Taxonomy & naming
Potamotrygon tatianae was formally described by Silva and Carvalho in 2011 in Papéis Avulsos de Zoologia (São Paulo) 51(8):139–154, making it one of the more recently added members of a genus that continues to yield new species as sampling of remote Amazonian tributaries intensifies. The Catalog of Fishes (Eschmeyer, CAS) treats it as a valid species within the genus Potamotrygon, family Potamotrygonidae, order Myliobatiformes — the stingrays.
Potamotrygonidae are elasmobranchs, a class of cartilaginous fish (Chondrichthyes) whose skeleton is composed entirely of cartilage, not bone. They are far more closely related to the sharks and the marine eagle rays and torpedo rays than to any of the bony fishes that dominate freshwater systems worldwide. Electro-sensory ampullae of Lorenzini, tooth-like dermal denticles in place of scales, internal fertilisation via claspers, and a venomous tail spine are features shared across the group and trace to their marine ancestry.
The type locality is the Río Madre de Dios in Peru, approximately 12°S–13°S, 71°W–72°W. The Madre de Dios drains the eastern Andean flanks before joining the Beni River and ultimately entering the upper Madeira system, placing this species in one of the most species-rich and topographically dynamic corners of the Amazon watershed.
Morphology
Like all Potamotrygonidae, P. tatianae presents the characteristic flattened, roughly circular pectoral disc evolved for a benthic lifestyle. The disc is blackish-brown in ground colour with scattered beige or pale spots, a pattern that, combined with the dark background, inspired the trade names 'otorongo' (jaguar) and 'tigrillo' (little tiger). The maximum disc width reported by FishBase is 14.5 in, with total length (including the tail) reaching up to 29.5 in and disc length up to 18.5 in.
The eyes are positioned on the dorsal surface of the disc along with the paired spiracles — openings through which the ray draws water for respiration, allowing it to breathe while lying buried in sediment. The mouth, nostrils, and five pairs of gill slits are on the ventral surface. The skin is covered in tiny tooth-like denticles rather than scales. The tail bears one or more serrated venomous spines near the base, modified dermal denticles encased in venom-producing tissue, which are replaced periodically. Males possess paired claspers — rod-like copulatory organs formed from the modified inner edges of the pelvic fins — absent in females, who tend to grow larger.
Habitat
Potamotrygon tatianae is known from the Río Madre de Dios and the upper Madeira river system in Peru. The Madre de Dios is a large, turbid lowland river fed by Andean-slope streams and carries moderately mineralised white-water characteristic of its geology, in contrast to the clear or black-water shield rivers to the east. The ray inhabits the warm, shallow margins of the river — sandy beaches, slow-flowing back-channels and floodplain pools — lying partly buried in fine substrate with only its eyes and spiracles exposed.
Water temperatures across this basin are warm year-round, consistent with the humid tropical lowland climate of the Madre de Dios region. Like all Potamotrygonidae it is strictly freshwater with no tolerance of salt. It respires by pumping water in through the paired spiracles on the dorsal head surface rather than through the mouth, an adaptation that allows it to continue breathing while buried and while pressing prey against the substrate.
Feeding
Potamotrygon tatianae is a benthic carnivore, like all members of its family. It detects buried prey using the ampullae of Lorenzini — pores scattered across the ventral disc that sense the faint bioelectric fields generated by living organisms — supplementing vision and olfaction in turbid water where visibility is low. Prey items for Potamotrygon species in this feeding niche typically include aquatic insect larvae, crustaceans, small molluscs, worms, and occasional small fishes.
In captivity, P. tatianae is fed a diet of meaty whole foods: earthworms, prawns, mussels, and other invertebrate fare presented on or near the substrate. It is a heavy feeder that produces a correspondingly large biological load, creating tension between its appetite and its acute sensitivity to accumulated waste products — a dynamic that demands sustained attention to water quality from the keeper.
Mating
Potamotrygon tatianae reproduces through internal fertilisation, the universal mode of reproduction in elasmobranchs. During mating the male grips the margin of the female's disc with his teeth — biting marks on the disc edge are a recognisable sign of successful mating — and inserts one of his paired claspers into the female's cloaca to transfer sperm. The claspers are rigid, rod-like structures formed from the modified inner edges of the pelvic fins and are entirely absent in females; their presence is the primary external feature distinguishing the sexes.
