Abstract
Henochilus wheatlandii, the only species of this genus, is critically endangered and was considered extinct for over a century. The rediscovery of this fish in 1996 made it possible to study its phylogenetic relationships with other species in the subfamily Bryconinae. The aim of this study was to characterise the karyotype of H. wheatlandii. Standard staining, C-positive heterochromatin and nucleolar organiser region (NOR) banding, chromomycin A3 staining, and fluorescent in situ hybridisation (FISH) using 5S rDNA and 18S rDNA probes were conducted on nineteen specimens collected in the Santo Antonio River, a sub-basin of the Doce River in Ferros municipality, Minas Gerais State, Brazil. Henochilus wheatlandii shared the same diploid number and chromosome morphology as other species of Bryconinae. However, its heterochromatin distribution patterns, NOR localisation, and FISH patterns revealed a cytogenetic profile unique among Neotropical Bryconinae, emphasizing the evolutionary uniqueness of this threatened species.
Highlights
Henochilus wheatlandii is the only species of this genus
In 1996, H. wheatlandii was collected in Preto do Itambe River, a tributary of the Santo Antonio River of the Doce River Basin in Minas Gerais State, Brazil
This study reports the first cytogenetic data for H. wheatlandii and compares the results with other species of Bryconinae from a biogeographic and phylogenetic perspective
Summary
Henochilus wheatlandii is the only species of this genus. It was first collected by the Thayer expedition in 1865 and 1866. In 1996, H. wheatlandii was collected in Preto do Itambe River, a tributary of the Santo Antonio River of the Doce River Basin in Minas Gerais State, Brazil Based on this finding, the absence of new captures in the Mucuri River Basin was considered a record error of the type locality of the holotype [6], and the current distribution of H. wheatlandii includes the Santo Antonio River Basin. The absence of new captures in the Mucuri River Basin was considered a record error of the type locality of the holotype [6], and the current distribution of H. wheatlandii includes the Santo Antonio River Basin This species could have become extinct in the type locality [6]
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