Rio Negro ‘Hystrix’ Stingray Gets a Name: Potamotrygon wallacei

21 May, 2016

A juvenile Potamotrygon wallacei awaiting export at a facility outside Manaus

A juvenile Potamotrygon wallacei awaiting export at a facility outside Manaus

The ‘Cururu’ or ‘Rio Negro Hystrix’ Ray, which has been known in the trade and hobby for some time, was recently described scientifically in a paper published in the journal Zootaxa this past month. Endemic to Brazil’s Rio Negro, the freshwater ray, was named Potamotrygon wallacei in honor of Alfred Russel Wallace, the famed British naturalist.

Wallace led the first major scientific exploration of the Rio Negro in the late 19th century, and his published account of the journey, A Narrative of Travels on the Amazon and Rio Negro (available free on Google Books), contains some of the first descriptions of the unique fish fauna of this blackwater tributary.

The species is distinguished by its unique pattern of curved, dark brown markings on the disc, relatively “tall” body, and the presence of dermal denticles (rough, spiky “scales”) along the back of the disc and tail.

P. wallacei, the 'cururu' or Rio Negro hystrix, in its natural habitat

P. wallacei, the ‘cururu’ or Rio Negro hystrix, in its natural habitat

Although still uncommon in the hobby, this ray has been exported in moderate numbers in recent years by way of Manaus, Brazil. It has often been confused with another similar ray, P. hystrix (the ‘true’ hystrix), which is only found in southern Brazil, Argentina, and possibly Paraguay along the Paraná-Paraguay River basin (P. hystrix is rarely, if ever, exported for the aquarium trade).

Adding to the confusion surrounding the name, a third species, P. orbignyi, is often exported from Colombia as ‘hystrix’ or ‘yellow hystrix’. Another common name for P. wallacei—‘cururu’—is derived from the local name for the ray, arraia cururu. Regardless, this new species is found only in the middle Rio Negro with populations restricted to the blackwater creeks and igarapes around the municipality of Barcelos, where it is fairly abundant.

Freshly-collected rays: 2 adults and a newborn pup caught in a blackwater pool near Barcelos

Freshly-collected rays: 2 adults and a newborn pup caught in a blackwater pool near Barcelos

With a maximum size of about 12″ (31cm) in diameter, P. wallacei is the smallest known freshwater ray, making it a desirable species for aquaria. Collecting these rays has become a significant source of income for some small fishing communities in the middle Negro, and it is currently protected under a quota system which limits the number of specimens which can be collected and exported each year.

Fortunately, this species matures earlier and has a much shorter gestation period than many other freshwater ray species, making P. wallacei fairly resilient. They tend to inhabit shallow, clear water areas where they remain partially buried beneath the sand, emerging at dusk to forage for food along the edges of the river or creek. The species, along with the other Rio Negro native rays, were profiled in the March/April 2016 issue of AMAZONAS.

Original open access paper:
Carvalho, M.R., Rosa, R. S., Araujo, M. L. (2016). A new species of Neotropical freshwater stingray (Chondrichthyes: Potamotrygonidae) from the Rio Negro, Amazonas, Brazil: the smallest species of Potamotrygon. Zootaxa 4107 (4) 566-585

http://www.biotaxa.org/Zootaxa/article/view/zootaxa.4107.4.5

Collection locations and range of P. wallacei

Collection locations and range of P. wallacei along Brazil’s Rio Negro

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About the author

Mike Tuccinardi
Mike Tuccinardi

With a background spanning retail, wholesale, and aquarium fish import, Mike Tuccinardi began working at a local fish store in his early teens and has been following the fish ever since. After a stint in Florida working for a major importer and tropical fish farm, Mike has traveled through Asia and South America visiting aquarium fish exporters, collectors, and fishing communities. He currently serves on the advisory board of Project Piaba as well as the steering committee for the IUCN’s Home Aquarium Fish Sub-Group (HAFSG). When not traveling, Mike resides in Boulder, CO with his wife and is pursuing a Master’s degree in Fisheries and Aquatic Science. He is a Senior Editor of AMAZONAS and CORAL Magazines.

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