Taxonomy & naming
Acanthodoras spinosissimus was described by Rosa Smith Eigenmann and Carl H. Eigenmann in 1888. It belongs to the family Doradidae — the thorny or talking catfishes — a exclusively South American family of armoured siluroids characterised by a midlateral row of bony, often spinous scutes (the "thorns" that give the family its common name) and the capacity to produce sounds. The Catalog of Fishes (Eschmeyer, California Academy of Sciences) treats Acanthodoras spinosissimus as the valid combination.
The genus Acanthodoras is a small group of thorny doradids found in the Amazon and Orinoco drainage systems. The genus name combines the Greek akanthos (thorn or spine) with doras (an old Greek word for skin, applied to various catfishes), alluding to the prominent spiny armour. The species epithet spinosissimus is Latin for "most spiny" or "extremely spiny" — the superlative of spinosus — marking this species as particularly heavily armed among its relatives. No synonyms are recorded for the species in the available literature, and there are no described subspecies or population variants.
Morphology
Acanthodoras spinosissimus has the typical doradid body plan: a broad, somewhat flattened head, a stout, tapering body, and a forked caudal fin. The skin is naked (scaleless) but protected by a midlateral row of bony scutes, each bearing a posteriorly directed spine; additional bony plates cover the head and nuchal region. The overall effect is a fish that looks and feels genuinely armoured. Three pairs of barbels are present — a long maxillary pair on the upper jaw and two shorter, often branched mandibular pairs below.
The dorsal fin carries a stout, serrated, locking spine that can be locked erect defensively; the pectoral fins likewise bear locking, serrated spines that are difficult to free once engaged in a net mesh. Primary-source size data for this specific species are not confirmed in the available literature; the genus Acanthodoras is recorded at roughly 4.5–7 in standard length in general doradid references, and the species is considered a small to medium thorny catfish. Aquarium specimens may remain somewhat smaller. Coloration is typically dark brown to greyish-black, often with a pale or cream ventral surface; the spiny scutes are paler and stand out against the darker flanks.
Habitat
The genus Acanthodoras is distributed across the Amazon and Orinoco river basins of South America, and A. spinosissimus is attributed to these drainage systems based on the geographic range of the genus. Doradids as a group favour slow to moderately flowing rivers, flooded forest streams, and marginal lagoons with soft substrates and abundant leaf litter, woody debris, or rocky cover that provides daytime refuges for these nocturnal fish.
Water conditions in typical Amazon lowland habitats are warm (around 75–82 °F), soft, and near-neutral to mildly acidic (pH roughly 6.0–7.5), though conditions vary considerably across the basin. Specific habitat data for A. spinosissimus are not confirmed in the primary literature; the above reflects the broader doradid ecological context. This is not a hard-alkaline water species — the rift-lake or brackish conditions required by some catfishes are not appropriate here.
Feeding
Acanthodoras spinosissimus is a benthic omnivore in the doradid mould. In its natural habitat it forages after dark across the bottom, taking aquatic invertebrates — insect larvae, worms, small crustaceans — along with detritus, plant material, and whatever organic matter accumulates in the substrate. The stout barbels are sensory tools for locating food in low-light or turbid conditions.
In the aquarium this feeding profile translates easily to sinking pellets, frozen bloodworm and brine shrimp, and other prepared bottom-feeder foods. Because doradids are predominantly nocturnal, it is best to offer food after the aquarium lights go out so the fish can forage without competition from more active daytime species. Variety helps condition adults and keeps the fish active and healthy.
Mating
Detailed mating observations for Acanthodoras spinosissimus in the wild or in the aquarium are not available in the literature consulted. Based on the general biology of the Doradidae, mating in thorny catfishes is thought to involve substrate or cavity spawning; some doradids are reported to construct simple nests or to scatter adhesive eggs in sheltered spots, with variable levels of parental involvement.
Sexual dimorphism has not been confirmed in published descriptions of this species. In doradids generally, ripe females may appear somewhat fuller-bodied than males during the spawning season, but reliable sexing characters for A. spinosissimus in aquarium conditions are not documented in the sources available.
Breeding
Breeding of Acanthodoras spinosissimus in the aquarium has not been documented in the literature reviewed. Doradidae are not, as a family, routinely bred in hobby aquaria; most aquarium-traded doradids are wild-collected from South American river systems. Some doradid species have been induced to spawn under aquarium conditions, but the specific trigger cues and detailed protocols are not established for this species in the available sources.
Hobbyists interested in attempting a spawn would likely need to condition a group on a varied live and frozen diet, provide an appropriate temperature drop to simulate seasonal cues, and offer sheltered, dimly lit spawning sites such as caves or dense leaf litter. Outcome would be uncertain, and the trade currently relies on wild-caught individuals. Given the data-sparse status of this species in the hobby literature, any successful captive-breeding attempt would be of significant interest.
In the aquarium
Acanthodoras spinosissimus is manageable in a suitably sized aquarium provided its core needs are met. Based on the genus size range of around 4.5–7 in standard length, a tank of at least 25–30 US gal is a reasonable minimum, but the fish should be sized up if it proves to reach the upper end of the genus range — the size trap is real with catfishes, and this species should not be purchased on the assumption it will stay very small. Soft, warm water (around 75–82 °F, pH 6.0–7.5) suits its Amazon origins.
Daytime shelter is essential: this is a nocturnal fish that spends the daylight hours hidden in caves, dense wood tangles, or under flat stones. Without adequate cover it will remain stressed and invisible. After dark it becomes active and will explore the full tank footprint. The skin is scaleless beneath the bony scutes — the armour protects against abrasion but the fish should still be treated as med-sensitive (use conservative doses of copper and other treatments). The locking, serrated pectoral and dorsal spines tangle firmly in a net; always move this fish in a container or bag, never with a net, to avoid injury to the fish and to the keeper. It is generally peaceful toward tankmates too large to swallow and can be kept in a community of similarly sized South American species.
Conservation
Acanthodoras spinosissimus has not been formally assessed by the IUCN Red List and carries a status of Not Evaluated (NE). No targeted conservation data are available for this species in the literature reviewed.
As an Amazonian doradid, its fortunes are broadly linked to the health of the Amazon and Orinoco river systems — the world's most biodiverse freshwater networks, but also subject to growing pressures from deforestation, river channelisation, gold-mining contamination, and dam development. Wild collection for the aquarium trade continues for most traded doradids, as captive breeding has not been established. Whether A. spinosissimus faces specific pressures beyond the general pressures on Amazonian fish communities is not documented in the available literature.