Moray eel Temporal range: Early Eocene– Recent PreꞒ Ꞓ O S D C P T J K Pg N [1]
Whitemouth Moray eel in the Maldives
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Anguilliformes
Suborder:	Muraenoidei
Family:	Muraenidae Rafinesque, 1810
Subfamiles
Muraeninae Rafinesque, 1815 Uropterygiinae Fowler, 1925

Moray eels, or Muraenidae (/ˈmɒreɪ, məˈreɪ/), are a family of eels whose members are found worldwide. There are approximately 200 species in 16 genera which are almost exclusively marine, but several species are regularly seen in brackish water, and a few are found in fresh water.^[2]

The English name, moray, dates back to the early 17th century, and is believed to be a derivative from Portuguese moreia, which itself derives from Latin mūrēna, in turn from Greek μύραινα, muraina; these are the Latin and Greek names of the Mediterranean moray.^[3]

Anatomy

The dorsal fin extends from just behind the head along the back and joins seamlessly with the caudal and anal fins, with the exception of members of the subfamily Uropterygiinae, which have fins restricted to the tip of the tail. Most species lack pectoral and pelvic fins, contributing to their elongated appearance. Their eyes are relatively small; morays rely mostly on their highly developed sense of smell, while remaining concealed to ambush prey.^[4]

The body is generally patterned. In some species, the interior of the mouth is patterned as well. Their jaws are wide, framing a protruding snout. Most possess large teeth suited for tearing flesh or grasping slippery prey. A smaller 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.^[5]

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 cells in the epidermis 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,^[6] thus making the walls of the burrow more permanent due to the glycosylation of mucins in mucus. Placement of their small, circular gills on their flanks, far behind the mouth, requires the moray to maintain a gape / gulping motion to facilitate respiration.^{[clarification needed]}

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.^[7][8][9]

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.^[10] 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.^[11][12][13] These morphological patterns carry over to teeth positioned on the pharyngeal jaw.^[14][15]

Feeding behavior

Morays are opportunistic, carnivorous predators,^[16] and feed primarily on smaller fish, crabs and octopuses.^[17] A spotted moray eel has been observed eating a red lionfish without harm.^[18][19] Groupers, barracudas and sea snakes are among their few known predators, making many morays (especially the larger species) apex predators in their ecosystems.^[20]

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.^[24][25]

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 and temperate environments.^[25] 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 reefs.^[26] 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.^[26]

Reproduction and lifecycle

The reproductive biology of moray eels remains incompletely understood. Most species are oviparous, with external fertilization occurring in the water column. During spawning, both males and females release gametes simultaneously, and the fertilized eggs are subsequently dispersed by ocean currents.

Following fertilization, the eggs develop into leptocephalus larvae, which are transparent and ribbon-like in appearance. These larvae remain in the pelagic zone for extended periods—often up to a year—feeding on microscopic plankton. This prolonged larval phase facilitates wide geographic dispersal prior to settlement in benthic habitats such as coral reefs or rocky substrates, where metamorphosis into juvenile eels occurs.^{[27][better source needed]}

The transition from larva to juvenile involves significant morphological and behavioral changes, including the development of adult pigmentation, body form, and ecological habits. Juvenile moray eels typically adopt the solitary and territorial behavior characteristic of adults.

Due to their nocturnal activity and the often inaccessible environments in which reproduction occurs, direct observations of moray eel courtship and spawning behavior are rare. Consequently, their reproductive mechanisms remain one of the least documented aspects of their biology.

Environmental factors such as water temperature, photoperiod, and food availability are believed to influence spawning events. Breeding in captivity is infrequent, which further limits opportunities for scientific study of their reproductive cycle.^{[28][user-generated source]}

Taxonomy

Genera

There are over 200 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.^[29] 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.^[29] In Uropterygiinae, both the dorsal and the anal fin are at the end of the tail.^[29] 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:^[30]

• †Eomuraena Casier, 1967 (fossil; Early Eocene of Germany)^[31]
• 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, 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

• 
  Anarchias seychellensis
• 
  Channomuraena vittata
• 
  Snowflake moray (Echidna nebulosa)
• 
  Barred moray (Echidna polyzona)
• 
  Viper moray (Enchelynassa canina)
• 
  Zebra moray (Gymnomuraena zebra)
• 
  Laced moray (Gymnothorax favagineus)
• 
  Gymnothorax rueppelliae
• 
  Monopenchelys acuta
• 
  Mediterranean moray (Muraena helena)
• 
  White ribbon eel (Pseudechidna brummeri)
• 
  Ribbon eel (Rhinomuraena quaesita)
• 
  Scuticaria tigrina
• 
  Slender giant moray (Strophidon sathete)
• 
  Uropterygius xanthopterus
• 
  Kidako moray (Gymnothorax kidako)

Evolution

The moray eel's elongation is due to an increase in the number of vertebrae, rather than a lengthening of each individual vertebra or a substantial decrease in body depth.^[32] Vertebrae have been added asynchronously between the pre-tail ("precaudal") and tail ("caudal") regions, unlike other groups of eels such as Ophicthids and Congrids.^[33]

Relationship with humans

References

Further reading

• Gross, Miriam J. The Moray Eel. United States: Rosen Publishing Group's PowerKids Press, 2005.
• Purser, Phillip. Keeping Moray Eels in Aquariums. United States: T.F.H., 2005.
• Didier, Dominique A. Moray Eel. United States: Cherry Lake Publishing, 2014.
• Goldish, Meish. Moray Eel: Dangerous Teeth. United Kingdom: Bearport Publishing, 2009.

External links

Wikimedia Commons has media related to Muraenidae.

Wikisource has the text of the 1905 New International Encyclopedia article "Moray".

• 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.