Editing Opah

{{Short description|Genus of fishes}}
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{{Use dmy dates|date=October 2020}}
{{Automatic taxobox
| name = Opah
| fossil_range = {{fossil range|Late Miocene|present}}{{r|sep2002}}
| image = Moonfish 600.jpg
| image_caption = ''[[Lampris guttatus]]''
| parent_authority = Gill, 1862
| taxon = Lampris
| authority = [[Anders Jahan Retzius|Retzius]], 1799
| subdivision_ranks = Species
| subdivision = See text
}}

The '''opah''', also commonly known as '''moonfish''', '''sunfish''' (not to be confused with [[Molidae]]),  '''cowfish''', '''kingfish''', and '''redfin ocean pan''' are large, colorful, deep-bodied [[Pelagic zone|pelagic]] [[lampriform]] [[Fish|fishes]] comprising the genus '''''Lampris''''', of the small [[Family (biology)|family]] '''Lampridae''' (also spelled '''Lamprididae'''). 

== Species ==
Two living species were traditionally recognized, but a [[Taxonomy (biology)|taxonomic]] review in 2018 suggests the idea of splitting ''L. guttatus'' into several species, each with a more restricted geographic range, bringing the total to six. The six species of ''Lampris'' have mostly non-overlapping geographical ranges, and can be recognized based on body shape and coloration pattern. 

*Southern Spotted Opah (''[[Lampris australensis]]):'' Found in the southern hemisphere, primarily in the [[Pacific Ocean|Pacific]] and [[Indian Ocean|Indian]] oceans.<ref name="Underkoffler20182">{{cite journal |author1=Karen E. Underkoffler |author2=Meagan A. Luers |author3=John R. Hyde |author4=Matthew T. Craig |year=2018 |title=A Taxonomic Review of Lampris guttatus (Brünnich 1788) (Lampridiformes; Lampridae) with Descriptions of Three New Species |journal=Zootaxa |volume=4413 |issue=3 |pages=551–565 |doi=10.11646/zootaxa.4413.3.9 |pmid=29690102}}</ref>

*North Atlantic Opah (''[[Lampris guttatus]]):'' Potentially located in the Northeastern Atlantic, including the Mediterranean [[Mediterranean Sea|Sea]].<ref name="Underkoffler20182" />

*Southern Opah (''[[Lampris immaculatus]]):'' Geographical range extends from 34° S to the [[Antarctic Convergence|Antarctic Polar Front]]. 

*Smalleye Pacific Opah (''Lampris incognitus):'' Found in eastern and central North [[Pacific Ocean]].<ref name="Underkoffler20183">{{cite journal |author1=Karen E. Underkoffler |author2=Meagan A. Luers |author3=John R. Hyde |author4=Matthew T. Craig |year=2018 |title=A Taxonomic Review of Lampris guttatus (Brünnich 1788) (Lampridiformes; Lampridae) with Descriptions of Three New Species |journal=Zootaxa |volume=4413 |issue=3 |pages=551–565 |doi=10.11646/zootaxa.4413.3.9 |pmid=29690102}}</ref>

*East Atlantic Opah ''(Lampris lauta):'' Found in Eastern [[Atlantic Ocean]], including the [[Mediterranean]], [[Azores]] and [[Canary Islands]].<ref name="Underkoffler20184">{{cite journal |author1=Karen E. Underkoffler |author2=Meagan A. Luers |author3=John R. Hyde |author4=Matthew T. Craig |year=2018 |title=A Taxonomic Review of Lampris guttatus (Brünnich 1788) (Lampridiformes; Lampridae) with Descriptions of Three New Species |journal=Zootaxa |volume=4413 |issue=3 |pages=551–565 |doi=10.11646/zootaxa.4413.3.9 |pmid=29690102}}</ref>

