Based on current knowledge, it thus remains impossible to deduce whether the group of putative species currently comprising S. jurupari, S. mapiritensis, and S. rhynchitis, plus populations from Amapá and the upper Negro/upper Orinoco region, represent distinct taxa or a single meta-population which can be referred to as S. jurupari sensu lato. Here on SF we include the named species separately, since they continue to be considered valid.

H. borealis is a member of the putative ‘H. heterorhabdus-group’ of closely-related species within the genus as proposed by Géry (1977).

There are around 15 members characterised by a ‘longitudinal pattern’ consisting of a thin, usu…

It’s known by various vernacular names including ‘Pirá-pacu’, ‘Pira-pucu’ or ‘Diente de cao’ (central Amazon), ‘Bicuda’ or ‘Uena’ (rio Tocantins), ‘Bicuda’ (rio Tapajós), ‘Aguejeta’ or ‘Picua’ (Venezuela), and ‘Moruwi’ or ‘Pirapoko’ (Guyana).

The entire dorsal-fin base is located anteriorly to a vertical through the anal-fin origin and this character distinguishes it from all other ctenolucids except B. lucius and B. xyrekes.

In a study conducted on the Arataye River, the main tributary of the Approuage, this species was mostly collected from stretches of rapids with rocky substrate which were reduced to a series of pools during the dry season. Other fishes observed at the same site were Auchenipterus nuchalis, Hypostomus gymnorhynchus and Moenkhausia cf. intermedia while at other localities in the river Bryconops affinis, Myleus ternetzi, M. rhomboidalis, Moenkhausia aff. barbouri, Curimata sp. and Serrasalmus sp. were collected.

This species occurs alongside the similar-looking congener C. oiapoquensis in nature, from which it can be told apart by the following combination of characters: larger adult size; narrower body (body breadth fits 4.0-4.4 times in standard length vs. 3.4-3.8 times in C. oiapoquensis); shorter pectoral spine (3.4-3.8 times in SL vs. 2.7-3.2 times); longer snout (1.7-1.9 times in SL vs. 2.0-2.2).

This is the type species of the genus, fairly ubiquitous in the aquarium trade, and represents an excellent choice for the newcomer to fishkeeping since it’s less demanding than most congeners. It’s sometimes referred to as ‘Beckford’s pencil fish’ or ‘brown pencilfish’.

Don’t worry if your fish look different when you switch on the aquarium lights after dark or in the morning as like most Nannostomus species it assumes a cryptic, vertically-barred colour pattern at ni…

This is the type species of the genus Aequidens and has the widest distribution of any member species. It exists in various colour forms depending on locality with variants from Ecuador and Peru being particularly sought after since they develop striking red (Ecuador) or orange (Peru) colouration on the lower part of the jaw, head and anterior portion of the belly whereas those from Brazil tend to have an overall grey/blue/green colouration, for example.

Despite its type status it's long…

Most Astyanax spp. are not popular in the aquarium hobby, though the genus is among the most speciose within the family Characidae. A. leopoldi is no exception in that you’ll rarely see it offered for sale but may find the occasional specimen mixed among other species in shipments of wild fishes from Peru.

This species is uncommon in the aquarium trade although its name is sometimes applied to other species.

It was originally described in the monotypic genus Pseudopristella, and can be distinguished from the vaguely similar Pristella maxillaris by possession of a relatively large (vs. relatively small) humeral spot and having black pigmentation in the anal-fin restricted to the first ray (vs. a prominent distal blotch).

This small species is a popular aquarium fish but there is some confusion surrounding its identity. Two colour forms have been traded, one of which also possesses tiny hooks on the fin rays.

It can be distinguished from congeners by colour pattern; the body is rose-coloured, fins red with no black markings, and the ovoid humeral spot is prominent, measuring around half of the body depth.