ribbon eel

Photograph by Tim Laman, National Geographic Society.

Although this creature may look like a colorful dragon straight out of Chinese mythology, it is actually a marine ribbon eel, Rhinomuraena quaesita, an eel commonly found in lagoons and reefs of the Indo-Pacific Ocean. These unusual sea creatures have long slender bodies and pointed snouts with a barbel-like appendage.

Ribbon eels are found in shallow waters and typically burrow into sand, mud, or coral rubble. However, they have also been observed living in holes in the hard reef substrate.

While the ribbon eel is part of the eel family, it has some very distinct characteristics that make it stand out. Furthermore, it has other aspects that make it very difficult to keep in captivity. Learn more about this eel and how special it is.

Misfit of the Morays

The ribbon eel is an unusual fish that is typically classified as a member of the moray eel family, Muraenidae, a group that consists of approximately 200 unique species. Morays are found across the world ocean, typically in tropical or subtropical waters. Despite its classic categorization as a moray eel, it bears a number of distinctive characteristics that suggest it may be a misfit of the morays or an eel worthy of a family all its own.

Juvenile Ribbon Eel

Juvenile Ribbon Eel

For one thing, these eels are protandrous hermaphrodites. This means that they are born as males but ultimately change sex to females later in their lifespans. The behavior of protandrous hermaphroditism likely evolved because ribbon eels continue to grow as they age, and females can reproduce more effectively when they are larger in size. This hypothesis is known as the size-advantage model of protandrous hermaphroditism. Additionally, as they develop sexually, they change color from black (juveniles) to blue with a yellow dorsal fin (adult males), to completely yellow (adult females). This unique change in color associated with protandrous hermaphroditism is not observed in any of the other morays, suggesting that the ribbon eel may not fit so nicely into the moray eel family.

Another factor that seems to set this eel apart from other morays is the unique positioning of its kidneys and most of its reproductive organs. These organs are located posterior to the anus, a morphological condition that has not been reported in any other vertebrate in the world. These unique characteristics have prompted some to classify this eel in its own family, Rhinomuraenidae.

Dangerous Times

Bleached Coral home of ribbon eel

Bleached Coral

Like other reef-dwelling fish, ribbon eels are susceptible to the imminent threat of global climate change. A primary concern is ocean acidification. The ocean acidification problem stems from human burning of fossil fuels, which releases carbon dioxide into the atmosphere. This carbon dioxide is absorbed into the oceans, and its unique chemistry results in decreased availability of the carbonate ion in ocean water. This has a direct effect on calcifying organisms, such as corals, which need carbonate ions to build their calcium carbonate skeletons. Ocean acidification can lead to coral bleaching events, large-scale occurrences of coral fatality, that degrade the coral reef habitat where the ribbon eel and other important sea creatures reside.

Ribbon eels also face the threat of commercial harvest for the aquarium trade, especially in Indonesia. Their bright, beautiful colors make them an attractive option for those who wish to include an eel in their aquarium. However, this threat is thought to be mostly localized and is not expected to significantly affect global ribbon eel population.

A Ribbon Eel in Captivity

An Adult Male Ribbon Eel

An Adult Male Ribbon Eel

While the ribbon eel is a beautiful fish, especially in its adult male stage, it is recommended that only those with extensive experience in keeping morays in captivity should purchase one for their personal aquarium. These eels have been observed to stop eating when placed in captivity, and often do not survive for more than a month. In addition, the normal color changes throughout the eel’s lifespan do not occur in the same in captivity.

The best things to feed a captive eel include squid, shrimp, krill, and live fish, such as guppies. When feeding, it is recommended to use tongs to avoid an accidental or intentional bite from an eager eel.

It is unlikely that breeding of ribbon eels would be effective in a personal aquarium. However, a recent study has demonstrated successful spawning in commercial tanks at the Vienna Zoo. All things considered, these eels can be successfully kept in captivity with a tank of the proper size, adequate water flow, and a bottom layer of sand with sufficient depth. They also perform better when kept in pairs. Though they may require a lot of work and a certain level of expertise, colorful ribbon eels make a fantastic addition to a tropical aquarium.

Last Word

The ribbon eel is just not like other eels. It really stands out in many distinct ways. This is why it gets it own part of the Moray family to hang out in. This unusual eel is beautiful to look at and can be a great addition to an aquarium, but if you choose to add one to yours, be ready for the specific care required to keep it healthy and happy.