View source for Remora

{{Short description|Family (Echeneidae) of ray-finned fish}}
{{About|the remora family|the genus|Remora (genus)|the rescue vehicle|Australian Submarine Rescue Vehicle Remora}}
{{Automatic taxobox
| name = Remora
| fossil_range = {{Geological range|33.9 |0|Early [[Oligocene]] – Recent<ref>Friedman, Matt, et al. "An early fossil remora (Echeneoidea) reveals the evolutionary assembly of the adhesion disc." Proc. R. Soc. B 280.1766 (2013): 20131200.</ref>}}
| image = Remora remora.jpg
| image_caption = [[Common remora]], ''Remora remora''
| taxon = Echeneidae
| authority = [[Constantine Samuel Rafinesque|Rafinesque]], 1810<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 | 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_ref = <ref name = CofF>{{Cof family|family=Echeneidae|access-date=16 November 2019}}</ref>
| subdivision = * ''[[Echeneis (fish)|Echeneis]]'' <small>[[Carolus Linnaeus|Linnaeus]], 1758</small>
* ''[[Slender suckerfish|Phtheirichthys]]'' <small>[[Theodore Nicholas Gill|Gill]], 1862</small>
* ''[[Remora (genus)|Remora]]'' <small>Gill, 1862</small>
| synonyms = Echeneididae
}}

The '''remora''' ({{IPAc-en|ˈ|r|ɛ|m|ə|r|ə|}}),  sometimes called '''suckerfish''' or '''sharksucker''', is any of a family ('''Echeneidae''') of [[Actinopterygii|ray-finned fish]] in the order [[Carangiformes]].<ref name = Nelson5>{{cite book |title=Fishes of the World |edition=5th |author1=J. S. Nelson |author2=T. C. Grande |author3=M. V. H. Wilson |year=2016 |page=384 |publisher=Wiley |isbn=978-1-118-34233-6 |url=https://sites.google.com/site/fotw5th/ |access-date=2019-11-16 |archive-date=2019-04-08 |archive-url=https://web.archive.org/web/20190408194051/https://sites.google.com/site/fotw5th/ }}</ref> Depending on species, they grow to {{cvt|30–110|cm}} long. Their distinctive first [[dorsal fin]]s take the form of a modified oval, sucker-like organ with slat-like structures that open and close to create suction and take a firm hold against the skin of larger marine animals.<ref>{{cite web|url=http://www.nhm.ac.uk/about-us/news/2013/january/sharksucker-fishs-strange-disc-explained118235.html |title=Sharksucker fish's strange disc explained |publisher=Natural History Museum |date=28 January 2013 |access-date=5 February 2013|archive-date=1 February 2013|archive-url=https://web.archive.org/web/20130201194123/http://www.nhm.ac.uk/about-us/news/2013/january/sharksucker-fishs-strange-disc-explained118235.html}}</ref> The disk is made up of stout, flexible membranes that can be raised and lowered to generate suction.<ref>{{Cite book|title=The Illustrated World Encyclopedia of Marine Fish & Sea Creatures|last=Beer, Amy-Jane. Derek Hall.|publisher=Lorenz Books | year=2012|isbn=978-0-7548-2290-5|location=Leicestershire|page=235}}</ref> By sliding backward, the remora can increase the suction, or it can release itself by swimming forward. Remoras sometimes attach to small boats, and have been observed attaching to divers as well. They swim well on their own, with a sinuous, or curved, motion.

== Evolution ==
[[File:Echeneis glaronensis.JPG|left|thumb|Fossil specimen of ''[[Opisthomyzon]]'']]
Remoras are thought to be most closely related to the [[cobia]] and the [[Coryphaena|dolphinfish]], two other elongate members of the suborder [[Carangoidei]]. Together, they are thought to comprise the superfamily [[Echeneoidea]]. In some treatments, the Echeneoidea is instead restricted to just the remoras and ''Opisthomyzon''.<ref name=":0">{{Cite journal |last1=Friedman |first1=Matt |last2=Johanson |first2=Zerina |last3=Harrington |first3=Richard C. |last4=Near |first4=Thomas J. |last5=Graham |first5=Mark R. |date=2013-09-07 |title=An early fossil remora (Echeneoidea) reveals the evolutionary assembly of the adhesion disc |journal=Proceedings of the Royal Society B: Biological Sciences |volume=280 |issue=1766 |article-number=20131200 |doi=10.1098/rspb.2013.1200 |pmc=3730593 |pmid=23864599}}</ref>

