Number and location of rDNA clusters in the superfamilies Tenthredinoidea and Cynipoidea (Hymenoptera): an update

To identify nucleolus organizing regions (NORs), fluorescence in situ hybridization (FISH) with 18S rDNA probe was performed on chromosomes of Tenthredo campestris Linnaeus, 1758 (Tenthredinidae), Arge ciliaris (Linnaeus, 1767) (Argidae) (n = 10 in both) and Aulacidea hieracii (Bouché, 1834) (Cynipidae) (2n = 20). In all these species, a single pericentromeric rDNA cluster per haploid karyotype was detected. This number of NORs is confirmed as ancestral for the order Hymenoptera.