Moray Eel

Moray eels that are also referred to as Muraenidae are the special and interesting creatures that are the centre of attention of scuba divers. They belong to the family of eels and are spread worldwide. They belong to the order Anguilliformes and of the suborder Muraenoidei. There are more than 200 species that are divided into 15 genera like Diaphenchelys that comprises 1 species, Echidna which comprises 11 species, Enchelynassa which comprises 13 species, Gymnomuraena which comprises 1 species, Gymnothorax which comprises 125 species and so on. These snake-like creatures belong to the class of Actinopterygii that is the class for ray-finned fishes.

They are exclusively marine species but many of their other species are almost seen regularly in brackish water and few of them are found in freshwater. They are the prime dwellers of tropical and sub-tropical water regions and are mostly seen in shallow water, especially, in the reefs and the marine rock where they hide in the crevices most of the time, especially when they are feel invaded and only comes out to catch prey to feed on them.

The fierce-looking moray is very sensitive and shy in nature and does not tend to attack humans until they are provoked. But they are highly toxic in nature and their bite results in very painful sensations and can cause infection. They can cause fish toxicity and poisoning in the body if consumed, especially the species that fall under the genus Gymnothorax.

They are of huge benefit to the ecosystem as compared to the danger they present. They help in balancing the food chain and the ecosystem of the marine environment by preying on fishes and invertebrates like mollusks, crustaceans and cephalopods. But they are also subjected to preying by few predators that are mainly groupers, another giant moray and barracudas. 

(Image will be uploaded soon) 

Image: Morey eel in Virginia Living Museum

Anatomy and Characteristics

Anatomy: the dorsal fins of moray eel species are well connected behind their head and runs along the back joining seamlessly with the anal as well as caudal fins. Due to the absence of the pectoral fins as well as pelvic fins, it provides them with a snake-like structure. Though their eyes are really small according to their physical structure they have a well-developed smelling sense that is strong enough to detect the approaching prey. Eventually, they lie quietly in the videos of the rock to ambush the prey. On the far posterior part of the mouth, the flank is where the small circular gills are attached. The gills require the moray to maintain a gap to facilitate an easy respiration process. The teeth of the creature are one of their biggest defence systems. They have wide jaws that frame their projecting snout.

Physical Dimension and Appearance

They are a colourful marine species that possess a smooth skin texture that is mostly grey or brown as their basic skin coat. Some of the other popular species are the green, orange, blue, white and ribbon eels. They have patches, spots and various patterns all over their body and some even have patterns inside their mouth that makes them the most desirable species to get a view. Generally, the average length of a moray eel ranges from 1 to 13 feet long. The smallest species of all of the species of eels known is dwarf that is native and is found in Hawaii. It just grows up to 1 foot long. The longest species is the slender eel that grows up to 13 feet long. The weight also varies widely with the variety of species of eels. Where the Hawaiian dwarf weighs about a few ounces whereas the heaviest species of eel known is the Giant moray that weighs around 66 pounds. Other than these the most giant moray eel that was ever caught by the fishermen are Giant Conger eel that is 21 feet tall with a weight of 131 pounds.

Mucus Secretion From the Skin

Morays usually secrets a mucus-like chemical through their skin that is smooth and scaleless. However, the mucus in some of the species is toxins. Due to the presence of a large density of goblet cells in the epidermis of the thick skin of the eels, the toxin mucus is produced and released in huge quantities. Due to the presence of the mucus, the sad granules adhere to the side of the burrows of the sand-dweller morays. This adhesion results in a glycosylation reaction that further makes the wall of the burrow side of the eel even more permanent. 

Jaws

The second set of jaws that is present in the throat of the moray eel which is also known as the pharyngeal jaws that are completed with tiny teeth closely resembles the oral jaw and is located at the back of the head. When they attack the prey with an open mouth, the pharyngeal jaws shift to the oral cavity as it holds the prey in the mouth and transports it down through the throat. The moral eels are the  

Moray eel mouth is wide open to the back of its head, which allows the water to flow out through the posterior side of the mouth to reduce the wave of water in front of the eel and do not distract the prey from its place. The sharp teeth help them in lunging and biting the prey down immediately. Sometimes with some of the species taxonomical advancement, aggressive preying becomes possible with reduced bite time. For instance, in California moray eels that belongs to the Gymnothorax genus have a set of teeth at the rooftop of their mouth that folds itself down as the prey in the mouth tries to slide itself out and that prevents any breakage of their teeth while they get a stable hold of the prey. Some of the species of Moray that primarily feeds on hard-shelled or exoskeleton bearing specimen have rounded jaws with molar like teeth. While the other species that feed on fishes have pointed jaws with long sharp teeth. Thus the different shapes of the jaws and the teeth setting tell a lot about the eel’s food habits.

(Image will be uploaded soon)

Image: Illustration of moray eel jaw anatomy     

Feeding and Behaviour

Morays are often dwelling in the temperate waters of tropical and subtropical regions at a maximum depth of 150 meters in the coral reefs where they spend most of their time inside the crevices and alcoves of rocks. They keep hiding in the crevices of the rocks and reefs until prey approaches them and is close enough to come out and capture them. They usually lung out and capture their prey with their strong jaws and sharp teeth. Their second set of jaws in the throat and at the back of their head with complete teeth plays an active part in preying.

