Aquarist Atlas
Aquarist Atlas · the river stingrays

Freshwater Stingrays

The freshwater stingrays of South America — the family Potamotrygonidae — are unlike anything else in the aquarium. They are cartilaginous fish, close relatives of the sharks rather than the bony fishes that fill the rest of this atlas; they are the only rays that spend their whole lives in fresh water; they give birth to live young rather than laying eggs; and they carry a venomous, serrated tail spine that makes them genuinely dangerous to handle. From the boldly-spotted motoro to the black-and-pearl Xingu ray, they are the prized, demanding apex of the hobby — flat, intelligent bottom-dwellers that need pond-sized tanks, deep fine sand and water cleaner than almost any other fish will tolerate. This section is built to the same standard as the cichlid, cory and pleco pages: researched, cited accounts with no Wikipedia and no invented facts.

© Adobe Stock

These are not bony fish. The Potamotrygonidae are elasmobranchs — cartilaginous fish of the order Myliobatiformes, sharing the sharks’ skeleton of cartilage, their electro-sensory ampullae of Lorenzini, and internal fertilisation by the males’ paired claspers. They are viviparous: a female carries a small litter of two to a dozen pups, nourished inside her by a uterine “milk,” and gives birth to fully-formed miniature rays — there are no eggs and no parental care. We cover only the true South American river stingrays here, and leave out the Old-World freshwater whiprays and the freshwater sawfish, which are different families. Three things define keeping them: a huge, wide-footprint tank (they grow large and live on the floor, not in the water column);pristine water (they are exquisitely sensitive to ammonia and nitrate, and take no salt); and respect for the venomous sting, which can deliver an agonising, medically-serious wound. Read each account before you buy — and check your local law, because several are protected and many jurisdictions restrict their keeping.

A motoro stingray on a gravel bed, its brown disc patterned with bright orange-ringed eyespots
The ocellate river stingray, or motoro (Potamotrygon motoro), is the ray most people start with — boldly spotted, wide-ranging across the Amazon and Paraná, and still a metre-class animal that needs a pond-sized tank and water cleaner than most aquarists keep.
A black-diamond stingray, jet-black with rounded white pearl spots across the disc
The black-diamond or Xingu ray (Potamotrygon leopoldi) — black with white pearl spots, from the clear blackwater of the Rio Xingu — is the prize of the hobby and the reason Brazil restricts the export of its wild rays.
A pale, orange-ringed river stingray resting on dark sand, its eyes and breathing spiracles set on top of the flat disc
Eyes and paired spiracles sit on top of the flat disc, so a ray can see and breathe while it lies on the bottom — drawing water in through the spiracles rather than the mouth. These are cartilaginous fish, kin to sharks, not bony fish — and they carry a venomous tail sting.

Photos © Adobe Stock

43 species in the atlas

We cover the family Potamotrygonidae — the South American river stingrays — grouped by genus: the large, familiar Potamotrygon, the giant Paratrygon ceja rays, the long-tailed Plesiotrygon, and the round Heliotrygon. Sizes are given as disc width, the standard measure for a ray. Following the Catalog of Fishes and FishBase, the valid set is being written up as each species is researched; the Old-World freshwater whiprays and the sawfish are deliberately left out.

Species

43 of 43 species

Potamotrygon · 32

The large core genus — the river stingrays of the whole of tropical South America, and almost everything the hobby keeps: the ocellate motoro (P. motoro), the black-diamond Xingu ray (P. leopoldi) and its relative P. henlei, the porcupine, reticulated and china rays. Round-disced, boldly patterned bottom-dwellers of sand and silt, ranging from teacup-sized to nearly a metre across.

Paratrygon · 7

The ceja or discus rays — very large, near-circular rays with a long, fragile, whip-thin tail and a translucent disc margin, of the deeper channels and lakes of the Amazon and Orinoco. Demanding and rarely kept; among the largest of the freshwater rays.

Plesiotrygon · 2

The long-tailed river rays (antenna or 'scubadiver' rays) — slender-disced Amazonian rays with an extraordinarily long, thread-like tail far exceeding the body. Specialists of soft river-bed sediment in the western Amazon.

Heliotrygon · 2

The round rays — recently-described, almost perfectly circular, flattened rays of the western Amazon with a short tail and reduced sting. Cryptic, little-known and not in the trade.

What’s new

All updates →