Moray eel
WARNING: I AM A PREDATOR AND I BITE!
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Actinopterygii
Superorder:
Elopomorpha
Order:
Anguilliformes
Family:
Muraenidae
Moray eels are cosmopolitan eels of the family Muraenidae. The approximately 200
species in 15 genera are almost exclusively marine, but several species are regularly
seen in brackish water and a few, for example the freshwater moray can sometimes
be found in freshwater. With a maximum length of 11.5 centimetres, the smallest
moray is likely the Snyder's moray, ]while the longest species, the slender giant moray
reaches up to 4 metres. The largest in terms of total mass is the giant moray, which
reaches almost 3 metres and can weigh over 36 kilograms.
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 serpentine 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. 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 sanddwelling 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, molluscs, and
crustaceans. Groupers, barracudas and sea snakes 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
Reef-associated roving coral groupers (Plectropomus pessuliferus), have been
observed to recruit morays to join them in hunting for food. The invitation to hunt is
initiated by head-shaking. The rationale for this joining of forces is the ability of
morays to enter narrow crevices and flush prey from niches not accessible to groupers.
This is the only known instance of interspecies cooperative hunting among fish.
Cooperation on other levels, such as at cleaning stations is well-known.
Fimbriated moray,
Gymnothorax fimbriatus
Reputation
The Morays are frequently thought of as particularly vicious or ill-tempered animals.
In truth, morays hide from humans in crevices and would rather flee than fight.
Morays are shy and secretive, and attack humans only in self-defence or mistaken
identity. Most attacks stem from disruption of a moray's burrow (to which they do
react strongly), but an increasing number also occur during hand-feeding of morays
by divers, an activity often used by dive companies to attract tourists. Morays have
poor vision and rely mostly on their acute sense of smell, making distinguishing
between fingers and held food difficult; numerous divers have lost fingers while
attempting hand feedings. For this reason the hand feeding of moray eels has been
banned in some locations, including the Great Barrier Reef. The moray's rear-hooked
teeth and primitive but strong bite mechanism also makes bites on humans more
severe, as the eel cannot release its grip even in death and must be manually pried off.
While the majority are not believed to be venomous, circumstantial evidence suggests
that a few species may be.
Eels that have eaten certain types of toxic algae, or more frequently that have eaten
fishes that have eaten some of these algae, can cause ciguatera fish poisoning if eaten.
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.[10]
Habitat
Moray eels are cosmopolitan, found in both tropical and temperate seas, although the
largest species richness is at reefs in warm oceans. Very few species occur outside the
tropics or subtropics, and the ones that do only extend marginally beyond these
regions. They live at depths of up to several hundred metres, where they spend most
of their time concealed inside crevices and alcoves. While several species regularly
are found in brackish water, very few species can be found in freshwater, for example
the freshwater moray (Gymnothorax polyuranodon) and the pink-lipped moray eel
(Echidna rhodochilus).