Remoras, also called shark suckers, are a group of eight species in the mostly tropical and sub-tropical fish family Echeneidae. Remoras live primarily in the open ocean, and although they can swim on their own, they do not have a swim bladder so have trouble maneuvering long distances. Remoras can attach themselves to larger fish and marine animals and even boats using their first dorsal fin, which is modified into a characteristic flat sucking disk. Remoras are dependant on attaching to hosts in order keep water flowing across their gills, so that they get enough oxygen. Some remoras have a purely phoretic relationship with their hosts, that is, they interact with their host for the purpose of transport only, while other species will eat parasites from their host, thus providing a more mutually beneficial interaction. Most attach close to their hosts mouths and gill areas and eat the remains from their host’s meals. Some remoras will attach to many different species of fish, whales, sea turtles, rays, sharks, dugongs, and even boats. Others have much more specific host interactions, (for example the whalesucker, Remora australis, only attaches to cetaceans; the white suckerfish, Remorina albescens, rides in the mouth and gill chamber of manta rays.)
Humans have used remoras for fishing by attaching them to a line and throwing them into the sea, then pulling in the line and harvesting the fish to which the remora has attached.
Extensive information and nice pictures for the most common of the remoras, Echeneis naucrates, can be found at the Ichthyology at Florida Museum of Natural History web collections.
(Froese and Pauly 2010; Wikipedia 2012)
Evolution and Systematics
A sucker-like structure on top of the head of a remora allows it to attach to sharks by creating a partial vacuum.
"The remora is a relative of the perch which habitually attaches itself to the belly of a shark using a specialized, corrugated, suckerlike structure on top of its head; this in fact develops from its dorsal fin. The remora is thus carried like a hitchhiker as the shark swims through the sea." (Shuker 2001:163)
Learn more about this functional adaptation.
- Shuker, KPN. 2001. The Hidden Powers of Animals: Uncovering the Secrets of Nature. London: Marshall Editions Ltd. 240 p.
Molecular Biology and Genetics
Statistics of barcoding coverage
Specimens with Sequences:73
Specimens with Barcodes:73
Species With Barcodes:8
The remoras (//), sometimes called suckerfish, are a family (Echeneidae) of ray-finned fish in the order Perciformes. They grow to 30–90 cm (0.98–2.95 ft) long, and their distinctive first dorsal fins 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. By sliding backward, the remora can increase the suction, or it can release itself by swimming forward. Remoras sometimes attach to small boats. They swim well on their own, with a sinuous, or curved, motion.
Remoras are primarily tropical open-ocean dwellers, occasionally found in temperate or coastal waters if they have attached to large fish that have wandered into these areas. In the mid-Atlantic, spawning usually takes place in June and July; in the Mediterranean, it occurs in August and September. The sucking disc begins to show when the young fish are about 1 cm (0.4 in) long. When the remora reaches about 3 cm (1.2 in), 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.
Some remoras associate primarily with specific host species. They are commonly found attached to sharks, manta rays, whales, turtles, and dugongs (hence the common names "sharksucker" and "whalesucker"). Smaller remoras also fasten onto fish such as tuna and swordfish, and some small 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 phoresy. Though it was originally thought that the host to which it attaches for transport gains nothing from the relationship, research indicates that hosts also benefit, given that remoras feed on parasites (such as copepods) and clean sloughing epidermal tissue as well as ingesting scraps of food, feces, and small nekton and zooplankton. The remora benefits by using the host as transport and protection, and also feeds on materials dropped by the host. Controversy surrounds whether a remora's diet is primarily leftover fragments, or the feces of the host. In some species (Echeneis naucrates and E. neucratoides), consumption of host feces is strongly indicated in gut dissections.For other species, such as those found in a host's mouth, scavenging of leftovers is more likely. On rare and even more rarely filmed occasions, such as the 2010 episode of Shark Week known as "Shark City", remoras that associate with sharks may end up as their prey as was the case of a lemon shark devouring a remora that attempted to adhere to it.
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, and from northern Australia near Cape York and Torres Strait.
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 apocryphal: 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.
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 εχειν, echein ("to hold") and ναυς, 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. A modern version of the story is given by Jorge Luis Borges in Book of Imaginary Beings (1957).
Because of the shape of the jaws, appearance of the sucker, and coloration of the remora, it sometimes appears to be swimming upside down. This probably led to the older common name reversus, although this might also derive from the fact that the remora frequently attaches itself to the tops of manta rays or other fish, so that the remora is upside down while attached.
- Froese, Rainer, and Daniel Pauly, eds. (2013). "Echeneidae" in FishBase. April 2013 version.
- "Echeneidae". Integrated Taxonomic Information System. Retrieved 20 March 2006.
- "Sharksucker fish's strange disc explained". Natural History Museum. 28 January 2013. Retrieved 5 February 2013.
- Cressey, R.; Lachner, E. (1970). "The parasitic copepod diet and life history of diskfishes (Echeneidae).". Copeia (2): 310–318.
- Shark City
- E. W. Gudger (1919). "On the Use of the Sucking-Fish for Catching Fish and Turtles: Studies in Echeneis or Remora, II., Part 1.". The American Naturalist 53 (627): 289–311. doi:10.1086/279716. JSTOR 2455925.
- E. W. Gudger (1919). "On the Use of the Sucking-Fish for Catching Fish and Turtles: Studies in Echeneis or Remora, II., Part 2". The American Naturalist 53 (628): 446–467. doi:10.1086/279724. JSTOR 2456185.
- Leo Wiener (1921). "Once more the sucking-fish". The American Naturalist 55 (637): 165–174. doi:10.1086/279802. JSTOR 2456418.
- Pliny the Elder. "Book 32, Chapter 1". Natural History. (cited in E. W. Gudger (1930). "Some old time figures of the shipholder, Echeneis or Remora, holding the ship". Isis 13 (2): 340–352. doi:10.1086/346461. JSTOR 224651.)
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