Amazon deforestation threatens newly discovered fish species in Brazil

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Murilo Pastana, a researcher at the Smithsonian’s National Museum of Natural History, and his colleagues have discovered and described two new species of Amazonian fish – one with striking red-orange fins and one so small it is technically considered as a species of miniature fish – in an article published today, May 16, in Linnean Society Zoological Journal.

Both species inhabit waters at the limit of human encroachment in the Amazon rainforest about 25 miles north of the Brazilian city of Apuí. Pastana and his co-authors, Willian Ohara of the Federal University of Rondônia and Priscila Camelier of the Federal University of Bahia, said ongoing deforestation in the region places these fish about an inch long, which are part of a group known colloquially as the South American fishes. darts, in imminent danger of extinction. In particular, the more colorful of the two species, Poecilocharax callipterusis at risk because its known range is restricted to a single stream comprising approximately 1.5 square miles of habitat.

“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 pasture for livestock. It made us feel that there was an urgent need to document these species and publish this item as soon as possible.”

As a Brazilian-born scientist, Pastana is passionate about preserving the country’s biological heritage, and he hopes that naming and describing these species will motivate the Brazilian government to protect and conserve these newly discovered endangered fish.

The small subfamily to which these previously unknown fish species belong is also highly sought after in the hobby aquarist market. Pastana, whose work is supported by the Sara E. and Bruce B. Collette Postdoctoral Fellowship in Systematic Ichthyology at the Smithsonian, said the trade in exotic aquarium fish could pose another threat to these two new species, even if the scientists begin by formally identifying them and learning of their existence.

Expeditions that discovered these new freshwater species took place between 2015 and 2016. Pastana said the overall goal of these forays into the Brazilian Amazon was to search for the still-undiscovered biological treasures of the basin’s many waterways. Madeira river basin, the richest river basin. in the world in terms of fish biodiversity according to a 2019 estimate.

“We went to sample places that have never been visited by scientists,” Pastana said. “This area is really important because it’s one of the borders where deforestation is moving north – the border between the new towns and the native forest.”

The Apuí region, where these scientific studies took place, ranks second on a recent list of Brazilian municipalities with the highest deforestation rates. Ironically, the same roads that facilitate accelerating habitat loss in the region have also facilitated access to streams, ponds and tributaries once inaccessible to Pastana and his colleagues.

So in 2015 and 2016 Pastana and others camped along a road called AM-174 and collected fish using nets, traps and other methods. All specimens were photographed, cataloged and preserved for further study at the Museum of Zoology of the University of São Paulo.

One of these specimens has bright red-orange fins and a distinctive dark spot just in front of its tail. This fish immediately established itself as a new species, Pastana said. The fish, which now bears the name P. callipterus, inhabits the margins of what scientists call a black water stream, so named because its waters are colored the color of coffee by the tannins leached from fallen leaves. The males of the species have even more intense coloration and sporty dorsal fins that can exceed half their body length, averaging just over an inch. Despite targeted efforts to search for this species in the vicinity during the 2016 return trip, Pastana and his colleagues were only able to find P. callipterus in the creek where it was first discovered.

The researchers encountered the second new species documented during these field expeditions among tangles of tree roots protruding from the banks of muddy streams – distinct from the relatively translucent blackwater streams, though stained black. Given the scientific name P.rhizophilus for his love (Phil) of roots (rhiz), this species is amber-yellow with males possessing dark streaks in their dorsal and anal fins. But perhaps the most distinctive quality of this new species is that it’s so small that scientists consider it miniature, a designation given to any fish that measures less than about an inch in length when fully grown, said pastana. He added that a lab study found that in these three-quarter-inch-long fish, parts of the skeleton that are usually bone are made up of cartilage instead.

Genetic research has confirmed the evolutionary relationship of these two new, closely related species and their relatives, bringing the total number of species in their small subfamily (Crenuchinae) to five. This is the first addition of a new species to the group in 57 years.

These fish, Pastana said, are like works of art and “losing any of these species would be like losing priceless masterpieces.” Like the masterpieces of Monet or Picasso, each species is full of irreplaceable details that might resemble other creatures on Earth, but together are utterly unique. Extinction would wipe out all those details, forged over millions of years of evolution. “You would lose everything on those species,” he said.

Funding and support for this research was provided by the Smithsonian and the São Paulo Research Foundation.

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