Courtship and mating can be vigorous. There is no persistent pair bond, no territory associated with breeding, and the male takes no further role once mating is complete. The Potamotrygonidae share this pattern with other elasmobranchs: all reproductive investment after fertilisation falls to the female.
Breeding
All Potamotrygonidae, including P. tatianae, are viviparous and give birth to live young — there are no eggs laid externally, no spawning aggregation, and no nest. After the small yolk supply of the egg is exhausted, the developing embryos are sustained inside the uterus by histotroph, a protein- and fat-rich secretion commonly called 'uterine milk', produced by specialised extensions of the uterine wall and absorbed directly by the pups. This mode is termed matrotrophic histotrophy, and it allows the young to grow considerably larger before birth than the initial egg would permit.
Litter sizes across related Potamotrygon species range from one to around a dozen pups depending on the size of the mother, with gestation periods of several months; precise figures for P. tatianae are not yet documented in the literature, but its size is consistent with the lower-to-mid range typical of the genus. Pups are born as fully formed miniature rays, independent from the moment of birth and capable of hunting immediately. There is no parental care after birth. The combination of small litters, long gestation, and late sexual maturity means river stingrays are biologically slow to recover from population depletion — a fact central to their conservation status.
In the aquarium
Potamotrygon tatianae circulates in the specialist freshwater stingray trade under the names 'otorongo ray' and 'tigrillo ray', attractive pattern names that reflect the spotted disc colouration. Like all Potamotrygonidae it is an advanced species suited only to highly experienced fishkeepers with purpose-built facilities. An adult specimen with a disc width approaching 14 in needs an aquarium with a floor area measured in square metres — width and length matter far more than depth. A deep bed of fine, soft sand is non-negotiable: the ray buries by day and abrasive substrate damages the unscaled disc.
Water quality requirements are stringent. River stingrays carry no scales and have thin, permeable skin that makes them exceptionally vulnerable to ammonia and accumulated nitrate; even brief exposure to substandard water can cause rapid decline. Heavy filtration and large, frequent water changes are essential. No salt should ever be added. Many common fish medications, particularly copper-based treatments, are acutely toxic to elasmobranchs and must not be used. Tankmates must be carefully chosen — no aggressive or fin-nipping species, and no large bottom-dwellers that will compete for resting space or stress the ray.
The venomous tail spine is a serious consideration. A wound inflicted by the serrated spine causes intense pain and can require medical attention; freshwater stingray ownership is unsuitable in households with young children and is regulated or prohibited in some jurisdictions. Captive-bred stock from reputable breeders is strongly preferred over wild-caught animals, both for the health of the individual fish and for the conservation of wild populations.
Conservation
Potamotrygon tatianae is assessed as Vulnerable (VU) on the IUCN Red List, with the assessment current as of December 2024. The species has a restricted distribution centred on the Río Madre de Dios and the upper Madeira basin in Peru, making it more exposed to localised pressures than the widespread P. motoro. The ornamental trade has been a primary driver of collection, and prior to the species' formal description in 2011 it was already being exported from Peru under the vernacular names 'otorongo' and 'tigrillo ray'.
All Potamotrygon species from Brazil and Colombia are listed on CITES Appendix III, with regulatory effect from 3 January 2017, requiring export documentation to confirm legal origin. Brazil at times imposed complete bans on wild-caught freshwater stingray exports before moving to quota systems; Peru regulates collection under national wildlife legislation. An estimated 4,600–5,700 individuals across six Potamotrygon species were exported annually from 2010–2015, illustrating the scale of commercial pressure on the group.
The slow reproductive biology of Potamotrygonidae — small litters, long gestation, late maturity — means populations recover slowly from over-harvest. Additional pressures on Madre de Dios basin rays include habitat alteration from deforestation and agricultural runoff on the Andean slopes feeding the system, and mercury contamination from artisanal gold mining, which is extensive across the Peruvian Amazon. Sustainable supply for the aquarium trade requires captive breeding, and the Vulnerable status of P. tatianae underscores that wild collection of this species cannot be treated as low-risk.