Moray eels, or Muraenidae (), are a

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

of eels whose members are found worldwide. There are approximately 200 species in 15 genera which are almost exclusively marine, but several species are regularly seen in

brackish water Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuary ...

, and a few are found in

fresh water Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salt (chemistry), salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include ...

. The English name, ''moray'', dates back to the early 17th century, and is believed to be a derivative from Portuguese , which itself derives from

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

, in turn from Greek , ; these are the Latin and Greek names of the Mediterranean moray.

Anatomy

The dorsal fin extends from just behind the head along the back and joins seamlessly with the caudal and

anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

s. Most species lack pectoral and

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral (belly) surface of fish, and are the lower of the only two sets of paired fins (the other being the laterally positioned pectoral fins). The pelvic fins are homologous to the hi ...

s, adding to their serpentine appearance. Their eyes are rather small; morays rely mostly on their highly developed sense of smell, lying in wait to

ambush An ambush is a surprise attack carried out by people lying in wait in a concealed position. The concealed position itself or the concealed person(s) may also be called an "". Ambushes as a basic military tactics, fighting tactic of soldi ...

prey. The body is generally patterned. In some species, the inside of the mouth is also patterned. Their jaws are wide, framing a protruding snout. Most possess large teeth used to tear flesh or grasp slippery prey. A relatively small number of species, for example the snowflake moray (''Echidna nebulosa'') and zebra moray (''Gymnomuraena zebra''), primarily feed on crustaceans and other hard-shelled animals, and they have blunt, molar-like teeth suitable for crushing. Morays secrete a protective mucus over their smooth, scaleless skin, which in some species contains a toxin. They have much thicker skin and high densities of

goblet cell Goblet cells are simple columnar epithelial cells that secrete gel-forming mucins, like mucin 2 in the lower gastrointestinal tract, and mucin 5AC in the respiratory tract. The goblet cells mainly use the merocrine method of secretion, secre ...

s in the

epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and Subcutaneous tissue, hypodermis. The epidermal layer provides a barrier to infection from environmental pathogens and regulates the ...

that allows mucus to be produced at a higher rate than in other eel species. This allows sand granules to adhere to the sides of their burrows in sand-dwelling morays, thus making the walls of the burrow more permanent due to the

glycosylation Glycosylation is the reaction in which a carbohydrate (or ' glycan'), i.e. a glycosyl donor, is attached to a hydroxyl or other functional group of another molecule (a glycosyl acceptor) in order to form a glycoconjugate. In biology (but not ...

of mucins in mucus. Placement of their small, circular

gill A gill () is a respiration organ, respiratory organ that many aquatic ecosystem, aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow r ...

s on their flanks, far behind the mouth, requires the moray to maintain a gape / gulping motion to facilitate respiration.

Jaw

The pharyngeal jaws of morays are located farther back in the head and closely resemble the oral jaws (complete with tiny "teeth"). When feeding, morays launch these jaws into the mouth cavity, where they grasp prey and transport it into the throat. Moray eels are the only known animals that use pharyngeal jaws to actively capture and restrain prey in this way. Pharyngeal jaws of moray eels

In addition to the presence of pharyngeal jaws, morays' mouth openings extend far back into the head, compared to fish which feed using suction. In the action of lunging at prey and biting down, water flows out the posterior side of the mouth opening, reducing waves in front of the eel which would otherwise displace prey. Thus, aggressive predation is still possible even with reduced bite times. In at least one species, the California moray (''Gymnothorax mordax''), teeth in the roof of the mouth are able to fold down as prey slides backwards, thus preventing the teeth from breaking and maintaining a hold on prey as it is transported to the throat. Differing shapes of the jaw and teeth reflect the respective diets of different species of moray eel. Evolving separately multiple times within the Muraenidae family, short, rounded jaws and molar-like teeth allow durophagous eels (e.g. zebra moray and genus '' Echidna'') to consume crustaceans, while other piscivorous genera of Muraenidae have pointed jaws and longer teeth. These morphological patterns carry over to teeth positioned on the pharyngeal jaw.

Feeding behavior

Morays are opportunistic, carnivorous predators, and feed primarily on smaller fish, crabs and octopuses. A spotted moray eel has been observed eating a red lionfish without harm. Groupers,

barracuda A barracuda is a large, predatory, ray-finned, saltwater fish of the genus ''Sphyraena'', the only genus in the family Sphyraenidae, which was named by Constantine Samuel Rafinesque in 1815. It is found in tropical and subtropical oceans worldw ...

s and

sea snake Sea snakes, or coral reef snakes, are Elapidae, elapid snakes that inhabit Marine (ocean), marine environments for most or all of their lives. They belong to two subfamilies, Hydrophiinae and Sea krait, Laticaudinae. Hydrophiinae also includes ...

s are among their few known

predator Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

s, making many morays (especially the larger species) apex predators in their ecosystems.

Cooperative hunting

Reef-associated roving coral groupers (''Plectropomus pessuliferus'') have been observed recruiting giant morays to help them hunt. The invitation to hunt is initiated by head-shaking. This style of hunting may allow morays to flush prey from niches not accessible to groupers.

Habitat

The moray eel can be found in both fresh and saltwater habitats. The vast majority of species are strictly marine, never entering freshwater. Of the few species known to live in freshwater, the most well-known is '' Gymnothorax polyuranodon''. Spotted moray eel

Within the marine realm, morays are found in shallow water nearshore areas, continental slopes, continental shelves, deep benthic habitats, and mesopelagic zones of the ocean, and in both

tropical The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...

and

temperate In geography, the temperate climates of Earth occur in the middle latitudes (approximately 23.5° to 66.5° N/S of the Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ran ...

environments. Most species are found in tropical or subtropical environments, with only a few species ( yellow moray) found in temperate ocean environments. Although the moray eel can occupy both tropical oceans and temperate oceans, as well as both freshwater and saltwater, the majority of moray eels occupy warm saltwater environments, which contain

reef A reef is a ridge or shoal of rock, coral, or similar relatively stable material lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic component, abiotic (non-living) processes such as deposition (geol ...

s. Within the tropical oceans and temperate oceans, the moray eel occupies shelters, such as dead patch reefs and coral rubble rocks, and less frequently occupies live coral reefs.

