Leptopanchax is a genus of small killifish in family Rivulidae, restricted in the atlas to Brazil. The 4 species are tiny, 1–2 in, and belong to the South American group of seasonal and semi-seasonal rivulids often sold as pearlfish - many of their relatives inhabit shallow, ephemeral pools of the Cerrado grasslands that dry up between wet seasons, with eggs able to survive a dormant period buried in damp substrate until the rains return, though the specific breeding mode of each Leptopanchax species is not detailed here.
The Opalescent Pearlfish (Leptopanchax opalescens) carries the most descriptive common name in the genus, a nod to the iridescent sheen typical of male rivulid killifish; L. aureoguttatus, L. citrinipinnis, and L. splendens are known mainly to killifish specialists rather than the general trade. All 4 species are Not Evaluated for conservation status, which for a small-range Cerrado genus like this usually reflects a lack of formal assessment rather than confirmed safety - 2 species already carry CARES status in the atlas, a sign that specialist keepers consider their populations vulnerable enough to warrant conservation breeding attention even ahead of a formal IUCN listing.