Karyotypic diversity in four species of the genus Gymnotus Linnaeus, 1758 (Teleostei, Gymnotiformes, Gymnotidae): physical mapping of ribosomal genes and telomeric sequences

Scacchetti, Priscilla C.; Pansonato-Alves, Jos&#233; Carlos; Utsunomia, Ricardo; Oliveira, Claudio de; Foresti, Fausto

doi:10.3897/compcytogen.v5i3.1375

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Article: Karyotypic diversity in four species of the genus Gymnotus Linnaeus, 1758 (Teleostei, Gymnotiformes, Gymnotidae): physical mapping of ribosomal genes and telomeric sequences

Title

Karyotypic diversity in four species of the genus Gymnotus Linnaeus, 1758 (Teleostei, Gymnotiformes, Gymnotidae): physical mapping of ribosomal genes and telomeric sequences

By

Scacchetti, Priscilla C.
Pansonato-Alves, José Carlos
Utsunomia, Ricardo
Oliveira, Claudio de
Foresti, Fausto

Type

Article

Date of Publication

2011

Original Publication

Comparative cytogenetics : international journal of plant & animal cytogenetics, karyosystematics and molecular systematics

Volume

Series / Issue

Issue: 3

Pages

223-235

Subjects

chromosomal rearrangements , cytogenetic , Fish , heterochromatin , rDNA

Contributed by

Pensoft Publishers

Language

English

Published by

St. Petersburg, Russia [Published] with technical support of Zoological Institute RAS [2007]-

Identifiers

DOI: https://doi.org/10.3897/compcytogen.v5i3.1375

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License Type URL: https://creativecommons.org/licenses/by/4.0/
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Copyright Status: In copyright. Digitized with the permission of the rights holder.
Rights Holder: Copyright held by individual article author(s).

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expand Abstract

Conventional (Giemsa, C-Banding, Ag-NORs, CMA3) and molecular (5S rDNA, 18S rDNA, telomeric sequences) cytogenetic studies were carried out in specimens of ten distinct fish populations of the genus Gymnotus (G. sylvius Albert and Fernandes-Matioli, 1999, G. inaequilabiatus Valenciennes, 1839, G. pantherinus Steindachner, 1908, and G. cf. carapo Linnaeus, 1758) from different Brazilian hydrographic basins. G. sylvius presented a diploid number of 40 chromosomes (22m+12sm+6st), G. pantherinus presented 52 chromosomes (32m+18sm+2st), while G. inaequilabiatus (42m+10sm+2a) and G. cf. carapo (38m+12sm+4st) presented 54 chromosomes. The C-banding technique revealed centromeric marks in all chromosomes of all species. Besides that, conspicuous blocks of heterochromatin were found interstitially on the chromosomes of G. inaequilabiatus, G. cf. carapo, and G. pantherinus. All four species showed single nucleolus organizing regions confirmed by results obtained through Ag-NORs and FISH experiments using 18S rDNA probes, which showed the NORs localized on the first chromosome pair in G. inaequilabiatus, G. cf. carapo, and G. pantherinus, and on pair 2 in G. sylvius. CMA3 staining revealed additional unrelated NORs marks in G. sylvius and G. pantherinus. The 5S rDNA probes revealed signals on one pair in G. sylvius and two pairs in G. pantherinus; G. inaequilabiatus had about seventeen pairs marked, and G. cf. carapo had about fifteen pairs marked. It is considered that the high amount of heterochromatin identified in the chromosomes of G. inaequilabiatus and G. cf. carapo could have facilitated the dispersion of 5S rDNA in these species. Interstitial signals were detected on the first metacentric pair of G. sylvius by telomeric probes (TTAGGG)n indicating the possible occurrence of chromosomal fusions in this species. The present study reveals valuable cytotaxonomic markers for this group and allows a more precise evaluation of the processes involved in the karyotype differentiation and the interrelationships among different species of the genus Gymnotus.