The earliest remora-like fish in the fossil record is ''[[Opisthomyzon]]'' from the [[Early Oligocene]] of Switzerland. This taxon appears to be closely related to modern remoras and shares several of the iconic traits present in modern remoras, including an [[Sucker (zoology)|adhesive disk]] (although located posterior to the head rather than directly on it). However, due to its distinctive morphological features from modern remoras, it is placed in its own family, Opisthomyzonidae.<ref name=":0" />

Also known from the Early Oligocene is the earliest true remora in the fossil record, ''[[Echeneis carpathica]]'' from Poland. From later in the Oligocene, the extinct genus ''[[Oligoremora]]'' is known from the [[Chattian]] of Germany.<ref>{{Cite journal |last1=Micklich |first1=Norbert |last2=Gregorová |first2=Růžena |last3=Bannikov |first3=Alexandre F. |last4=Baciu |first4=Dorin-Sorin |last5=Grădianu |first5=Ionuţ |last6=Carnevale |first6=Giorgio |date=2016-09-01 |title=Oligoremora rhenana n. g. n. sp., a new echeneid fish (Percomorpha, Echeneoidei) from the Oligocene of the Grube Unterfeld ("Frauenweiler") clay pit |url=https://link.springer.com/article/10.1007/s12542-016-0303-y |journal=PalZ |language=en |volume=90 |issue=3 |pages=561–592 |doi=10.1007/s12542-016-0303-y |issn=1867-6812|url-access=subscription }}</ref>

== Characteristics ==
Remora front dorsal fins have evolved to enable them to adhere by suction to smooth surfaces, and they spend most of their lives clinging to a [[Host (biology)|host animal]] such as a [[whale]], [[turtle]], [[shark]] or [[Batoidea|ray]]. It is probably a [[Mutualism (biology)|mutualistic]] arrangement as the remora can move around on the host, removing ectoparasites and loose flakes of skin, while benefiting from the protection provided by the host and the constant flow of water across its gills.<ref>{{cite news |title=How does the Remora develop its sucker? |author=Jackson, John |url=http://www.nhm.ac.uk/natureplus/blogs/science-news/2012/11/30/how-does-the-remora-develop-its-sucker?fromGateway=true |newspaper=National History Museum |date=30 November 2012 |access-date=2 January 2016}}</ref>  Although many believe that remoras feed on particulate matter from the host's meals, some posit alternative theories; they claim their diets to be [[Coprophagia|composed primarily of host feces]].<ref>{{cite journal|doi=10.1046/j.1095-8649.2003.00236.x|title=Echeneid-sirenian associations, with information on sharksucker diet|journal=Journal of Fish Biology|volume=63|issue=5|page=1176|year=2003|last1=Williams|first1=E. H.|last2=Mignucci-Giannoni|first2=A. A.|last3=Bunkley-Williams|first3=L.|last4=Bonde|first4=R. K.|last5=Self-Sullivan|first5=C.|last6=Preen|first6=A.|last7=Cockcroft|first7=V. G.|bibcode=2003JFBio..63.1176W |citeseerx=10.1.1.619.4020}}</ref> Further research is needed to validate the extent of this alternative feeding mechanism.

== Habitat ==
[[File:Echeneis naucrates Indonesia.jpg|thumb|right|upright|Some remoras, such as this ''[[Echeneis naucrates]]'', may attach themselves to scuba divers.]]
Remoras are [[Tropics|tropical]] open-ocean dwellers, but are occasionally found in [[Temperate climate|temperate]] or coastal waters if they have attached to large fish that have wandered into these areas. In the mid-[[Atlantic Ocean]], spawning usually takes place in June and July; in the [[Mediterranean Sea]], it occurs in August and September. The sucking disc begins to show when the young fish are about {{convert|1|cm|1|abbr=on}} long. When the remora reaches about {{convert|3|cm|abbr=on}}, the disc is fully formed and the remora can then attach to other animals. The remora's lower jaw projects beyond the upper, and the animal lacks a [[swim bladder]].<ref name=FishBase>{{FishBase family|family=Echeneididae|month=August|year=2019}}</ref>

Some remoras associate with specific host species. They are commonly found attached to sharks, [[manta ray]]s, whales, turtles, and [[dugong]]s, hence the common names "sharksucker" and "whalesucker".  Smaller remoras also fasten onto fish such as [[tuna]] and [[swordfish]], and some of the smallest remoras travel in the mouths or gills of large manta rays, [[ocean sunfish]], swordfish and [[sailfish]].

