‘Armored' river creature — known to sting fishermen — discovered as new species
They didn't know it, but they'd just discovered a new species.
A team of scientists visited several rivers in the State of Pará in 2023 as part of a crowdfunded project to document the region's fish diversity. Some of these fish were known from the aquarium trade but had never been formally identified or studied in their natural habitats, according to a study published April 7 in the peer-reviewed journal Neotropical Ichthyology.
During the surveys, researchers went night fishing with local fishermen and noticed some wild catfish that looked similar to known aquarium pets, the study said. They took a closer look at the fish and realized they'd discovered a new species: Hoplisoma noxium, or the noxium armored catfish.
Noxium armored catfish can reach about 2.5 inches in length, the study said. They have plate-like scales forming a 'mosaic-like pattern.' Their heads are 'roughly triangular' with a 'small' mouth and bumpy lips.
Photos show the color variation of the new species. Wild-caught fish were usually 'light brownish orange,' while aquarium-bred fish were a paler 'greyish yellow.' Almost all of the fish had a 'dark mask-like blotch' across their eyes and more blotches down their sides.
Noxium armored catfish live in shallow rivers with 'relatively clear tea-colored water,' the study said. They were only seen at night 'in small numbers' sitting 'stationary along the banks.'
Fishermen told researchers that the new species 'must be separated from any other fish species just after capture, otherwise they can rapidly kill (the other fish), making the transport water milky and foamy on the surface.' Fishermen also reported 'getting 'stung'' by the new species, a 'painful' experience 'eventually causing minor allergic/inflammatory processes.'
Researchers said they named the new species after the Latin word for 'injury' or 'damage' because of its 'powerful toxin.' In the aquarium trade, the new species has been sold under a variety of names and labels.
So far, noxium armored catfish have only been found at three sites in the State of Pará, a region of northern Brazil, the study said.
The new species was identified by its body plates, color pattern, skeleton and other subtle physical features, the study said. Researchers did not provide a DNA analysis of the new species.
The research team included Luiz Fernando Caserta Tencatt, Willian Massaharu Ohara, Vandergleison de Carvalho, Steven Grant and Marcelo Britto. The team also discovered a second new species of armored catfish.
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