Taxonomy & naming
Cryptomyrus ona belongs to the order Osteoglossiformes, the bonytongues — a scattered, deep-time radiation of freshwater fishes found today across South America, Africa, Southeast Asia and Australasia, and named for a toothed bone on the floor of the mouth that bites against a toothed pad on the roof. Within that order, the family Mormyridae, the elephantnoses and mormyrids, is an exclusively African branch defined as much by each species' electric organ discharge (EOD) as by outward appearance. Cryptomyrus ona was described in 2016 by Jacob Sullivan, Sébastien Lavoué and Carl Hopkins in the journal ZooKeys, based on molecular and morphological evidence that it did not belong in any existing mormyrid genus — making Cryptomyrus the first new genus erected in the family since 1977, a genuinely rare event in a group whose ~200 known species are more often reshuffled between existing genera than assigned to new ones. The type locality is the Moukalaba River at its confluence with the Nyanga River, Nyanga Province, Gabon (2°47.34′S, 10°43.72′E).
The genus name Cryptomyrus combines the Greek kryptos, "hidden", with the -myrus suffix common to mormyrid genus names (from myros, "eel", after the family's elongate, eel-like body plan) — a name that plays on how this genetically distinct lineage went unrecognised among Africa's other small mormyrids until targeted study revealed it. The species epithet ona is a patronym honouring Marc Ona Essangui, a Gabonese environmental activist and founder of the conservation NGO Brainforest, who won the 2009 Goldman Environmental Prize for his work opposing environmentally destructive mining and logging projects in Gabon; the name was chosen to recognise that conservation work rather than to describe any trait of the fish.
Morphology
Cryptomyrus ona is a small mormyrid, with FishBase reporting a maximum recorded length of about 4.3 in — modest even among the mormyrids, most of which are already modestly sized fish. As in the rest of the family, the defining feature is internal rather than visible: a specialised electric organ in the caudal peduncle generates a continuous, low-voltage, pulse-type electric field that is unique enough in waveform to help identify the species and distinguish it from superficially similar mormyrids. Mormyrids as a group are also noted for some of the highest brain-to-body mass ratios of any fish, built around an enlarged cerebellum that processes the constant stream of electrosensory information from that organ.
Beyond size and the electric organ, a detailed external description — colour pattern, fin proportions, presence or absence of a chin appendage — is confined to the original taxonomic description and has not been distilled into accessible secondary sources; this account does not assert specifics that are not solidly documented. What is established is that the genus was diagnosed as distinct enough, on genetic and morphological grounds together, to warrant separation from every other mormyrid genus then recognised.
Habitat
Cryptomyrus ona is known only from Gabon, in West-Central Africa, recorded from the Nyanga River drainage (the type locality lies on the Moukalaba River near its confluence with the Nyanga) and from the Ngounié River, a major tributary of the Ogooué system — meaning its documented range spans two separate coastal drainages rather than a single river. FishBase describes the species as a tropical, benthopelagic freshwater fish, recording a field temperature near 75 °F and a pH around 8.0.
Beyond those bare figures, the finer habitat detail — substrate, cover, position in the water column day versus night — has not been published in any source accessible for this account, so it is fairest to say the species' ecology is largely undescribed. Gabon's coastal river basins are generally warm, structurally complex lowland forest streams, but the specific character of Cryptomyrus ona's stretch of the Nyanga and Ngounié systems remains data-sparse.
Feeding
No diet has been documented specifically for Cryptomyrus ona in the sources available for this account. What can be said comes from the biology of the family it belongs to: mormyrids are generally invertebrate feeders, using their electric sense to detect insect larvae, worms and small crustaceans hidden in sediment or cover in the dark, sediment-laden water typical of the group's African river habitats.
Given the species has no established presence in the aquarium trade, there is no hobbyist feeding experience to draw on either. Any statement about this particular fish's feeding ecology beyond the general mormyrid pattern would be speculation rather than documented fact.
Mating
Courtship and mate recognition in mormyrids generally runs through the electric channel — species- and often sex-specific differences in the EOD waveform are thought to play a role in signalling identity and readiness to breed — but no study of courtship behaviour in Cryptomyrus ona specifically has been published in the sources available here.
As a fish described only in 2016 from a narrow stretch of Gabon and never established in captivity, essentially nothing is known about how, where or when this species pairs or spawns in the wild. It would be a fabrication to describe a specific mating sequence for this species; the honest position is that its reproductive behaviour is entirely undocumented.
Breeding
Cryptomyrus ona has never been bred in captivity, and its wild breeding biology is essentially unknown — a data gap even by the standards of the mormyrids, a family notorious for rarely reproducing in aquaria at all. General mormyrid biology points to seasonal, flood-cued spawning tied to the rains, but no nest description, egg account or fry-rearing record exists for this species specifically.
Parental care is likewise undocumented. Some mormyrids are thought to guard eggs among roots or plant cover, but nothing confirms that pattern, or any other, for Cryptomyrus ona. It should be treated as a fish with no known breeding record in or out of the aquarium, not assigned a generic egg-scattering or guarding strategy borrowed from better-studied relatives.
In the aquarium
Cryptomyrus ona has no established place in the aquarium hobby. It was described only in 2016 from a small area of Gabon, has no recorded trade or common name, and there is no documented aquarium-keeping history to draw on for this account — any care sheet claiming otherwise for this specific species should be treated with suspicion.
What can be said comes from the biology of small mormyrids as a group, offered here as general context rather than confirmed species-specific guidance: they tend to want dim, structurally complex tanks with driftwood and root cover, soft and stable water chemistry, and food that most will not take reliably as flake or pellet; they are also considered sensitive to copper and to some medications, and can be intolerant of tankmates or conspecifics in cramped quarters. Anyone who did encounter this species — most likely as an unidentified fish within a mixed shipment of small African mormyrids — should treat it as a poorly understood, likely wild-collected fish rather than an established aquarium species, and research the family's general needs rather than assume specifics that have not been documented.
Conservation
The IUCN Red List has not evaluated Cryptomyrus ona; its status is Not Evaluated. This is unsurprising for a fish described only in 2016 from a narrow part of Gabon, with no population survey or trend data published since.
Gabon retains a comparatively large proportion of intact rainforest and river habitat by regional standards, which is a point in the species' favour, but its known range is limited to parts of the Nyanga and Ngounié drainages, and no assessment exists to say whether logging, mining or other development pressure in those catchments poses a meaningful risk. Given how little is documented about its distribution and abundance, the most honest statement is that its conservation status is simply unknown rather than presumed safe.