Taxonomy & naming
Sturisoma graffini was formally described by Londoño-Burbano in 2018 in the Journal of Fish Biology (volume 92, pages 999–1015). The type locality is Picaflor Creek at Pakitza guard post, on the Castanel Trail and Caña Brava Trail corridor, within the Madre de Dios River basin of Amazonian Peru (11°49'60"S, 71°20'59"W). The Catalog of Fishes (Eschmeyer, CAS) recognises Sturisoma graffini as the valid name; no synonyms are recorded.
The genus Sturisoma is placed in the subfamily Loricariinae of the family Loricariidae — the armoured suckermouth catfishes. Loricariinae is characterised by elongated, dorsoventrally flattened bodies, a reduced or absent adipose fin in many members, and the diagnostic whiptail caudal filaments that give the group its vernacular name. Sturisoma itself was coined by combining the German sturio (sturgeon, attested from 1525, alluding to the elongated, armoured form) with the Greek soma (body): effectively 'sturgeon-bodied'. The genus contains roughly twenty species distributed across northern and central South America.
The species description also includes a revised key to all congeners and comments on the type series of Sturisoma rostratum, making it a significant contribution to the taxonomy of the group beyond the single new species.
Morphology
Adults reach a recorded maximum of 10.5 in standard length (SL) — standard length excludes the elongated caudal filaments that can add further length in undamaged specimens. Like all members of the genus, S. graffini has a highly elongated, flattened body covered in overlapping bony scutes, a ventrally positioned suckermouth, and the long filamentous extensions on the upper and lower caudal fin lobes that typify the whiptail group.
The body profile is narrow and torpedo-like when viewed from above, tapering to the caudal peduncle and the tail streamers. Colouration in Sturisoma whiptails is generally cryptic — brown to tan ground colour with a pattern of darker spots, blotches, or reticulations that varies among species and provides camouflage against sandy or rocky substrate. Specific coloration data for S. graffini beyond what the original description captures are sparse in the available literature; keepers should expect the typical genus pattern rather than a distinctive species-specific livery.
The genus is generally considered to exhibit mild sexual dimorphism: mature males develop short bristle-like odontodes on the snout and pectoral spine, more pronounced during the breeding season. Females in breeding condition tend to be broader-bodied. Whether these characters are fully expressed in S. graffini is not documented from field material.
Habitat
Sturisoma graffini is known from the Madre de Dios River basin in the Madre de Dios Region of Peru, a major tributary of the Madeira River and thus part of the greater Amazon drainage. The type locality — Picaflor Creek near the Pakitza guard post of the Manu Biosphere Reserve — places the species within one of the most biodiverse stretches of the western Amazon basin, where protected lowland rainforest streams flow over sandy and rocky beds.
Mother-of-God system rivers in this region are typically blackwater-influenced or clearwater streams in the lowlands, with warm temperatures (ambient tropical range roughly 75–82 °F), low to moderately acidic pH, and low conductivity. Benthic microhabitat for whiptail catfishes in this biome generally consists of flat rocky surfaces, leaf litter beds, or sandy substrates with submerged woody debris, where the animals rest in contact with the substrate and graze aufwuchs.
No detailed field measurements of water chemistry at the collection site for S. graffini have been published in the available literature; the parameters above reflect regional conditions for comparable lowland Amazon streams rather than direct measurement.
Feeding
Sturisoma and its close relatives in Loricariinae are primarily aufwuchs grazers — they use their modified suckermouth to rasp biofilm, algae, diatoms, and fine detritus from flat hard surfaces such as rocks, submerged wood, and broad plant leaves. The FishBase-recorded trophic level for S. graffini is 2.4 (±0.2), consistent with a diet dominated by algae and microbial material rather than substantial invertebrate or detrital fractions.
In the aquarium, members of this feeding guild do well on a diet centred on algae-based sinking wafers, spirulina discs, and blanched vegetables (courgette, cucumber, spinach), supplemented with good growth of natural biofilm on flat hardscape surfaces. Smooth flat rocks or pieces of broad bogwood provide ideal grazing surfaces that mimic the flat rocky substrates whiptail catfishes inhabit in the wild. Small live or frozen invertebrates can be offered as supplementary protein.
