Tetra (Hyphessobrycon Myrmex)

Hyphessobrycon myrmex sp. nov. is a newly described Brazilian tetra that captivates both researchers and aquarists with its precise pigment patterns and dramatic color dimorphism. Described from the Rio Formiga in the upper Rio Juruena, with connections to the upper Rio Tapajós basin in Mato Grosso, Brazil, this small characiform fish stands out for its distinctive markings and natural history.

Distinctive coloration and diagnostic features

• Lower-half pigmentation: the ventral portion of the body is deeply pigmented with dark chromatophores, creating a striking contrast along the midline.
• Midlateral stripe: chromatophores concentrated above the anal fin form a broad, diffuse dark midlateral stripe that runs along the body.
• Dorsal-fin patching: a dense concentration of dark chromatophores along the unbranched dorsal-fin rays and the distal portions of the two or three subsequent branched rays.

Life coloration and sexual dichromatism

In life, Hyphessobrycon myrmex exhibits conspicuous sexual dichromatism. Adult males display red to orange hues, while females and immatures are pale yellow. This clear color difference provides a dynamic viewing experience and a natural cue for behavior and social interactions within a display setting.

Geographic and taxonomic context

Originating from the upper tributaries of the Amazon basin in Mato Grosso, this species adds to our understanding of Characiformes diversity. Notably, a broader review discusses 108 sexually dichromatic taxa across six Characiform families, highlighting how dimorphism is distributed within this order. Hyphessobrycon myrmex serves as a concrete example of how pigment patterns and color expression relate to geography and lineage.

Ideal for collectors and educational displays

Hyphessobrycon myrmex is a compelling centerpiece for experienced hobbyists seeking to broaden a tropical freshwater collection with a regionally specific, scientifically described species. Its striking male coloration and the pronounced patterning provide ongoing interest for observers, while its Brazilian origin makes it a valuable addition to biotope-focused displays or classroom setups that illustrate taxonomy, coloration, and biodiversity within Characiformes.

Care considerations and sourcing notes

As a newly described species with a defined natural range, it’s important to source Hyphessobrycon myrmex from reputable suppliers who prioritize welfare and accurate species identification. When planning a display, consider how the fish’s distinctive coloration and dimorphism can be observed and appreciated, and follow the supplier’s care guidelines to support healthy development and natural behavior.

With its combination of deep pigment patterns, a broad midlateral dark stripe, dorsal-fin chromatophores, and dramatic sexually dimorphic coloration, Hyphessobrycon myrmex offers a rare, scientifically rich addition to any serious Characiformes collection.