Cytogenetic Analysis of Two Species of Brachyhypopomus (Hypopomidae): New Inferences about Karyotypic Diversification of Grass Knifefish

Among the bluntnose knifefish of the Hypopomidae family, Brachyhypopomus is the most specious genus, with 28 species widespread in hydrographic watersheds of South America. It is considered a monophyletic clade; however, some groups remain species complex and require taxonomic revision. In this stud...

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Bibliographic Details
Published inJournal of ichthyology Vol. 62; no. 5; pp. 828 - 839
Main Authors Takagui, F. H., Cardoso, A. L., Dionisio, J. F., Shibatta, O. A., Giuliano-Caetano, L.
Format Journal Article
LanguageEnglish
Published Moscow Pleiades Publishing 01.10.2022
Springer Nature B.V
Subjects
Biomedical and Life Sciences
Brachyhypopomus
Chromosome translocations
Chromosomes
Cytogenetics
Diversification
Hypopomidae
Inversions
Karyotypes
Life Sciences
Nucleoli
Sex chromosomes
Species
Taxonomic revision
Watersheds
Zoology
Robertsonian translocations
Tramandaí River
18S rDNA
Paranapanema River
diploid number
sex chromosome
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Summary:Among the bluntnose knifefish of the Hypopomidae family, Brachyhypopomus is the most specious genus, with 28 species widespread in hydrographic watersheds of South America. It is considered a monophyletic clade; however, some groups remain species complex and require taxonomic revision. In this study, Brachyhypopomus cf. draco and Brachyhypopomus gauderio were analyzed through cytogenetics to identify species-specific markers and propose evolutionary trends of the genus. Brachyhypopomus cf. draco had 2 n  = 26 (2m + 24 a ) and 18S terminal rDNA sites on pair 23. Brachyhypopomus gauderio exhibited a multiple sex chromosomes system, females had 2 n = 42 (X 1 X 1 X 2 X 2 ) and males had 2 n = 41 (X 1 X 2 Y), both revealing a multiple nucleolus organizer regions system. The two species presented a similar heterochromatic pattern: pericentromeric, interstitial, and terminal blocks coincident with the nucleolus organizer regions. ChromEvol software evidenced 2 n = 44 as a plesiomorphic characteristic of Brachyhypopomus . The karyotype evolution of this group is a dynamic process based on Robertsonian translocations, pericentric inversions, and intense reorganization of the heterochromatic elements.
ISSN:0032-9452
1555-6425
DOI:10.1134/S0032945222050198