‘Sharp’-toothed predator pulled from a river in Bolivia. It’s a new species
In a river of northern Bolivia, a silvery predator with “sharp” teeth swam through the murky waters. Its white eyes scanned the aquatic landscape, but it wasn’t the only one looking around.
Nearby scientists caught the lurking animal — and discovered a new species.
A team of researchers visited several sites in the Madeira River drainage system, a large tributary of the Amazon River, between 2001 and 2012 to survey aquatic ecosystems, according to a study published June 10 in the peer-reviewed Journal of Ichthyology.
During their visits, researchers found several vaguely familiar-looking piranhas, the study said. At first, they identified the fish as a variant of a known species, but, when they looked closer, they noticed the fish were subtly but consistently different.
The team realized they’d discovered a new species: Serrasalmus castellonae, or Castellón’s piranha.
Castellón’s piranhas have flattened bodies reaching about 7 inches long, the study said. Their eyes are white, and their mouths are slightly upturned with “sharp” three-pointed teeth.
A photo shared June 11 on Facebook by Fish in the News shows the new species. Overall, the fish has a silvery body with a slight yellow tinge on its upper half and a scattering of small spots. Its tail and top fin have black edges.
In general, “piranhas play a crucial ecological role as predators, feeding on fishes, invertebrates, and even plant material such as fruits and seeds,” researchers said. These fish “also support commercial and subsistence fisheries across the Amazon basin, providing an important protein source for local communities.”
Castellón’s piranhas were found in “streams and lagoons” but seem “to be rare,” the study said. Much about their lifestyle remains unknown.
Researchers said they named the new species after the late Dylian Castellón “in recognition of her permanent support to the ichthyological studies in Bolivia.”
So far, Castellón’s piranhas have been found in the upper Madeira River in northern Bolivia, a landlocked country bordering Argentina, Brazil, Chile, Paraguay and Peru.
The new species was identified by its DNA, body proportions, head shape, scale pattern, coloring, teeth and other subtle physical features, the study said.
The research team included Flavio Gallo-Cardozo, Matías Careaga and Fernando Carvajal-Vallejos.
This story was originally published June 16, 2025 at 3:18 PM with the headline "‘Sharp’-toothed predator pulled from a river in Bolivia. It’s a new species."
