FISH was carried out according to Pinkel et al. (1986)
using 5S rDNA probes obtained by PCR from Prochilodus genomic DNA using the primers A (5_-TACGCCCGATCTCG TCCGATC-3_) and B (5_-CAGGCTGGTATGGCCGTAAGC-3_) (Pendás et al., 1994).