Taxonomy & naming
Ancistrus lithurgicus was formally described by Carl H. Eigenmann in 1912 in his monograph 'The Freshwater Fishes of British Guiana' (Memoirs of the Carnegie Museum, vol. 5, no. 1, p. 241, fig. 36, pl. 25 fig. 3). The type locality is Crab Falls on the Essequibo River, Guyana, approximately 5.40°N, 58.82°W. The Catalog of Fishes (Eschmeyer, CAS) recognises Ancistrus lithurgicus Eigenmann, 1912 as a valid species with no junior synonyms.
The species belongs to subfamily Hypostominae within Loricariidae, the largest family of catfishes, and sits in the diverse and taxonomically challenging genus Ancistrus — the bristlenose plecos. A 2019 review of Ancistrus from the northwestern Guiana Shield (published in Zootaxa 4552(1)) confirmed A. lithurgicus as a valid, dorsoventrally flattened species endemic to Guiana Shield drainages. No L-number or ornamental trade code has been assigned.
Morphology
Adults reach up to 5 in standard length (SL), making A. lithurgicus a mid-sized member of the genus. The body is dorsoventrally flattened — an adaptation shared by most loricariids for life in flowing water — and covered in overlapping bony scutes forming an armoured carapace. Ground coloration in typical Ancistrus fashion is brown to grey-brown, usually with small pale spots or mottling that provides camouflage against rocky substrates.
The most distinctive secondary character of the genus is the development of fleshy tentacles — odontodes on soft, fleshy stalks — on the snout. In adult males these tentacles become elaborate and branched, forming a dense rosette around the snout tip. Females may develop tentacles along the snout margin but never to the elaborate extent seen in breeding males. This feature is the primary means of sexing the species. Interopercular odontodes — cheek spines — are also present and more pronounced in males, especially during the breeding season.
Habitat
Ancistrus lithurgicus is known from the Essequibo and Berbice river basins of Guyana — classic Guiana Shield river systems characterised by clear to blackwater conditions over rocky or sandy substrates, with rapids and cascades common along their courses. The type locality at Crab Falls on the Essequibo underscores an association with turbulent, well-oxygenated water over hard substrates.
The species epithet lithurgicus (Greek: lithourgos, stonemason) alludes precisely to this rocky-substrate ecology — these fish are adapted to clinging to stones and boulders in current using their ventral suckermouth. FishBase notes the species as benthopelagic freshwater tropical, with facultative air-breathing capability recorded for the broader genus. No specific temperature or pH records from field collections have been published.
Feeding
Like all Ancistrus, A. lithurgicus is primarily an aufwuchs and algae grazer in the wild, rasping biofilm, periphyton, and algal mats from rock surfaces using its transverse rows of spoon-tipped teeth. Decaying organic matter and detritus adhering to rocks are also consumed. The dentition is multicusped and adapted for scraping rather than gouging — these fish do not process wood in the manner of the xylophagous Panaque or Panaqolus genera.
In the aquarium, the diet should reflect this vegetarian emphasis: algae wafers, spirulina-based sinking pellets, and blanched vegetables (courgette/zucchini, cucumber, peas) form the backbone of the diet. Small amounts of protein-rich foods such as frozen bloodworm can be offered occasionally without harm, but the bulk of caloric intake should come from plant-based sources. The fish will also graze naturally on any algae film that develops on aquarium glass and décor.
Mating
Courtship in Ancistrus follows a well-documented pattern consistent across the genus, and A. lithurgicus likely conforms to it. Males establish and defend cave or crevice territories — tight recesses within rockwork, hollow driftwood, or ceramic tubes — and use their elaborate snout tentacles and interopercular odontodes in displays and confrontations with rival males. In the wild, suitable cavities beneath boulders and within rock crevices in rapids provide abundant nesting sites.
Males coax ripe females into the nest cavity. A conditioned female ready to spawn shows a visibly broader body profile when viewed from above, particularly in the mid-body region. In tanks with multiple males, territorial aggression between males increases during the breeding season, and adequate shelter spacing is important to prevent chronic stress.
Breeding
Ancistrus lithurgicus is a cave-spawner with paternal brood care, following the typical Ancistrus reproductive strategy. The male selects a narrow cavity and, after mating, remains inside to guard the clutch. He fans the eggs continuously using his pectoral fins to maintain oxygen flow across the egg mass and removes any infertile or fungused eggs. No captive breeding report for A. lithurgicus specifically has been recorded in the hobbyist literature, but the reproductive biology is consistent with the well-documented patterns of the wider genus.
Eggs are adhesive and are deposited on the cave interior walls or ceiling. Incubation duration at typical tropical temperatures runs approximately five to seven days in related species, after which the fry hatch and absorb their yolk sacs while still under paternal guard. The male continues to protect the fry until they begin dispersing and feeding independently on biofilm and fine particulate matter.
In the aquarium
Ancistrus lithurgicus is not commonly encountered in the aquarium hobby, and captive specimens are rarely traded — it is primarily known as a wild-caught species from Guyana. Care requirements can be inferred reliably from the genus. A tank of 25 US gal or more is appropriate for a single adult given its size of up to 5 in SL; pairs or trios benefit from larger quarters.
Rockwork is the priority in décor, reflecting the species' natural rocky-river habitat. Smooth or rounded stones arranged to create crevices and overhangs will be used heavily for shelter and as potential breeding sites. Driftwood is appreciated as a secondary shelter element and contributes tannins that soften water chemistry, though this species is not wood-dependent for nutrition. Water should be clean and well-filtered with moderate current; temperature in the range of 75–82 °F is appropriate for a Guiana Shield species.
The species is peaceful toward other fish and can be housed with community tankmates that share similar water requirements — small tetras, rasboras, and Corydoras are compatible choices. Males are territorial toward conspecific males, particularly in confined spaces; if multiple males are kept, the tank must be large with ample separated cave territories.
Conservation
The IUCN Red List assessed Ancistrus lithurgicus as Least Concern (LC) in September 2020, based on a distribution spanning the Essequibo and Berbice river systems of Guyana — a geographically contiguous range without evidence of significant population decline. The interior rivers of Guyana remain relatively free of the intensive agricultural and industrial development pressures that threaten many South American freshwater fish, and no major threats to this species have been identified.
The Guiana Shield as a whole is considered one of the most intact freshwater ecoregions in South America, supporting high endemism. While ornamental fish collection occurs in Guyana, A. lithurgicus is not among the heavily traded species, and there is no indication that collection pressure poses a risk to wild populations. Ongoing monitoring of Guiana Shield river systems remains important given broader regional pressures from mining and deforestation.