Taxonomy

Genera

There are about 202 known species of moray eels, in 16 genera. These genera are in two sub-families, Muraeninae and Uropterygiinae, which are distinguished by the location of their fins. In Muraeninae the dorsal fin is near the gill slits and runs down the back of the eel, and the anal fin is behind the anus. In Uropterygiinae, both the dorsal and the anal fin are at the end of the tail. Though this distinction can be seen between the two sub-families, there are still many varieties of genera within Muraeninae and Uropterygiinae. Of these, the genus '' Gymnothorax'' is by far the broadest, including more than half of the total number of species. The family Muraenidae comprises the following subfamiles and genera: * Subfamily Muraeninae Rafinesque, 1815 ** '' Diaphenchelys'' McCosker & Randall, 2007 ** '' Echidna'' Forster, 1788 **'' Enchelycore'' Kaup, 1856 ** '' Enchelynassa'' Kaup, 1855 ** '' Gymnomuraena'' Lacepède, 1803 ** '' Gymnothorax'' Bloch, 1795 ** '' Monopenchelys'' Böhlke & McCosker, 1982 ** '' Muraena''

Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...

, 1758 ** '' Pseudechidna'' Bleeker, 1863 ** '' Rhinomuraena'' Garman, 1888 ** '' Strophidon'' McClelland, 1844 * Subfamily Uropterygiinae Fowler 1925 ** '' Anarchias'' D. S. Jordan & Starks, 1906 ** '' Channomuraena'' Richardson, 1848 ** '' Cirrimaxilla'' H.-M. Chen & K.-T .Shao, 1995 ** '' Scuticaria'' D. S. Jordan & Snyder, 1901 ** '' Uropterygius'' Rüppell, 1838 File:TakamayuUBf.jpg, '' Anarchias seychellensis'' File:FMIB 47184 Gymomuraena vittata, from Cuba.jpeg, '' Channomuraena vittata'' File:Echidna nebulosa Réunion.jpg, Snowflake moray (''Echidna nebulosa'') File:Echida polyzona.jpg, Barred moray (Echidna polyzona) File:FMIB 42381 Enchelynassa vinolentus (Jordan & Evermann).jpeg, Viper moray (''Enchelynassa canina'') File:Gymnomuraena zebra by NPS.jpg, Zebra moray (''Gymnomuraena zebra'') File:Laced Moray.jpg, Laced moray (''Gymnothorax favagineus'') File:Gymnothorax rueppelliae Réunion.JPG, '' Gymnothorax rueppelliae'' File:Monopenchelys acuta - pone.0010676.g012.png, '' Monopenchelys acuta'' File:Muraena helena swimming v2.jpg, Mediterranean moray (''Muraena helena'') File:Pseudechidna brummer).JPG, White ribbon eel (''Pseudechidna brummeri'') File:Ribbon Moray (Rhinomuraena quaesita) (6052858389).jpg, Ribbon eel (R''hinomuraena quaesita'') File:Scuticaria tigrina.jpg, '' Scuticaria tigrina'' File:Strophidon sathete.jpg, Slender giant moray (''Strophidon sathete'') File:Uropterygius xanthopterus - 2.JPG, '' Uropterygius xanthopterus'' File:Kidako moray.JPG, Kidako moray (''Gymnothorax kidako'')

Evolution

The moray eel's elongation is due to an increase in the number of

vertebra Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spina ...

e, rather than a lengthening of each individual vertebra or a substantial decrease in body depth. Vertebrae have been added asynchronously between the pre-tail ("precaudal") and tail ("caudal") regions, unlike other groups of eels such as Ophicthids and Congrids.

Relationship with humans

Aquarium trade

Several moray species are popular among aquarium hobbyists for their hardiness, flexible diets, and disease resistance. The most commonly traded species are the snowflake, zebra and goldentail moray ('' Gymnothorax miliaris''). Several other species are occasionally seen, but are more difficult to obtain and can command a steep price on the market.

Food poisoning

Moray eels, particularly the giant moray (''Gymnothorax javanicus'') and yellow-edged moray ('' G. flavimarginatus''), are known to accumulate high levels of ciguatoxins, unlike other reef fish; if consumed by humans, ciguatera fish poisoning may result. Ciguatera is characterised by neurological, gastrointestinal, and cardiovascular problems that may persist for days after eating tainted fish. In morays, the toxins are most concentrated in the liver. In an especially remarkable instance, 57 people in the

Northern Mariana Islands The Northern Mariana Islands, officially the Commonwealth of the Northern Mariana Islands (CNMI), is an Territories of the United States, unincorporated territory and Commonwealth (U.S. insular area), commonwealth of the United States consistin ...

were poisoned after eating just the head and half of a cooked yellow-edged moray. Thus, morays are not recommended for human consumption.

References

External links

Moray Eels Grab Prey With ''Alien'' Jaws
* Smith, J.L.B. 1962
The moray eels of the Western Indian Ocean and the Red Sea. Ichthyological Bulletin; No. 23
Department of Ichthyology, Rhodes University, Grahamstown, South Africa. {{DEFAULTSORT:Moray Eel * Articles containing video clips Extant Miocene first appearances Taxa named by Constantine Samuel Rafinesque