Taxonomy & naming
Ancistrus kellerae was formally described by de Souza, Taphorn, and Armbruster in 2019 as part of a comprehensive review of Ancistrus from the northwestern Guiana Shield, published in Zootaxa (volume 4552, pages 1–67, with the species treated on page 16 and illustrated in figures 9–10). The Catalog of Fishes (Eschmeyer, CAS) recognises Ancistrus kellerae de Souza, Taphorn & Armbruster, 2019 as a valid species.
The species is placed in the tribe Ancistrini, subfamily Hypostominae, family Loricariidae — the suckermouth armoured catfishes. The genus Ancistrus is the largest in its tribe and encompasses the familiar bristlenose plecos of the aquarium trade, characterised by the distinctive interopercular spines and, in adult males, the branched fleshy tentacles on the snout. Within the Guiana Shield, the northwestern drainages harbour considerable Ancistrus diversity, and the de Souza et al. (2019) monograph represented a major taxonomic advance in delimiting species boundaries in this region.
The specific epithet kellerae honours Constance Templeton Keller, who served as Chair of the Field Museum Board of Trustees. The Field Museum in Chicago has contributed significantly to Neotropical ichthyology through specimen collections and curatorial support.
Morphology
Ancistrus kellerae is a small-bodied species, reaching a maximum recorded standard length of 2 in SL — placing it toward the smaller end of the genus. Like all Ancistrus, the body is armoured in overlapping bony scutes. The species was described from holotype specimens with detailed photographs (side, dorsal, and ventral views) archived at PlanetCatfish, illustrating the characteristic depressed head, broad pectoral girdle, and ventral sucker-mouth of a current-adapted loricariid.
Sexual dimorphism in A. kellerae follows the genus pattern. Mature males develop the branched, bushy snout tentacles that give bristlenoses their common name; females may develop short tentacles along the snout margin, but never achieve the elaborate, multi-branched array of adult males. This tentacle dimorphism, combined with differences in the genital papilla (smaller and pointed in males; larger and rounded in breeding females), provides the most reliable field characters for sexing the species. Gravid females also appear broader in body profile when viewed from above.
The description in de Souza et al. (2019) provides full meristic, morphometric, and colouration data; specific counts and measurements are not reproduced in the sources available to this cache.
Habitat
Ancistrus kellerae is known from the Potaro River drainage within the Essequibo basin of Guyana. The type locality is the Kuribrong River at Grass Shoals, located downstream to Amaila Falls, at coordinates approximately 5.408°N, 59.532°W (Region 8, Potaro/Siparuni). Additional records come from a few sites in the broader Potaro River.
The IUCN assessment characterises the microhabitat as rapids — fast-flowing, well-oxygenated rocky reaches with ample hard substrate for biofilm grazing and shelter. FishBase notes clear-flowing streams with rooted vegetation as associated habitat. Grass Shoals represents the last rapids above Amaila Falls on the Kuribrong River, a geomorphological feature that effectively limits upstream dispersal for current-adapted rheophilic species and may have contributed to the evolution of a distinct local taxon.
The species' total distribution is extremely restricted. The IUCN-calculated extent of occurrence (EOO) is 5,258 mi² and the area of occupancy (AOO) is 3,363 mi², with a maximum of four threat-based locations recognised. This narrow endemic footprint, concentrated in a single Guyanese river system, underpins the Vulnerable listing.
Feeding
No species-specific dietary study of Ancistrus kellerae has been published. Based on genus-level biology and the IUCN habitat characterisation of clear-flowing rapids with rocky substrate, A. kellerae is expected to be an algae and biofilm grazer — rasping periphyton, diatoms, and organic detritus from submerged rock and root surfaces using the fine multi-cusped teeth typical of Ancistrus.
PlanetCatfish records the species as primarily vegetarian in aquarium conditions, consistent with all described Ancistrus, and lists algae wafers, spirulina-based sinking foods, and supplementary vegetables (courgette/zucchini, cucumber) as appropriate captive foods. The clear, swift water of its natural habitat suggests the species is accustomed to well-oxygenated conditions and biofilm communities characteristic of oligotrophic Guiana Shield rivers, which differ from the more productive whitewater systems of Andean origin.
