Episode 124 – Giant Moray Eel: The Alien of the Deep

“And today we’re talking about a sci-fi fish with some grumpy gills. But more on that later.”

If you were to go diving almost anywhere in the shallows of an Indo-Pacific ocean, there’s a good chance you’ll find a moray eel stationed in some of the porous holes left in the rocky coral reefs. Looking like a cross between a snake, a dragon, and a cartoon witch, the moray eel poses little threat to humans, but is a menace to reef fish. With an unusual jaw that you might find in a painting by H.R. Geiger, the moray may seem a little unhinged when he eats. But getting a good grip on your prey is the best way to catch a slippery fish here in Life, Death, and Taxonomy.


  • Moray eels are essentially long fish with snake-like bodies.
  • They have dorsal and anal fins that run the length of their bodies.
  • Giant morays come in greenish grey to brown colors. 
  • Young eels can be tan while adults have black speckles or leopard prints on their backs.
  • Their gills are small and circular.
  • They have no scales and their skin is covered in mucous. 

Measure Up

Welcome to the beloved Measure Up segment. The official listener’s favorite part of the show! The part of the show when we present the animal’s size and dimension in relatable terms through a quiz that’s fun for the whole family. It’s also the part of the show that’s introduced by you when you send in audio of yourself saying, singing, or chittering the words measure up into ldtaxonomy at gmail dot com. We don’t have a measure up intro so that means we get to hear from an animal and Carlos will guess what it is.

  1. Squirrel
  2. Crow
  3. Heron
  4. Baby bear


  • The Giant Moray is the longest in its family at 3m (9.8 ft)
  • How many moray eels go into the longest ever sushi roll?
  • The record was achieved in Tamana, Kumamoto, Japan in November of 2016. The roll was created with the help of almost 400 people.
  • 952.3 eels. The roll was 2,844.61 m (9,332 ft 8 in).


  • 30 kg (66 lb)
  • How many krill go into the weight of a giant moray?
  • Krill are shrimp like crustacean that are a big part of the diets of whales, seals, squid, icefish, and penguins.
  • 15,000 Krill. Krill are 2 grams (0.071 oz).

Fast Facts

  • Giant morays are widely distributed throughout the ocean, especially the indo-pacific.
    • They can be found on the coast of Africa, red sea, Polynesia, Japan, Fiji, and other places.
    • They enjoy lagoons, coral reefs, and anywhere they can find little crvasses to hide in. 
    • They can be found anywhere between 1 and 50 meters deep.
  • They are carnivorous, hunting prey at night.
    • Sometimes they hunt cooperatively with other fish. Specifically the roving coral grouper.
    • Grouper hunt in open water near reefs. Eel scare prey out of cover while grouper do the opposite.
    • Whatever one doesn’t catch, the other gets.
    • They often hunt by ambush by striking from the cover of the reef.
  • Their long bodies are adapted for life in reefs and rocks where they can slip through small spaces, aided by their slimy bodies.
    • They eat crustaceans and fish with strong jaws designed for catching and monching. 
    • Moray eels are natural predators of the lionfish, which is significant for Florida waters where the invasive fish is wreaking havoc, unchecked.
    • Moray eels may be the heroes we need to safe Florida reefs.
  • Because of something called, biomagnification, eels may be hazardous to humans when consumed.
    • Biomagnification happens when toxins like pesticide and food-borne illnesses like ciguatera.
    • Animals that are high on the food chain eat things, that eat things that eat things which all have these toxins in their bodies.
    • Top predators often have enough toxins to make people sick.
    • Other fish like tuna can also be harmful.
    • The livers of these animals are particularly dangerous.


  • Morays have a unique way of getting a grip on things.
  • Fish and cephalopods are slippery and fast, which can be a problem for ambush predators like the moray
  • So when a tasty morsel swims by, it strikes at it with its fierce jaws that are able to crush bone. But it also has a secret weapon.
    • A second, smaller set of jaws located just behind the first
    • These secondary jaws, called pharyngeal jaws, rest at the top of the eel’s throat and shoot out to grasp the prey that’s already clutched in the main oral jaws. Then they retract, dragging the prey into the throat whole.
    • Moray eels aren’t the only animals with pharyngeal jaws, but they are the only ones that can extend them out to capture prey.
  • The question is, why do they need these junior jaws?
    • Other predatory fish like barracudas, groupers, and sharks seem to have no problem eating slippery smackerels without the help of a little xenomouth.
    • The understanding behind this is the fact that most other fish swallow prey by sucking water in with negative pressure like a vacuum. All they need to do is expand their mouths and throats to let water and prey come rushing in. But the moray eel can’t create this vacuum.
    • Instead, the moray sacrifices suction power for speed and accuracy when striking.
    • When anything moves in underwater, it displaces the water around it. So if you were to try and punch a ball suspended underwater, you would actually move the ball before your fist ever reached it. This can be a problem when you’re an eel trying to get a meal. The fish or crab you’re going for might be accidentally pushed away when you lunge.
    • So the moray instead lets water flow through its gills as it strikes, streamlining the eel’s head and reducing the amount of water it’s pushing forward.
    • That allows it to strike its prey, but now it doesn’t have a way to bring it down into the throat – enter, junior jaws.

Ending: So stay in your den, keep an eye out for food and danger, and always make sure to take advantage of your secondary pharyngeal jaw when feeding like the moray eel here in LDT.


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