Remora

This article is about the remora family. For the genus, see Remora (genus). For the rescue vehicle, see Australian Submarine Rescue Vehicle Remora.

Remora
Spearfish remora, Remora brachyptera
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Perciformes
Suborder:	Percoidei
Superfamily:	Percoidea
Family:	Echeneidae Rafinesque, 1810
Genera
Echeneis Phtheirichthys Remora
Synonyms
Echeneididae

The remoras (pronounced /rəˈmɔːrə/ or /ˈrɛmərə/), 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.

Characteristics

Remoras have their front dorsal fins modified into large suckers with which they cling onto a host animal such as a whale, turtle, shark or ray. It is probably a commensal arrangement as the remora can move around on the host, removing ectoparasites and loose flakes of skin, and feeding on discarded food fragments and faeces, while benefiting from the protection provided by the host, the constant flow of water across its gills, and the effortless supply of food.

Habitat

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.

Some remoras, such as this Echeneis naucrates, may attach themselves to scuba divers.

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.

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 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.

Gallery

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  Remora shows its sucker-like organ

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  Nurse shark with remoras attending

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  Manta ray with remoras

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  Dugong with attached remora (Lamen Island, Epi, Vanuatu)

Timeline

See also

• List of fish families

External links

• Flickr: Photos tagged with "remora"

• National Aquarium Article About Remoras