Mating
Courtship biology has not been specifically documented for Ancistrus kellerae. The species is expected to follow the territorial cave-centred mating system that characterises the genus. Adult males defend cave or crevice sites within the rocky rapid habitat, using their prominent snout tentacles in rival male interactions and potentially as visual signals to prospective mates. In Ancistrus generally, female mate-choice favours males already brooding eggs — a form of brood amplification that benefits both sexes, as males gain a larger genetic investment per territory and females minimise risk by choosing experienced brooders.
The restricted range and small-stream, rapid-dwelling ecology of A. kellerae suggests that individual males have access to a limited pool of suitable cave territories within each accessible stretch of river, making territory quality and male tentacle development likely important determinants of mating success. Males may become aggressive toward rivals in confined quarters, in line with typical Ancistrus behaviour. No captive observations are on record.
Breeding
Ancistrus kellerae is a cave-spawner with paternal brood care, as is universal within the genus. No captive breeding record specific to this species is reported at PlanetCatfish. Genus-level breeding parameters documented in the literature describe females depositing adhesive eggs on the interior walls of a cavity nest; the clutch is guarded and aerated by the male, who fans the eggs with his pectoral fins throughout the incubation period. Incubation in Ancistrus generally lasts 4–10 days at tropical temperatures; fry absorb the yolk sac within 2–4 days of hatching and begin foraging shortly thereafter. The male may continue guarding the fry for up to ten days post-hatching.
Given A. kellerae's small adult size (2 in SL), clutch sizes are likely at the lower end of the genus range. The clear, cool Guiana Shield stream conditions at the type locality may translate into slightly longer incubation at cooler temperatures compared to lowland Ancistrus, though no data are available to confirm this.
In the aquarium
Ancistrus kellerae is not established in the ornamental trade, and its restricted Guyanese range and very recent description (2019) make it unlikely that this species has entered the hobby in any meaningful numbers. Any specimens in captivity would most plausibly be from scientific collection and study rather than commercial import.
If maintained, A. kellerae's small adult size (2 in SL) would in theory make it manageable in modest tank volumes. PlanetCatfish characterises the genus as peaceful community fish, with males exhibiting territorial tendencies toward each other — the standard Ancistrus social pattern. The rapid, clear Guiana Shield habitat indicates a preference for high oxygen saturation, stable water chemistry, and moderate to brisk water movement. Soft, slightly acidic water characteristic of Guiana Shield blackwater and clearwater rivers would be appropriate, though the precise water chemistry parameters for the Kuribrong/Potaro system at the type locality are not available in this cache.
Cave or crevice retreats are essential for the species' behavioural well-being, and provision of smooth-surfaced rock or ceramic caves would replicate the rapid-boulder microhabitat. The vegetarian feeding protocol standard for the genus applies: algae wafers and vegetables as dietary staples.
Conservation
The IUCN Red List assessed Ancistrus kellerae as Vulnerable (VU B1ab(iii)) on 27 October 2020, with the assessment published in 2022 (assessor: Calegari B.B.; reviewers: Ballen G.A. and de Souza L.). The criterion B1ab(iii) reflects a restricted extent of occurrence (EOO: 5,258 mi²; AOO: 3,363 mi²; no more than four threat-based locations) combined with a continuing decline in the quality of habitat at known locations.
The primary and most acute threat is gold and diamond mining in the Kuribrong River valley. Artisanal and small-scale mining involving dredging and sediment disturbance directly degrades the clear-water rapids that A. kellerae requires. The IUCN assessment specifically identifies the construction of a new road to the base of Amaila Falls as a threat multiplier, as improved access will accelerate mining operations and associated habitat degradation in this previously remote watershed. Sediment loading from dredging is particularly damaging to a small-bodied rheophilic species dependent on clean substrate biofilm and interstices among cobbles for foraging and nesting.
The Grass Shoals type locality — the last rapids on the Kuribrong before Amaila Falls — represents a geographically constrained refuge, and any upstream habitat deterioration could eliminate a significant portion of the known population. No formal conservation measures are in place for this species; the IUCN assessment recommends establishment of a monitoring programme. Given that the species was described only five years before the IUCN assessment, population baseline data are limited.