Taxonomy & naming
Ancistrus agostinhoi was formally described by Bifi, Pavanelli and Zawadzki in 2009, published in Zootaxa 2275 (pages 41–59), alongside two other new Ancistrus species from the same river system. The type locality is Foz do Jordão, coordinates 25°39'12"S, 51°58'15"W, lower Rio Iguaçu basin, Paraná State, Brazil. The Catalog of Fishes (Eschmeyer, CAS) recognises Ancistrus agostinhoi Bifi, Pavanelli & Zawadzki, 2009 as the valid combination.
The species is distinguished from most congeners in the Río de la Plata drainage and southern Brazilian coastal basins by a shorter maxillary barbel that is not free from the lower lip — a character it shares only with A. abilhoai, A. formoso, A. mullerae, A. multispinis, and A. taunayi within that broader clade. Meristic features recorded in the original description include a dentary tooth count of 38–78, head length 37.8–41.4% of SL (mean 38.9%), and caudal peduncle depth 10.6–12.0% of SL.
The genus name Ancistrus derives from the Greek agkistron, meaning hook, a reference to the hooked interopercular odontodes that males deploy in territorial encounters. Ancistrus belongs to the tribe Ancistrini within subfamily Hypostominae, one of the five major subfamilial groupings of Loricariidae (Armbruster, 2004).
Morphology
Adults are recorded to 4 in SL for males and unsexed specimens, with females reaching a smaller 3 in SL (FishBase, Ref. 83296). The body plan follows the characteristic loricariid template: a flattened ventral surface, a dorsal profile armoured in overlapping bony scutes, and a ventrally positioned suctorial mouth suited to rasping hard surfaces.
Sexual dimorphism centres on the snout. Mature males develop the fleshy, branched tentacles on the rostral pad and snout margins that are the hallmark of the genus; females may bear rudimentary tentacles but never approach the bushy, branched development seen in fully adult males. This distinction is conspicuous and reliable for sexing fish above approximately 2 in SL.
Dorsal fin formula records one spine and seven soft rays; anal fin carries one spine and three to four soft rays. The species possesses the facultative or obligate air-breathing capacity noted across Ancistrus — an adaptation to hypoxic conditions in slow or degraded water. Body shape is described as elongated for the genus.
Habitat
Ancistrus agostinhoi is endemic to the lower Rio Iguaçu basin in Paraná State, southern Brazil. The Iguaçu is a major left-bank tributary of the Paraná River and forms part of the broader La Plata drainage. Its lower reaches below Iguaçu Falls are ichthyologically distinct from the upper basin, cut off by the falls as a dispersal barrier, which has driven high local endemism in the downstream section where this species occurs.
The lower Iguaçu runs through subtropical terrain with a seasonal temperature regime cooler than the tropical Amazon. As a demersal, benthic catfish, A. agostinhoi occupies hard substrates — rock faces, submerged boulders, and driftwood — in riverine zones with at least moderate current. No detailed field measurements of water chemistry at capture sites were included in the original description, but the La Plata system generally supports moderate to moderately hard, circumneutral water.
Feeding
Ancistrus agostinhoi is primarily a vegetarian rasper, in keeping with the genus-wide feeding strategy. In the wild, individuals graze biofilm, periphyton, and soft algae from hard surfaces — rocks, wood, and compacted substrate — using the fine, multi-cusped teeth and suctorial mouth characteristic of Ancistrini.
In captivity the diet transfers readily. Spirulina-enriched sinking wafers and algae tabs form the dietary backbone; blanched vegetables such as courgette (zucchini), cucumber, and spinach are accepted and provide moisture and plant matter. Small amounts of meaty foods — frozen bloodworm or high-protein sinking pellets — can be offered occasionally but should not dominate the diet. A piece of driftwood in the tank provides both a rasping surface and refuge, and is strongly recommended. Overfeeding protein-rich foods to Ancistrus has been linked to digestive and hepatic issues in the aquarium literature.
Mating
Courtship behaviour in A. agostinhoi has not been documented in detail in the literature, but the pattern follows the well-characterised Ancistrus model. Males establish and defend territory centred on a favoured cave or crevice site. The branched snout tentacles of the male appear to function in both rival assessment and female attraction; males may display lateral to one another and use the hooked interopercular odontodes in contact sparring.
A reproductively conditioned female develops a visibly rounder, wider body profile behind the pectoral fins. Males may become aggressive toward conspecific males when a gravid female is present, and in tanks smaller than approximately 20 US gal housing two males, chronic territorial stress is likely. Providing multiple cave sites spaced across the tank reduces conflict.
Breeding
Like all members of the genus, A. agostinhoi is a cave-spawning species with paternal brood care. The male selects a confined cavity — a narrow tube, a hollow section of driftwood, or a tight rock crevice — and attracts or courts a female into the spawning site. Eggs are adhesive and deposited on the cave interior walls in a compact clutch.
The male remains with the clutch throughout incubation, fanning the eggs with his fins to maintain oxygenation and removing infertile or fungused eggs. At tropical aquarium temperatures the incubation period for Ancistrus typically runs five to seven days. Newly hatched fry carry a yolk sac and remain in the cave; the male continues to guard until the fry become free-swimming and disperse. No confirmed captive breeding reports for A. agostinhoi specifically are on record at PlanetCatfish, though the species's husbandry requirements do not differ fundamentally from well-bred congeners.
In the aquarium
Ancistrus agostinhoi is not widely available in the hobby and lacks a common name or L-number, making it primarily a species of interest to catfish specialists and collectors focused on Iguaçu endemics. Its modest adult size — under 4 in SL — places it well within the range manageable in standard community tanks.
A single individual can be housed in a tank of approximately 15–20 US gal, provided sufficient hard surfaces and at least one suitable cave are present. Males are territorial toward conspecifics; if keeping a pair or group, multiple caves and visual breaks reduce aggression. The species is described as generally peaceful toward other fish outside territorial disputes over caves.
Water parameters should reflect the subtropical Paraná drainage origin. A temperature range of approximately 64–79 °F is appropriate, cooler than many tropical catfish species. pH near neutral (6.8–7.5) and moderate hardness suit the species well. Strong filtration and regular partial water changes maintain the water quality that benthic raspers — heavy producers of waste — require. Driftwood is recommended both as a dietary supplement and as shelter.
Conservation
The IUCN Red List assessed Ancistrus agostinhoi as Least Concern, with the assessment completed on 7 November 2018. The species is restricted to the lower Rio Iguaçu basin in Paraná State, Brazil — a geographically confined range, but one where the population was not considered to be facing significant decline at the time of assessment.
The lower Iguaçu is subject to ongoing pressures from agriculture, hydroelectric development, and altered flow regimes in the Paraná system. The high endemism of the lower Iguaçu ichthyofauna, shaped by the natural isolation imposed by Iguaçu Falls, makes any range-contracted species potentially sensitive to local habitat deterioration. Future reassessments may need to revisit the population status if riverine habitat in the lower Iguaçu continues to be modified.