*Bigeye Pacific Opah (''Lampris megalopsis)'': Found in the [[Gulf of Mexico]], [[Indian Ocean]], the western [[Pacific Ocean]] and [[Chile]].<ref name="Underkoffler20185">{{cite journal |author1=Karen E. Underkoffler |author2=Meagan A. Luers |author3=John R. Hyde |author4=Matthew T. Craig |year=2018 |title=A Taxonomic Review of Lampris guttatus (Brünnich 1788) (Lampridiformes; Lampridae) with Descriptions of Three New Species |journal=Zootaxa |volume=4413 |issue=3 |pages=551–565 |doi=10.11646/zootaxa.4413.3.9 |pmid=29690102}}</ref>

===Extinct species===
* † ''[[Lampris zatima]]'', also known as ''Diatomœca zatima'', is a very small, [[extinct]] species from the late [[Miocene]] of what is now [[Southern California]] known primarily from fragments, and occasional headless specimens.<ref>David, Lore Rose. 10 January 1943. <u>Miocene Fishes of Southern California</u> The Society</ref>
* † ''[[Megalampris keyesi]]'' is an extinct species estimated to be about {{Convert|4|m|abbr=on}} in length. Fossil remains date back to the late [[Oligocene]] of what is now [[New Zealand]], and it is the first fossil lampridiform found in the Southern Hemisphere.<ref name="JVP">Gottfried, Michael D., Fordyce, R. Ewan, Rust, Seabourne. ''Journal of Vertebrate Paleontology''. [http://www.bioone.org/perlserv/?request=get-abstract&doi=10.1671%2F0272-4634(2006)26%5B544%3AMKAGMT%5D2.0.CO%3B2 "''Megalampris keyesi'', A Giant Moonfish (Teleostei, Lampridiformes), from the Late Oligocene of New Zealand"]. pp. 544–551.</ref>

==Description==
Opahs are deeply keeled, laterally compressed, discoid fish with conspicuous coloration: the body is a deep red-orange grading to rosy on the belly, with white spots covering the flanks. Both the median and paired fins are a bright [[vermilion]]. The large eyes stand out as well, ringed with golden yellow. The body is covered in minute [[Cycloid scale|cycloid scales]] and its silvery, [[Iridescence|iridescent]] [[guanine]] coating is easily abraded. The snout of the opah is pointed as the [[lateral line]] (the sensory system in fish) forms a high arch over the pectoral fins before sweeping down to the [[caudal peduncle]]. The ''Lampris'' species vary in size. For instance, the larger ''Lampris'' species, ''[[Lampris guttatus]]'', has a small, terminal, and [[Tooth|toothless]] mouth and can reach a total length of {{Convert|2|m|ft|abbr=on}} and a weight of {{Convert|86|kg|lb|abbr=on}}, but has been reported up to {{Convert|270|kg|lb|abbr=on}}, while the lesser-known ''[[Lampris immaculatus]]'' reaches a recorded total length of just {{Convert|1.1|m|ft|abbr=on}}.
[[File:Moonfish (Opah).jpg|thumb|Ventral view of an opah]]
Opahs closely resemble the shape of the unrelated [[Stromateidae|butterfish]] (family Stromateidae). Both have falcated (curved) [[Pectoral fin|pectoral fins]] and forked, emarginated (notched) [[Caudal fin|caudal fins]]. Aside from being significantly larger than butterfish, opahs have enlarged, falcated [[Pelvic fin|pelvic fins]] with about 14 to 17 [[Fish fin#Ray-fins|rays]], which distinguish them from superficially similar [[Carangidae|carangids]]—positioned thoracically; adult butterfish lack pelvic fins. The pectorals of opahs are also inserted horizontally rather than vertically. The anterior portion of an opah's single [[dorsal fin]] (with about 50–55 rays) is greatly elongated, also in a falcated profile similar to the pelvic fins. The [[anal fin]] (around 34 to 41 rays) is about as high and as long as the shorter portion of the [[dorsal fin]], and both fins have corresponding grooves into which they can be depressed.

