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Green Moray Gymnothorax prasinus
(Richardson, 1848)

Common name

Green Moray

Scientific name

Gymnothorax prasinus
gymno - bare, naked (Greek)
thorax - chest (Greek)
prasinos - leek green (Greek)

Family name

Muraenidae
muraena - eel (Latin)
idae - suffix meaning that this a family name. All animal family names end in -idae.

Green Moray Gymnothorax prasinus, photographed at Halifax Park, Nelson Bay, New South Wales. Green Morays can be yellowish-brown, like the one shown here, to bright green.

Size

Morays range in size from the 20 cm Redface Eel Monopenchelys acuta, found in the Atlantic and Indian Oceans, to the huge 3.75 m Longtail Moray Strophidon sathete, found in the Indo-Pacific. The Green Moray grows to a maximum of 1.5 m in length, although it commonly reaches about 1 m.

Number of species

The family Muraenidae is one of the most abundant and widespread of all eel families. It contains an estimated 200 or more species in 15 genera. The genus Gymnothorax contains an estimated 120 species worldwide, with about 30 species in Australia. Around Sydney, there are 4 local species, with several other tropical species that occur in the region as juveniles. The is still much work to be done on revising the taxonomy (classification) of this group of fishes.

Distribution

Moray Eels occur in all tropical and temperate oceans of the world. In Australia the Green Moray occurs in temperate coastal waters from south-eastern Queensland to Shark Bay, Western Australia, including northern Tasmania.

View a map of the collecting localities of specimens in the Australian Museum Fish Collection.

Habitat requirements

Green Morays can be found in shallow rocky and weed-covered marine waters, in estuaries and in deeper offshore waters. They are usually seen with only the head protruding from a crevice in the rocks or occasionally a person-made object such as a pipe.

This image shows A Sieve-Patterned Moray (view fact sheet) with its head protruding from a hole in the reef. Photograph taken at Clifton Gardens, Sydney Harbour.

Structural, physiological and behavioural adaptations

Despite their fearsome appearance morays are not considered dangerous to people, although larger individuals can inflict serious wounds. It has been reported that some species have poor eyesight. This may account for morays sometimes attacking the hands of divers, which may be mistaken for an octopus. Moray eels have no pectoral or pelvic fins. They are very successful fishes which have several interesting adaptations.

Tubed nares (nostrils)

Morays have an excellent sense of smell, and have the nares (nostrils) developed into tubes. Most fishes have two nostrils on each side of the head. Water passes in the anterior nostril and out through the posterior nostril. Under the skin, between the 2 nostrils, lies the nasal apparatus, which gives the fish its sense of smell.

For most fish species it is common for the 2 nostrils to be close together. In the Green Moray however, the nostrils are widely separated. The anterior nostrils, located on the snout are extended into tubes, whereas the posterior nostrils have shorter tubes and are situated above the eyes. The nostrils of some morays have been developed to an extraordinary extent. Those of the ribbon eel Rhinomuraena quaesita are highly developed.

The Tessellate Moray has dagger-like teeth in the roof of the mouth. Image © B. Goldman.

Large mouth with sharp teeth

All morays are carnivorous (meat eaters). Their teeth vary in size and shape, from the huge fangs of the Dragon Morays, genus Enchelycore, to the low, rounded teeth found in the genera Echidna and Gymnomuraena. Morays of the genus Gymnothorax have large mouths and an impressive array of teeth. The Green Moray's mouth extends back to well behind the eye. The large, sharp teeth are arranged in single rows in both jaws and also in a row along the roof of the mouth.

Morays have the ability to tie their bodies in knots and use this to gain leverage when tearing food. It was long thought that this was only a story, not based on fact, but has since been verified.

The image above shows some of the impressive teeth of a small Tessellate Moray. This species is one of the largest morays, growing to 1.8 m. It is found in tropical waters of the Indo-West Pacific.

View larger image.

Reclusive habit

During the day, many morays are found in crevices and holes in both rock and coral reefs. This habit affords the moray protection from predators and allows it to strike at prey from a hidden position. Despite their reclusive habits, in some places Morays make up a huge proportion of the carnivorous fishes. On some reefs in Hawaii morays make up 46 percent of the total weight of carnivorous fishes.

Anguilliform swimming

Long, flexible fishes such as eels swim by flexing the whole body into lateral waves. This is known as anguilliform swimming. Most eels (including the Green Moray) have laterally compressed tails. The Green Moray also has well a developed dorsal fin (see image) which results in further compression of the body.

This increases swimming efficiency in the same way that a flattened oar is more efficient for rowing than a rounded pole. The morays use anguilliform swimming to great effect when they dart forward out of a crevice to seize prey (invertebrates and fishes), and they can swim nearly as well backward, which is handy for entering into the shelter of a crevice or hole to avoid predators.

Anguilliform swimming is named after a genus of freshwater eel, Anguilla (view fact sheet for A. reinhardtii). Four species of this genus live in Australian freshwaters, 2 in the Sydney region. All morays are marine fishes and are in a different family to the freshwater eels.

Leptocephalus larval phase

The life cycle of all eels involves a larval phase during which time the developing eel is known as a leptocephalus. Unlike many (but not all) species of adult eels which are bottom living fishes, leptocephali are found in the plankton in open water. The leptocephali of the freshwater eels make incredible journeys of thousands of kilometres from the open ocean spawning grounds of the adults into freshwater streams.

Follow-up questions

Do any other fishes, other than eels have a leptocephalus larval phase?
Morays do not have pectoral fins. Name a family of eels that do.
How does the anguilliform swimming of the Green Moray differ from the swimming mode of a tuna?