Taxonomy & naming
Tatia dunni was described by the American ichthyologist Henry Weed Fowler in 1945. It belongs to the family Auchenipteridae, the driftwood catfishes, within the genus Tatia — a group of small, laterally compressed, mostly nocturnal South American catfishes. The Catalog of Fishes (Eschmeyer, California Academy of Sciences) recognises Tatia dunni as the valid combination; older literature on driftwood catfishes has at times placed species across a tangle of auchenipterid genera, but dunni has stood in Tatia since its description.
The genus name Tatia derives from a local South American name for these small catfishes. The species epithet dunni honours a collector or naturalist associated with the type material, a common convention in mid-20th-century American ichthyology; Fowler described numerous South American fishes during this period, many named for colleagues or expedition members.
Morphology
Tatia dunni is a small, slender, laterally compressed catfish reaching about 4.5 in standard length, with three pairs of barbels and the naked, scaleless skin typical of catfishes generally. Like other auchenipterids it carries a stiff spine at the leading edge of the dorsal fin and a single spine in each pectoral fin, formed of one hardened spine plus 4–5 soft rays in the dorsal — these can lock erect and are not smooth to net.
Sexual maturity is reached at roughly 3 in SL, at which point males undergo a striking anatomical change: the anal fin remodels into a copulatory organ used to transfer sperm internally to the female. This modified anal fin is the clearest external mark of a mature male and is the visible sign of the species' unusual breeding biology (see "Mating").
Habitat
The species is native to the Amazon basin of South America, recorded from the upper Amazon in Ecuador and Colombia, the central Amazon in Brazil, and the Caquetá River drainage in Colombia. Like most driftwood cats it lives closely associated with submerged wood — fallen branches, root tangles and driftwood piles — which provide both daytime cover and the surfaces on which eggs are later deposited.
Water in these drainages runs warm and is not especially demanding chemically; aquarium sources report the species tolerant of a fairly wide range provided extremes are avoided, with reported temperatures spanning roughly 72–86 °F and pH around 6.5–7.5. This places it in the broad, moderate soft-to-neutral tropical range typical of many Amazonian tributary fishes, without needing the very soft, acidic blackwater conditions some Amazon species require.
Feeding
Tatia dunni is a nocturnal, benthic micro-predator and omnivore, foraging over and around wood and substrate mostly after dark for small invertebrates. In the aquarium it takes bloodworm, prawns, catfish tablets, and white worm in moderation, along with other sinking prepared foods.
Because it is shy and largely inactive by day, it does best when fed after the lights go out, when it emerges from cover to forage; in a mixed community offered food only during the day it can easily be out-competed by more active daytime fish.
Mating
Tatia dunni breeds by internal fertilisation, a genuinely unusual strategy among catfishes and one of the defining features of the driftwood catfish family. From about 3 in SL the male's anal fin remodels into an intromittent organ, and mating takes place through direct contact between male and female rather than the broadcast release of eggs and milt seen in most catfishes.
Following mating, the female stores the sperm internally rather than laying immediately. Fertilised, adhesive eggs are deposited some 24–48 hours later, typically on the underside of submerged wood — the same driftwood the species shelters around by day. No parental care follows; once laid, the eggs and subsequent fry are on their own.
Breeding
Breeding in Tatia dunni follows straight from its mating biology: internal fertilisation via the modified male anal fin, with the female storing sperm and spawning adhesive eggs on the underside of wood a day or two after mating, and no parental care afterward. This mode is shared across driftwood catfishes (Auchenipteridae) and stands apart from the egg-scattering or nest-guarding strategies seen in most other catfish families.
Deliberate captive breeding of Tatia dunni is not well documented in the hobby literature; the species is more often maintained than intentionally spawned. Aquarium populations have nonetheless persisted since import, with breeding stock reportedly established from early importations, suggesting that incidental reproduction can occur in a well-furnished, wood-rich tank even without a targeted breeding effort.
In the aquarium
Tatia dunni stays modest in size — about 4.5 in — but should still be given a properly furnished tank rather than treated as a nano fish: a mature setup with soft sand substrate and abundant hiding places (driftwood, rocky caves, bamboo tubes) suits it best, since it is a genuinely wood-dependent, cryptic species that hides through the day and only becomes active after dark. Water values are not especially critical as long as extremes are avoided, with a workable range around 72–86 °F and pH 6.5–7.5.
As with other scaleless catfishes, Tatia dunni is more sensitive to copper and many medications than scaled fish, so any treatment should be dosed conservatively. It also carries locking dorsal and pectoral spines that can snag a net and jab the handler, so it is best moved in a container rather than netted; the spines are not known to be venomous. Because it is nocturnal and secretive, keepers should not mistake daytime inactivity for poor health — offer food after lights-out and expect to see the fish mainly at night.
Conservation
Tatia dunni has not been formally assessed by the IUCN Red List and is classified here as Not Evaluated. It is known from a reasonably broad swath of the upper and central Amazon basin across Ecuador, Colombia and Brazil, without documented major threats specific to the species.
As with many small, wide-ranging Amazonian tributary fishes, the main long-term pressures are generic ones affecting the basin as a whole — deforestation, water quality changes and habitat disturbance along the rivers it inhabits — rather than anything species-specific currently on record.