| 词条 | Threadfin |
| 释义 |
| name = Threadfin | image = Atlantic threadfin ( Polydactylus octonemus ).jpg | image_caption = Atlantic threadfin, Polydactylus octonemus | regnum = Animalia | phylum = Chordata | classis = Actinopterygii | ordo = Perciformes | familia = Polynemidae | subdivision_ranks = Genera | subdivision =Eleutheronema Filimanus Galeoides Leptomelanosoma Parapolynemus Pentanemus Polydactylus Polynemus See text for species. }} Threadfins are silvery grey perciform fish of the family Polynemidae. Found in tropical to subtropical waters throughout the world, the threadfin family contains eight genera and about 40 species. An unrelated species sometimes known by the name threadfin, Alectis indicus, 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. DescriptionTheir 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. 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 habitatThreadfins 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 are able to 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. ReproductionPresumed 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. CuisineThreadfin has been used as an ingredient in creating crab stick. MaricultureIn Hawaii, sixfinger threadfins are the subject of commercial open-ocean cage mariculture.[1][2] SpeciesThe species in eight genera are:
Timeline of generaImageSize = 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= color:miocene bar:NAM1 from: -23.03 till: 0 text: Pentanemus color:miocene bar:NAM2 from: -11.608 till: 0 text: Polydactylus PlotData= 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. References1. ^http://www.int-res.com/abstracts/meps/v371/p65-72/ {{more footnotes|date=November 2008}}2. ^http://www.int-res.com/abstracts/meps/v307/p175-185/
External links
2 : Polynemidae|Fish of Hawaii |
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