Possible Common Origin of B Chromosomes in Neotropical Fish (Siluriformes, Auchenipteridae) Reinforced by Repetitive DNA Mapping

Abstract

The aim of this paper was to present the second case of B chromosomes in Auchenipteridae (Trachelyopterus sp.), and to test the hypothesis that the B chromosomes of this species and Parauchenipterus galeatus might have a common origin, since these two species have phylogenetic proximity. Both species have 58 chromosomes in the A complement, heterochromatin preferentially located at terminal region of the most of chromosomes, simple Ag-NORs located at the short arm of a subtelocentric pair, which was confirmed by hybridization with 18S rDNA, two submetacentric pairs carrying 5S rDNA sites, and presence of B chromosomes. The B chromosomes of the two species are small, metacentric, and almost totally heterochromatic, with variation of number intra and interindividual. In addition, for the first time in fish, the telomeric sequence [TTAGGG]n was dispersed along the B chromosomes (both species). The [GATA]n microsatellite were scattered in all chromosomes of the A complement and absent in the B chromosomes, in both species. These aspects confirm the phylogenetic proximity between the genus Parauchenipterus and Trachelyopterus, and they suggest the hypothesis that HIGHLIGHTS  B chromosomes of different species have a common origin.

Karyotype Evolution of Talking Thorny Catfishes Anadoras (Doradidae, Astrodoradinae): A Process Mediated by Structural Rearrangements and Intense Reorganization of Repetitive DNAs

“…According to Takagui et al [2021], the ancestral diploid number for the Doradidae family still remains as an open question, but several lines of evidence support the 2n = 58 chromosomes as a plesiomorphic feature in the family and as the likely ancestral karyotype configuration. Furthermore, this diploid number also occurs in most species of Auchenipteridae [Lui et al, 2009[Lui et al, , 2010[Lui et al, , 2013a[Lui et al, , 2013b[Lui et al, , 2015[Lui et al, , 2021Felicetti et al, 2021;Machado et al, 2021;Santos et al, 2021], the sister group to Doradidae family [Arce et al, 2013;Birindelli, 2014;Sabaj and Arce, 2021].…”

Are scattered microsatellites weak chromosomal markers? Guided mapping reveals new insights into Trachelyopterus (Siluriformes: Auchenipteridae) diversity

“…In chromosomal mapping, although studies are still scarce for most species, they have provided a useful tool for understand the genome and chromosomal evolution of many different taxa [ 18 – 20 ]. They can be cytogenetically identified in large accumulations on a few chromosomal pairs [ 20 , 21 ] or with scattered signals throughout the chromosomes [ 20 , 22 , 23 ]. Furthermore, SSRs are commonly described associated to heterochromatic regions (e.g., [ 24 , 25 ]), often participating in its origin and increase (cHC) (for reviews, see [ 26 – 28 ]), and with crucial roles in the origin and evolution of specific chromosomes, mainly B chromosomes [ 22 , 23 , 29 ] and sex chromosomes [ 21 , 30 , 31 ].…”

“…They can be cytogenetically identified in large accumulations on a few chromosomal pairs [ 20 , 21 ] or with scattered signals throughout the chromosomes [ 20 , 22 , 23 ]. Furthermore, SSRs are commonly described associated to heterochromatic regions (e.g., [ 24 , 25 ]), often participating in its origin and increase (cHC) (for reviews, see [ 26 – 28 ]), and with crucial roles in the origin and evolution of specific chromosomes, mainly B chromosomes [ 22 , 23 , 29 ] and sex chromosomes [ 21 , 30 , 31 ]. However, in complement A chromosomes and populations without sex or B chromosomes, the cytogenetic studies are still concentrated only in the type of array and presence or absence of the marker, considering the whole karyotype [ 32 , 33 ].…”

“…coriaceus (cited as Trachelyopterus sp.) [ 23 , 90 ]; whereas the SSR (GATA) n sites were described in only three species: T . galeatus [ 22 , 23 ], T .…”

B Chromosomes in Psalidodon scabripinnis (Characiformes, Characidae) Species Complex

“…In most cases, B chromosomes are a mixture of DNA sequences acquired from several chromosomes of the standard genome [ 12 , 13 , 14 ] and/or organelles [ 15 ]. Most B chromosomes have a large repetitive DNA content, such as ribosomal DNA, satellite DNAs, U snRNA genes, histone genes, amplified telomeric sequences and transposable elements [ 6 , 16 , 17 , 18 , 19 ]. Even though these elements are frequently heterochromatic, young B chromosomes may show few repetitive DNA sequences, since they are euchromatic [ 7 , 20 ].…”