Moray Eels: Characteristics, Behavior and Species

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laced moray eel (Gymnothorax favagineus)

Moray eels (Scientific name: Muraenidae) are a family 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, and a few are found in fresh water. The English name “moray” was first used in the early 17th century, and comes from Portuguese “moréia”, which is derivesd from Latin “mūrēna” and from Greek “muraina”, Latin and Greek names for the Mediterranean moray.

Moray eels generally spend their day in their tunnel homes and emerge at night to hunt prey with sensitive sense of smell and corner prey in crevasses and caves. The bigger ones can reach a length of four meters (13 feet). A favorite meal of many moray eels is fresh octopus. It often looks like moray eels are gasping for air. They open and close their mouths in the gasping way they do to pump water through their gills.

Moray eels are generally very shy. They generally don't attack people unless provoked.. Some will let divers hand feed them. Some divers have been seriously bitten after sticking their hands in a moray eel's cave. Some moray eels permit butterflyfish swim in and out of their mouth to do cleaning.

Two of the best friends at the Great Barrier Reef of famed marine biologist Ron and Valerie Taylor, who frequently contributed to National Geographic, were are a pair of morays nicknamed Harry and Fang. Harry was particularly good tempered. Once Valerie pulled him from his cave and swam 12 meters (40 feet) with him to show him to some school children, and he didn't show the slightest bit of resistance.

Websites and Resources: Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); Fishbase ; Encyclopedia of Life ; Smithsonian Oceans Portal ; Woods Hole Oceanographic Institute ; Cousteau Society ; Monterey Bay Aquarium ; MarineBio

Moral Eel Habitat and Where They Are Found

20120517-800px-Moray_eel.jpg Moray eels can be found in both fresh and saltwater habitats, but are generally occur in saltwater marine environments. Of the few species known to live in freshwater, the most well-known is the freshwater moray (Gymnothorax polyuranodon), which is native to the Indo-Pacific region, and found in Sri Lanka, the Philippines, Indonesia, Papua New Guinea and the northern coastline of Australia. [Source: Wikipedia]

Moray eels can be found in the Atlantic, Pacific and Indian Oceans. The tend to live in warm tropical and subtropical waters, and are associated with coral reefs, but that can be found elsewhere. Morays are usually found in shallow water nearshore areas, continental slopes, continental shelves, deep benthic habitats, and mesopelagic zones (between about 200 and 1,000 meters), in both tropical and temperate environments. Only a few species such as the yellow moray are found in temperate ocean environments.

Within tropical and temperate seas, moray eels often live in shelters such as dead patch reefs and coral rubble rocks, and less frequently occupies live coral reefs.

Moral Eel Physical Characteristics

Moray eels have snake-like bodies, with no scales or lateral line. Most species lack pectoral and pelvic fins which distinguishes them from all other eel-like fishes. They have small, round gill opening, located on the flanks far from the mouth, creating a gap that makes taking in oxygen more difficult. Their method of respiration requires them to constantly open and close their mouthes to push oxygenated water over their gills. [Source: Rosie Clarke, Animal Diversity Web (ADW) /=]

The dorsal fin of moray eels extends from just behind the head along the back and joins seamlessly with the caudal and anal fins.. Their eyes are small (morays rely mostly on their highly developed sense of smell and lying in wait to ambush prey). Evolution-wise the moray eel's elongation is due to an increase d number of vertebrae, rather than a lengthening of each individual vertebra or expansion of the space between them. [Source: Wikipedia]

The body of the moral eel is generally patterned, often quite colorfully so. In some species, even the inside of the mouth is patterned. Their jaws are wide. Most possess large teeth used to tear flesh or grasp slippery prey. Morays secrete a protective mucus over their smooth, scaleless skin, which in some species is venomous. They have much thicker skin and high densities of goblet cells in their skin layers that allows mucus to be produced at a higher rate than in other eel species.

