Muraenidae, better known as moray eels, are a family of 200 species of eels. Most moray eels live in the ocean among coral reefs. But some species live in brackish and freshwater ecosystems. Moray eels have snake-like bodies and two sets of jaws for hunting. Exposed to predators in the open water, moray eels prefer to ambush prey in coral reefs.
1. Despite their snake-like appearance, moray eels are actually fish
Moray eels have long, serpentine bodies. When they swim, it looks like they're slithering in the water. However, moray eels are actually fish. Unlike snakes, moray eels do not have scales. Like fish, they have gills and fins. Moray eels don’t have pelvic fins, but they have a dorsal fin that runs from the top of their head to the end of their tails.
Moray Eels are the only fish that can swim backwards and forwards
A moray eel’s dorsal and anal fins are fused with their caudal fin. The moray eel swims by moving like a ribbon. The back and forth sends waves throughout the eel’s body that propel it forward. To swim backwards, the eel just has to reverse the direction of the wave. Other fish have a separate caudal fin at the end of their bodies. The fin is connected to their spine, and they can shake it side to side to only propel forward.
2. Moray eels have two teethy jaws for capturing and devouring prey
Each moray eel jaw has its own function for consuming prey. The primary jaw at the front has two rows of sharp, backwards facing teeth. The moray eel uses the primary jaw to grab prey. The secondary jaw is called the pharyngeal jaw. This jaw is in the eel’s throat, and also has small, sharp teeth. After an eel grabs the prey with the primary jaw, the pharyngeal jaw extends into the mouth cavity and pulls the prey down the eel’s throat.
Like snakes, moray eels cannot create suction in their mouths
Unlike most fish, moray eels cannot create suction in their mouths to swallow prey. They have this in common with snakes. However, snakes eat by holding food on one side of the jaw and working it with the other. Moray eels use their powerful second jaw to bring food down their throats. This is an example of convergent evolution, where two unrelated species with the same problem evolved different solutions.
Snowflake Moray Eels have round, blunt teeth evolved for crushing shells
Most species of moray eel have sharp teeth for puncturing fish and octopi. But the snowflake moray eel and other species have round, blunt teeth. These eels only eat crustaceans, like crabs or lobsters. Their rounder teeth are adapted to crush shells.
3. Moray eels have poor eyesight, and rely on smell and taste to hunt
Even though they live in shallow tropical waters, moray eels have very poor eyesight. But since moray eels are nocturnal, they have evolved to hunt in the dark. With poor vision, moray eels hunt using chemoreception. Chemoreception is the ability to detect and react to chemicals in one’s environment. An average moray eel has a strong sense of smell. Those large nostrils allow them to sniff out nearby prey.
Moray eels have two sets of nostrils
Not only do moray eels have two jaws, but they also have two sets of nostrils. The large, obvious nostrils on the end of an eel’s nose are the anterior nostrils. While the posterior nostrils are near its eyes. On a dragon moray eel, the nostrils are long and thick. The posterior nostrils almost look like antlers. Dragon moray eel nostrils also have the same vibrant orange and white pattern as the body.
Despite the large nostrils, moray eels breathe through their mouths to force water over their gills
Many divers get nervous when they see a moray eel opening its mouth and flashing those sharp teeth. But the eel is not threatening them, or preparing to attack. Moray eels have to breathe through their mouths in order to pump water over their gills. Those pronounced nostrils are better suited for hunting than breathing. Plus, moray eels are usually shy around humans.
4. Moray eels are ambush hunters
Moray eels are carnivorous. They usually eat fish, octopi, or crustaceans. A moray eel that leaves the reef and swims in open waters is at risk of being eaten itself. So moray eels are ambush hunters. The green moray eel doesn’t like to chase after prey. Instead, the eel will stay in its coral nook. When they sense prey approaching, the eel lunges forward and hooks the prey on its teeth.
