The majority of records pertain to the rio Guaporé (Río Iténez in Bolivia), the main affluent of the rio Mamoré, which drains the vast tropical wetland known as the Pantanal, and the upper rio Paraguai, which also has its headwaters in the Pantanal but flows in the opposite direction. The Guaporé and Paraguai are connected due to rising water levels during the annual wet season.

Its name appears to have been misapplied to similar-looking fishes occurring throughout much of the middle and lower Amazon in Brazil and Colombia, plus the rio Orinoco drainage in Colombia and Venezuela, and coastal systems of the Guianas. Some of these have been described as distinct species (e.g. Hyphessobrycon amapaensis Zarske & Géry 1998; H. eschwartzae García-Alzate, Román-Valencia & Ortega 2013; H. montagi Lima, Couthino & Woziacki 2014), whereas the identity of others remains un…

In the igarapés Baré and Ubim, western Brazil H. erythrostigma was collected from stretches measuring 5-7 metres in width with thick riparian and overhanging vegetation.

The substrate was mostly composed of sand and the fish displayed a preference for boundary zones between shallow and deeper water. Conductivity was measured at 14.2-62.1 mS/cm³, dissolved oxy…

Metynnis lippincottianus is occasionally seen for sale, sometimes under the name of "Silver Dollar". It is easily distinguishable from m. argenteus and m. hypsauchen (which are more commonly sold as Silver Dollars) by its spotted pattern, hence the common name. M. lippincottianus shares a common name with m. maculatus but the two can be distinguished as the spots on m. maculatus are more pronounced.

Silver dollars are common and popular fish in the hobby. They are related to piranh…

The broad dark stripe in the dorsal portion of the body extends into the ventral portion on the caudal peduncle, and this character can be used to distinguish it from the very similar-looking C. zygatus, with which it is often confused. In C. zygatus the dark stripe does not extend ventrally on the caudal peduncle and is present only on the dorsal part.

In the aquarium hobby, the population from the rio Tiquié has been referred to as ‘C084’, while a similar, but larger, form from the Río Huallaga in Peru is known as ‘C085’. Both forms have been marketed as C. sp. ‘mega metae’.

The existence of multiple, similarly-coloured species which coexist and sometimes form mixed schools is relatively common in the genus.

There are currently over 180 described species of Corydoras (commonly shortened to "cory"), making it one of the most speciose of all South American fish genera. There are also loads of undescribed species, many of which have been assigned a "C number" for identification purposes. This is a very simple system of numbering and is similar to the L number scheme used to identify undescribed Loricariids. Both systems were implemented by the German aquarium magazine DATZ (Die Aqua…

Endemic to the upper rio Negro basin in Amazonas state, northern Brazil, and Amazonas state, southern Venezuela. One specific locality is Igarapé Muiá (00°09’03″N 66°48’10″W).

Type locality is ‘Upper Rio Negro, eastern Amazonas, Brazil’, which is thought to refer to forest brooks crossing the “new army road”, north of São Gabriel da Cachoeira municipality.

It exhibits slightly different behaviour to the majority of congeners in that it tends to swim in midwater and spends a large proportion of its time away from the substrate. Its morphology exhibits corresponding adaptations towards a pelagic existence with a relatively large eye, a more terminal mouth position, more strongly-forked caudal-fin, and more symmetrical body shape than most other Corydoras species.

The congener C. seussi, which is also native to the rio Mamoré, has a similar colour pattern but its snout is noticeably prolonged compared with that of C. gossei, plus there are some subtle differences in pigmentation. There is a third variant which has been referred to as ‘CW069’ in the aquarium hobby and appears to be somewhat intermediate, with a short, rounded snout as in C. gossei but a colour pattern more reminiscent of C. seussi.