Unusual Jaws of the Moray Eel

moray eel jaws
Moray eels have two sets of jaws, including a pair set way down the creatures throat that can slide forward and backward sort of like the multiple jaws in creature in the Alien films. The primary uses of the rear set of of jaws is to restrain prey, position it so that it can slide easily through the eel’s long narrow esophagus and digestive tract so the digestive process can take place. The rears jaws have been compared to the hook that places a car body on an assembly line. [Source: National Geographic]

When a moray eel catches a fish with its sharp teeth, the second set of jaws extend forward from the throat and grab the fish from the front teeth, and then retreats with the fish into the eel’s esophagus. Unlike most other fish, Rita Mehta of the University of California at Davis told National Geographic, morays don’t seem to generate enough suction to help it swallow, and need the jaw to restrain and transport the fish. Snakes, which have long slender bodies like moray eels, have a set of ratcheting jaws that grip and maneuver food into the gullet.

Mehta used a high-speed video to shot a reticulated moray eel eating a squid with its mouth open and was amazed to find how quick the second jaw in the throat surged forward it grab food and how far it came. Further investigation using a fluoroscope and an X-ray movie machine revealed that the second set of jaws slide all the way forward so its teeth were equal with the eel’s eye.

Morays have another way of seizing prey and eating. They will loop their bodies around prey similar to the way a python does but instead of squeezing the victim to death a moray pulls its head through the loop, holding the victim in a a tight grasp while ripping off bite-size chunks flesh.

Moral Eel Behavior and Feeding

Moray eels are generally solitary and nocturnal (active at night) and can be both motile (move around as opposed to being stationary) and sedentary (remain in the same area). Adults are rarely active outside of feeding and spawning. They sense using vision, touch and chemicals usually detected with smell. Because of their solitary lifestyle, they rarely communicate with their own kind. Little is known about how they communicate with potential mates. Their senses, of which is smell is the strongest, are mainly used for locating food and a spawning site. [Source: Kyle Wilson, Animal Diversity Web (ADW) /=]

moray eel and fish
Morays feed primarily on smaller fish, crabs, and octopuses. They generally are opportunistic, lay-in-wait ambush hunters, emerging from their caves to grab prey and using their coloring and darkness to camouflage and conceal themselves. Groupers, barracudas and sea snakes are among their few creatures that prey on them, making many morays (especially the larger ones) the apex predators in their realms.

Adults actively hunt fish in caves and crevices along coral reefs or shorelines. When an eel encounters a fish too large to swallow whole, it wraps itself around its prey in a characteristic knot, allowing for leverage against the fish. It then tears its prey into smaller pieces, which can be swallowed more easily. Moray eel larvae are active predators of zooplankton. /=\

A spotted moray eel has been observed eating a red lionfish without harm. A relatively small number of species such as the snowflake moray (Echidna nebulosa) and zebra moray (Gymnomuraena zebra) that feed primarily feed on crustaceans and other hard-shelled animals have blunt, molar-like teeth suitable for crushing.. 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. [Source: Wikipedia]

Moray Eeel Mating, Reproduction and Offspring

Moray eels are oviparous (young are hatched from eggs) and iteroparous (offspring are produced in groups). They engage in external reproduction in which sperm from the male fertilizes the female’s egg outside her body and employ broadcast (group) spawning, the main mode of reproduction in the sea. It involves the release of both eggs and sperm into the water and contact between sperm and egg and fertilization occur externally. It is unknown how frequently many moray species breed. Spawning is believed to take place at a designated place. After they have spawned, adult eels leave the area to die or return to their home range. Pre-fertilization provisioning and protecting is done by females. There is no parental involvement after the eggs have been fertilized. [Source: Rosie Clarke, Animal Diversity Web (ADW) /=]

According to Animal Diversity Web: California morays reproduces by external fertilization. Eggs hatch into a specialized planktonic larva called a leptocehalus that eventually settle to the bottom. Juvenile morays can be found in tidal pools, but upon maturation seek deeper water. Very little is know about the leptocephali and juvenile stages of their life cycle, because most specimens found are probably over thiry years old.