The relationship between a remora and its host is most often taken to be one of [[commensalism]], specifically [[Phoresis|phoresy]].

While some of the relationships are mutualistic, it is believed that dolphins with remoras attached do not benefit from the relationship. The attachment of the remora increases the dolphin's [[Drag (physics)|drag]], which increases the energy needed for swimming. The remora is also thought to irritate the skin of the dolphin.<ref>{{cite journal |last1=Weihs |first1=Daniel |last2=Fish |first2=Frank E. |last3=Nicastro |first3=Anthony J. |title=Mechanics of Remora Removal by Dolphin Spinning |journal=Marine Mammal Science |date=11 June 2007 |volume=23 |issue=3 |pages=707–714 |doi=10.1111/j.1748-7692.2007.00131.x|bibcode=2007MMamS..23..707W }}</ref>

== Physiology ==
Research into the [[physiology]] of the remora has been of significant benefit to the understanding of [[Ventilation (physiology)|ventilation]] costs in fish.

Remoras, like many other fishes, have  two different modes of ventilation. Ram ventilation<ref name="Willmer">{{Cite book|url=https://books.google.com/books?id=r9gvbjRFyRgC|title=Environmental Physiology of Animals|last1=Willmer|first1=Pat|last2=Stone|first2=Graham|last3=Johnston|first3=Ian|date=2009-03-12|publisher=John Wiley & Sons|isbn=978-1-4443-0922-5|language=en}}</ref> is the process in which at higher speeds, the remora uses the force of the water moving past it to create movement of fluid in the gills. At lower speeds, the remora will use a form of active ventilation,<ref name="Willmer" /> in which the fish actively moves fluid through its gills. In order to use active ventilation, a fish must actively use energy to move the fluid; however, determining this energy cost is normally complicated due to the fish's movement when using either method. As a result, the remora has proved invaluable in finding this cost difference (since they will stick to a shark or tube, and hence remain stationary despite the movement, or lack thereof, of water). Experimental data from studies on remora found that the associated cost for active ventilation created a 3.7–5.1% increased energy consumption in order to maintain the same quantity of fluid flow the fish obtained by using ram ventilation.<ref>{{Cite journal|last1=Steffensen|first1=J. F.|last2=Lomholt|first2=J. P.|date=1983-03-01|title=Energetic cost of active branchial ventilation in the sharksucker, ''Echeneis naucrates''|url=http://jeb.biologists.org/content/103/1/185|journal=Journal of Experimental Biology|language=en|volume=103|issue=1|pages=185–192|doi=10.1242/jeb.103.1.185 |issn=0022-0949|pmid=6854201|url-access=subscription}}</ref>

Other research into the remora's physiology came about as a result of studies across multiple taxa, or using the remora as an out-group for certain evolutionary studies. Concerning the latter case, remoras were used as an outgroup when investigating [[tetrodotoxin]] resistance in remoras, pufferfish, and related species, finding remoras (specifically ''[[Echeneis naucrates]]'') had a resistance of 6.1–5.5{{e|-8}}&nbsp;M.<ref>{{cite journal|doi=10.1007/BF00696163|title=Tetrodotoxin sensitivity of muscle action potentials in pufferfishes and related fishes|journal=Journal of Comparative Physiology|volume=89|pages=59–72|year=1974|last1=Kidokoro|first1=Yoshiaki|last2=Grinnell|first2=Alan D.|last3=Eaton|first3=Douglas C.|s2cid=33178106 }}</ref>

