Moray eel

Moray eel Fossil range: Late Miocene–Recent PreЄ Є O S D C P T J K Pg N [1]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Superorder:	Elopomorpha
Order:	Anguilliformes
Family:	Muraenidae
Genera
See text.

Moray eels are large cosmopolitan eels of the family Muraenidae. There are approximately 200 species in 15 genera. The typical length of a moray is 1.5 metres (4.9 ft). The longest is the slender giant moray, Strophidon sathete, at up to 4 metres (13 ft). The largest in terms of total mass is the Giant moray (Gymnothorax javanicus), which reaches almost 3 metres (9.8 ft) and can weigh over 36 kilograms (79 lb).

Anatomy

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

The dorsal fin 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 is generally patterned. Camouflage is also present inside the mouth. Their jaws are wide, framing a protruding snout. 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 second set of jaws in their throat called pharyngeal jaws, which also possess teeth. When feeding, morays launch these jaws into the mouth, where they grasp prey and transport it into the throat and digestive system. Moray eels are the only animal that uses pharyngeal jaws to actively capture and restrain prey.^[2][3][4] Larger morays are capable of seriously wounding humans.

Morays secrete a protective mucus over their smooth, scaleless skin which in some species contains a toxin. 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^[5], 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 cause ciguatera fish poisoning. Morays hide in reef crevices 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

A species of reef-associated grouper, the roving coral grouper (Plectropomus pessuliferus), often recruits morays to aid them while hunting for food. This is the only known instance of interspecies cooperation among fish.^[6][7]

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. Morays are shy and secretive, and attack humans only in self-defense. Most attacks involve accidental bites during human initiated interaction. 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.

Eels that 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 amputating a diver's finger. Morays rest in crevices during the day and hunt nocturnally, although they may ensnare small fish and crustaceans that pass near them during the day.^[7]

Habitat

Moray eels are cosmopolitan, found in tropical and temperate seas, although they prefer subtropical coral reefs in warm waters. They live at depths up to 150 metres (490 ft), where they spend most of their time concealed inside crevices and alcoves.

Taxonomy

Genera

Whitemouth moray, Gymnothorax meleagris

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

References

Wikimedia Commons has media related to: Muraenidae

External links

• Moray Eels Grab Prey With Alien Jaws