The yellow edged moray eel (Gymnothorax flavimarginatus) is also known as the yellow margin moray eel. They are one of the larger moray eels. As they are nocturnal they are not commonly seen in the open.
The yellow edged moray eel is a dark brown color with irregular yellow markings. The head is large and it has fairly long rear facing teeth for gripping prey. On older specimens the head usually appears darker during the day but at night this darker coloration seems to lighten. On the center of the roof of the mouth there is an additional large tooth, sometimes two. This extra row of teeth can be seen in the image below and these teeth are far larger than the outer teeth.
On the lower jaw there are small holes and these are assumed to be sensory organs. These can also be clearly seen in the image below. The iris is a yellow or orange color. There is a black blotch in the gill area. They do not have pectoral or pelvic fins and the dorsal fin runs the length of the body. They grow up to 2.4 meters in length and the eel in the video below is about that size.
Some researchers speculate that moray eels contain toxins in their mouths and are poisonous. From many years of catching crayfish on the Kwa Zulu Natal coast I have never had a bite go sceptic. After every bite I have soaked the bite area in hot water as hot as I can take it. Much of the bite damage occurs when one pulls ones hand back after being bitten. Many experts say that one should not pull back, however they should go try it themselves. The bite is usually sudden and unexpected and it is natural to pull away from it. I have personally seen one diver who lost the use of his thumb from a giant moray bite but that is unusual.
Morays secrete mucus over their scaleless skin, which in some species contains toxins. They have a thick skin and a large number of cells that secrete mucus epidermis. Moray eels have proportionately small circular gills, located on posterior of the mouth. Moray eels constantly open and close their mouths to facilitate sufficient water flow over their gills. In general the opening and closing of the mouth is not threatening behavior but one should not approach too closely. They will bite if they feel threatened.
IN THE WILD
The yellow edged moray eel are generally seen protruding from a hole or small cave during the day. They are sometimes seen out on the reef at night. The larger specimens are fairly aggressive as can be seen in the video below. They can deliver a fearsome bite and can knot themselves and run the knot up the body to push against the prey, providing additional force to rip pieces of the prey off.
Moray eels have proportionately small circular gills, located on posterior of the mouth. As a result the moray is constantly opening and closing its mouth to facilitate sufficient water flow over its gills. In general the opening and closing of the mouth is not threatening behavior but one should not approach too closely.
The yellow edged moray eel is found across the Indian ocean and in the Pacific.
The yellow edged moray eel is carnivorous, and does most of its hunting at night. They feed mainly on fish and crustaceans. As with most other morays they will probably feed on carrion if the opportunity presents its self.
Moray eels have a second set of toothed jaws in their throat called pharyngeal jaws. When feeding, morays latch onto the prey with their outer jaws. They then push their pharyngeal jaws, which are set back in the pharynx, forward into the mouth. These jaws then grasp the prey and pull it back into the stomach. Moray eels are the only fish that use pharyngeal jaws to capture prey. Their main hunting tool is their excellent sense of smell which makes up for their poor eyesight.
Studies have shown hermaphroditism in morays, some being sequential and others synchronous which can reproduce with either sex. Courtship usually occurs when water temperatures are high. After posturing to each other they wrap their bodies around each other and simultaneously release sperm and eggs. Once they hatch the larvae float in the ocean for around 8 months before becoming elvers and eventually a moray eel.
Ciguatoxin, the main toxin of ciguatera, is produced by a toxic dinoflagellate and accumulated up through the food chain, of which moray eels are top. Because the toxins accumulate at the top this makes them potentially dangerous for humans to eat. They are fished and do take bait but because of the potential toxins should not be eaten. There are recorded cases of poisoning from eating the yellow edged moray.
Once caught they are extremely troublesome to deal with. They wrap around the line and secrete a large amount of mucus and as a result the line has to be changed. As with the mucus from puffer fish, no other fish will bite on the line once it has the mucus on it. It is not uncommon for a caught moray eel to actually bite its self while it is busy wrapping around the line.
The yellow edged moray is not commonly kept in private aquariums because of its propensity to eat anything that moves that it comes across. Most fish would not be safe in a tank with them. Some specialist collectors do keep them individually in tanks.