DAR ES SALAAM: THE United Republic of Tanzania is blessed with remarkable aquatic biodiversity, supported by its extensive coastline, great lakes, rivers and wetlands.
From Lake Tanganyika, near Mahale Mountains National Park, to the Indian Ocean shores of Saadani National Park, these aquatic environments sustain diverse flora and fauna, including fish species with extraordinary adaptations.
Among the fascinating creatures found in Tanzania’s waters are the leopard moray eel, a master of camouflage in coral reefs, and the electric catfish of Lake Tanganyika, which produces powerful electrical discharges to capture prey and defend itself.
Although they inhabit very different environments, both demonstrate how evolution enables animals to survive and thrive under challenging conditions.
The leopard moray eel, also known as the honeycomb moray or laced moray (Gymnothorax favagineus), is among the striking marine predators of the IndoPacific region.
It occurs in the waters around Tanzania, including areas off Dar es Salaam, Mbudya, Bongoyo and Mnemba, where coral reefs provide suitable hiding places and hunting grounds. Known by some Swahili
speaking divers as mkunga chui, the eel is recognisable by its elongated body, pale yellowish or whitish background and numerous dark spots resembling a leopard’s coat.
Large individuals can approach three metres in length, although size varies considerably. Its appearance is impressive, but its mouth is an equally remarkable feature.
The eel has sharp, backward-pointing teeth suited to gripping slippery prey. It also possesses a second set of jaws, known as pharyngeal jaws, inside its throat. These specialised jaws move forward to grasp prey and pull it towards the stomach.
During the day, leopard morays typically shelter in reef crevices, caves and other protected spaces. They generally inhabit shallow to moderately deep reef environments, although their distribution extends to greater depths.
At night, they become more active, hunting fish, octopuses and other suitable prey. The eel’s habit of repeatedly opening and closing its mouth can make it appear threatening.
However, this movement primarily helps circulate water over its gills for breathing. Morays should nevertheless be treated with caution. They are capable of inflicting serious bites, particularly when threatened, cornered or provoked.
Divers should never put their hands into reef holes or attempt to touch or feed a moray. Although these eels are not normally inclined to attack people without provocation, their powerful jaws can cause injuries that may become infected.
The leopard moray belongs to the family Muraenidae, which contains approximately 200 recognised species, depending on the classification used.
Morays are part of the larger eel group, whose evolutionary history stretches back tens of millions of years.
Over evolutionary time, morays developed long, flexible bodies that allow them to enter narrow crevices and move through complicated reef structures. Unlike many other fish, they lack pectoral and pelvic fins.
They also have reduced gill openings and lack the prominent gill covers found in many bony fishes. Their breathing depends on water passing through the mouth and over the gills.
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This explains why morays frequently open and close their mouths while resting in their shelters.
Their pharyngeal jaws are among their most distinctive adaptations. Many fish capture prey by creating suction in the mouth, but this method can be less effective when an animal hunts inside tight spaces.
A moray instead uses its oral jaws to seize prey before the pharyngeal jaws move forward to secure it and transport it into the throat. This mechanism makes the eel an efficient predator in the confined spaces of coral reefs.
The leopard-like markings also help the animal blend into its surroundings. The combination of light and dark patches breaks up the outline of its long body, making it less conspicuous against the changing patterns of coral, rock and shadow.
Although the precise developmental mechanisms responsible for the species’ pattern require further study, pigmentation and genetic processes play important roles in producing the spots.
Such markings illustrate how natural selection can favour appearances that improve an animal’s chances of surviving and reproducing.
The pattern should not, however, be assumed to follow exactly the same genetic pathway as the spots of leopards and cheetahs. Similar appearances in unrelated animals can evolve through different biological mechanisms.
While the leopard moray relies on camouflage and its powerful jaws, the electric catfish of Lake Tanganyika uses a very different strategy.
Lake Tanganyika, bordered by Tanzania, the Democratic Republic of the Congo, Burundi and Zambia, is one of Africa’s most remarkable freshwater ecosystems.
It is exceptionally deep, reaching approximately 1,470 metres, and supports a rich diversity of fish, many of which occur nowhere else in the world.
Among its inhabitants is the electric catfish, a freshwater fish belonging to the family Malapteruridae.
Members of this family occur in several African river and lake systems, and the Tanganyika basin has its own recognised species, including Malapterurus tanganyikaensis.
Unlike the leopard moray, which inhabits salty marine water, the electric catfish lives in freshwater. It has a relatively thick body, smooth skin and prominent sensory barbels around its mouth, which help it locate food in its environment. Its most extraordinary feature is an electric organ beneath the skin.
This organ is made up of specialised cells called electrocytes, which produce electrical discharges when activated. The electric catfish can generate shocks powerful enough to stun prey and deter potential predators.
