Just another Sex-Changing Eel...

Tenzin Choezom
Jun 24, 2021
3 min read

The ribbon eel (Rhinomuraena quaesita), also known as the bernis eel or leaf-nosed moray eel, dwells predominantly in warm lagoons and coastal coral reefs in the Indo-Pacific ocean and leads a fascinating life!

Basic Facts

Males can range from 26-40 inches in length, while females are around 51 inches.
Ribbon eels get their name from their slender bodies, which create ribbon-like movement when they swim.
They are also frequently spotted when scuba diving!

Habitat

As aforementioned, the ribbon eel is most commonly found in warm lagoons and coastal coral reefs in regions that encompass the Great Barrier Reef of Australia, French Polynesia as well as parts of East Africa and southern Japan. They tend to spend most of their time tucked away inside of caves, under the coral rubbles, or on mud and sand.

Life Cycle

What is interesting about the ribbon eel is that they actually undergo sequential hermaphroditism, meaning they change sex during their lifetimes!

First, the leaf-shaped eggs laid by a female ribbon eel float about in the ocean for approximately eight weeks, after which they hatch as males. You got that right- all ribbon eels are born male! The ribbon eel's juvenile phase is marked by its bright yellow dorsal fin and black underside. Juveniles live completely without parental care. After the juvenile phase, the jet-black underside of the ribbon eel matures into a brighter blue coloration while maintaining its yellow dorsal fin. When the ribbon eel grows to a length of around four feet, it not only loses its blue color to become fully yellow, it also develops female organs and changes in sex. In fact, when the ribbon eel was first discovered, the differences in coloration caused the juvenile, male, and female eels to be regarded as different species.

Mating is the only time when male and female ribbon eels meet each other and occurs when the water is the warmest. After the female ribbon eel lays her eggs, she dies within a month. Due to this short period, it is quite difficult to spot a female ribbon eel. The ribbon eel has an average life span of 20 years in its natural habitat.

Juvenile phase:

Male phase:

Female phase:

Diet

The carnivorous ribbon eel's diet consists mostly of small fish like guppies, fathead minnows, damselfish, mollies, shrimps, and other small crustaceans. They have rows of teeth that are sharp and great for shredding apart their prey. Their clamped nostril senses vibrations in the water and helps for defense and to locate their prey. They use their strong jaw to help catch them.

Behavior

Ribbon eels stick only their head out from inside a cave or a mudhole in order to keep an eye out for potential food.
The repetitive opening and closing of their mouth often are misunderstood as aggression, but it is actually just the ribbon eel breathing! This action helps the eel orally pump water through the gills.
They are not very territorial. It is said that two male ribbon eels can stay together for quite a long time. In some cases, one of the males will change sexes as a survival adaptation.
Ribbon eels are nocturnal, so it is uncommon to see them swimming freely in the open water during the day.
These eels are often kept as pets inside an aquarium but unfortunately, they do not survive for more than a month in captivity. They tend to stop eating altogether because they are quite picky eaters and eventually die.