The Granite Moray Eel (Uropterygius sp.) appears to be an undescribed Moray Eel found on the Tanzanian mainland coast which is probably in the Uropterygius genus. To date no one has been able to identify them. They are rarely seen and are not common.
They have only been seen in the Dar es Salaam region and have not been sighted on Mafia Island although one diver has seen them off Mombasa in Kenya. Because their colouration resembles that of granite and the fact that these eels do not usually move at all, after a call for suggestions in our local dive club, Sarah Zetterli came up with the name of the Granite Moray Eel.
The Granite Moray Eel grows up to approximately 100 cm in length. Their colouration varies from a blue gray speckled color to a grey speckled color and a light brown speckled colour. The body is thick the whole length all the way to the tail which tapers off to a short point. The head has a short set of jaws. The mouth is proportionally small for moray eels and appears to have short rounded teeth although these eels never open their mouths very wide so it is difficult to tell.
GRANITE MORAY EEL IN THE WILD
Granite Moray Eel are usually seen hiding in small caves with just the head protruding but quite often they are seen lying on the reef out in the open curled around soft corals. Although I have now seen some 12 to 15 of these eels, I have only seen one move and this was at night and the eel appeared to be out feeding. Even when one goes within a meter or so of them, they just sit there without moving or opening their mouth.
Most Moray eels have proportionately small circular gills and are constantly opening and closing their mouths to facilitate water flow over their gills, but this eel does not open its mouth at all . It just sits there and does not move, whether this is a defense strategy or whether it does not feel threatened is hard to say.
From the shape of the jaw which can be seen below, one presumes they have rounded teeth rather than sharp teeth , but this is merely a guess.
So far to our knowledge, this eel has only been seen off Dar es Salaam in Tanzania and off Mombasa in Kenya. They are rare and I have seen 12 to 15 in some six or seven hundred dives.
We can only presume that this moray feeds on either crustaceans or mollusks but this could be completely wrong. On one occasion we saw one out at night, presumably feeding and it went slowly back into a hole.
Granite Moray Eels have poor eyesight and their main hunting tool is their excellent sense of smell. This means that weakened or dead creatures are the moray eel’s favoured food.
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, making them potentially dangerous for humans to eat. Moray Eels are fished and do take bait. There is documented evidence of Ciguatoxin poisoning from some species of moray eels and because of this they should not be eaten.
Once caught on a line they are extremely troublesome to deal with. They wrap around the line and secrete a large amount of mucus. Unless the line is changed, much as with the mucus from puffer fish, no other fish will bite on the line. It is not uncommon for a caught moray eel to actually bite its self while it is busy wrapping around the line.
If anyone is able to assist in identifying this eel we would be grateful.