Comparative cytogenetics of Serrasalmidae (Teleostei: Characiformes): The relationship between chromosomal evolution and molecular phylogenies

Abstract

Serrasalmidae has high morphological and chromosomal diversity. Based on molecular hypotheses, the family is currently divided into two subfamilies, Colossomatinae and Serrasalminae, with Serrasalminae composed of two tribes: Myleini (comprising most of pacus species) and Serrasalmini (represented by Metynnis, Catoprion, and remaining piranha’s genera). This study aimed to analyze species of the tribes Myleini (Myloplus asterias, M. lobatus, M. rubripinnis, M. schomburgki, and Tometes camunani) and Serrasalmini (Metynnis cuiaba, M. hypsauchen, and M. longipinnis) using classical and molecular cytogenetic techniques in order to understand the chromosomal evolution of the family. The four species of the genus Myloplus and T. camunani presented 2n = 58 chromosomes, while the species of Metynnis presented 2n = 62 chromosomes. The distribution of heterochromatin occurred predominantly in pericentromeric regions in all species. Tometes camunani and Myloplus spp. presented only one site with 5S rDNA. Multiple markers of 18S rDNA were observed in T. camunani, M. asterias, M. lobatus, M. rubripinnis, and M. schomburgkii. For Metynnis, however, synteny of the 18S and 5S rDNA was observed in the three species, in addition to an additional 5S marker in M. longipinnis. These data, when superimposed on the phylogeny of the family, suggest a tendency to increase the diploid chromosome number from 54 to 62 chromosomes, which occurred in a nonlinear manner and is the result of several chromosomal rearrangements. In addition, the different karyotype formulas and locations of ribosomal sequences can be used as cytotaxonomic markers and assist in the identification of species.

Chromosomal characterization of three species of Serrasalmini (Serrasalmidae: Characiformes)

“…In the family Serrasalmidae, the diploid number varies from 54 to 64; however, within each clade, 2n seems to be conserved (Favarato et al, 2021), except in Serrasalmus (Muramoto et al, 1968;Nakayama et al, 2002). Our data showed 2n=62 chromosomes in the three analyzed, with 2n being shared with species of the genus Metynnis (Favarato et al, 2019(Favarato et al, , 2021.…”

“…Fully heterochromatic short arms, C + NORs, and 18S and 5S rDNA sites coincident with C + blocks are common among Serrasalmidae, though species-specific interstitial blocks are also present (Nakayama et al, 2008(Nakayama et al, , 2012Ribeiro et al, 2014;Favarato et al, 2021). Considering the Serrasalmidae family, an increase in the diploid number and different karyotypic formulas are observed, which we associate with the presence of Robertsonian and non-Robertsonian rearrangements, but with a large participation of heterochromatin and probable mobile elements.…”

“…In the family Serrasalmidae, the diploid number varies from 54 to 64; however, within each clade, 2n seems to be conserved (Favarato et al, 2021), except in Serrasalmus (Muramoto et al, 1968;Nakayama et al, 2002). Our data showed 2n=62 chromosomes in the three analyzed, with 2n being shared with species of the genus Metynnis (Favarato et al, 2019(Favarato et al, , 2021. Nonetheless, although 2n is conserved among these species, the karyotypic formulas (KF) differ from each other, mainly by the number of st-a chromosomes, thus evidencing the presence of non-Robertsonian rearrangements such as inversions, translocations, duplications and heterochromatinization, given the presence of chromosomes with totally heterochromatic short arms (Figure 5).…”

“…Cytogenetic data in the family Serrasalmidae demonstrate that the fish of this family have high karyotypic diversity (Favarato et al, 2021). However, the clade formed by Catoprion, "Pristobrycon" and Pygopristis still lacks cytogenetic analysis, because, although 2n=62 has already been suggested by Nakayama (personal communication), no chromosomal data on these species are found in the literature.…”

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

“…Neotropical freshwater fishes represent one of the most diversified animal groups on earth due to their remarkable morphological and chromosomal diversity, and they are considered an excellent model for evolutionary studies [Machado et al, 2018;de Moraes et al, 2021;Favarato et al, 2021;Sassi et al, 2021;Takagui et al, 2021]. Over the past years, comparative cytogenetic studies have generated relevant information that contributes to the understanding of phylogenetic relationships, taxonomy, and diversification of some Brazilian freshwater fish lineages [Ferreira et al, 2017[Ferreira et al, , 2020Prizon et al, 2017;Usso et al, 2018].…”