Moray Eel

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 (Gymnothorax polyuranodon) can sometimes be found in freshwater. With a maximum length of 11.5 centimetres (4.5 in), the smallest moray is likely the Synder's moray (Anarchias leucurus), while the longest species, the slender giant moray (Strophidon sathete) reaches 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

The dorsal fin extends from just behind the head along the back and joins seamlessly with the caudal and anal fins. Most species lack pecktoral 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 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 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, barracudas and sea snakes are among their few predators. There is a commercial fishery for several species, but some cause ciguatera fish pois 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.

Cooperative hunting

A species of reef-associated grouper, the roving coral grouper (Plectropomus pessuliferus), have been observed to recruit morays to aid them while hunting for food. This is the only known instance of interspecies cooperation among fish.

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 or mistaken identity (for example, a finger placed in a crevice where a moray resides may resemble a prey-item). Most attacks involve accidental bites during human-initiated interaction. Morays cannot see very well and rely mostly on their acute sense of smell. Morays, however, do inflict a nasty bite, and 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 fish that have eaten some of these algae can cause ciguatera fish poisoning if eaten. Large morays can also cause extreme physical trauma, in some cases removing an incautious 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.

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).


source : http://en.wikipedia.org, Youtube