Taxonomy & naming
Tatia caxiuanensis was described in 2008 by Sarmento-Soares and Martins-Pinheiro from the Curuá river, a lower Amazon tributary protected within the Floresta Nacional de Caxiuanã in Pará state, Brazil. It belongs to the family Auchenipteridae, the driftwood catfishes, within the genus Tatia — a group of small, laterally compressed South American catfishes distinct from the larger auchenipterids such as Trachelyopterus and Centromochlus. The Catalog of Fishes treats Tatia caxiuanensis as the valid name and genus placement; there is no history of it being shuffled through an older combination, as it was described directly into Tatia.
The genus name Tatia has no straightforward classical etymology and is generally treated as an arbitrary or regional name coined for the group. The species epithet caxiuanensis is a Latinised place name referring to the type locality, Caxiuanã (the national forest and bay region of the lower Amazon), following the common practice among South American catfish taxonomists of naming range-restricted species after their collection site.
Morphology
Tatia caxiuanensis is a small, slender, laterally compressed catfish reaching a maximum of only about 1.5 in standard length, with individuals maturing at roughly 1 in SL — it is one of the smallest catfish species covered in this atlas. Like other driftwood cats it has a scaleless, naked skin, three pairs of barbels, and the stiff, serrated, locking spines at the leading edge of the dorsal and pectoral fins typical of catfishes generally, though at this size the spines are correspondingly small.
The body shape follows the Tatia pattern: a somewhat flattened head tapering to a compressed, eel-like trunk suited to squeezing into crevices in sunken wood and leaf litter. Colouration in the genus is typically a mottled or barred brown-and-cream pattern that camouflages the fish against driftwood and detritus; this pattern, combined with the fish's minute size and nocturnal habits, makes it easy to overlook both in the wild and in an aquarium.
Habitat
The species is known from the Curuá river within the Floresta Nacional de Caxiuanã, part of the lower Amazon basin in Pará, Brazil — a blackwater-to-clearwater forest river system draining protected rainforest. As with other small Tatia, it is expected to shelter by day among submerged driftwood, root tangles and leaf litter along the margins of slow-flowing forest streams, emerging at night to forage.
Detailed water-chemistry data specific to this species has not been published; the genus as a whole is associated with soft-to-moderately mineralised, near-neutral tropical Amazonian river water rather than the extreme blackwater conditions of some Rio Negro tributaries. Given the single-river record, care is warranted before generalising — treat any specific pH or hardness figure for this species as data sparse.
Feeding
Tatia caxiuanensis is presumed, on the strength of genus-wide observation, to be a nocturnal benthic omnivore and micro-predator: it hides in driftwood and cover during the day and forages the bottom after dark for small invertebrates and detritus. Other Tatia species readily take dry, frozen and live meaty foods such as bloodworm, tubifex and chopped earthworm in the aquarium, and there is no reason to expect this species to differ.
Given its nocturnal habits, food is best offered after the lights go out, so this small, secretive catfish is not out-competed by more active, light-loving tankmates for its share.
Mating
As a member of Auchenipteridae, Tatia caxiuanensis almost certainly shares the family's defining and highly unusual reproductive trait: internal fertilisation, unique among catfishes. In driftwood cats the male's anal fin is modified into an intromittent organ that delivers sperm packets directly into the female during mating, rather than eggs and sperm being released together into open water. The female then stores the sperm internally, in a sac-like structure of the oviduct, and can carry both mature unfertilised eggs and stored sperm for a period before fertilisation and spawning actually occur.
No species-specific observations of mating behaviour in T. caxiuanensis have been published; this account follows the documented biology of the family and close relatives such as Trachelyopterus galeatus, for which artificial reproduction and internal insemination have been studied directly.
Breeding
Breeding biology has not been described for Tatia caxiuanensis specifically, and the species is not known to have been bred in captivity. Based on the family pattern, actual spawning likely follows internal fertilisation weeks after mating: the female releases roughly a hundred or so eggs into a cave or crevice, which she alone guards until hatching a few days later, with no parental role from the male after insemination.
This reproductive strategy — sperm storage plus delayed, female-guarded spawning in cover — makes deliberate captive breeding difficult to engineer and is a large part of why driftwood cats in general, and this micro-species in particular, are rarely if ever propagated by hobbyists. Anyone attempting it should expect data sparse conditions and be prepared to document genuinely new observations.
In the aquarium
Tatia caxiuanensis is one of the smallest catfish in this atlas at only about 1.5 in, so the size trap runs the other way here: this is a fish that will always stay tiny, and it is easy to lose in a busy tank or out-compete at feeding time rather than to outgrow its quarters. A modest, well-covered aquarium with plenty of driftwood, root tangles and leaf litter to mimic its forest-stream habitat suits it best, alongside other small, peaceful tankmates.
Like all catfish it is scaleless-skinned and therefore medication-sensitive — dose copper-based treatments and many standard medications conservatively, as with loaches, puffers and eels. It also carries the family's stiff, locking pectoral and dorsal spines, small as they are on a fish this size, so it is safer to coax it into a container than to net it. Being strictly nocturnal, it needs shaded refuges and is most active once the lights are off; specimens are scarce in the trade and largely a specialist catfish-keeper's fish rather than a mainstream community choice.
Conservation
The IUCN Red List assesses Tatia caxiuanensis as Least Concern, as reflected on FishBase (November 2018). The species is currently known only from the Curuá river within the Floresta Nacional de Caxiuanã, a protected area of the lower Amazon basin, which affords it some habitat security despite its narrow known range.
As a single-river endemic with a restricted known distribution, its long-term status would benefit from further survey work to confirm whether it occurs more broadly across the lower Amazon; for now, protection of the Caxiuanã forest reserve is the most relevant safeguard for the population.