Apistogramma commbrae and other members of the commbrae complex can be distinguished from congeners by the conspicuous double caudal peduncle spot. This species may also be polymorphic, with some males exhibiting red and blue markings on the cheeks and a yellow gular region.

The smallest and most delicate of the nominal hatchetfishes. The rounded keel is shallower than related species, giving this fish a distinctive elongate profile.

The family Gasteropelecidae is separated from other Characiformes by the following combination of characters: front…

Despite its extensive natural distribution S. lilith is uncommon in the ornamental trade, where it is sometimes referred to as ‘one-spotted demon fish’ or ‘one spot eartheater’.

It can be distinguished from other members of the genus by possessing a single dark blotch on the flank and a prominent ocellus at the caudal-fin base. Among the named species it is most similar to S. daemon, but that species possesses two blotches on the flank.

It can be distinguished from the majority of other Corydoras species by its distinctive colour pattern, comprising a uniform, lightish base pigmentation with a dark arched stripe extending over the upper portion of each flank, from the tip of the snout to the caudal-fin base. This is shared with a few congeners, however, including C. arcuatus, C. narcissus, and C. urucu.

This species has been recorded from the Guaporé, Madeira, Branco, Trombetas, and Urubu river systems within the Amazon river basin, Brazil.

Type locality is ‘Igarapé Jatuarana, 5 kilometers above Samuel, Rio Guaporé, Rondonia, Brazil’.

I. geisleri is typically exported for the aquarium trade alongside the similar-looking congener I. adujai (Géry, 1970) but can be identified by presence (vs. absence in I. adujai) of a black lateral stripe on the body beneath the red stripe, and possession of 20-25 (vs. 28-34) anal-fin rays.

This species is relatively rare in the aquarium hobby but is occasionally traded as ‘red-tailed flag tetra’.

It lends its name to the H. aghula group of closely-related species within the genus as proposed by Géry (1977, see below) of which members share the following characters which set them apart from other characids: lower half of the body dark, especially above the anal-fin; usually possessing a laterally-elongate humeral spot, more-or-less united wit…

This unidentified species was originally traded under the C-numbers C115 and C116 but these two are now thought to represent the same species, while fish collected from Manú National Park and sold as C. sp. ‘Manu 1 long nose’, C. sp. ‘Manu 4’, C. sp. ‘Manu 7’, and C. sp. ‘Manu 8’ may represent this species as well.

It’s highly variable in terms of colour patter…

This species is relatively common in the aquarium hobby but is not easy to maintain and recommended only for experienced aquarists.

It can be told apart from all congeners by specimens larger than 60 mm SL possessing an extended pectoral-fin spine forming an extremely long filament that may be more than four times the length of the first branched pectoral-fin ray (vs. not possessing such a filament in other species of Lamontichthys).

Gasteropelecids are commonly-referred to as ‘freshwater hatchetfishes’ due to their heavily-keeled body shape which has evolved in such a way due to possessing an enlarged, heavily-muscled pectoral girdle, and which resembles the shape of a hatchet head.

They are sometimes said to be capable of propelled flight above the water surface by beating their pectoral fins but in fact this is not the case and was disproven by Wiest (1995) who used…