Taxonomy & naming
Chaetostoma spondylus was described by Natalí Salcedo and Hernán Ortega in 2015, in a paper published in Neotropical Ichthyology (13(1): 151–156). The holotype — MUSM 33341, a specimen of 4.5 in SL — was collected on 15 October 2008 from the Río Sendamal, a tributary of the Río Marañón in the district of Sorochuco, province of Celendín, department of Cajamarca, Peru (6°51′29.5″S, 78°15′35.2″W), at an altitude within the 1,500–2,0 ft range typical of the described population.
The species is the fifth member of the genus Chaetostoma known from tributaries of the Río Marañón. Within the genus, C. spondylus was diagnosed as distinct from its congeners by a unique combination of characters: tufts of odontodes surrounded by naked skin in the middle of each trunk lateral dermal plate, and more than twenty hypertrophied evertible odontodes on the three cheek plates. It shares several synapomorphies with C. loborhynchos, C. marmorescens, and C. mollinasum — including a short, slender fourth branchiostegal ray and conspicuous blister-like papillae densely packed on the naked snout — but is readily separated from C. loborhynchos by its naked (unplated) snout versus the plated snout of that species.
The Catalog of Fishes (Eschmeyer, CAS) recognises the valid combination Chaetostoma spondylus Salcedo & Ortega, 2015. The genus Chaetostoma belongs to the tribe Chaetostomini of subfamily Hypostominae within Loricariidae, a grouping of mid-sized to small armoured catfishes broadly distributed across Andean and sub-Andean river systems.
Morphology
Adults of Chaetostoma spondylus reach at least 5 in SL, with the largest paratypes indicating a maximum of approximately 5 in SL (5 in from proportional tables in the original description). The body is elongated relative to many Chaetostoma species, reflecting the streamlined morphology common in high-gradient Andean loricariids. The dorsal fin has 8–9 soft rays; the anal fin has 1–3 soft rays, and the vertebral count is 28–29.
The most conspicuous diagnostic character is the arrangement of odontodes on the lateral body plates: each trunk lateral dermal plate bears a tuft of evertible odontodes rising from a central patch of naked skin — an unusual texture described by the authors as reminiscent of the thorny projections of the Spondylus (spiny oyster) bivalve. The three cheek plates bear more than 20 hypertrophied evertible odontodes per side, substantially more than related species. The snout is naked (unplated), covered instead with dense, conspicuous blister-like rounded papillae.
Like other members of Chaetostomini, C. spondylus is a facultative air-breather, capable of using atmospheric oxygen when dissolved oxygen levels fall — an adaptation of value in the variably oxygenated waters of high Andean streams during low-flow periods.
Habitat
Chaetostoma spondylus is known from four rivers in north-central Peru: the Río Chotano, Río Huancabamba, Río Sendamal, and Río Utcubamba — all mountain tributaries of the Río Marañón, which forms the main headwater axis of the Amazon in this region. All collection localities fall in the range of 1,500–2,0 ft elevation, placing the species firmly in the upper Andean cloud-forest zone.
Water conditions at the type-locality sites were measured as pH 7.1 (near-neutral) and dissolved oxygen 8.2 mg/L, values consistent with cold, well-oxygenated, fast-flowing mountain streams. The substrate at collection sites is described as boulder-dominated, with the fish associated with high-gradient rapids — the typical microhabitat for the sucker-mouth guild in Andean rivers, where powerful ventral suckers and a flattened body allow the fish to maintain position against vigorous current.
At elevations above 1,1640 ft in the Andes, water temperatures are substantially cooler than in the lowland Amazon. Specific temperature data are not recorded in the original description, but conditions at these elevations in Peru generally fall in the range of approximately 54–68 °F depending on season and elevation.
Feeding
No feeding study specific to Chaetostoma spondylus has been published. Members of Chaetostoma are scraping herbivores and detritivores, equipped with a ventrally positioned sucker-mouth and numerous small teeth adapted for rasping periphyton (algal films, diatoms, cyanobacteria) and fine detritus from rock surfaces in fast-flowing streams.
The high current velocities and boulder substrates of the Río Marañón tributaries occupied by this species are typically productive for periphyton growth, providing a reliable food supply for suckermouth catfishes. Gut-content studies of related high-Andean Chaetostoma consistently document algae, diatoms, and fine sediment particles as the dominant dietary components.
In an aquarium setting, a diet of algae wafers, spirulina-enriched sinking foods, and blanched vegetables would be appropriate by analogy with the genus, though captive maintenance of this high-altitude species presents challenges related to its temperature requirements (see In the aquarium).
Mating
No observations of mating behaviour in Chaetostoma spondylus have been published. The genus Chaetostoma follows the general loricariid pattern in which males are territorial around preferred refuges in stream rapids, and males in breeding condition develop more pronounced evertible cheek odontodes. Given the high-altitude, remote-stream habitat of this species, field observations of reproductive behaviour are unlikely to have been made.
Data are too sparse to characterise the mating system of this species beyond inference from loricariid general biology.
Breeding
No breeding data are available for Chaetostoma spondylus. The species has not been documented in captive collections or bred in aquaria, and the original description contains no information on reproductive biology. By analogy with the broader Loricariidae, a cave-spawning or crevice-spawning strategy with paternal brood care is likely, but no account specific to this species or its close relatives in the Río Marañón drainage has been published.
Data sparse.
In the aquarium
Chaetostoma spondylus has not been documented in the ornamental fish trade and is unlikely to be available to hobbyists under this name. The Río Marañón tributaries at 1,500–2,0 ft elevation are remote collection areas, and the export of high-altitude Andean fish from Peru is limited by the logistical difficulty of the region and by export regulations.
If ever maintained in captivity, the species would require cool-water conditions reflecting its high-altitude origin — likely in the range of 57–72 °F — well-oxygenated water with strong circulation simulating mountain-stream currents, and a substrate of smooth boulders providing both grazing surface and refuge. Near-neutral to slightly alkaline pH (7.0–7.5) reflects the field measurement of pH 7.1 at the type locality.
The elaborate evertible odontode tufts on the body plates make this species of interest to specialists, but its ecological requirements place it outside the range of most standard tropical fishkeeping setups.
Conservation
Chaetostoma spondylus has not been assessed by the IUCN Red List. The species was described only in 2015, and no population estimates or trend data are available. Its known range is restricted to four river drainages in north-central Peru within a relatively narrow elevational band of 1,500–2,0 ft.
Andean mountain streams in this region face pressures from agriculture, small-scale mining, and increasing human settlement in cloud-forest watersheds. High-altitude endemics with restricted ranges are inherently vulnerable to habitat degradation. Without a dedicated field survey and population assessment, the conservation status of C. spondylus cannot be evaluated — an assessment under IUCN criteria would likely require consideration of its small known area of occupancy and the ongoing pressures on Peruvian Andean watersheds.