Moray eels, belonging to the family Muraenidae, are fascinating creatures found in oceans worldwide. With over 200 known species, these eels exhibit a wide variety of colors and patterns, and they play a vital role in their ecosystems. This article delves into the dietary habits of moray eels, exploring what they eat, how they hunt, and the unique adaptations that make them successful predators.
General Characteristics of Moray Eels
Moray eels possess elongated, snake-like bodies, often brightly colored and patterned for camouflage. Most species lack pectoral and pelvic fins, enhancing their serpentine appearance. A long dorsal fin extends from just behind the head, running along the back and seamlessly joining the caudal and anal fins. Their skin is thick, smooth, and scaleless, covered in a protective mucus that, in some species, contains toxins. This mucus protects them as they navigate jagged coral and rocky crevices.
Moray eels have poor eyesight and rely heavily on their sense of smell to locate prey. Their faces feature two nostrils, visible as small openings, which aid in sensing their surroundings. The jaws of moray eels are wide, framing a protruding snout, and most possess large teeth used to tear flesh or grasp slippery prey. Uniquely, moray eels have two sets of jaws: oral jaws with sharp teeth and pharyngeal jaws located further back in the head.
Diverse Diets of Moray Eels
Moray eels are carnivorous, opportunistic predators. They are not picky eaters and will prey on any fish that is small enough for them to consume, as well as crustaceans and cephalopods.
- Fish: Moray eels hunt for fish in small crevices along coral reefs and shorelines. They consume a variety of fish species, making them important in maintaining the balance of reef ecosystems.
- Crustaceans: Crabs and shrimp are common components of the moray eel diet.
- Cephalopods: Octopuses, squid, and cuttlefish are also preyed upon by moray eels.
- Other Marine Life: Some moray eels have been observed eating groupers, sea snakes, lionfish, and barracudas.
Moray eels are also known to consume invasive lionfish, helping to control populations of this harmful species in some reef environments.
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Hunting Strategies and Feeding Behaviors
Moray eels are primarily nocturnal, meaning they are active at night and asleep during the day. During the daytime, they are sedentary or sit-and-wait predators, preferring small spaces and hiding places in rocks and caves. They lie in wait, concealed in their habitat, until prey swims by.
When a potential meal appears, the moray eel uses its keen sense of smell to detect the prey. Once located, they propel forward with jaws open. Their mouth openings extend far back into the head, which, combined with the presence of pharyngeal jaws, allows them to capture and consume prey efficiently.
- Pharyngeal Jaws: Moray eels are the only known animals that use pharyngeal jaws to actively capture and restrain prey. When feeding, they launch these jaws into the mouth cavity, where they grasp the prey and transport it into the throat. The pharyngeal teeth point backwards, making it nearly impossible for prey to escape.
- Mouth and Jaw Adaptations: In the action of lunging at prey and biting down, water flows out the posterior side of the mouth opening, reducing waves in front of the eel which would otherwise displace prey. Differing shapes of the jaw and teeth reflect the respective diets of different species of moray eel. Short, rounded jaws and molar-like teeth allow durophagous eels to crush shelled prey.
- Knotting Behavior: If the fish appears too large to consume whole, the eel can wrap itself around the fish in a knot to disable it and then consumes it after tearing it into smaller pieces. When attacking an octopus, the moray can tie itself in a knot to avoid the grip of the octopus’ arms.
Cooperative Hunting
Reef-associated roving coral groupers (Plectropomus pessuliferus) have been observed recruiting giant morays to help them hunt. The invitation to hunt is initiated by head-shaking. This interspecies cooperative hunting demonstrates the adaptability and intelligence of moray eels as predators. 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.
Habitat and Food Availability
Moray eels can be found in both fresh and saltwater habitats, though the vast majority of species are strictly marine. They inhabit tropical and temperate ocean environments with reefs, preferring dead patch reefs and coral rubble rocks over living coral reefs. Their diet is influenced by the availability of prey in their specific habitat.
Examples of Moray Eel Species and Their Diets
- Green Moray Eel (Gymnothorax funebris): Found in coral reefs, mangroves, tidal creeks, and areas with sandy or muddy bottoms. Their diet typically includes crustaceans, octopus, and small fish.
- Giant Moray Eel (Gymnothorax javanicus): Distributed throughout the Indo-Pacific region, including the Red Sea, East Africa, and Micronesia. They primarily feed on reef fish and crustaceans.
- Snowflake Moray Eel: A popular choice for aquariums due to their flexible diets.
- Zebra Moray Eel: Another popular aquarium species known for its distinctive black and white stripes.
- Honeycomb Moray Eel: These eels are white with large brown spots.
Human Interactions and Conservation
While green moray eels are not currently threatened, their coral reef habitat is under pressure-primarily from global warming. Since the 80’s our oceans have absorbed 90% of the excess heat in the atmosphere and up to 30% of carbon emissions from the fossil fuel industry. This mixture of heat and carbon emissions leads to a domino effect of negative consequences starting with increased acidity in our oceans and leading to mass bleaching of coral reefs. If the planet heats up by 2°C, nearly all of the world’s coral reefs, including places where moray eels live, will die. Though these eels are considered not threatened with extinction, they are still highly impacted by changes in the environment, and very susceptible to the damaging effects of overfishing and ocean pollution.
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Moray eels, particularly the giant moray (Gymnothorax javanicus) and yellow-edged moray (G. flavimarginatus), are known to accumulate high levels of ciguatoxins, unlike other reef fish; if consumed by humans, ciguatera fish poisoning may result. Ciguatera is characterised by neurological, gastrointestinal, and cardiovascular problems that may persist for days after eating tainted fish.
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