Taxonomy & naming
Mastacembelus zebratus was described by Hubert Matthes in 1962, with the type locality recorded as Makobola, Lake Tanganyika, in what is now the Democratic Republic of Congo. The holotype is held at the Royal Museum for Central Africa (MRAC 130397). The Catalog of Fishes (Eschmeyer, California Academy of Sciences — the authority for valid names) treats it as Mastacembelus zebratus Matthes, 1962.
The species passed through two intermediate generic placements before settling at its current name. It was for a time placed as Caecomastacembelus zebratus, and later as Afromastacembelus zebratus, reflecting the decades-long practice of splitting African mastacembelids into separate genera on the basis of eye reduction, lateral-line characters, and other features. Both Caecomastacembelus and Afromastacembelus were subsequently placed in synonymy with Mastacembelus following the revisionary work of Vreven (2005) and Vreven and Snoeks (2009), returning the species to the type genus of the family.
The placement of this species in Mastacembelidae within the order Synbranchiformes is the key taxonomic fact: these are not true eels. The true eels belong to the Anguilliformes, an entirely separate order; the eel-like body of spiny eels is a case of convergent evolution on an elongate, burrowing lifestyle. Mastacembelus zebratus is also part of a celebrated example of adaptive radiation — the Lake Tanganyika mastacembelids form an endemic species flock that diversified within the lake, paralleling the better-known cichlid radiations in the same system.
Morphology
Mastacembelus zebratus is a small spiny eel, reaching a recorded maximum of 7.5 in standard length. The body is greatly elongate and slender, scaleless to the naked eye and covered in a mucus coat that protects the skin from the abrasive rocky substrate it inhabits. The snout is drawn out into a soft, mobile proboscis tipped with tubular nostrils — the sensory instrument this and other mastacembelids use to probe crevices and sediment for food. Along the dorsal ridge ahead of the soft dorsal fin runs a row of short isolated spines, the defining character of the spiny-eel group.
The common and species epithets both allude to a striped or banded pattern: zebratus is Latin for 'zebra-marked', suggesting a bold transverse or longitudinal striping against a paler background. The soft dorsal and anal fins are continuous around the tapered tail. Like other spiny eels the fish lacks true scales, making it sensitive to copper-based treatments and physical abrasion. Little information on external sexual dimorphism has been published for this species, though ripe females of mastacembelids generally show a fuller abdomen than males.
Habitat
Mastacembelus zebratus is endemic to Lake Tanganyika and has been recorded from shallow inshore waters around the lake, where it hides between rocks or buries itself in sediments. Lake Tanganyika is an ancient, deep, oligotrophic rift lake with water chemistry quite unlike the soft, slightly acidic conditions of most tropical rivers: pH ranges from approximately 8.0 to 9.5, hardness from roughly 8 to 25 degrees of hardness, and temperature from about 73–84 °F, varying with depth and season. The water is exceptionally clear and well oxygenated at the surface and in the shallow littoral zones where this species lives.
This profile — hard, alkaline, stable, oxygen-rich — is the defining environmental context for M. zebratus and is the opposite of the soft, acidic or neutral conditions typical of the West and Central African river mastacembelids. The fish is thus an obligate hardwater rift-lake species; it requires these stable alkaline conditions and cannot be kept in the generalised 'tropical community' soft-water parameters appropriate for other spiny eels. The rocky shallow littoral zone provides both the crevice retreats it uses during the day and the micro-habitat it searches for invertebrate prey.
Feeding
Like other mastacembelids, Mastacembelus zebratus is a carnivore that uses its sensitive, probing snout to locate invertebrate prey in and around the substrate. FishBase records a trophic level of 3.7 for the species, consistent with a diet of benthic invertebrates — insect larvae, worms, small crustaceans and other bottom-dwelling organisms detected by olfactory and tactile sensation rather than by sight alone.
