Taxonomy & naming
Spatuloricaria caquetae was described by Henry Weed Fowler in 1943 in the Proceedings of the Academy of Natural Sciences of Philadelphia (volume 95, page 261, figures 60–62), under the original combination Loricaria caquetae. The type locality is the Río Orteguasa at Florencia, Caquetá department, Colombia. The Catalog of Fishes (Eschmeyer, CAS) recognises the valid combination Spatuloricaria caquetae (Fowler, 1943).
The genus Spatuloricaria belongs to the subfamily Loricariinae within Loricariidae — the armoured whiptail catfishes. Loricariinae lack the adipose fin and are characterised by an elongate, depressed body with a filamentous caudal extension. Ferraris (2003, in Reis et al., Checklist of Freshwater Fishes of South and Central America, EDIPUCRS, Porto Alegre) is the main reference treatment for this group.
Morphology
Spatuloricaria caquetae reaches approximately 14.5 in standard length (SL) — a substantial size for a loricariine whiptail. The body is elongate and strongly depressed, with a broad, flattened head and the characteristic long filamentous caudal ray of the genus. Bony scutes armour the dorsal surface; the ventral surface is reduced in plate coverage consistent with the benthic lifestyle.
Sexual dimorphism is present and follows the pattern of the genus: adult males develop pronounced odontodal growth on the cheeks and along the pectoral fin spines, and the pectoral spines of males are described as thicker and slightly shorter than those of females. The male head is isosceles-triangle shaped when viewed from above, whereas the female head is more equilateral — a distinction also noted in the closely related P. platycephalus and other Spatuloricaria. Coloration is not described in detail in available sources.
Habitat
The type locality of Spatuloricaria caquetae is the Río Orteguasa at Florencia, in the Colombian department of Caquetá. The Orteguaza is a tributary of the Caquetá River, which flows eastward from the Andean cordillera through the Amazon lowlands of Colombia before entering the Brazilian Amazon as the Japurá. The species is also recorded from the broader Japurá and Solimões (Amazon mainstream) systems, giving it a range that spans the Colombian Amazon and its extensions into Brazil.
FishBase records water parameters in the 72–77 °F temperature range, pH 6.5–7.5, and moderate hardness (dH ≤20) — reflecting the variably clear-to-turbid lowland rivers of the upper Amazon drainage. As a benthic, demersal species at trophic level 2.2, it is expected to inhabit sandy and muddy substrates in slow to moderate current sectors of larger river channels and their tributaries. Resilience is rated Very Low (minimum population doubling time >14 years), a flag for caution in any collection scenario.
Feeding
Spatuloricaria caquetae is a benthic grazer, feeding on biofilm, diatoms, fine algae, and detritus from sandy and soft substrates. The trophic level (2.2) recorded by FishBase is consistent with primary consumption of plant-origin material and microorganisms from the substrate surface. In the aquarium, fine sand that allows natural foraging behaviour should be provided, with supplementary feeding via sinking algae wafers, spirulina tablets, and blanched vegetables such as courgette or cucumber. The fish's large adult size means it produces significant waste, and the filtration load should be planned accordingly.
Mating
No breeding account for Spatuloricaria caquetae is recorded in the PlanetCatfish database or published literature reviewed for this article. Mating behaviour is therefore extrapolated from the general Spatuloricaria and Loricariinae biology. Males in breeding condition are identifiable by pronounced odontodal development on the cheeks and pectoral spine region, and by the head-shape difference from females. A breeding pair would be expected to require a large area of undisturbed fine sand substrate. Conditioning on a varied diet and the provision of excellent water quality are the standard preparatory steps recommended for loricariinae in general.
Given the Very Low resilience rating (long generation time), this species is likely slow to mature, and aquarists should expect a longer conditioning period than for faster-maturing loricariids.
Breeding
No captive breeding of Spatuloricaria caquetae has been reported in any source consulted. Based on the biology of Spatuloricaria and the broader Loricariinae, the genus is expected to practice paternal brooding on open substrate, with the male guarding the egg mass on or near sandy riverbottom — the open-substrate brooding strategy that distinguishes loricariinae from cave-spawning Hypostominae.
Given the large adult size (14.5 in SL) and very low resilience rating of this species, breeders would need a correspondingly large aquarium and should approach reproduction efforts with patience. The absence of any registered breeding report suggests that this species has not been kept in numbers sufficient for captive reproduction to have been attempted or documented.
In the aquarium
Spatuloricaria caquetae is occasionally encountered in the hobby — seven registered keepers and nine spotters are listed on PlanetCatfish, with five images on file — but it remains a specialist's species. The common name 'Longtail Pleco' reflects the elongate whiptail body form but is not widely used.
The fish's eventual size of around 14.5 in SL demands a correspondingly large aquarium: a minimum footprint of 150 × 19.5 in would be appropriate for a single adult, with larger setups needed for a pair or group. The substrate must be fine, smooth sand — deep enough to allow the fish to partially bury itself if it chooses. Bright lighting is inadvisable; subdued illumination with shaded areas will produce a more active and visible specimen. Water parameters should reflect the Caquetá origin: temperature 72–77 °F, pH 6.5–7.5, moderate softness.
This species should not be housed with aggressive or territorial fish. Suitable tankmates are peaceful, similarly-sized species that do not compete on the substrate. Given the Very Low resilience rating, wild-caught individuals should be handled with care, and the hobby should prioritise captive breeding efforts to reduce pressure on wild populations.
Conservation
The IUCN Red List assessed Spatuloricaria caquetae as Data Deficient in 2014 (IUCN ID 49830134). The Data Deficient listing reflects that available information was inadequate to assess risk of extinction based on distribution and population status at the time of assessment — not that the species is necessarily rare, but that sufficient survey data was lacking.
FishBase records a Very Low resilience rating (minimum population doubling time >14 years), suggesting that this species has life-history characteristics that make it inherently slow to recover from population declines. The Caquetá drainage of Colombia has been subject to deforestation, agricultural expansion, and, historically, disruption associated with armed conflict in the region — all factors that may affect water quality and habitat integrity without having been systematically assessed in the context of this species. The 2014 assessment represents the most recent IUCN evaluation; updated survey data from the Orteguaza and Caquetá systems would be valuable for determining whether the Data Deficient status remains appropriate or whether a more substantive assessment is now possible.