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…

The two ponds where H. auca was collected were located on a sand bar deposited by the nearby Paraná river during the Pleistocene.

At time of collection the substrates were composed of sand with submerged vegetation dominated by Egeria najas plus floating Eichhornia in marginal areas.

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…

It differs from H. paucilepis by possessing 30-31 scales in the lateral row (vs. 28-29), 3 scales between the lateral line and anal-fin (vs. 4), 10 predorsal scales (vs. 9), ii, 9 dorsal-fin rays (vs. iii, 8), 4 maxillary teeth (vs. 1), and the distance between the dorsal-fi…

Known only from headwaters of the upper Paraná river basin in the Federal District plus the neighbouring state of Goiás, central Brazil.

Type locality is ‘Planaltina, Lagoa Fervedeira, Goiás, Brazil’ with additional records existing mostly from the rio São Bartolomeu including the Bananal, Santa Maria-Torto and Gama tributary systems.

Collected from small streams flowing through savanna grassland containing clear, light brown-coloured water with substrates of sand and gravel and little in the way of submerged or riparian vegetation.

At the type locality pH varied between 5.8 – 6.3, GH and KH were both <1°, conductivity was 9-13 μs and temperature 24.7 – 27.2°C/76.6 – 80.1°F.

The surrounding area is semi-arid and the Bolsón de Sandia was once a beautiful oasis with a number of springs, abundant vegetation and diverse wildlife but has dried up over the last twenty to thirty years due to indiscriminate water extraction for agriculture and other human uses.

Three endemic species of Cyprinodon, namely C. veronicae, C. longidorsalis and C. ceciliae, have been described from separate springs within the system…

Need not be too complicated so long as there are plenty of broken lines-of-sight.

Provide plenty of cover in the form of aquatic plants, wool mops, etc., and if using filtration air-powered, sponge-type units are best as these will not harm eggs or fry.

Lighting is unimportant but can be use…

El Pandeño de los Pando has a surface area of around 287 m² with depth ranging from 40-80 cm but there is an abandoned artificial channel which has an area of approximately 437 m².

Water temperature fluctuates between 38-48°C/100.4-118.4°F and the spring is considered one of the hottest environments inhabited by fish in the world.

The type locality originally consisted of a single spring-fed pond located in an endorheic basin known as ‘La Hediondilla’ at the foot of the ‘Cerro Potosí’ mountain and around 1880 m AMSL.

It had been modified to make it larger via an earth and rock dam, and below the pond were several distributaries running for a distance of 1-1.5 km.