Stylephorus

{{Short description|Genus of ray-finned fishes}}

{{Speciesbox

| image = Stylephorus chordatus1.jpg

| image_caption =

| status = LC

| status_system = IUCN3.1

| display_parents = 4

| greatgrandparent_authority = Miya et al. 2007

| grandparent_authority = Regan, 1924

| parent_authority = G. Shaw, 1791

| taxon = Stylephorus chordatus

| authority = G. Shaw, 1791

| range_map = Stylephorus chordatus range.png

}}

Stylephorus chordatus, the tube-eye or thread-tail, is a deep-sea ray-finned fish, the only species in the genus Stylephorus and family Stylephoridae.{{FishBase family | family = Stylephoridae | month = February | year = 2006}}{{FishBase | genus = Stylephorus | species = chordatus | month = April| year = 2012}}

It is found in deep subtropical and tropical oceans around the world, living at depths during the day and making nightly vertical migrations to feed on plankton. It is an extremely elongated fish; although its body grows only to {{convert|28|cm|in|abbr=on}} long, its pair of tail fin rays triple its length to about {{convert|90|cm|in|abbr=on}}. Its eyes are tubular in shape, resembling a pair of binoculars.{{cite book |editor=Paxton, J.R. |editor2=Eschmeyer, W.N. |author= Olney, John E.|year=1998|title=Encyclopedia of Fishes|publisher= Academic Press|location=San Diego|isbn= 0-12-547665-5|page= 158}}

It has a tubular mouth through which it sucks seawater by enlarging its oral cavity to about 40 times its original size. It then expels the water through the gills, leaving behind the copepods on which it feeds.

The phylogenetic position of the tube-eye has been controversial. It has been historically placed amongst Lampriformes, but a study involving mitochondrial and nuclear DNA{{cite journal |last1=Miya |first1=M. |last2=Holcroft|first2=N.I. |last3=Satoh|first3=T.P.|last4=Yamaguchi|first4=M.|last5=Nishida|first5=M.|last6=Wiley|first6=E.O. |author7=Masaki Miya |author8=Nancy I. Holcroft |author9=Takashi P. Satoh |author10=Motoomi Yamaguchi |author11=Mutsumi Nishida |author12= E.O. Wiley |title=Mitochondrial genome and a nuclear gene indicate a novel phylogenetic position of deep-sea tube-eye fish (Stylephoridae) |journal=Ichthyological Research|volume=54 |issue=4 |pages=323–332 |year=2007 |doi=10.1007/s10228-007-0408-0

|bibcode=2007IchtR..54..323M |s2cid=38375399 }} sequences analysis suggested Stylephorus is instead a close relative of the order Gadiformes (cods and hakes).