Based on what is known about European eels (Anguilla anguilla), it is plausible that morays are promiscuous and that spawning sites are farther from the shoreline than the eel's foraging habitat, between 400 meters and 500 meters deep. Close relatives of Green moray eel are known to spawn in the early months of the year, around January or February. At a given spawning site, millions of eggs are released, but significantly less are fertilized and fewer still (on the order of one in every six million) survive into adulthood.

Their life cycle of moray eels is characterized by metamorphosis — a process of development in which individuals change in shape or structure as they grow. Larvae often must migrate from the spawning site to a suitable habitat. When the fertilized eggs of green morays hatch, prolarvae emerge. Shortly thereafter the prolarvae transform into leptocephalus larvae, which grow to be between five and 10 centimeters in length. The leptocephalus larva shares a number of morphological characteristics with its adult counterparts: both are long and laterally compressed and their dorsal, caudal and anal fins are continuous. Unlike adults, they have a "gelatinous" consistency and their tissues (with the exception of bone) are transparent. [Source: Kyle Wilson, Animal Diversity Web (ADW) /=]

The leptocephalus larva will undergo its final metamorphosis in open water. The juvenile resembles the mature animal, save that it is smaller in size. Ocean currents disperse the animals after metamorphosis and, once they have reached a permanent habitat, they mature.

This process not only involves an increase in size, but two stages of sexual maturity: a hermaphroditic stage as a juvenile (during which individuals possess both male and female sex organs) before a determined male or female stage as an adult. Experts speculate that environment plays a role in the final sex determination, with more stressful environments producing more females. Based on the documented larval development of the European eel,the larval stage of the green moray probably lasts on the order of 2.5 years.

Moray Eel Species and Genera

There are 202 known species of moray eels, divided among 16 genera. These genera fall into the two sub-families of Muraeninae and Uropterygiinae, which can be distinguished by the location of their fins. In Muraeninae the dorsal fin is found near the gill slits and runs down the back of the eel, while the anal fin is behind the anus. The Uropterygiinnae are defined by both their dorsal and anal fin being located at the end of their tails. There are still many varieties of genera within Muraeninae and Uropterygiinae. Of these, the genus Gymnothorax is by far the biggest, including more than half of the total number of moral eel species. Several moray species are popular among aquarium enthusiasts for their hardiness, flexible diets, and resistance to diseas. The most commonly traded species are the snowflake, zebra and goldentail moray. [Source: Wikipedia]

Types of Eels, From Animal Spot

List of genera according to the World Register of Marine Species: Subfamily Muraeninae
Genus Diaphenchelys — 1 species
Genus Echidna — 11 species
Genus Enchelycore — 13 species
Genus Enchelynassa — 1 species
Genus Gymnomuraena — 1 species
Genus Gymnothorax — 125 species
Genus Monopenchelys — 1 species
Genus Muraena — 10 species

Subfamily Uropterygiinae
Genus Anarchias — 11 species
Genus Channomuraena — 2 species
Genus Cirrimaxilla — 1 species
Genus Scuticaria — 2 species
Genus Uropterygius — 20 species

Some moray eel species:
Snowflake moray (Echidna nebulosa)
Kidako moray (Gymnothorax kidako)
Slender giant moray (Strophidon sathete)
Viper moray (Enchelynassa canina)
Zebra moray (Gymnomuraena zebra)
Laced moray (Gymnothorax favagineus)
Mediterranean moray (Muraena helena)
White ribbon eel (Pseudechidna brummeri)
Ribbon eel (Rhinomuraena quaesita)
Scuticaria tigrina
Uropterygius xanthopterus
Enchelycore schismatorhynchus
Gymnothorax rueppelliae
Monopenchelys acuta

