Taxonomy & naming
Hylopanchax ndeko was formally described in 2013 by Jos van der Zee, Rainer Sonnenberg, and Ulrich Schliewen on the basis of type material collected by Schliewen from the left bank of the Lokoro River, within Salonga National Park, between 23 and 27 August 2002. The species belongs to the family Procatopodidae — the African lampeyes — a group of small egg-laying killifishes distributed across sub-Saharan Africa from West Africa through the Congo basin and into East Africa. Eschmeyer's Catalog of Fishes (Fricke, Eschmeyer & Fong) treats Hylopanchax ndeko van der Zee, Sonnenberg & Schliewen, 2013 as the valid name.
The genus Hylopanchax was erected by Poll and Lambert in 1965. The genus name combines the Greek hyle or hylo (wood or forest) with Panchax, the old generic name long used as a common shorthand for Old World egg-laying killies; the combination evokes a forest-dwelling panchax — apt for a fish of shaded Congo woodland streams. The species epithet ndeko is a Lingala word meaning 'sibling' or 'relative', chosen by the authors to underscore the particularly close affinity between H. ndeko and its sister species H. leki. Lingala is one of the major Bantu languages of the Democratic Republic of the Congo, and its use here reflects a commendable practice of drawing species names from the languages of the country of origin.
Morphology
Hylopanchax ndeko is a miniature fish, with FishBase recording a maximum standard length of 1 in for males and unsexed individuals. Like all members of the procatopodid lampeyes, it possesses the group's defining optical feature: a patch of iridescent blue-green photophores or light-reflecting cells arranged above and behind the eye, producing the characteristic luminous 'lamp' that gives the group its common name. This structure is used in intraspecific signalling and is particularly vivid in males.
The body form is slender and laterally compressed in the manner typical of the genus — a shape well suited to navigating dense aquatic vegetation and submerged root masses in forest streams. Coloration in life is typically subdued on the body — silvery to pale olive flanks — with the lampeye patch providing the most striking ornamentation. Sexual dimorphism in the genus runs to males carrying brighter eye patches and often deeper colouration in the unpaired fins, while females are generally plainer and more uniformly coloured.
Habitat
This species is known from permanent freshwater in two distinct drainages of the middle Congo basin: the Lokoro River, a westward-flowing stream that runs through the core of Salonga National Park, and the Kangara River of the Lukenie drainage. Both localities lie within the vast Congo rainforest interior of the Democratic Republic of the Congo. The Lokoro type locality is specifically on the left bank within the national park, in conditions typical of lowland Congo forest streams: heavy canopy cover, shaded water, soft substrates of fallen leaf litter and root mats, and slow to gently flowing current.
Permanent, shaded forest streams are the defining habitat of Hylopanchax and most of its procatopodid relatives in this part of Africa. Unlike annual killies, which exploit temporary pools and seasonal floodplain pools that dry completely, lampeyes of this kind inhabit watercourses that persist year-round. The water in closed-canopy Congo streams tends to be cool by equatorial standards, soft, and slightly acidic from the accumulation of forest organic matter, with low conductivity. Dense riparian vegetation and floating mats of roots and submerged plants provide both cover and spawning sites for these small fishes.
Feeding
Hylopanchax ndeko, like other lampeyes of the Congo forest, is a micropredator. The small body size and terminal mouth typical of procatopodids indicate a diet of tiny invertebrates: aquatic insect larvae, microcrustaceans (copepods, ostracods, small cladocerans), and other zooplankton encountered in the slow forest streams it inhabits. Surface and mid-water feeding is characteristic of the group, in keeping with the structure of small, clear forest streams where invertebrate drift and zooplankton concentrations are highest near the surface.
In the aquarium setting, lampeyes accept a range of small live and frozen foods — Daphnia, Artemia nauplii, micro worms, and similarly sized fare. Finely ground prepared foods are also accepted, though live and frozen invertebrate foods best support condition and breeding readiness. Because the fish is small and the mouth correspondingly small, food particle size is a practical consideration.
Mating
Hylopanchax ndeko is a non-annual lampeye — a continuous spawner of permanent water rather than a seasonal annual that deposits diapausing eggs in ephemeral pools. The procatopodid reproductive strategy involves repeated, low-clutch spawning events extended over a long period rather than a single explosive spawning season. Males court females with lateral displays that emphasise the iridescent lampeye patch above the eye; the patch likely functions as a species-recognition and fitness signal in the shaded forest environment where visual contrast is reduced.
Spawning in lampeyes of this type is typically a brief pairing event in which one to a few adhesive eggs are deposited among fine plant stems, floating root masses, or submerged vegetation during each encounter. The pair separates after egg deposition and may repeat spawning many times over days or weeks. No lasting pair bond or territory defence has been documented for Hylopanchax; males compete loosely for access to females in a schooling group.
Breeding
Eggs of non-annual lampeyes are small, adhesive, and relatively few in number per spawning bout — a clutch may be a single egg or a handful, deposited in plant matter or fine-leaved vegetation and left without parental attention. The adhesive coat anchors eggs among roots and plant fibres where they are sheltered from both current and predation. Incubation times vary with temperature; at the cooler temperatures characteristic of shaded forest streams incubation typically runs one to two weeks.
In the aquarium, lampeye breeding is best facilitated by providing spawning mops of fine-leaved plants or Java moss, into which eggs are deposited daily. Because adults do not guard eggs and may consume them given the opportunity, eggs or spawning mops can be moved to a separate rearing vessel. Fry are tiny at hatching and require correspondingly fine first foods — infusoria or commercial fry powder — before being graduated to micro worm and freshly hatched Artemia nauplii. Water quality must be maintained carefully for fry, as procatopodid larvae are sensitive to deterioration in the rearing environment.
In the aquarium
Hylopanchax ndeko is a genuine rarity in the hobby and not commonly available through the ornamental trade. As a miniature Congo forest lampeye it is best suited to a small, well-planted species tank or a carefully chosen community of similarly sized, peaceful fishes from the same region. A densely planted aquarium with floating plants to diffuse lighting mimics the shaded forest-stream environment and encourages natural behaviour; the fish show at their best when the iridescent lampeye patches catch available light against dark background planting.
Soft, slightly acidic water in the range typical of Congo forest streams is recommended, with gentle filtration and minimal flow to replicate the slow, permanent streams of the type locality. The species is a schooling fish and should be kept in groups of six or more to allow natural social behaviour and reduce stress. Because it is a continuous spawner, a colony in a suitable planted tank will produce eggs without special intervention, and small numbers of fry may survive to adulthood in a well-planted setup even without deliberate intervention by the keeper.
Conservation
Hylopanchax ndeko has not been formally assessed by the IUCN Red List and carries a status of Not Evaluated (NE). This absence from the assessment queue is common for newly described, narrowly distributed Central African stream fishes — the taxonomic and survey work needed to document them often precedes the conservation machinery required to evaluate them.
The species is known from only two river systems within the middle Congo basin: the Lokoro River in Salonga National Park and the Kangara River of the Lukenie drainage. The Lokoro type locality lies within Salonga National Park — the largest tropical rainforest national park in Africa and a UNESCO World Heritage Site — which provides a degree of habitat protection for populations there. However, Salonga faces documented pressures including illegal logging, bushmeat hunting, and artisanal mining within its boundaries, all of which can degrade stream habitats through sedimentation and chemical input. The Kangara River population outside the park has no such formal protection. Given the extremely limited known range, any assessment under IUCN criteria would likely place this species in a threatened category; formal evaluation is warranted.