other, with very little way to come in contact. The two lineages have different rivers of origin; the first is from the Paraguay, Bento Gomes and Cuiabá Rivers, and the second is from the Bento Gomes and Cuiabá Rivers only. Genetic flow between populations is aided by wetland flood cycles, which offer temporary transportation for relevant species. Etymology The genus name "piabucus" is a Latinization of the Brazilian Portuguese word "piaba", which is and was used to refer to various small characiform fishes. "Melano-" means "black" (consider the word "melanin"), and "stoma" is a Greek word that means "mouth" or "opening", in reference to the black lower lip and chin that P. melanostoma sports. Modern scientists more often use melanostoma for the specific epithet, but the species is also easily found under the name melanostomus. This is because taxonomic convention dictates that the species name match the genus name in terms of linguistic gender, and "piabucus" is considered male, while "melanostoma" is considered female; "melanostomus" is considered male, and therefore matches the genus name. Locals around the Rio Manso Reservoir sometimes use the common name "sardinha-de-gato", which means "cat sardine", for P. melanostoma. Argentinians sometimes refer to it as "mojarra de boca negra", which means "blackmouth minnow". Distribution and habitat First described from Argentina, P. melanostoma is the only species from the family Iguanodectidae to be found in the Paraguay river basin. It is also found in the Maderia river basin, and is widespread across various floodplain areas in both regions. P. melanostoma is found especially easily in the Pantanal wetland region, which is largely within Mato Grosso, Brazil. Diet and ecology Piabucus melanostoma is an omnivore that eats leaf litter, algae, invertebrates, and detritus. While little is known of sympatry with other species, P. melanostoma is known to occur in schools, as is the case with all members of the genus. It tends to swim near the surface of the water. Behavioral study is lacking. Presence and behavior in aquaria Piabucus melanostoma is known in the aquarium industry, but is not incredibly popular. It has been exported from Paraguay to various locations, including Germany. It is apparently amongst the largest ornamental fishes, specifically in comparison to other fishes that are also considered tetras. Conservation status Piabucus melanostoma has not been evaluated by the IUCN. Some researchers consider it a rare species. One of its preferred habitats, the Pantanal wetlands,