Taxonomy & naming
Ancistrus cuiabae was described by Knaack in 1999, together with the closely related Ancistrus claro, from material collected in the Cuiabá River basin of Mato Grosso, Brazil — part of the upper Paraguay River drainage. The type locality is the Bento Gomes River, approximately 22 mi south-east of Poconé in the Pantanal transition zone. Both species were described in the same publication, and the two share a broadly similar morphology; they are distinguished by subtle but consistent differences in squamation and tentacle development.
The Catalog of Fishes (Eschmeyer, CAS) recognises Ancistrus cuiabae Knaack, 1999 as the valid name. No L-number has been assigned in the DATZ coding system, and the species does not appear to have circulated widely in the European or North American ornamental trade under a catalogue designation.
Ancistrus is a large genus within the tribe Ancistrini of subfamily Hypostominae. The genus is defined by the iconic fleshy tentacles — odontodes borne on elongated dermal appendages — that develop on the snout of sexually mature males. Phylogenetic boundaries within Ancistrus remain in revision as molecular studies continue to reveal cryptic diversity across Amazonian and Pantanal drainages.
Morphology
FishBase records a maximum size of 4.5 in standard length (SL) for Ancistrus cuiabae. Total length is not formally confirmed in the primary literature; based on the SL/TL ratio typical of the genus, adult total length is likely in the range of 5–6 in.
The body plan is typical of Ancistrus: dorsoventrally flattened, covered in keeled bony scutes, with a broad disc-shaped ventral mouth armed with fine, bicuspid teeth suited to rasping algae and biofilm from hard surfaces. Coloration in Ancistrus is highly variable within and among populations; without specific field or aquarium data for A. cuiabae, precise pattern notes cannot be stated here.
Sexual dimorphism follows the genus-level pattern. Adult males develop fleshy, branched tentacles on the tip and sides of the snout — the defining character of Ancistrus sensu lato. Females typically bear shorter, less-elaborated nasal tentacles or may lack snout tentacles entirely, though tentacle expression varies among species. Mature females are deeper-bodied than males of equivalent age.
Habitat
Ancistrus cuiabae is endemic to Brazil, where it inhabits the Cuiabá River basin in Mato Grosso State — a tributary system of the upper Paraguay River. The type locality, the Bento Gomes River near Poconé, sits at the edge of the Pantanal, the world's largest tropical wetland. A subsequent Check List record extended the known range into the Southern Pantanal proper, confirming that the species is present in the vast seasonally inundated floodplain as well as its fringing river channels.
The Cuiabá drainage is warm throughout the year, with temperatures typical of central-western Brazil. Water parameters for A. cuiabae have not been formally measured in the peer-reviewed literature; by inference from the closely related A. claro described from the same drainage and from Pantanal limnological data, conditions are likely soft to moderately hard, slightly acid to near-neutral (pH approximately 6.0–7.5), and warm (approximately 75–82 °F). The Pantanal seasonal flood pulse means that fish in this region experience pronounced changes in water depth, current velocity, and water chemistry between wet and dry seasons.
FishBase notes that Ancistrus cuiabae is a facultative air-breather — a trait shared with several loricariids that inhabit hypoxic floodplain waters. This adaptation allows the fish to survive in the poorly oxygenated pools and flooded marginal habitat characteristic of the Pantanal dry-down.
Feeding
Ancistrus species are primarily algivores and detritivores, using their toothed suckermouth to rasp algae, biofilm, and fine organic detritus from hard substrates including rock, submerged wood, and compacted leaf litter. The ventral disc mouth and spatulate dentition are adapted for this mode of feeding rather than for processing coarse plant matter or wood fibre in the manner of true xylophages.
No species-specific dietary data exist for A. cuiabae in the literature. By genus-level inference, the diet in nature consists predominantly of periphyton (the biofilm community), algae, and the fine detritus that accumulates on bottom substrates in Pantanal backwaters. The facultative air-breathing ability recorded for this species suggests it inhabits oxygen-depleted floodplain environments where decomposing organic matter is abundant, consistent with a diet that includes substantial detrital input.
In an aquarium setting, standard Ancistrus provisioning applies: a diet centred on algae wafers, spirulina-based tablets, blanched vegetables (courgette, cucumber, peas, sweet potato), and the natural algae growth that develops on tank surfaces. Occasional meaty foods such as bloodworm or small invertebrates are accepted.
Mating
Reproductive behaviour in Ancistrus cuiabae has not been documented in the primary scientific literature. The following account is based on the well-established genus-level reproductive strategy, which is highly conserved across Ancistrus.
Males become territorial and competitive as breeding condition develops, with their snout tentacles — already a defining secondary sex character — becoming more elaborately developed during the breeding season. Males establish and defend preferred cave or crevice sites, which serve both as the mating locus and the nest. Encounters between rival males typically involve lateral displays and, if space is limiting, physical contact using the pectoral spine and odontodes. Females select among available males and nest sites; after oviposition the female is ejected from the cavity by the guarding male.
Breeding
Ancistrus cuiabae, like all members of the genus for which breeding data exist, is a cave spawner with exclusively paternal brood care. The male selects a sheltered cavity — a rock crevice, hollow piece of wood, or purpose-made breeding tube in captivity — cleans the spawning surface, and induces the female to deposit her eggs within the cavity.
After spawning, the male remains at the cave entrance or inside the cavity, fanning the egg mass with his fins to maintain oxygenation and removing infertile or fungused eggs. Clutch sizes in closely related Ancistrus species are typically in the range of 30–80 relatively large, adhesive eggs. Incubation period at tropical temperatures is generally 4–7 days; fry remain in or near the nest for a further period before becoming independent. No published breeding reports specific to A. cuiabae are available; data for congeners described from the same drainage (particularly A. claro) suggest broadly similar clutch sizes and incubation times.
In the aquarium
Ancistrus cuiabae does not appear to be established in the ornamental fish trade and is unlikely to be found outside specialist collectors or researchers with direct contacts in Brazil. Information on aquarium husbandry is therefore inferential, drawn from the care of Ancistrus congeners from Mato Grosso and adjacent drainages.
A tank of 20–30 US gal is adequate for a pair or small group, with caves, crevices, and driftwood pieces essential both as shelter and as foraging substrate. Target water conditions reflecting the Cuiabá drainage: temperature 75–82 °F, pH 6.0–7.5, soft to moderately hard water. Good filtration and regular partial water changes are important; like all Ancistrus, this species produces moderate waste and benefits from clean, well-oxygenated water despite its tolerance for hypoxic conditions in the wild.
The species is likely peaceful toward dissimilar tankmates. Males may be territorial with conspecific males if shelter sites are scarce. A single male kept with one or two females in a well-furnished tank should breed readily if conditioned on a varied diet.
Conservation
The IUCN Red List assessed Ancistrus cuiabae as Least Concern in 2018, citing a high population resilience and a minimum population doubling time of less than 15 months — a metric reflecting the species' productive life history typical of small-bodied loricariids.
The Pantanal is one of the most ecologically significant wetland systems on Earth and is subject to growing pressure from agricultural expansion, water management for cattle ranching, and sedimentation from the surrounding Cerrado agricultural frontier. Deforestation in the upper Cuiabá basin increases dry-season low flows and alters the flood pulse dynamics that drive Pantanal ecology. While A. cuiabae is currently not considered threatened, the health of its Pantanal and Cuiabá River habitat is not guaranteed over the long term.