Moray Eels

There are many animals whose potential harm to humans has been sensationalized. Sharks, giant octopuses and barracuda are all examples of sea creatures with people-biting proclivities that have been overblown in movies, news articles and even documentaries. Even as more people explore the underwater world and better understand its inhabitants, there are still those who exaggerate the dangers these animals pose to people.

Click image to enlarge Smaller morays make excellent aquarium pets if their care requirements are met. This is the ubiquitous goldentail moray (Gymnothorax miliaris).

The yellowmouth moray (Gymnothorax nudivomer) is a unique member of the family because it exudes a toxic mucus that may dissuade predators and parasites.

Another group of marine creatures given a bad rap is the moray eels. Members of this family have been implicated in few unprovoked attacks on divers. But these moray eels rarely bite people, unless they are harassed or if a human does something stupid, such as stick a hand in a moray eel’s lair or try to hand-feed one.

Some aquarists are attracted to the idea of keeping an eel in their marine aquarium because of their undeserved reputation (this is the same guild of folks that would keep piranhas for similar reasons in a freshwater tank). But there are aquarists who are attracted to moray eels because many sport dramatic color patterns, exhibit interesting behaviors and can make fascinating pets.

I’d now like to survey what you should know before making the commitment to becoming a moray eel keeper.

Family Overview
Moray eels belong to the family Muraenidae. This family is comprised of 15 genera and approximately 200 species. All are characterized by a lack of pectoral and pelvic fins; gill openings that consist of small holes with no bony covers; large, toothy jaws; and dorsal and anal fins that are continuous around the tail. Morays lack scales but instead exude large amounts of body slime to protect themselves from parasites.

A few moray eels (e.g., yellowmouth moray eel, Gymnothorax nudivomer) are known to exude a toxic slime that may dissuade parasites from attaching to them. Morays almost always have their mouths open. Although this looks menacing, it is simply how morays respire. The mouth remains open as they pump water over the gills with the muscles in the gill cavity. While the color of some morays is dull and monochromatic, other species sport dramatic patterns that may include bands, spots and mottling.

While some moray eels have fanglike dentition (e.g., dragon moray eel, Enchelycore pardalis), there are other species with molarlike teeth (e.g., zebra moray eel, Gymnomuranea zebra) that are perfectly adapted to crushing hard-shelled invertebrates (e.g., crustaceans, snails, sea urchins).

When it comes to food habits, moray eels can be classified into one of three general categories: mainly fish-eaters, mainly invertebrate-eaters and those that feed almost equally on fish and inverts.

A classic fish-eater is the purplemouth moray eel (Gymnothorax vicinus). This moray has smaller teeth on the sides of the jaws and sharp, daggerlike dentition running along the roof of the mouth. A classic invertebrate-eater is the banded moray eel (Echidna polyzona). This species uses the pebblelike teeth in its jaws to crush the crabs that it hunts. The stout moray eel (G. eurostus) is a species that feeds on both benthic fish and invertebrates (namely crustaceans).

Obviously, it is important to know something about the diet of the moray before you add it to your community aquarium.

Alienlike
Recently, a fascinating discovery was made about the moray eel feeding apparatus. It turns out that morays have a second set of jaws in the pharynx that possess recurved teeth. When a moray bites its quarry with its main jaws and begins to move it into the mouth, the jaws in the pharynx are extended to grasp the prey item and pull it deeper into the esophagus (they are something like the jaws of the creature in the Alien movies). It has been speculated that they have these specialized pharyngeal jaws because it is often difficult for them to open their primary jaws fully while hunting in tight spaces, such as in reef crevices and interstices. The pharyngeal jaws enable the moray to transport the food into the gullet without having to achieve a full jaw gape.

Deciding on a Moray
Is a moray eel right for you? These marine animals do have special care requirements. Most cannot be dropped in the average marine aquarium without serious repercussions. Therefore, the careful aquarist will want to consider some specific questions before deciding to purchase a moray eel.

First, what moray eel species are you considering? This family is comprised of quite a few species, and as you might expect, the family members can vary considerably in dimensions and behavior. They also exhibit some dietary diversity. The species you choose will determine the dimension of the tank required and possible tankmates you keep it with. Therefore, thorough research into the characteristics of the various species is in order before you make your selection. Next Page>>

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