Molecular and cytogenetic data for Rhamphichthys Müller and Troschel, 1848 (Rhamphichthyidae - Gymnotiformes): Evidence of chromosomal differentiation in R. heleios, R. hahni, R. rostratus and R. pantherinus.

Authors

Marlyson Jeremias Rodrigues da Costa, Patricia Correa da Silva, Cleusa Yoshiko Nagamachi, Wilsea Maria B Figueiredo Ready, Jonathan Stuart Ready, Julio Cesar Pieczarka

Published in

Genetics and molecular biology. Volume 49Suppl 4. Issue Suppl 4. Pages e20250092. Epub Aug 03, 2026.

Abstract

Rhamphichthys (Gymnotiformes), a genus with uncertain taxonomy due to rarity and morphological similarity, exhibits greater diversity in the Amazon Basin. Phylogenetic analysis of COI data from specimens collected in the Amazon Basin, in Guamá River (Belém and Barcarena), Caripetuba River, and Anequara River (Abaetetuba) and deposited in the collection of the Museu Paraense Emílio Goeldi identified two major monophyletic clades within Rhamphichthys, encompassing R. pantherinus and R. rostratus. Cytogenetic analysis of 24 specimens, both with 2n=50 but differing fundamental number (FN) and karyotype formula (KF), enabled their differentiation. Although 2n=50 is likely ancestral, karyotype constitution varies among species. By combining cytogenetic and molecular data, we reclassified the previously described Rhamphichthys "marmoratus" (2n=50, FN=94, KF=44m/sm+6st/a) as R. heleios, and previous R. rostratus (2n=50, FN=92, KF=42m/sm+8st/a) as R. pantherinus. This study provides the first cytogenetic data for the real R. rostratus species and reports novel B chromosomes within the Rhamphichthyidae family.

PMID:
42566659
Bibliographic data and abstract were imported from PubMed on 08 Aug 2026.

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