Piabucus

Piabucus contains the following valid species:^[12]

• Piabucus caudomaculatus Vari, 1977
• Piabucus dentatus (Kölreuter, 1763)
• Piabucus melanostoma Holmberg, 1891

When originally classified, Piabucus was considered a characin (member of Characidae). In 1929, ichthyologist Carl H. Eigenmann moved it to the subfamily Iguanodectinae alongside the genus Iguanodectes, still in Characidae.^[2] James Erwin Böhlke reconfirmed this move through use of morphology in 1954.^[3] In 2011, research by Oliviera et al. showed that Bryconops was closely related to Iguanodectinae, and posited that the two clades be moved to the new family Iguanodectidae.^[13]

Piabucus was first described in 1817 by German biologist Lorenz Oken when he named the species Piabucus dentatus.^[14] The true first member of the genus was not given a binomial name when described by Joseph Gottlieb Kölreuter in 1760, though he did introduce a genus Piabucu,^[15][16][17] and this was based on the work of Georg Marcgrave in his book Historia Naturalis Brasiliae from 1648.^[18][19]

Many sources mistakenly report the baisonym of Piabucus dentatus as being Trutta dentata,^[20][21] partially because James Erwin Böhlke reported it as such in a 1954 paper.^[3] Subsequently, French ichthyologist Jacques Géry followed Böhlke's lead in a paper from 1972.^[22] However, "trutta dentata" is simply Latin for "toothed trout", which is one of the most general labels that researchers give to fish. (The opposite is "trutta edentula", which means "toothless trout".)This is further evidenced in the fact that "trutta dentata" as a phrase appears as far back as 1740.^[23] Furthermore, the genus Trutta (now obsolete, synonymized with Salmo) was not available as a classification until 1764, upon proposition by French zoologist François Alexandre Pierre de Garsault.^[24]

Like all members of Iguanodectidae, members of Piabucus reside solely in South America.^[25][26] They are found in freshwater environments, though they are known to tolerate brackish water as well, venturing into estuaries.^[27] Piabucus is known from the Mamoré, Paraguay, and Madeira rivers, as well as the lower Amazon river basin.^[28] In the Paraguay river, it is only represented by P. melanostoma, which is also the only species from the subfamily Iguanodectinae to reside therein.^[29] P. dentatus is the only species to reside in Guyana.^[30] P. dentatus was also mistakenly listed as appearing in Peru by Eigenmann in 1910, but this is not the case.^[27]

Members of Piabucus, while all inhabiting freshwater, prefer varying environments. At least one species, P. caudomaculatus, is known to occur in blackwater habitats.^[31] P. dentatus is found in muddy, unclear waters.^[32] P. melanostoma lives in an area subject to regular flooding and takes advantage of bodies of still water left behind, feeding on plants, algae, and small invertebrates that are swept in.^[29] P. dentatus and P. caudomaculatus are more insectivorous than omnivorous.^[31][32]

Piabucus, while taken from the wild for the ornamental fish trade, is not being collected at a high enough rate to warrant concern for the genus. P. caudomaculatus and P. dentatus have both been assessed by the IUCN as species of least concern;^[31][32] reports from hobbyists show that collection of P. dentatus is ongoing.^[33] P. melanostoma, while not assessed, is assumed to have a stable population due to its wide range, despite dispersion abilities limited by a flood-cycle wetland habitat.^[29]