They are also involved in co-operative hunting as per the report published in 2006 in a prestigious journal named Public Library of Science Biology. According to the study, the spotted coral groupers that are marine ray fishes that are closely associated with coral reefs tends to recruit giant morays to help them in hunting down the prey. The invitation from the groupers is initiated by shaking their head. The main reason for the groupers to involve the giant morays is because of their hunting style where they flush prey through niches that are otherwise not accessible to the groupers. This is the first discovery of cooperative hunting among the fishes.    

They are mostly solidarity and natural predators. They mostly spend their time inside the cervices and prey on the fishes and the crustaceans that come closer to them but they become highly active at night and comes out of the crevices to hunt down the prey. Though they look ill-tempered and vicious, they are very shy and docile in nature and only attack if they feel threatened. As they have an acute smelling sense but cannot see or hear very well they tend to sometimes accidentally bite the fingers of the people feeding them. They hide from humans and flee away rather than confronting them. But they sometimes tend to inflect nasty bites if provoked. The bites are non-poisonous but they can be infections as the teeth present on the pharyngeal jaws contain active bacteria that can inflect serious infection to the bitten area.     

Distribution and Habitat

Morays are generally found in the temperate waters that are around the tropical and subtropical regions but they are spread worldwide. Most of the species are strictly marine but some of them are found in brackish water and some others are freshwater dwellers. They mostly hide in the crevices of the reefs and the wracks and comes out only to prey. They are the dwellers of shallow water and are mostly found near the seashore areas, continental slopes, mesopelagic zones of the ocean, deep benthic habitat as well as continental shelves. Two of their most exclusive habitat is temperate waters that are away from the equator and the tropical water that are nearer to the equator. Most of their population density and the most number of species are found in the tropical and sub-tropical areas but very few species and low population densities are seen in temperate marine zones.

Reproduction in Moray Eel

They have an oviparous mode of reproduction that is the fertilization takes place in the water when the female moray discharges her eggs in the water current that is fertilized by the male sperms in the water and that process is also known as sprawling. A female moray can pour out as many as 10,000 eggs at a time and as they are fertilized by the males, they form larvae as a part of the plankton. They survive to stay alive in the open ocean water. After a year the larvas that survive predation becomes mature enough to swim down to the ocean bed and hide in rock crevices. The average lifespan of a moray eel ranges from 10 to 40 years depending upon the ecological condition and density of their predators in a particular region. 

Types of Moray Eel

There are more than 200 species of moray eels but a few of them that are of the highest study interests are discussed below: 1. Giant Moray: they are the largest of all moray species in terms of mass. They have a set of intimidating rear-facing teeth in order to balance out their giant mouth. In addition to the sharp pointed teeth on the jaws, they also possess a set of teeth on the roof of their mouth that helps in grabbing the prey and not let it escape from the mouth once caught. 

They have a length of 3 meters and weighs up to 30 kg though a record of giant moray of 36kg is also present. Their body is brownish in colour and darken with the age. They have a thick neck beneath their head and as they attain their maximum length the neck even thickens more. They usually have black and yellow spots behind their head and the juvenile giant morays are lighter browns with more dark spots.

They are the specimen of the Indo-Pacific area and are largely found from the coast of Africa to south of Durban northwards, red sea across to the Pitcairn group, Hawaii islands and Polynesia. They are also found in the north to south of Japan, south of New Caledonia, Fiji and Australia.

(Image will be uploaded soon)

Image: Illustration of a giant moray 2. Green Moray: the average length of a green moray eel from its nose to the tip of the tail is 5.91 feet tall. Their maximum length that was recorded is 8 feet and they generally weigh 65 pounds. They have two projected nostrils that are prominently visible on their face. They have two full rows of teeth in the upper jaw and a single row of teeth in the lower jaw.

They are mostly found in the western Atlantic Ocean from New Jersey to Bermuda and from the Gulf of Mexico southwards to Brazil. they are mostly found in the shorelines in the coral reefs hidden in the cracks and crevices of the rocks. They feed mostly at night on fishes, crabs, shrimps, squids and octopuses.

Since the 80s, the ocean is absorbing 90% more heat than its actual limit from the environment with 30% more carbon absorption due to high emissions from the fossil fuel industry. This has increased the acidity of the ocean water that led to bleaching out of many coral reefs. This resulted in endangering the green eel. Though the green moray eels are not listed as threatened but their habitat is under the pressure of global warming and increased carbon emission.

(Image will be uploaded soon)

Image: Illustration of a green moray 3. Freshwater Moray Eel: Freshwater moray is commonly known as Indian mud moray eel as well as freshwater snowflake eel.  They have an average length of 24inches and can live up to 30 years if the conditions are ideal. They have a black body with orange and white specs covering the whole body from top to tail tip. They have very weak eyesight but have an excellent and well-developed sense of smell and vibrations in the water to detect their prey or approaching danger. 

The main habitat of the freshwater morays is actually marine water. It mostly dwells in the soft debris or substrates on the mud and sands. It also enters into the low portion of the river. It lives in marine conditions but travels into freshwater for breeding where they follow the process of sprawling. They actually are in a better condition in brackish water.

They are solidarity and feeds mostly on crustaceans and small fish. The scavengers mostly feed on the dead fishes, shrimps and other such food.

(Image will be uploaded soon)

Image: Illustration of a freshwater moray eel

Fun Facts About Moray Eel

1. The strongest sense that the moray eel possesses is the sense of smell and vibrations in the water.

2. A large species of eels are solidarity though they are the first fish species to involve in cooperative hunting nature with the groupers.

3. They do not involve in any parental activity for their offspring.

4. They eat almost all varieties of marine fish as long as they can tear and consume the fish.