''Corydoras arcuatus'' is a species of freshwater fish in the armored catfish family Callichthyidae. It is restricted to the western

Amazon basin The Amazon basin is the part of South America drained by the Amazon River and its tributaries. The Amazon drainage basin covers an area of about , or about 35.5 percent of the South American continent. It is located in the countries of Bolivi ...

, where only known from small

blackwater Blackwater or Black Water may refer to: Health and ecology * Blackwater (coal), liquid waste from coal preparation * Blackwater (waste), wastewater containing feces, urine, and flushwater from flush toilets * Blackwater fever, an acute kidney disea ...

clearwater Clearwater or Clear Water may refer to: Places Canada * Clear Water Academy, a private Catholic school located in Calgary, Alberta * Clearwater (provincial electoral district), a former provincial electoral district in Alberta * Clearwater, Briti ...

streams in the middle Juruá River basin, the Javari River basin and streams near Leticia in western Brazil, far northeastern Peru and far southeastern

Colombia Colombia (, ; ), officially the Republic of Colombia, is a country in South America with insular regions in North America—near Nicaragua's Caribbean coast—as well as in the Pacific Ocean. The Colombian mainland is bordered by the Car ...

. The separation of ''C. arcuatus'' and '' C. granti'' was only fully clarified in 2019; information published for "''C. arcuatus''" before this was almost invariably for ''C. granti''. Similarly, the common name skunk corydoras has often been used for ''C. arcuatus'', but the vast majority of skunk corydoras in the aquarium trade are actually ''C. granti'' (leading several authorities to transfer the common name skunk corydoras to ''C. granti''). The two species are very similar and locally they occur together, with both being restricted to the western Amazon basin, but ''C. granti'' is more widespread. In addition to these two, a few other '' Corydoras'' species (for example, '' C. bethanae'', '' C. narcissus'' and '' C. urucu'') from the western Amazon basin have similar color patterns, as does ''

Brachyrhamdia ''Brachyrhamdia'' is a genus of three-barbeled catfishes native to South America. Species There are currently six recognized species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well ...

thayeria''; they all have spiny fins with a (to humans) painful but not dangerous venom and their similarity is an example of Müllerian mimicry.

References

{{Taxonbar, from1=Q672523 arcuatus Catfish of Brazil Freshwater fish of Colombia Freshwater fish of Peru Fish of the Amazon basin Fish described in 1938