Gymnothorax griseus – Geometric Moray
Gymnothorax griseus was first described by Bernard Germain de Lacépède in 1803. This species belongs to the family Muraenidae or the Morays. The genus name “Gymnothorax” comes from the Greek “gymnos” (naked) and “thorax” (chest), referring to the lack of pectoral fins. The species name “griseus” means gray in Latin, referring to the color of the fish. It’s commonly known as Geometric moray, a reference to the species name Muraena geometric, which has now become a synonym.
Synonyms: Muraenophis grisea, Siderea grisea, Siderea schonlandi, Muraena geometrica.
Description
Gymnothorax griseus has a slender, eel-like body that can grow up to 65 centimeters long. The head is grey or lilac with characteristic black spots that form a geometric pattern. The fins are not conspicuously colored, and the fish has no pectoral or pelvic fins. A striking feature is the lack of scales, which enables them to hunt smoothly in tight cracks and crevices.
Differences between sexes:
There is no clear sexual dimorphism in this species. As hermaphrodites, both males and females can function as both sexes at the same time.
Behavior and Temperament:
The Gymnothorax griseus is generally a solitary and non-aggressive fish. It is nocturnal and hunts primarily at night. It often lives in caves or crevices in coral reefs.
Life expectancy:
In the wild, they can live up to 30 years.
Opening and closing the mouth a threat?
Gymnothorax griseus has proportionally small, round gills located at the back of the mouth. This forces the fish to open and close its mouth constantly. This ensures sufficient water flow over the gills, which is essential for the fish to breathe.
The regular opening and closing of the mouth, which can often seem threatening to divers and snorkelers, does not serve as a threat but is simply a necessary breathing activity for this moray eel. The small gills and the constant opening and closing of the mouth are characteristic adaptations of moray eels to take in sufficient oxygen.
Biotope
Gymnothorax griseus is found in the western Indian Ocean, including the Red Sea, the Arabian Sea, and the Persian Gulf. They live mainly in coral reefs and rocky environments up to a depth of 40 meters. Their natural habitat consists of many corals and rocks, which provide them with shelter. They are hunters themselves and have no specific natural predators.
Diet
In the wild:
Gymnothorax griseus feeds on small fish, shrimp and other small marine animals.
In the aquarium:
In an aquarium, they can be fed meaty foods such as fish, shrimp, and squid. It is not advisable to feed them coral or polyps, as they are not reef-safe.
The Aquarium
Aquarium size:
An aquarium of at least 2000 liters is recommended for this species. An even larger aquarium is necessary for keeping multiple specimens.
Decoration:
Decorate the aquarium with lots of rocks and hiding places. Sand is the best substrate.
Water parameters:
The ideal water parameters are a temperature of 24-28 °C, a pH of 8.1-8.4, and a salinity of 1.020-1.025.
Compatibility:
They can live with larger, non-aggressive fish, such as certain types of groupers. However, due to their diet, they are not suitable for a reef tank.
Breeding in the Aquarium
There is no specific data on breeding Gymnothorax griseus in an aquarium. In the wild, they are oviparous, and the eggs are pelagic. This means that they are laid in open water. They float in the ocean until they hatch, and the young moray find a place between some rocks.
Particularities
Gymnothorax griseus is known for its association with groupers during hunting. These groupers drive prey out of their hiding places. Gymnothorax griseus has an excellent sense of smell, which helps them in hunting.
Conclusion
Gymnothorax griseus is a fascinating species for advanced aquarists due to its unique behavior and appearance. However, it requires a large aquarium and specific care, making it less suitable for beginners. One notable feature is its ability to cooperate with other predatory fish during hunting.
Video
Author
John de Lange
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