Taxonomy & naming
Peckoltia amjikin was formally described by Araújo, Ferreira, Silva and Wosiacki in 2025 in the Journal of Fish Biology (volume 108, issue 1, pages 351–360; DOI 10.1111/jfb.70235). The holotype (MPEG 40735, 2.5 in SL) was collected from the rio Tocantins basin, municipality of Bom Jesus do Tocantins, Tocantins State, Brazil. The Catalog of Fishes (Eschmeyer, CAS) recognises the valid name Peckoltia amjikin Araújo, Ferreira, Silva & Wosiacki, 2025.
The species was previously misidentified as Peckoltia vittata (Steindachner, 1881) in museum collections from the Tocantins-Araguaia drainage. Integrative taxonomy — combining detailed morphological diagnosis with a Cytochrome b molecular phylogeny — resolved P. amjikin as a distinct entity within the Peckoltia clade, separate from P. vittata. The type series comprised 18 specimens ranging from 2–2.5 in SL (mean 2.5 in SL).
The genus Peckoltia (Miranda Ribeiro, 1912) is placed within the subfamily Hypostominae, tribe Ancistrini, and encompasses small to medium-sized loricariids distributed across Amazonian and Atlantic slope drainages of South America. The etymology of the species name honours the Krahô people: 'amjikin' is a Timbira language word (Macro-Jê trunk) meaning a state of happiness, used here as a noun in apposition — a recognition of the indigenous community located east of Tocantins State, within whose territorial waters the species was discovered.
Morphology
FishBase records a maximum standard length of 2.5 in SL for P. amjikin, consistent with the type series range of 2–2.5 in SL. This makes it a small species within Peckoltia, in keeping with the generally compact body size of the genus.
The morphological diagnosis from Araújo et al. (2025) provides a detailed character set distinguishing P. amjikin from P. vittata and related species. The ventral region bears diffuse stripes rather than spots or discrete blotches. Elongated odontodes on the cheeks reach the pectoral-fin spine when adpressed. The interorbital space is not entirely covered by a single blotch. The parieto-supraoccipital bone is moderately elevated, not forming a pronounced crest. Dentition ranges from 14–26 teeth on the premaxilla and 15–24 on the dentary. Minute plates with short odontodes are present at the pectoral-fin base and anterior urogenital opening. The suspensorium is relatively less developed compared to closely related species.
Colour pattern in life includes seven saddles along the body, four oblique bars behind the head, and dark bars crossing the dorsal-fin membranes. Yellow stripes on the head are obliquely positioned and do not exceed the diameter of the eye orbit. The overall patterning of oblique bars and saddles is broadly similar to P. vittata, which explains the historical misidentification.
Sexual dimorphism: no data are published for P. amjikin. Based on general Peckoltia biology, males typically have a slimmer body profile, and mature males may develop elongated interopercular or body odontodes during the breeding season. Females in breeding condition tend to be noticeably wider when viewed from above.
Habitat
Peckoltia amjikin is known from rapids in the Tocantins-Araguaia basin, Brazil. The holotype locality (Bom Jesus do Tocantins, Tocantins State) places it in the central Brazilian plateau river system — a large drainage flowing northward from the Brazilian cerrado (savanna) through tropical forest into the lower Amazon near Belém, Pará State.
Rapid-dwelling loricariids are strongly associated with rocky outcrops and fast-flowing, well-oxygenated water. The Tocantins and its tributaries at the type locality are typically clear to slightly turbid with a moderate mineral content, contrasting with the blackwater of the Negro system or the whitewater of Andean tributaries. No specific water-chemistry data (temperature, pH, conductivity) from the collection site are recorded in available sources.
The Tocantins-Araguaia basin has a strongly seasonal rainfall regime — wet season from October to April, dry season from May to September — with corresponding fluctuations in water level, temperature, and chemistry. Rocky rapids habitats tend to retain higher dissolved oxygen year-round even as water levels drop significantly in the dry season, potentially concentrating fish in diminishing refugia.
Feeding
No published feeding data are available for P. amjikin. The genus Peckoltia is regarded as omnivorous within the loricariid guild, feeding on a combination of periphyton and biofilm scraped from rocky surfaces, small invertebrates, and organic detritus. The fine, slightly spatulate teeth typical of the genus allow both algae grazing and processing of softer food items.
In the aquarium, Peckoltia species are generally maintained on a diet of sinking algae wafers, spirulina-based foods, blanched vegetables, and occasional protein supplements such as bloodworm or small crustaceans. Driftwood is beneficial as a grazing and shelter substrate. P. amjikin, as a rapid-dwelling species, would be expected to thrive with good water flow over rocky surfaces colonised by algae and diatoms.
Mating
No field or aquarium observations of mating behaviour in P. amjikin are on record. The species was described only in 2025 and has not been established in the aquarium hobby. Based on the reproductive biology of other Peckoltia species, mating is expected to occur in crevices among rocks or in hollow wood, with territorial males defending a favoured spawning cavity and competing with rivals through lateral displays and odontode engagement.
Rapid-dwelling loricariids often show attachment to specific rocky territories that provide both shelter and sufficient water flow to oxygenate developing eggs. The downstream displacement of eggs or fry in fast current is a likely selection pressure favouring adhesive egg deposition deep within rocky crevices.
Breeding
No captive breeding reports for P. amjikin exist. As a 2025-described species not yet established in trade, reproductive biology is entirely inferred from genus-level expectations. Peckoltia species are generally regarded as cave or crevice spawners with adhesive eggs and paternal brood care — the male fans and guards the clutch until the fry are free-swimming and able to forage independently.
Future hobbyist breeding attempts with P. amjikin, should specimens become available, would provide the first documented data on clutch size, incubation period, and parental-care behaviour for this species. Rocky-terrain décor and strong aeration would be important conditioning factors given the rapids origin.
In the aquarium
Peckoltia amjikin is not currently in the aquarium trade. No specimens have been reported in hobbyist collections as of the time of writing, and the species' description appeared only in early 2025. PlanetCatfish has not yet established a dedicated species page, though a forum post from October 2025 notes the species is likely the same fish that had been circulating in the hobby as unidentified Peckoltia from the Tocantins drainage.
If specimens become available, the small adult size (approximately 2.5 in SL) makes this species manageable in a tank of 15–20 US gal. The rapids habitat origin suggests a preference for well-oxygenated, moderate-to-fast-moving water and rocky substrate or smooth driftwood. Water temperature and chemistry parameters from the central Brazilian plateau would serve as a guide — warm (75–82 °F estimated), moderately soft to medium-hard, and near-neutral pH is a reasonable starting point in the absence of site-specific data.
Caves, rock piles, and driftwood tangles should be provided. The fish's previous misidentification as P. vittata suggests visual similarity sufficient to cause confusion; obtaining specimens with verified locality data would be important for any conservation-oriented breeding effort.
Conservation
Peckoltia amjikin has not been assessed by the IUCN Red List. Described in 2025, it is too recently named for a formal assessment to have been completed. Its known range — rapids of the Tocantins-Araguaia basin, central Brazil — encompasses a river system under substantial development pressure, including significant hydroelectric infrastructure. The Tocantins River has been dammed at multiple points; the Tucuruí Dam in particular has altered hydrology and habitat across a large portion of the lower drainage, though the type locality in Tocantins State is in the upper-to-middle portion of the basin.
Rapid-dwelling specialists are often among the most impacted by dam construction, as inundation of rapids habitat eliminates the fast-flowing, rocky substrate that defines their ecological niche. Given this context, a conservation assessment once baseline population data become available would be warranted.