The giant moray eel sometimes hunts with roving coral groupers
Roving coral groupers are large ray finned fish that prey on smaller fish, octopi, and moray eels. But sometimes a grouper will recruit a giant moray eel to help it hunt. The grouper shakes its head at the eel to signal it wants to work together. Groupers are too big to fit in reefs, and hunt in open water. Groupers will chase fish, and the moray eel will sneak up on it when it thinks it has escaped. But if the eel tries to escape before the grouper gets dinner, the eel becomes dinner.
5. Moray eels have a layer of mucus on their skin that allows them to slip through narrow crevices
Moray eels secrete mucus all over their body. The mucus is slimy, and works like grease for the eels. With a layer of mucus, a moray eel can slip through narrow, tight crevices throughout a coral reef. The secretion also protects the eel against cuts from abrasive coral. The mucus layer is also thick enough to change an eel’s appearance. A green moray eel is actually brown, but the mucus gives it the green color.
Crinotoxins in the Mucus Makes A Moray Eel Bite Dangerous
A moray eel bite won’t kill you, but it will hurt. You’ll also probably bleed more than if another fish the same size bit you. The mucus contains a protein that causes red blood cells to clump. This protein is called hemagglutinin. The mucus also contains toxins that are haemolytic. This means that they destroy red blood cells. If you touch a moray eel and the eel bites back, you can get very sick.
6. Small Moray Eels are popular pets for advanced aquarists
Smaller species of Moray eels, such as the zebra moray eel, can be pets in home aquariums. The zebra moray eel doesn’t grow any bigger than five feet, and has striking black and white stripes. However, only experienced aquarists should keep them. Moray eels are sneaky, and will try to sneak out of its tank. You don’t want to wake up one day and find your beloved eel dried up and dead on the floor.
The freshwater moray eel has slightly toxic saliva that intensifies bite pain
Gymnothorax polyuranodon, known as the freshwater moray eel, is popular among aquarists. This eel has yellow and brown coloring, like an overripe banana. It also has toxic saliva that makes bites extra painful. The toxicity level is low, so the bite won’t kill you. However, it has been known to prolong and intensify pain from bites. It also carries the risk of infection.
Only 5 species of moray eel can cohabitate with other fish
Out of 200 moray eel species, only five can share a tank with other fish. That’s only 2.5%. Moray eels are solitary, and don’t socialize well. If you introduce fish or crustaceans to a moray eel’s tank, the eel will likely eat them.
Keep your distance from these colorful eels
Moray eels come in hundreds of stunning colors and patterns. But if you ever go scuba diving and see one, it's best to admire the eel from a safe distance. Also remember, moray eels are not related to snakes. But with their powerful secondary jaws, you can think of them as xenomorphs that look like they told a really bad joke and are waiting for everyone to laugh.
How endangered is this animal?
- Moray Eels are not directly threatened by humans
Giant Moray eel meat is poisonous unless it is cooked well-done. You won’t find it in sushi rolls. But even cooked giant moray eel doesn’t taste good. With its bad taste, slippery movements, and hide and seek expertise, moray eels aren’t viable for commercial fishing. So human activity is not a direct threat to moray eels.
- As shark populations decline, moray eel populations increase
Sharks prey on moray eels. However, commercial overfishing has devastated the shark population in the wild. A recent study conducted by Florida International University found that eel populations are thriving in coral reefs close to large populations of humans. Reefs near large cities are prime spots for fishermen, who capture sharks to sell their exotic meat and fins. While moray eels are fantastic fish, sharks are awesome and deserve to thrive in the wild!
- Moray eels need healthy coral reefs to survive
Even as moray eel populations boom, they are still dependent on healthy coral reefs to survive. Climate change threatens the world’s coral reefs. Scientists believe that a global temperature increase of 2℃ will kill over 90% of the world’s coral reefs. Without coral reefs, moray eels, and millions of other species, will not survive.
Also Known As
1.5 - 3.5 metres (5 - 11.5 feet)
Worldwide but are most commonly found in tropical and temperate waters
Rocky tidal areas, coral reefs, mangroves or sandy bottoms
Crustaceans, octopus and small fish
On average 10-40 years