Mating
Courtship behaviour in Sturisoma is well-documented in related species kept in the aquarium hobby, and the general loricariid pattern is expected to apply to S. graffini. Males establish and defend flat surface territories — a smooth rock face, a broad piece of slate, or the glass pane of an aquarium — and court females by nudging and following behaviour. Males of related Sturisoma species develop more pronounced odontodes on the snout and pectoral spine during the breeding season, which function in both competition with rival males and in sensory contact during courtship.
Males of Sturisoma species are known to be site-faithful; the same flat surface may be defended and reused across multiple spawning events. Conditioning adults with varied foods and stable water parameters encourages breeding readiness.
Breeding
Sturisoma catfishes are flat-surface spawners — they deposit adhesive eggs directly onto a cleaned flat substrate rather than inside caves or tubes. This reproductive strategy distinguishes them from cave-spawning plecos such as Ancistrus or Hypancistrus. A male defends and selects a spawning site — typically a smooth rock face, slate, or equivalent flat surface — and after courtship and spawning, remains with the egg clutch, fanning it continuously with his pectoral and ventral fins to oxygenate the eggs and remove debris.
Paternal care is the rule in Sturisoma: the male guards and fans the eggs throughout incubation (typically around 6–10 days in related species at tropical temperatures) and continues to attend the newly hatched larvae until they become free-swimming. Spawning has been achieved in the aquarium hobby for several congeners — S. panamense and S. aureum are among the more regularly bred — using soft, warm, slightly acidic water and flat smooth surfaces such as a piece of slate. Whether S. graffini has been bred in captivity is not recorded in the available literature.
In the aquarium
Sturisoma graffini is not established in the ornamental trade as of the time of writing; no captive husbandry records or PlanetCatfish breeding reports exist for this species. General guidance must therefore be drawn from the closely related congeners that are available in the hobby.
Whiptail catfishes of the Sturisoma genus are generally considered moderately demanding aquarium subjects compared with more forgiving plecos. They require clean, well-oxygenated water with some flow, stable parameters reflecting Amazonian lowland conditions (temperature approximately 75–82 °F, pH 5.5–7.0, soft to moderately soft water), and flat smooth surfaces on which they can graze and potentially spawn. Flat slate or smooth sandstone is ideal hardscape. Tanks should be large enough to accommodate the adult's maximum length of approximately 10.5 in SL plus tail streamers; a minimum footprint of 120 × 17.5 in is sensible.
Whiptails are peaceful toward other species and do well in community setups with small to medium-sized fish that do not compete for their grazing territory. They can be kept in pairs or small groups in spacious aquaria. Robust plant growth and a biofilm-rich environment benefit them; avoid strong turbulence in all areas of the tank, as the whiptail's flattened body is adapted to resting in moderate current rather than turbulent rapids.
Conservation
The IUCN Red List assessed Sturisoma graffini as Vulnerable under criterion B1ab(iii)+2ab(iii), with the assessment published on 23 November 2020. The dual B1/B2 criteria indicate that both the extent of occurrence and the area of occupancy are restricted, and that a continuing decline in the area, extent, or quality of habitat has been inferred or projected — specifically in area/quality of habitat (sub-criterion iii).
The species is endemic to the Madre de Dios River basin, a relatively circumscribed watershed even within the broader Amazon system. While the type locality near Pakitza falls within the protected Manu Biosphere Reserve, the Madre de Dios basin as a whole faces significant pressure from illegal gold mining (alluvial dredging and hydraulic mining operations are widespread in the Peruvian lowlands), deforestation driven by smallholder agriculture and road construction, and associated sedimentation and mercury contamination of river systems. These threats degrade the clean-water, hard-substrate habitat on which whiptail catfishes depend.
The Vulnerable designation carries real conservation weight for a species with as restricted a range as S. graffini. Given the absence of captive-bred populations, any collection for the ornamental trade draws directly on wild fish from this single basin. Hobbyists seeking to keep this species, if it does become available, should prioritise captive-bred specimens and support the protected area network in the Madre de Dios region.