Moray eel

Moray eel Temporal range:
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Superorder:	Elopomorpha
Order:	Anguilliformes
Family:	Muraenidae
Genera
See text.

Moray eels are huge cosmopolitan eels of the family Muraenidae. There are approximately 200 species in 15 genera. The typical length of a moray is 1.5 m (5 ft), with the longest being the slender giant moray, Strophidon sathete, at up to 4 m (13 ft), and the largest, in terms of total mass being the Giant moray (Gymnothorax javanicus), which reaches almost 3 m (10 ft) and can weigh over 36 kg (80 lb).

Anatomy

Muraena helena showing typical moray eel morphology: robust anguilliform shape, lack of pectoral fins and circular gill openings

The dorsal fin of the moray extends from just behind the head, along the back and joins seamlessly with the caudal and anal fins. Most species lack pectoral and pelvic fins, adding to their snake-like appearance. Their eyes are rather small; morays rely on their highly developed sense of smell, lying in wait to ambush prey.

The body of the moray is generally patterned, camouflage also being present inside the mouth. Their jaws are wide, with a snout that protrudes forward. They possess large teeth, designed to tear flesh as opposed to holding or chewing.

Moray eel jaw anatomy

Moray eels' heads are too narrow to create the negative pressure that most fish use to swallow prey. Quite possibly because of this, they have a well-developed second set of jaws in their throat called pharyngeal jaws, which also possess teeth. When feeding, morays launch these jaws into the oral cavity, where they grasp struggling prey and transport it into the throat and down to the rest of the digestive system. Moray eels are the only known type of animal that uses pharyngeal jaws to actively capture and restrain prey. Larger morays are capable of inflicting serious wounds to humans.

Morays secrete a protective mucus over their smooth scaleless skin which contains a toxin in some species. Morays 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, thus making the walls of the burrow more permanent due to the glycosylation of mucins in mucus. Their small circular gills, located on the flanks far posterior to the mouth, require the moray to maintain a gap in order to facilitate respiration.

Morays are carnivorous and feed primarily on other fish, cephalopods, mollusks, and crustaceans. Groupers, other morays, and barracudas are among their few predators. There is a commercial fishery for several species, but some have been known to cause ciguatera fish poisoning. Morays hide in crevices in the reefs, and wait until their prey is close enough for capture. They then lunge out and clamp the prey in their strong jaws.

Behavior

Cooperative hunting

A Pacific cleaner shrimp cleans the mouth of a moray eel

Ribbon moray,
Rhinomuraena quaesita

In the December 2006 issue of the journal Public Library of Science Biology, a team of biologists announced the discovery of interspecies cooperative hunting involving morays. The biologists, who were engaged in a study of Red Sea cleaner fish (fish that enter the mouths of other fish to rid them of parasites), discovered that a species of reef-associated grouper, the roving coral grouper (Plectropomus pessuliferus), often recruited morays to aid them while hunting for food. This is the first discovery of cooperation between fish in general.

Fimbriated moray,
Gymnothorax fimbriatus

Reputation

The Morays have sometimes been described as vicious or ill-tempered. Morays hide from humans and would rather flee than fight. In fact, morays are shy and secretive, and they only attack humans in self-defense. Most attacks on humans involve accidental bites during human initiated interaction, likely caused by the fact that Morays cannot see or hear very well and rely mostly on their acute sense of smell. Morays, however, do inflict a nasty bite, because, although not poisonous, their backward-pointing teeth are covered with bacteria which may infect the wound. Another danger that morays present is when they are eaten. If the eels have eaten certain types of toxic algae, or fish that have eaten some of these algae, they can cause ciguatera fish poisoning if eaten. Large morays can also cause extreme physical trauma, in some cases biting off a finger of a careless diver. Morays rest in crevices during the day and are nocturnal predators, and although they may ensnare small fish and crustaceans that pass near them during the day, they mostly come out at night.

Distribution

Moray eels are cosmopolitan, found in tropical and temperate seas.

Habitat

Morays usually live in warm waters, and subtropical coral reefs to depths of 150 m (about 492 ft), where they spend most of their time concealed inside crevices and alcoves. Echidna rhodochilus, commonly called the Freshwater Moray Eel live in colder waters to depths of 32 m (about 105 ft), are found in the northern United States Great Lakes and Eastern Thailand, where they spend most of their time in sand block alcoves.

Classification

Genera

Whitemouth moray, Gymnothorax meleagris

• Subfamily Muraeninae
  • Cirrimaxilla
  • Echidna
  • Enchelycore
  • Enchelynassa
  • Gymnomuraena
  • Gymnothorax
  • Monopenchelys
  • Muraena
  • Pseudechidna
  • Rhinomuraena
  • Scuticaria
• Subfamily Uropteryginae
  • Anarchias
  • Channomuraena
  • Uropterygius

External links

• Moray Eels Grab Prey With Alien Jaws