The [[genome]] of ''Lampris megalopsis'' was analyzed in 2022.<ref>{{Cite journal |last1=Bo |first1=Jing |last2=Lv |first2=Wen-Qi |last3=Sun |first3=Ning |last4=Wang |first4=Cheng |last5=Wang |first5=Kun |last6=Liu |first6=Pan |last7=Feng |first7=Chen-Guang |last8=He |first8=Shun-Ping |last9=Yang |first9=Lian-Dong |date=2022-01-18 |title=Opah (Lampris megalopsis) genome sheds light on the evolution of aquatic endothermy |journal=Zoological Research |language=en |volume=43 |issue=1 |pages=26–29 |doi=10.24272/j.issn.2095-8137.2021.183 |issn=2095-8137 |pmc=8743259 |pmid=34766478}}</ref>

===Endothermy===
[[File:Lampris guttatus X-ray.jpg|thumb|Skeleton]]
Opah fishes use two methods for [[thermogenesis]]: pectoral muscle metabolism and specialized tissues in their brain. The opah is the only fish known to exhibit whole body [[endothermy]] where all the internal organs are kept at a higher temperature than the surrounding water.<ref name="Wegner2015">{{Cite journal |last1=Wegner |first1=Nicholas C. |last2=Snodgrass |first2=Owyn E. |last3=Dewar |first3=Heidi |last4=Hyde |first4=John R. |date=2015-05-15 |title=Whole-body endothermy in a mesopelagic fish, the opah, Lampris guttatus |url=https://www.science.org/doi/10.1126/science.aaa8902 |journal=Science |volume=348 |issue=6236 |pages=786–789 |doi=10.1126/science.aaa8902 |issn=0036-8075 |pmid=25977549 |bibcode=2015Sci...348..786W |accessdate=2021-02-18|url-access=subscription }}</ref> This feature allows opahs to maintain an active lifestyle in the cold waters they inhabit.<ref name="SWFSC">[https://swfsc.noaa.gov/news.aspx?ParentMenuId=39&id=20466 "Warm Blood Makes Opah an Agile Predator"]. Fisheries Resources Division of the Southwest Fisheries Science Center of the [[National Oceanic and Atmospheric Administration]]. 12 May 2015. Retrieved 15 May 2015. "New research by NOAA Fisheries has revealed the opah, or moonfish, as the first fully warm-blooded fish that circulates heated blood throughout its body..."</ref> Unlike birds and mammals, the opah is not a [[homeotherm]] despite being an endotherm: while its body temperature is raised above the surrounding water temperature, it still varies with the external temperature and is not held constant.<ref name=Runcie2009>{{Cite journal|  pmc=2726851|  doi = 10.1242/jeb.022814| issn = 0022-0949 | eissn=1477-9145| volume = 212| issue = 4| pages = 461–470| last1 = Runcie| first1 = Rosa M.| last2 = Dewar| first2 = Heidi| last3 = Hawn| first3 = Donald R.| last4 = Frank| first4 = Lawrence R.| last5 = Dickson| first5 = Kathryn A.| title = Evidence for cranial endothermy in the opah (Lampris guttatus)| journal = Journal of Experimental Biology| accessdate = 2021-02-18| date = 2009-02-15| url = https://jeb.biologists.org/content/212/4/461| pmid = 19181893| doi-access = free| bibcode = 2009JExpB.212..461R}}</ref> In addition to whole body endothermy, the opah also exhibits [[Endotherm#Regional endothermy|regional endothermy]] by raising the temperature of its brain and eyes above that of the rest of the body.<ref name=Runcie2009/> Regional endothermy also arose by [[convergent evolution]] in [[tuna]], [[Lamnidae|lamnid sharks]] and [[billfish]]es where the swimming muscles and cranial organs are maintained at an elevated temperature compared with the surrounding water.