California Moray

California moray (Scientific name: Gymnothorax mordax) is native to the eastern Pacific Ocean and ranges from Magdalena Bay, Baja, California in the south to Point Conception in the north. Population densities are greater in southern California with the highest being in the Southern Channel Islands, and Catalina. California morays are usually found in reefs and inhabit cracks and crevices within rocky reefs in the subtidal zone to 40 meters, but is usually found at depths of 0.6 to 20 meters. A full grown adult can reach lengths up to 152 centimeters (five feet). [Source: Rosie Clarke, Animal Diversity Web (ADW) /=]

California moray feed on small reef fishes, octopi, shrimp, crabs, lobster, and sea urchins, using their well developed sense of smell to hunt prey. They have a mutualistic relationship with red rock shrimp (Lysmata claifornica(. The rock shrimp clean the moray of dead skin and parasites; in return the moray provides the shrimp with protection by allowing the shrimp to coinhabit the moray's crevice.

According to Animal Diversity Web: It is hypothesized that the morays off the coast of southern California do not reproduce because the water is too cold. Instead the ocean currents bring the leptocehalali north from Baja California, which then settled out of the upper water column to mature in southern California. The life span of the California moray is speculated to be thirty years or more.

The California moray is popular with divers. Unlike some other eels, California moray is not poisonous to humans and, therefore, can be eaten. California moray eels usually won't leave their crevices to attack divers, unless they are harassed or hunted. Since they do have numerous razor sharp teeth they can inflict serious lacerations on a diver if they do bite. These fish are not endangered. International Union for Conservation of Nature (IUCN) Red List: Convention on International Trade in Endangered Species (CITES): No special status

Green Moray Eel

Green moray eels (Scientific name:Gymnothorax funebris) are also known as morena verde. They are found in the western Atlantic Ocean, the Gulf of Mexico and Caribbean Sea., ranging as far north as New Jersey and as far south as Brazil and is most common in the Gulf of Mexico, the Caribbean Sea, the Bahamas, and the Florida Keys. These eels make small migrations to spawning sites. Green morays live in rocky, intertidal areas, coral reefs, mangroves, tidal creeks, harbors, seagrass beds, and other areas over sandy or muddy bottoms. They typicall reside in rock crevices and small caves at depths of one to 30 meters (3.28 to 98.43 feet).[Source: Kyle Wilson, Animal Diversity Web (ADW) /=]

The body of Green moray eel is dark brown or grey and covered by a yellow mucus. This mucus serves to protect these eels from parasites and bacteria. The yellow color of the mucus, when mixed with the brown or grey color of the eel's skin, results in a green hue, for which the animal is named. On the face there are two cylindrical structures — its incurrent nostrils. The excurrent nostrils are marked by simple openings. On the upper jaw, there are two rows of teeth, while on the bottom, there is only one. The teeth are large and smooth-edged. The largest specimen ever recorded was 2.5 meters (8.2 feet) from nose to tail, and weighed of 29 kilograms (63.4 pounds). Average ones are around 1.8 meters (5.9 feet) from nose to tail and weigh 13.3 kilograms (29 pounds),. Both sexes are roughly equal in size and look similar.

Green moray eel is a dietary generalist. They will eat most species of fish, as long as they are small enough to swallow whole or can be ripped into manageable pieces. Green morays also prey on crustaceans and cephalopods. Larvae prey on diatoms, smaller crustaceans, and other zooplankton. These larvae in turn are eaten by most any animal that consumes zooplankton. Presumably, large adults have very few natural predators, since they are relatively large and will viciously attack any potential threats. Reportedly, some maintain a mutualistic relationship with gobies, wrasses, and some shrimp, all of which eat microbes off of the eel's skin.

Green morays are of interest to divers and tourists at coral reefs and are sold as pets for aquariums. Less often, they are eaten by humans as food. These creatures are feared for their vicious bite but rarely do so unless provoked. Ciguatera fish poisoning has been reported with the fish. Green moray eels are not currently threatened. IUCN Red List and CITES: No special status.

Image Sources: Wikimedia Commons; YouTube, Animal Diversity Web, NOAA

Text Sources: Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated March 2023

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