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

Abstract

Within the genus Prochilodus Agassiz, 1829, five species are known to carry B chromosomes, i.e. chromosomes beyond the usual diploid number that have been traditionally considered as accessory for the genome. Chromosome microdissection and mapping of repetitive DNA sequences are effective tools to assess the DNA content and allow a better understanding about the origin and composition of these elements in an array of species. In this study, a novel characterization of B chromosomes in Prochilodus costatus Valenciennes, 1850 (2n=54) was reported for the first time and their sequence complementarity with the supernumerary chromosomes observed in Prochilodus lineatus (Valenciennes, 1836) and Prochilodus argenteus Agassiz, 1829 was investigated. The hybridization patterns obtained with chromosome painting using the micro B probe of P. costatus and the satDNA SATH1 mapping made it possible to assume homology of sequences between the B chromosomes of these congeneric species. Our results suggest that the origin of B chromosomes in the genus Prochilodus is a phylogenetically old event.

The B Chromosomes of Prochilodus lineatus (Teleostei, Characiformes) Are Highly Enriched in Satellite DNAs

“…The chromosomes of the Prochilodus species have been extensively analyzed in the last 40 years and a conserved karyotype structure with 2 n = 54 chromosomes has been reported to date and is primarily composed of metacentric and submetacentric chromosomes [ 23 , 28 , 48 , 49 ]. Remarkably, several Prochilodus species exhibit a micro-B chromosome system, which is assumed to have emerged once in this group diverged into multiple B-variants in distinct lineages over time [ 21 , 22 , 23 , 28 , 50 ]. Our results corroborate the common origin of the three observed B-types in P. lineatus , despite it showing morphological differences, all carry the same satDNAs with similar hybridization patterns.…”

“…In addition, all populations of P. lineatus analyzed to date exhibit a B chromosome system composed of at least three micro-B variants [ 14 , 19 , 20 , 21 ]. Likewise, congeneric species also show similar micro-B chromosomes and it is hypothesized that these elements originated in the last common ancestor of several Prochilodus species [ 22 , 23 ]. In a pioneering study, Jesus et al [ 24 ] isolated two pericentromeric satDNAs from the genome of P. lineatus (SATH1 and SATH2) out of which one (SATH1) was also clustered on the B chromosomes, suggesting an intraspecific origin for these elements [ 14 , 24 ].…”