential | 1 = ''Parapolynemus verekeri'' | 2 = ''"Polydactylus" macrochir'' }} | 2 = ''"Polydactylus" multiradiatus'' | 3 = ''"Polydactylus" nigripinnis'' }} | 3 = {{Clade sequential | 1 = ''Eleutheronema rhadinum'' | 2 = ''Eleutheronema tetradactylum'' }} | 4 = ''Filistriatus bifurcus'' | 5 = ''Filistriatus plebeius'' | 6 = ''Filistriatus sexfilis'' }} | 5 = {{Clade sequential | 1 = ''Polynemus multifilis'' | 2 = ''Polynemus aquilonaris'' | 3 = ''Polynemus melanochir'' | 4 = ''Polynemus paradiseus'' }} | 6 = {{Clade sequential | 1 = ''Leptomelanosoma indicum'' | 2 = ''Leptomelanosoma macrophthalmus'' }} | 7 = {{Clade sequential | 1 = ''Filimanus perplexa'' | 2 = ''Filimanus similis'' | 3 = ''Filimanus sealei'' | 4 = ''Filimanus xanthonema'' }} | 8 = ''"Polydactylus" longipes'' | 9 = ''"Polydactylus" mullani'' | 10 = ''"Polydactylus" microstomus'' | 11 = ''"Polydactylus" malagasyensis'' | 12 = ''"Polydactylus" sextarius'' }} }}
==Timeline of genera==
<timeline> ImageSize = width:1000px height:auto barincrement:15px PlotArea = left:10px bottom:50px top:10px right:10px
Period = from:-65.5 till:10 TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:5 start:-65.5 ScaleMinor = unit:year increment:1 start:-65.5 TimeAxis = orientation:hor AlignBars = justify
Colors = #legends id:CAR value:claret id:ANK value:rgb(0.4,0.3,0.196) id:HER value:teal id:HAD value:green id:OMN value:blue id:black value:black id:white value:white id:cenozoic value:rgb(0.54,0.54,0.258) id:paleogene value:rgb(0.99,0.6,0.32) id:paleocene value:rgb(0.99,0.65,0.37) id:eocene value:rgb(0.99,0.71,0.42) id:oligocene value:rgb(0.99,0.75,0.48) id:neogene value:rgb(0.999999,0.9,0.1) id:miocene value:rgb(0.999999,0.999999,0) id:pliocene value:rgb(0.97,0.98,0.68) id:quaternary value:rgb(0.98,0.98,0.5) id:pleistocene value:rgb(0.999999,0.95,0.68) id:holocene value:rgb(0.999,0.95,0.88) BarData= bar:eratop bar:space bar:periodtop bar:space bar:NAM1 bar:NAM2
bar:space bar:period bar:space bar:era
PlotData= align:center textcolor:black fontsize:M mark:(line,black) width:25 shift:(7,-4) bar:periodtop from: -65.5 till: -55.8 color:paleocene text:Paleocene from: -55.8 till: -33.9 color:eocene text:Eocene from: -33.9 till: -23.03 color:oligocene text:Oligocene from: -23.03 till: -5.332 color:miocene text:Miocene from: -5.332 till: -2.588 color:pliocene text:Plio. from: -2.588 till: -0.0117 color:pleistocene text:Pleist. from: -0.0117 till: 0 color:holocene text:H.
bar:eratop from: -65.5 till: -23.03 color:paleogene text:Paleogene from: -23.03 till: -2.588 color:neogene text:Neogene from: -2.588 till: 0 color:quaternary text:Q.
PlotData= align:left fontsize:M mark:(line,white) width:5 anchor:till align:left
color:miocene bar:NAM1 from: -23.03 till: 0 text: Pentanemus color:miocene bar:NAM2 from: -11.608 till: 0 text: Polydactylus
PlotData= align:center textcolor:black fontsize:M mark:(line,black) width:25
bar:period from: -65.5 till: -55.8 color:paleocene text:Paleocene from: -55.8 till: -33.9 color:eocene text:Eocene from: -33.9 till: -23.03 color:oligocene text:Oligocene from: -23.03 till: -5.332 color:miocene text:Miocene from: -5.332 till: -2.588 color:pliocene text:Plio. from: -2.588 till: -0.0117 color:pleistocene text:Pleist. from: -0.0117 till: 0 color:holocene text:H.
bar:era from: -65.5 till: -23.03 color:paleogene text:Paleogene from: -23.03 till: -2.588 color:neogene text:Neogene from: -2.588 till: 0 color:quaternary text:Q.
</timeline>
==References== {{Reflist|30em|refs= <ref name=krisnawati&umemoto>{{cite journal|last1=Suryanata |first1=Krisnawati |author-link1=<!--Krisnawati Suryanata-->|last2=Umemoto |first2=Karen N. |author-link2=<!--Karen N. Umemoto--> |title=Tension at the nexus of the global and local: culture, property, and marine aquaculture in Hawaiʻi |journal=Environment and Planning A |volume=35 |issue=2 |year=2005 |pages=199, 206<!--199–213--> |doi=10.1068/a35116|citeseerx=10.1.1.456.680 |s2cid=143928957 }}</ref> }} {{more footnotes|date=November 2008}} * {{FishBase family | family = Polynemidae | month = January | year = 2006}} * {{cite journal|last=Sepkoski |first=Jack |title=A compendium of fossil marine animal genera |journal=Bulletins of American Paleontology |volume=364 |page=560 |year=2002 |url=http://strata.ummp.lsa.umich.edu/jack/showgenera.php?taxon=611&rank=class |access-date=2011-05-19 |archive-url=https://web.archive.org/web/20090220223520/http://strata.ummp.lsa.umich.edu/jack/showgenera.php?taxon=611&rank=class |archive-date=2009-02-20 }}
==External links== *[http://www.fish.wa.gov.au/About-Us/Publications/Recreational-Fishing/Pages/Fact-Sheets.aspx Fisheries Western Australia - Threadfins Fact Sheet] *[https://web.archive.org/web/20040217232857/http://www.practicalfishkeeping.co.uk/pfk/pages/show_article.php?article_id=111 The Paradise threadfin, Polynemus paradiseus] *[https://web.archive.org/web/20040223170521/http://www.oar.noaa.gov/spotlite/archive/spot_hawaii.html Offshore aquaculture project yields a traditional Hawaiian delicacy]
{{Taxonbar|from=Q924957}}
Category:Polynemidae Category:Fish of Hawaii Category:Taxa named by Constantine Samuel Rafinesque