== Use for fishing ==
Some cultures use remoras to catch turtles. A cord or rope is fastened to the remora's tail, and when a turtle is sighted, the fish is released from the boat; it usually heads directly for the turtle and fastens itself to the turtle's shell, and then both remora and turtle are hauled in. Smaller turtles can be pulled completely into the boat by this method, while larger ones are hauled within harpooning range. This practice has been reported throughout the [[Indian Ocean]], especially from eastern Africa near [[Zanzibar]] and [[Mozambique]],<ref>{{Cite journal | author=Gudger, E. W. | year=1919 | title=On the Use of the Sucking-Fish for Catching Fish and Turtles: Studies in ''Echeneis'' or ''Remora'', II., Part 1. | journal=The American Naturalist | volume=53 | issue=627 | pages=289–311 | doi=10.1086/279716 | jstor=2455925 | url=https://zenodo.org/record/1431359 | doi-access=free }}</ref> and from northern Australia near [[Cape York Peninsula|Cape York]] and [[Torres Strait]].<ref>{{cite journal | author=Gudger, E. W. | year=1919 | title=On the Use of the Sucking-Fish for Catching Fish and Turtles: Studies in ''Echeneis'' or ''Remora'', II., Part 2 | journal=The American Naturalist | volume=53 | issue=628 | pages=446–467 | doi=10.1086/279724 | jstor=2456185 | url=https://zenodo.org/record/1431359 | doi-access=free }}</ref><ref>{{Cite book | url=http://www.gutenberg.org/ebooks/12525 | title=Narrative of the Voyage of H.M.S. Rattlesnake, Commanded By the Late Captain Owen Stanley, R.N., F.R.S. etc. During the Years 1846–1850 | last=MacGillivray | first=John | volume=2 | date=1852 | publisher=Lords Commissioners of the Admiralty | location=London}} (Dr. Gudger's accounts are more authoritative, but this source is noted as an early account that Gudger appears to have missed.)</ref>

Similar reports come from Japan and from the Americas. Some of the first records of the "fishing fish" in the Western literature come from the accounts of the second voyage of [[Christopher Columbus]]. However, [[Leo Wiener]] considers the Columbus accounts to be [[apocrypha]]l: what was taken for accounts of the Americas may have been, in fact, notes Columbus derived from accounts of the East Indies, his desired destination.<ref>{{cite journal | author=Wiener, Leo | author-link=Leo Wiener | year=1921 | title=Once more the sucking-fish | journal=The American Naturalist | volume=55 | issue=637 | pages=165–174 | doi=10.1086/279802 | jstor=2456418 | s2cid=85369826 | url=https://zenodo.org/record/1431361}}</ref>

== Mythology ==
{{See also|Echeneis}}
In ancient times, the remora was believed to stop a ship from sailing. In Latin, ''remora'' means "delay", while the genus name ''Echeneis'' comes from Greek ἔχειν, ''echein'' ("to hold") and ναῦς, ''naus'' ("a ship"). In a notable account by [[Pliny the Elder]], the remora is blamed for the defeat of [[Mark Antony]] at the [[Battle of Actium]] and, indirectly, for the death of [[Caligula]].<ref>{{cite book | author = Pliny the Elder | title = Natural History | chapter = Book 32, Chapter 1| author-link = Pliny the Elder }} (cited in {{cite journal | author = Gudger, E. W. | year = 1930 | title = Some old time figures of the shipholder, ''Echeneis'' or ''Remora'', holding the ship | journal = Isis | volume = 13 | issue = 2 | pages = 340–352 | doi = 10.1086/346461 | jstor=224651| s2cid = 143773548 }})</ref> A modern version of the story is given by [[Jorge Luis Borges]] in ''[[Book of Imaginary Beings]]'' (1957).

==Gallery==
<gallery mode="packed">
Remora SI.jpg
Remora Belize Reef.jpg|[[Live sharksucker]], ''Echeneis naucrates''
Remora remora 1.jpg|[[Common remora]], ''Remora remora''
Nurse shark with remoras.jpg|[[Nurse shark]] with remoras attending
</gallery>

==See also==
* [[List of fish families]]

== References ==
{{Reflist}}

== External links ==
{{Commons category|Echeneidae}}

{{Taxonbar|from=Q239771}}
{{Authority control}}

[[Category:Echeneidae| ]]
[[Category:Scavengers]]
[[Category:Taxa named by Constantine Samuel Rafinesque]]