Moray Eels: Double-Jawed, Oddball Fish

Moray Eels Would you believe moray eels are actually fish? Moray eels are such interesting creatures that are often a highlight of a scuba diving adventure. When on a dive, it becomes a sort of treasure hunt, looking into all the cracks and crevices to get that glimpse of an eel. On the other hand, if you are lucky, you may even see an eel out swimming on the reef! While moray eels are truly interesting creatures that many divers wish to encounter, it can be terrifying to some divers that may have had the chance encounter of an eel lunging at them! Be aware of your surroundings and keep your hands off the reef or you might get a mouth full of eel on your hand! Overall, moray eels are beautiful, colorful, creatures that should have their space respected.

Despite the common use of moray eel as a specific type of eel, it is actually a family of eels that includes about 200 species. The snowflake moray and zebra moray eels are the two most popular choices of species to keep in an aquarium. Moray eels are known for their slithering snake-like appearance, but they spend most of their time hiding in rocks and crevices.

Biology of Moray Eels

Moray Eel FangToothThese snake-like creatures belong to the Class Actinopterygii, the ray-finned fishes. These bony fish lack scales. Even though moray eels appear to be smooth, they do have fins! They have a dorsal fin that connects all the way to the caudal and anal fins giving the eels a mohawk appearance. The body of moray eels is covered in a mucus layer, and in some species, this mucus is toxic. The mucus is secreted by goblet cells and acts a protective barrier against abrasions from hiding out in the rocks.

Moray eels have very poor vision. They rely on chemoreception, a physiological response to chemical stimuli, to catch their food. The large nostrils also aid in sensing what is around them. Moray eels are nocturnal, thus good eyesight is not a necessity for these creatures. A night dive in warm, shallow water will often allow you to witness the beauty of moray eels out swimming on the reef.

Moray eels are very colorful. They can be black, gray, brown, yellow, green, blue, orange, or white. All these colors can appear as stripes, spots, or some other pattern on the eel. Some moray eels, such as the banded moray eel, can even change their colors to better camouflage. An interesting fact about the green moray eel is that is actually brown! The mucus covering its body is what gives the green moray eel a green-like appearance.

Moray Eel Distribution

Moray eels can be found worldwide but are most commonly found in tropical and temperate waters. Most moray eels are found in seawater, but some can be found in brackish water or even freshwater. Moray eels hide out in the crevices of reefs or wrecks, swimming out only to catch their prey or if they feel their space has been invaded.

Reproduction of Moray Eels

Similan Moray Moray eels reproduce by fertilization that is oviparous, when eggs and sperm are fertilized in the water outside the womb, also known as spawning. On average, female moray eels can release 10,000 eggs at a time. These eggs are fertilized by the sperm of male eels and become part of the plankton as larvae, fighting to survive in the open ocean. After about a year, the moray eel larvae are big enough to swim down to the ocean floor and hide in rocks and crevices. Moray eels will live on average 10-40 years.

Predators: What eats moray eels?

Moray eels have few predators. Their predators are usually the apex predator in their ecosystem. Grouper, barracuda, sharks, and humans are common predators of moray eels. However, moray eels and grouper have been found to work together at times to hunt. The grouper will come in and shake its head vigorously at a moray eel, signaling that it wants help feeding. The moray eel swims with the grouper and traps fish. If the moray eel tries to escape, it gets eaten by the grouper! Just when you thought the moray eel was viscous looking with its mouth wide open, the grouper is actually the one that tells the eel what to do!

Humans commercially fish moray eels, but most eels’ skin is toxic and could kill humans. Moray eels are not yet endangered, but as they are vital to the underwater ecosystem, overfishing of moray eels could disrupt the abundance and behavior of fish on coral reefs.

What do moray eels eat?

Moray eels are carnivorous. They are ambush predators that pounce on a prey as it passes by. They eat fish, molluscs (squid and cuttlefish), and crustaceans (crabs). I once witnessed the beautiful zebra moray eel demolish an urchin!

Why do moray eels always look like they are ready to bite?

Moray eels are often seen with their mouths open, but do not be afraid! Although it looks like they are mad and about to bite, this is how they breathe. They breathe by passing water through their mouths past their gills. However, caution should always be taken around moray eels as they can lunge and bite in an instant if they feel threatened! I would not want to get my hand stuck in their two jaws!

Moray eels have two jaws?

Yes, this is correct. Moray eels have two jaws! Moray eels have a regular jaw with big teeth often called the oral jaw. A second jaw, the pharyngeal jaw, sits in the throat. The regular oral jaw initially bites the prey, and the pharyngeal jaw lunges forward to grab the prey and pull it into the animal’s gullet. The pharyngeal teeth are backwards pointing making it impossible to escape its grasp. Some moray eels have teeth on the top of their mouth to aid in pulling prey in.

How big are moray eels?

Moray eels are typically between 10 cm to 10 feet long, but there seems to be no consensus on this. The longest moray eel, the Slender Giant Moray, has been recorded at 13 feet long! The Giant Moray, although smaller in length at 8 feet, is the largest because it also weighs 66 pounds.
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