The exact voltage varies with species, body size and measurement conditions, so figures reported for one electric catfish should not automatically be applied to every species.
The electric discharge is primarily associated with hunting and defence rather than the sophisticated environmental sensing used by certain other electric fishes.
When hunting, the catfish can use a strong discharge to incapacitate nearby prey, including smaller fish. It can then capture the stunned animal and swallow it. The shock also discourages predators that might otherwise attempt to attack it.
For fishermen and other people handling these fish, the electrical discharge presents a genuine hazard. An electric catfish should not be picked up with bare hands, even when it appears inactive.
Safe handling requires appropriate precautions and should be left to people with relevant experience. Electricity-producing animals have evolved independently in several groups of fish.
Electric catfish are different from South American electric eels, despite their shared ability to deliver powerful shocks. The electric organ of the catfish is distributed around much of its body beneath the skin. It consists of specialised tissue derived from muscle cells.
During evolution, cells that originally served a role in movement became adapted to produce electrical discharges instead. Individual electrocytes generate relatively small electrical potentials.
When many are organised together, their contributions combine to produce a much stronger discharge.
This biological arrangement resembles a series of small batteries working together, although the cells operate through biological differences in electrical potential rather than through the chemical processes of an ordinary battery.
The resulting shock gives the catfish an advantage in environments where visibility is poor. Rather than relying exclusively on speed or pursuit, it can incapacitate prey at close range.
However, it would be misleading to conclude that all freshwater fish in Lake Tanganyika use electricity. The lake’s fish community is extraordinarily diverse, and electric catfish represent only one specialised group.
Nor should weakly electric fish from other regions be confused with the strongly electric catfish found in African waters. The evolutionary story of the electric catfish is closely connected to the geological history of Lake Tanganyika.
The lake lies within the western branch of the East African Rift System, where the African crust has been stretching and fracturing over millions of years.
As the crust pulled apart, blocks of land sank between major faults, creating deep depressions that eventually filled with water.
Research has commonly placed the beginning of the central Tanganyika basin’s formation at approximately nine to 12 million years ago, although estimates differ according to the geological evidence and methods used.
The northern and southern sections developed at different times, and the deep lake familiar today emerged through a more complex process of basin development and connection.
The lake’s great depth and long history have helped preserve habitats through major climatic changes.
Its shorelines include rocky areas, sandy stretches, muddy bays and places where rivers deliver nutrients and sediment.
These environments support different fish communities and provide opportunities for species to adapt to particular ecological conditions.
Lake Tanganyika is especially famous for its cichlids, which have diversified into numerous species with different feeding habits, body shapes and behaviours. Its other fish groups also reflect a long history of colonisation, isolation and adaptation.
The presence of electric catfish in the lake is part of this wider biological story. However, their evolutionary history cannot be explained simply by assuming that a particular river connection existed at a precise time.
Establishing the origins and relationships of individual species requires taxonomic, genetic and geological evidence.
The lake’s isolation, changing drainage patterns and environmental diversity may all have contributed to the development of distinctive populations. Researchers continue to investigate how these factors shaped the region’s freshwater biodiversity.
The leopard moray and the electric catfish demonstrate how different environments can favour different survival strategies.
The leopard moray lives among coral reefs, where crevices provide shelter and opportunities for ambush.
Its elongated body allows it to enter narrow spaces, its teeth secure prey, and its pharyngeal jaws help move food towards the throat.
Its spotted appearance can also help conceal it among reef structures. The electric catfish, by contrast, is adapted to freshwater habitats and possesses an electrical organ capable of delivering powerful shocks.
This adaptation helps it capture prey and protect itself without depending entirely on a conventional bite. Both animals illustrate the power of evolutionary adaptation, but their similarities should not obscure their biological differences. The moray is a marine eel, while the electric catfish is a freshwater catfish.
Their body forms, feeding mechanisms and sensory adaptations reflect different evolutionary histories. Their stories also demonstrate why Tanzania’s aquatic ecosystems deserve continued scientific attention.
The Indian Ocean’s coral reefs and Lake Tanganyika’s freshwater habitats are not merely scenic landscapes; they are living systems that preserve evidence of evolutionary change over millions of years.
Protecting these environments is essential for maintaining biodiversity, supporting scientific research and sustaining the livelihoods of communities that depend on fishing and tourism.
From the spotted moray hidden in a coral crevice to the electric catfish moving through freshwater habitats, Tanzania’s waters reveal nature’s remarkable ability to produce different solutions to the challenges of survival.
Together, these creatures offer a compelling reminder that the country’s natural heritage extends far beyond its celebrated terrestrial wildlife and into the extraordinary world beneath the water.
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