The fish belong to a subfamily called South American darters. This discovery brings the known number of stinger species to five.
One species, Poecilocharax callipterus, is distinguished by its striking long red-orange fins and a dark patch at the base of its tail.
The other new species, Poecilocharax rhizophilus is the most miniature darter ever identified. This small fish is only about three-quarters of an inch (2 centimeters) in length when fully grown. It is bright yellow with a black stripe along its flanks and has a silver to white belly.
Deforestation and other human impacts are pushing the Amazon rainforest towards a tipping point that would transform the biologically rich and diverse ecosystem into a grassy savannah – and these stressors can be felt below the surface of the water as well as at the -above.
Study author Murilo Pastana, a postdoctoral researcher at the Smithsonian National Museum of Natural History in Washington, and his colleagues saw evidence of this during their expeditions between 2015 and 2016.
“It was exciting to find new species,” Pastana said. “But on the ground, we saw the forest on fire, logging trucks carrying huge trees and cleared plots turned into cattle pasture. It made us feel the urgency to document these species and publish this article on as soon as possible.”
An unexpected find
Pastana, who was born in Brazil, and his colleagues undertook the expeditions, funded by the São Paulo Research Foundation, to better understand the diversity and evolution of fish like tetras, piranhas and others in the backyards of water from the Madeira river basin, which is rich in fish biodiversity.
Researchers packed food, supplies, medicine and scientific instruments for several two-week trips, during which the team camped along rivers and streams, Pastana said.
“These expeditions are complicated to organize and follow. Most of the Amazon is still disconnected from the Brazilian roadmap, and access is only possible by rivers or dirt roads,” he said. -he declares. “We went to sample places that have never been visited by scientists.”
The area is like a border between new towns and native forest as deforestation pushes north, he said. The region lies about 25 miles (40 kilometers) north of the Brazilian city of Apuí and is home to one of the highest rates of deforestation – meaning the roads that helped Pastana and his colleagues reach the streams, tributaries and ponds are also part of the growing habitat loss.
When the researchers dunked their fishing nets and traps in the water, they were amazed to find fish they didn’t recognize.
“The last species of Poecilocharax was described in 1965, more than half a century ago,” Pastana said. “So seeing these fish in our net was a big ‘wow’ moment.”
Scientists photographed and preserved the fish for study at the Museum of Zoology at the University of São Paulo.
Poecilocharax callipterus was found in a black water stream, where the waters are stained with tannins leached from dead leaves which give it the color of coffee. Despite a follow-up trip to locate this fish in other waterways, it was only found in a single stream spanning approximately 1.5 square miles (4 square kilometers).
The second species, the tiny Poecilocharax rhizophilus, was spotted among tangled roots protruding from the banks of muddy streams.
“Miniaturization is rare in fish, and only about 100 of the 2,700 known for the Amazon are considered miniature,” Pastana said.
Already in danger
Pastana and his co-authors, including Willian Ohara of the Federal University of Rondônia and Priscila Camelier of the Federal University of Bahia, believe the fish may already be “threatened with extinction” and at risk of becoming endangered.
Given the small size and shrinking habitat where the fish are found and the fact that they may appeal to the hobbyist aquarist market, Pastana hopes that the discovery and naming of the species could prompt the Brazilian government to continue its conservation efforts.
“To lose either of these species would be to lose priceless masterpieces,” he said.
The data collected by Pastana and his colleagues “should be sufficient to classify both species as Near Threatened according to the International Union for Conservation of Nature – and Poecilocharax callipterus could even be classified as Critically Endangered”, a- he declared.
Meanwhile, the Amazon remains vulnerable as mining, logging and agricultural practices continue – and Pastana worries about the lack of action to curb these illegal activities.
Pastana may be involved in further research to better understand new fish species, but his primary focus “will be given to other species that still have no name.” Some of them come from similarly affected areas and hopefully they will get a name before their habitat. is destroyed,” he said.
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