Taxonomy & naming
Cynolebias penaforte was described in 2026 by Telton P. A. Ramos, Yuri G. Abrantes, Dalton T. B. Nielsen and Sergio M. Q. Lima, in Zootaxa (volume 5845, issue 2, pages 369–379). It belongs to the genus Cynolebias within the subfamily Cynolebiinae of the family Rivulidae — the New World annual and non-annual killifishes, one of the ten most species-rich fish families. The holotype is deposited at the Universidade Federal da Paraíba (UFPB 15314), with paratypes at the same institution (UFPB 14084, 8 specimens; UFPB 15315, 15 specimens). Eschmeyer's Catalog of Fishes treats Cynolebias penaforte Ramos, Abrantes, Nielsen & Lima, 2026 as a valid, currently accepted name.
Before this description, Cynolebias microphthalmus was the only species of the genus known from the Northeastern Caatinga and Coastal Drainages hydrographic ecoregion, recorded from seasonal pools of the rio Apodi-Mossoró basin in Rio Grande do Norte and the lower rio Jaguaribe basin in Ceará. Cynolebias penaforte extends the genus's known range into the upper Jaguaribe, and the authors diagnosed it from all congeners using a combination of morphological and molecular (mitochondrial DNA) evidence. Diagnostic characters include the absence of contact organs on the inner surface of the pectoral-fin rays in males (present in related species), a higher number of supraorbital scales, a dorsal-fin origin positioned through the base of the eighth anal-fin ray, and a higher number of neuromasts in the anterior rostral, otic and post-otic sensory series.
The species epithet is not accompanied by a published etymological note in the material available to us, but it directly matches the name of the type locality — the municipality of Penaforte, Ceará — and is presented as a noun in apposition in the standard convention for place-based species names.
Morphology
No standard length has been recorded for Cynolebias penaforte in the material available to us, and the original description's full morphometric tables were not accessible for this article; the size given for the species below reflects that gap rather than a documented figure. As with other Cynolebias, the body is expected to follow the deep-bodied, laterally compressed 'cloud fish' plan typical of the genus — a description the original authors themselves used in their paper's title for the genus as a whole — but specific proportions for this species are not stated in the sources available here.
What is documented is the combination of characters that separates Cynolebias penaforte from its relatives: males lack the small contact organs found on the inner surface of the pectoral-fin rays in related species, a difference visible only on close examination. The species also carries a higher count of supraorbital scales than its congeners, a dorsal-fin origin set further back — through the base of the eighth anal-fin ray — and elevated neuromast counts in three head sensory-canal series (anterior rostral, otic, and post-otic). These are technical, comparative characters rather than field marks, and no photograph-based description of live coloration was available to us.
Habitat
Cynolebias penaforte is known only from a temporary pool along the BR-116 highway in the upper rio Jaguaribe River basin, in the municipality of Penaforte, Ceará State, Brazil (07°47'18.7"S, 39°04'30.0"W). This is inland, semiarid Caatinga country — a landscape of thorny scrub and highly seasonal rainfall where fish survival depends on pools that fill during the rains and vanish again in the dry season.
The discovery locality sits close to the canal infrastructure of the rio São Francisco inter-basin water transfer project, an engineering scheme that redirects water across Brazil's semiarid northeast. The describing authors specifically noted this proximity as a concern: changes to regional hydrology from projects of this kind have the potential to alter the filling and drying cycles that seasonal killifishes like this one depend on for their entire life cycle. Beyond the type locality, no other population of the species is currently known.
Feeding
No dietary data have been published for Cynolebias penaforte specifically. As a general matter of annual-killifish biology — labeled here as genus- and tribe-level context rather than a documented fact about this species — Cynolebiini and related annual rivulids in Caatinga seasonal pools are microcarnivores, taking small aquatic invertebrates such as insect larvae, micro-crustaceans and worms, along with terrestrial invertebrates that fall onto the water surface. Their compressed growing season, bounded by the life of the pool itself, favours opportunistic feeding on whatever prey is available.
Mating
No species-specific account of courtship or spawning behaviour has been published for Cynolebias penaforte. As background genus-level and tribe-level context: Cynolebias and its relatives in the subfamily Cynolebiinae are annual killifishes, meaning their entire reproductive strategy is built around the certainty that the pool they inhabit will dry out. Spawning in this group typically takes place in or on the soft substrate at the bottom of the pool rather than among plants, with pairs diving into the mud or detritus to release eggs and sperm before the eggs are buried. None of this has been directly documented for C. penaforte itself, and it is presented here only as general biology of the group to which the species belongs.
Breeding
As with mating behaviour, no breeding data specific to Cynolebias penaforte have been published. Presented as tribe-level context rather than species-specific fact: annual rivulids of the Cynolebiinae produce eggs with a thickened chorion capable of surviving complete desiccation of the pool through a period of embryonic diapause, hatching only once the rains return and the pool refills. Killifish hobbyists who keep annual Rivulidae typically collect eggs on a peat or coir spawning medium, store the slightly dried substrate through the diapause period, and re-wet it to trigger hatching — a technique standard across the annual-killifish hobby generally, though it has not been demonstrated for this species, which is not established in captivity.
In the aquarium
Cynolebias penaforte is not an aquarium-trade species. It was described only in 2026 from a single wild population, and no captive stock or hobbyist husbandry record is known to us. Anyone attempting to keep an annual Cynolebias of this kind would, by analogy with the wider genus and the Cynolebiinae generally, need to replicate a soft substrate for egg-laying, dim cover, and water chemistry approximating the neutral, seasonally variable conditions of a semiarid Caatinga pool — but none of this has been tested for C. penaforte specifically, and it should be treated as inference from relatives rather than documented care advice.
Conservation
Cynolebias penaforte has not been formally assessed on the IUCN Red List; as a species described in 2026, that is expected rather than unusual. The describing authors themselves flagged conservation concern in the paper's own framing — the species appears among keywords tagging it a 'threatened species' — and the biology they documented gives good reason for caution: the fish is known from a single temporary pool, in a genus where seasonal Caatinga pools are already under pressure from agriculture, water extraction and land-use change across the region.
The most specific threat identified by the authors is the proximity of the type locality to canal infrastructure of the rio São Francisco inter-basin water transfer project — a large-scale hydrological engineering scheme whose effects on the natural filling-and-drying rhythm of nearby seasonal pools are not yet fully understood, but which the describing team explicitly raised as a possible risk to Brazilian semiarid seasonal killifishes generally. The species' discovery itself, via citizen science from two local residents, underscores how much of the Caatinga's temporary-pool fish fauna likely remains undocumented, and how vulnerable any single-locality population is to changes in a landscape already shaped by large infrastructure projects.