B chromosomes in the species Prochilodus argenteus (Characiformes, Prochilodontidae): morphologicalidentity and dispersion

Abstract

B chromosomes have attracted the attention of Neotropical fish cytogeneticists in recent years, both for their remarkable occurrence in this group and also because of the interest in studies of the genetic structure and role played in the genome of these organisms. The aim of this study was to report the first occurrence of supernumerary chromosomes in Prochilodus argenteus (Agassiz, 1829), this being the fifth carrier species among thirteen within the genus Prochilodus (Agassiz, 1829). The extra elements identified in this species are small sized heterochromatic chromosomes characterized by a low mitotic instability index, being very similar to other supernumerary chromosomes described in the species of the genus Prochilodus. Morphology, structure and dispersion of the supernumerary genomic elements which occur in species of this genus are discussed aiming to better understand aspects involved the origin of supernumerary chromosomes and the differentiation process and relationships among species of this family.

B chromosome dynamics in Prochilodus costatus (Teleostei, Characiformes) and comparisons with supernumerary chromosome system in other Prochilodus species

“…1), a conserved trait among Prochilodontidae, indicating that large chromosome rearrangements are apparently unusual in this fish group (Feldberg et al 1987, Pauls and Bertollo 1983, 1990, Venere et al 1999, Oliveira et al 2003, Voltolin et al 2013, Penitente et al 2015). …”

“…Although chromosome numbers and karyotype structure are highly stable in Prochilodus species, the frequency of different B chromosomes in distinct species/populations is remarkable (Cavallaro et al 2000, Artoni et al 2006, Penitente et al 2015). For instance, two populations of P. costatus were analyzed until now and none of them showed B chromosomes in their cells (Pauls and Bertollo 1990, Voltolin et al 2013a, 2013b).…”

“…However, prominent intra- and interspecific differences have been reported regarding the frequency and occurrence of B chromosomes. To date, supernumerary elements were reported in five species: Prochilodus lineatus (Valenciennes, 1836), Prochilodus brevis Steindachner, 1874, Prochilodus nigricans Agassiz, 1829, Prochilodus mariae Eigenmann, 1922, and Prochilodus argenteus Agassiz, 1829 (Pauls and Bertollo 1983, 1990, Venere et al 1999, Oliveira et al 2003, Penitente et al 2015); however, information regarding the origin, molecular content, and populational dynamics of these B chromosomes are restricted to P. lineatus (Maistro et al 2000, Jesus et al 2003, Artoni et al 2006, Voltolin et al 2010, 2013a, Penitente et al 2013). …”

First cytogenetic analysis of Ichthyoelephas humeralis (Günther, 1860) by conventional and molecular methods with comments on the karyotypic evolution in Prochilodontidae

“…Cytogenetic studies conducted with 12 representatives of the genera Prochilodus and Semaprochilodus show that they have an evolutionarily conserved karyotype with 2n=54 biarmed elements, composed of 40 metacentric and 14 submetacentric chromosomes with a fundamental number (FN)=108 (Arai 2011). The exception lies in a few Prochilodus species or populations showing intra and interpopulation karyotype variation related to supernumerary B chromosomes (Pauls and Bertollo 1983, 1990, Oliveira et al 2003, Gras et al 2007, Penitente et al 2015). The present data about Ichthyoelephas humeralis confirm the occurrence of a conservative chromosome diploid complement and fundamental number in Prochilodontidae.…”

“…Ribosomal sites in Prochilodontidae (5S and 18S ribosomal clusters) are syntenic, commonly located in the interstitial position on chromosome pair 2 in all species of Prochilodus and Semaprochilodus analyzed (Pauls and Bertollo 1990, Oliveira et al 1997, 2003; Venere et al 1999, Cavallaro et al 2000, Maistro et al 2000, Jesus and Moreira-Filho 2003, Hatanaka and Galetti Jr. 2004, Artoni et al 2006, Vicari et al 2006, Gras et al 2007, Voltolin et al 2009, 2013, Jorge et al 2011, Terencio et al 2012a, 2012b, Penitente et al 2015). …”