title: Common descent of B chromosomes in two species of the fish genus Prochilodus (Characiformes, Prochilodontidae).
abstract: To ascertain the origin of B chromosomes in 2 fish species of the genus Prochilodus, i.e. P. lineatus and P. nigricans, we microdissected them and generated B-specific DNA probes. These probes were used to perform chromosome painting in both species and in 3 further ones belonging to the same genus (P. argenteus, P. brevis and P. costatus). Both probes hybridized with the B chromosomes in P. lineatus and P. nigricans, but with none of the chromosomes in the 5 species. This indicates that the B chromosomes have low similarity with DNAs located in the A chromosomes and suggests the possibility that the B chromosomes in the 2 species have a common origin. The most parsimonious explanation would imply intergeneric hybridization in an ancestor of P. lineatus and P. nigricans yielding the B chromosome as a byproduct, which remained in these 2 species after their phylogenetic origin, but was perhaps lost in other Prochilodus species. This hypothesis predicts that B chromosomes are old genomic elements in this genus, and this could be tested once a species from a relative genus would be found showing homology of its A chromosomes with the B-probes employed here, through a comparison of B chromosome DNA sequences with those in the A chromosomes of this other species.
authors.affiliation: Departamento Ciências Biológicas, Faculdade de Ciências, Universidade Estadual Paulista (UNESP), Campus de Bauru, Bauru, Brazil.
authors.forename: T A
authors.initials: TA
authors.lastname: Voltolin
authors.forename: J C
authors.initials: JC
authors.lastname: Pansonato Alves
authors.forename: J A
authors.initials: JA
authors.lastname: Senhorini
authors.forename: F
authors.initials: F
authors.lastname: Foresti
authors.forename: J P M
authors.initials: JP
authors.lastname: Camacho
authors.forename: F
authors.initials: F
authors.lastname: Porto-Foresti
mesh_terms: D000818:Animals; D060125:Characiformes / Q000235:genetics*; D020223:Chromosome Painting; D002875:Chromosomes / Q000235:genetics*