The large muscles powering the [[Fish fin#Types of fins|pectoral fins]] generate most of the heat in the opah. In addition to the heat they generate while moving, these muscles have special regions that can generate additional heat without contracting.<ref name=Legendre2020>{{Cite journal| doi = 10.1098/rstb.2019.0136|pmc=7017440| volume = 375| issue = 1793| pages = 20190136| last1 = Legendre| first1 = Lucas J.| last2 = Davesne| first2 = Donald| title = The evolution of mechanisms involved in vertebrate endothermy| journal = Philosophical Transactions of the Royal Society B: Biological Sciences| date = 2020-03-02| doi-access = free|pmid=31928191 }}</ref> The opah has a thick layer of fat that insulates its internal organs and cranium from the surrounding water. However, fat alone is insufficient to retain heat within a fish's body. The [[gill]]s are the main point of heat loss in fishes as this is where blood from the entire body must continuously be brought in close contact with the surrounding water. Opahs prevent heat loss through their gills using a special structure in the gill blood vessels called the [[rete mirabile]]. The rete mirabile is a dense network of blood vessels where the warm blood  flowing from the heart to the gills transfers its heat to the cold blood returning from the gills. Hence, the rete mirabile prevents warm blood from coming in contact with the cold water (and losing its heat) and also ensures that the blood returning to the internal organs is warmed up to body temperature. Within the rete, the warm and cold blood flow past each other in opposite directions through thin vessels to maximize the heat transferred. This mechanism is called a [[counter-current heat exchange]]r.

In addition to the rete mirabile in its gills, the opah also has a rete in the blood supply to its brain and eyes. This helps to trap heat in the cranium and further raise its temperature above the rest of the body. While the rete mirabile in the gills is unique to the opah,<ref name="Wegner2015" /> the cranial rete mirabile has also evolved independently in other fishes. Unlike in [[billfish]] which have a specialized non-contractile tissue that functions as a brain heater, the opah cranium is heated by the contractions of the large eye muscles.<ref name=Runcie2009/>

==Behavior==
[[File:Opah 6.jpg|thumb|''Lampris guttatus'']]
Much research explores the endothermic attributes of the Opah but knowledge is limited to the specific aspects of the ''Lampris'' genus, and live specimens are rarely observed.<ref>{{Cite journal |last1=Albano |first1=Marco |last2=D'Iglio |first2=Claudio |last3=Spanò |first3=Nunziacarla |last4=Manuel de Oliveira Fernandes |first4=Jorge |last5=Savoca |first5=Serena |last6=Capillo |first6=Gioele |date=2022 |title=Distribution of the Order Lampriformes in the Mediterranean Sea with Notes on Their Biology, Morphology, and Taxonomy |journal=Biology |volume=11 |issue=1543 |pages=33 |doi=10.3390/biology11101534 |doi-access=free |pmid=36290437 |pmc=9598601 }}</ref> They are presumed to live out their entire lives in the open ocean, at [[mesopelagic]] depths of {{Convert|50 to 500|m|abbr=on}} with possible forays into the [[Bathyal zone|bathypelagic]] zone. They are apparently solitary, but are known to [[Fish school|school]] with [[tuna]] and other [[Scombridae|scombrids]]. The fish propel themselves by a lift-based [[Labriform locomotion|labriform]] mode of swimming, that is, by flapping their pectoral fins. This, together with their forked caudal fins and depressible median fins, indicates they swim at constantly high speeds like tuna.

