Karyotypic diversity in a population of Bryconamericus aff. iheringii (Characidae)

Abstract

ABSTRACT. Bryconamericus comprises 56 species distributed into three groups, on the basis of the position and shape of the maxillary teeth: B. exodon, B. microcephalus and B. iheringii groups. Few cytogenetic data are available for this genus, but the diploid number of 52 chromosomes is quite common, although the karyotypic variability is extensive. This study aimed to characterize a population of B. aff. iheringii and thus contribute more cytogenetic information and better understanding of the structure and karyotypic evolution of this genus. We found 6 cytotypes with different NOR patterns: cytotype I showed a karyotype formula of 12m+10sm+16st+14a (FN = 90) and single NORs; cytotype II with 18m+14sm+10st+10a (FN = 94) and cytotype III with 20m+18sm+4st+10a (FN = 94), showing both single and multiple NORs; cytotype IV with 20m+14sm+12st+6a (NF = 98), cytotype V with 22m+18sm+8st+4a (FN = 100) and cytotype VI with 18m+24sm+6st+4a (FN = 100), all with multiple NORs. Cytotype I is the most different in relation to FN and NOR pattern, and can be regarded as belonging to another species of the genus Bryconamericus, living in sympatry in Três Bocas Stream. The remaining cytotypes may have been generated by crosses between them and by pericentric inversions. Meiotic cells were also analyzed and showed that despite the high karyotypic variability, chromosome pairing occurred normally. The great variability found in B. aff. iheringii may be related to a high degree of polymorphism; nevertheless, the possibility of occurrence of more than one species in this location is not ruled out, demonstrating the need for conservation of the Três Bocas Stream.

Cytogenetic markers as tools in delimiting species of the highly diverse Neotropical fish Bryconamericus (Characiformes: Characidae)

“…Cytogenetic studies in trans-Andean Bryconamericus species evidenced the maintenance of the diploid number of 52 chromosomes, with inter and intraspecific divergences regarding the karyotype formula and the fundamental number (FN) (Paintner-Marques et al, 2002a, 2002bCapistano et al, 2008;Portela-Castro et al, 2008;among others). Likewise, other cytogenetic characters were shown to be variable, such as the distribution of heterochromatin and the number and location of the nucleolar organizer regions (NORs) (Eberhardt et al, 2012;Santos et al, 2012Santos et al, , 2017Silva et al, 2014), with variation even among individuals of the same population. In relation to 5S rDNA ribosomal genes, the data are restricted to only four species, revealing simple cistrons in B. cf.…”

Constitutive heterochromatin heteromorphism in the Neotropical armored catfish Hypostomus regani (Ihering, 1905) (Loricariidae, Hypostominae) from the Paraguay River basin (Mato Grosso do Sul, Brazil)

“…Regarding the molecular composition of heterochromatin in Hypostomus species, analysis has demonstrated CG- or AT-rich content (Chromomycin A 3 or Mithramycin A and 4´-6-Diamin-2-Phenylindole–CMA 3 /DAPI) revealing heterogeneity in these regions, which suggests important implications for the karyotype evolution of this genus (see e.g. Artoni and Bertollo 2001, Kavalco et al 2004, Rubert et al 2008, 2011, Milhomem et al 2010, Maurutto et al 2013) and other groups of fishes, such as Gymnotus Linnaeus, 1758 (Scacchetti et al 2011), Bryconamericus Eigenmann, 1907 (da Silva et al 2014) and Ancistrus Kner, 1854 (Prizon et al 2016). In addition, analyses with restriction enzymes banding (as AluI, BamHI, HaeIII and DdeI), associated with C-banding technique, revealed heterogeneous heterochromatin patterns in four populations of Hypostomuspropeunae (Steindachner, 1878) (Bittencourt et al 2011a) and the existence of distinct evolutionary units in allopatric populations of Hypostomuspropewulchereri (Günther, 1864) (Bittencourt et al 2011b).…”