It is described as secretive and is most likely a nocturnal or crepuscular forager, resting concealed between rocks or buried in sediment during the day and becoming active after dark. In the aquarium it should be offered meaty foods placed after the lights have dimmed: bloodworm, small earthworm pieces, and small frozen invertebrates are suitable, and sinking pellets may eventually be accepted by settled individuals.
Mating
Mastacembelus zebratus is a spiny eel and, as such, is an egg-scattering spawner that gives no parental care. It is not a true eel and does not undertake any catadromous migration; spawning takes place entirely in fresh water. In the wild, breeding in Lake Tanganyika's mastacembelids is likely triggered by seasonal changes in water level, temperature, or rainfall, following the broader pattern seen across the family.
No detailed wild observations of courtship in this species have been published. In mastacembelids generally, a courting pair entwine and swim together among fine vegetation or root tangles before scattering adhesive eggs, and this is the probable mode for M. zebratus as well. No nest is built and no pair bond persists beyond spawning; the adults do not tend the eggs.
Breeding
Mastacembelus zebratus is very rarely, if ever, bred in the home aquarium; it is a specialist Lake Tanganyika species for which captive breeding accounts are essentially absent from the published hobby literature. The general pattern for spiny eels — adhesive eggs scattered among vegetation or substrate, no parental care, small and demanding larvae requiring fine first foods — applies here, but the lake-specific water chemistry requirement (high pH, high hardness, warm temperature) adds an additional constraint that most generalist aquarium set-ups do not meet.
Any attempt at breeding would require a mature, well-filtered system precisely matched to Lake Tanganyika parameters, mature and well-conditioned adults, and a trigger such as a gradual temperature change or increased water movement to simulate seasonal cues. Until such accounts are documented, this species should be regarded as not bred in captivity.
In the aquarium
Mastacembelus zebratus is an uncommon aquarium species kept mainly by dedicated Tanganyika biotope enthusiasts rather than in the general trade. At up to 7.5 in it is compact for a spiny eel, but its requirements are exacting and non-negotiable: the tank must replicate Lake Tanganyika chemistry, meaning hard, alkaline water at pH 8.0–9.0, a temperature of 73–81 °F, and excellent filtration with strong oxygenation. Soft or acidic water will stress the fish and compromise its immune function. A rocky aquascape with plenty of crevices, overhangs, and cave-like retreats is essential, as the fish is secretive and spends much of the day sheltering between stones.
As with all mastacembelids, a fully sealed lid with no gaps is mandatory: spiny eels are accomplished escape artists that can squeeze through surprisingly small openings and will not survive a fall to the floor. The scaleless skin makes the fish sensitive to copper-based medications, which should never be used in its tank, and to chronically poor water quality. It is best kept with other Tanganyika endemics — shell-dwellers, small Julidochromis, or Neolamprologus — that share its water-chemistry requirements, and should not be housed with very small fishes that it might take as prey after dark.
Because it comes from an endemic lake fauna, wild collection pressure and the quality of the collection and transport chain matter: specimens should be bought from reputable importers and quarantined carefully before introduction to a display tank.
Conservation
Mastacembelus zebratus is assessed as Least Concern on the IUCN Red List, with the most recent assessment dated 31 January 2006. The species is endemic to Lake Tanganyika and, while its range is by definition restricted to a single water body, the lake itself is vast — the world's second deepest lake and one of the largest by volume — and the rocky littoral habitat the fish occupies extends around much of its shoreline across four countries (Tanzania, the Democratic Republic of Congo, Zambia, and Burundi).
Lake Tanganyika faces long-term pressures from sedimentation driven by deforestation in surrounding catchments, overfishing of key prey species, and the gradual effects of climate change on its thermal stratification and mixing. These threats affect the lake ecosystem broadly rather than targeting this species specifically, and no population-level decline has been documented for M. zebratus. However, the narrow endemism of all Tanganyika species means that the lake's health is the species' only buffer, and any deterioration of the littoral rocky zone or water quality at the shoreline would directly affect it.