The opah can be found worldwide in temperate and tropical oceans.<ref name=":0">{{Cite journal |last1=Francour |first1=Patrice |last2=Cottalorda |first2=Jean-Michael |last3=Aubert |first3=Maurice |last4=Bava |first4=Simone |last5=Colombey |first5=Marine |last6=Gilles |first6=Pierre |last7=Hichem |first7=Kara |last8=Lelong |first8=Patrick |last9=Mangialago |first9=Luisa |last10=Miniconi |first10=Roger |last11=Quignard |first11=Jean-Pierre |date=2010 |title=RECENT OCCURRENCES OF OPAH, LAMPRIS GUTTATUS (ACTINOPTERYGII, LAMPRIFORMES, LAMPRIDAE), IN THE WESTERN MEDITERRANEAN SEA |url=https://www.proquest.com/docview/746441016 |journal=Szczecin: West Pomeranian University of Technology |volume=40 |issue=1 |pages=91–98 |id={{ProQuest|746441016}} |via=ProQuest}}</ref> However, their migration is determined by season and temperature.<ref name=":0" /> In [[Diel vertical migration|Diel Vertical Migration]] opah fishes do not pass {{Convert|50|m|sp=us}} from the surface, to avoid predation, and they prefer to remain in ocean waters above {{Convert|7|C}}.<ref name=":1">{{Cite journal |last1=Polovina |first1=Jeffrey J. |last2=Hawn |first2=Donald |last3=Abecassis |first3=Melanie |date=2008-01-01 |title=Vertical movement and habitat of opah (Lampris guttatus) in the central North Pacific recorded with pop-up archival tags |url=https://link.springer.com/article/10.1007/s00227-007-0801-2 |journal=Marine Biology |language=en |volume=153 |issue=3 |pages=257–267 |doi=10.1007/s00227-007-0801-2 |bibcode=2008MarBi.153..257P |issn=1432-1793|url-access=subscription }}</ref> For instance, in the North Pacific, during the day, opah fish can be found in the {{Convert|100 to 400|m|sp=us|adj=on}} range that is between {{Convert|8 and 22|C}}; and at night, the fish are restricted to the {{Convert|50 to 100|m|sp=us|adj=on}} range; they rarely surpass a depth of 400 meters.<ref name=":1" />

''Lampris guttatus'' are able to maintain their eyes and brain at {{Convert|2|C-change}} warmer than their bodies, a phenomenon called cranial endothermy and one they share with sharks in the family [[Lamnidae]], [[Billfish|billfishes]], and some tunas. This may allow their eyes and brains to continue functioning during deep dives into water below {{Convert|4|C}}.

Large pelagic sharks, such as [[Great white shark|great white sharks]] and [[Mako shark|mako sharks]], are the primary predators of the Opah as shown from [[Pop-up satellite archival tag|archival transmitting tagging operations]]. The opah fish eats a lot of food, typically, smaller fishes, invertebrates like [[squid]] and euphausiids ([[krill]]) – that make up the bulk of the opah diet – and large pelagic organisms. Opah fish also carry many parasites such as the [[Tetraphyllidea|tetraphyllidean]] [[tapeworm]], which has been found in ''L. guttatus'', which may be an [[Intermediate host|intermediate]] or [[paratenic]] host.

The [[Plankton|planktonic]] opah larvae initially resemble those of [[ribbonfishes]] (Trachipteridae), but are distinguished by the lack of dorsal and pelvic fin ornamentation. The slender hatchlings later undergo a marked and rapid transformation to a deep-bodied form; this transformation is complete by {{Convert|10.6|mm|in|abbr=on}} standard length in ''L. guttatus''.

==References==
{{Reflist|refs=
<ref name=sep2002>{{cite journal |last=Sepkoski |first=Jack |title=A compendium of fossil marine animal genera |journal=Bulletins of American Paleontology |volume=364 |page=560 |date=2002 |url=http://strata.ummp.lsa.umich.edu/jack/showgenera.php?taxon=611&rank=class |access-date=8 January 2008 |url-status=dead |archive-url=https://web.archive.org/web/20090220223520/http://strata.ummp.lsa.umich.edu/jack/showgenera.php?taxon=611&rank=class |archive-date=20 February 2009 }}</ref>
}}

{{Taxonbar|from1=Q16607623|from2=Q220801}}
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[[Category:Lampridae]]
[[Category:Extant Miocene first appearances]]