The evolution of a neo-XY1Y2 sex chromosome system by autosome-sex chromosome fusion in Dundocoris nodulicarinus Jacobs (Heteroptera: Aradidae: Carventinae)

Chromosome Res. 2004;12(2):175-91. doi: 10.1023/b:chro.0000013155.99614.57.


Sibling subspecies of Dundocoris nodulicarinus, inhabiting different isolated indigenous evergreen forests in South Africa, have chromosome numbers of 2n(male) = 14XY, 9XY1Y2 and 7XY1Y2. The ancestral chromosome number of Dundocoris is probably 2n(male) = 28XY and several chromosome fusions were involved in the karyotype evolution of these taxa. The XY1Y2 sex chromosome system of the 9XY1Y2 D. nodulicarinus novenus originated by the fusion of a large autosome with the X-chromosome, forming a neo-X with the homologue of the fused autosome forming the neo-Y (=Y1) and the original Y-chromosome, the Y2. While the original X- and Y-chromosomes are heterochromatic and heteropycnotic during prophase I, the autosomal part of the neo-X and the neo-Y stay euchromatic and behave like a normal autosomal pair, forming synapsis and chiasmata. The XY1Y2 sex chromosome system of the 7XY1Y2 D. nodulicarinus septeni probably originated from the 9XY1Y2 karyotype when the homologous chromosomes of a small autosomal pair fused with the original X- and Y-chromosomes, respectively. In both the subspecies with the neo-XY1Y2 systems, the original sex chromosomes still undergo chromatid segregation at anaphase I (= post-reductional). The evolution and behaviour of the karyotypes and sex chromosome systems during the course of meiosis in the subspecies of D. nodulicarinus are described, discussed and illustrated.

Publication types

  • Review

MeSH terms

  • Animals
  • Evolution, Molecular*
  • Female
  • Genetics, Population*
  • Heterochromatin
  • Heteroptera / genetics*
  • Karyotyping
  • Male
  • Meiosis
  • Sexual Behavior, Animal
  • X Chromosome / genetics*
  • Y Chromosome / genetics*


  • Heterochromatin