R. vulpinus is the most widely-distributed member of the family Cynodontidae.

Type locality is given simply as ‘Brazilian rivers’, but this species is currently understood to be distributed in the Amazon basin from the Río Ucayali system in Peru, eastward as far as the rio Xingu in Brazil, plus the rio Tocantins and Rio Capim basins.

It’s also known from the Río Orinoco ba…

This species may be referred to using a variety of names including ‘scomb’, ‘sabre tooth tetra’, ‘sabre tusk barracuda’, ‘dog tooth characin, ‘vampire fish’, ‘Cachorra’ or Pirandirá (the latter two names being used in Brazil where they’re also applied to congeners).

It’s regularly confused with the payara, H. armatus, though that species grows considerably larger, is pop…

C. hujeta is traded under various names including 'slant-nosed gar', 'hujeta gar', 'rocket gar' and 'freshwater barracuda' but it and other members of the family Ctenoluciidae have traditionally been referred to as 'pike characids'. They're all predatory fishes native to South America, included in the order Characiformes and currently spread across two genera; Ctenolucius with two species and Boulengerella with five.

The two genera are …

This species is currently the only described member of its genus although colour pattern and morphology vary considerably across its range.

You may see reference to this species being the only fish species to possess infra-red vision, but other species also possess this ability and we suspect that infra-red plays an important role in the reproductive cycle of many fishes.

Quite widely distributed having been recorded from Brazil, Colombia, Peru and Venezuela. It’s been collected from the upper parts of several major river drainages including the Río Negro, Río Orinoco (including the Río Inírida and Casiquiare canal) and Río Solimões.

The type series was collected from ‘Igarapé Préto’, Brazil, said to be 60 kilometres to the south of the Colombian border city Leticia. Populations from Colombia and Brazil tend to be more intensely-coloured, and the Peruvian populations may apparently represent an undescribed species.

The precise extent of this species’ range is unclear. The majority of records pertain to the lower rio Xingu basin in the state of Pará, northern Brazil, including middle and lower reaches of its major tributary the rio Iriri, although the type locality is in Mato Grosso state several hundred kilometres upstream.

There also exist a handful of records from the rio Jamanxim (a major affluent of the rio Tapajós which drain…

This species is relatively rare in the aquarium trade.

It can be differentiated from all congeners by a combination of possessing ctenoid (vs. cycloid) scales on the sides of the head plus lacking a dark spot at the caudal-fin base.

Also known as the Spilotum or Moga, this is a popular and beautiful cichlid that exists in several different colour forms, depending on collection locality. It has also been hybridised with the convict cichlid (Archocentrus nigrofasciatus), although this is not to be encouraged. A study in 2004 found an apparent close genetic association between this species and Neetroplus nematopus, another cichlid found in the same area in nature. The 2 show remarkable similarities strategy, patterning and uni…

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