EVOLUTION OF THE BLACK MUNTJAC (MUNTIACUS CRINIFRONS) KARYOTYPE REVEALED BY COMPARATIVE CHROMOSOME PAINTING

The black muntjac (Muntiacus crinifrons) has an unusual karyotype of 2 n = 8 in females and 2n = 9 in males. We have studied the evolution of this karyotype by hybridising chromosome-specific paints derived from flow-sorted chromosomes of the Chinese muntjac (M. reevesi, 2n = 46) to chromosomes of the black muntjac. The hybridisation pattern allowed us to infer chromosomal homologies between these two species. Tandem and centromeric fusions, reciprocal translocations, and insertions are involved in the reduction of the diploid number from 2n = 46 to 2n = 8, 9. The painting patterns further show complex chromosomal rearrange ments in the male black muntjac which involve more than half the karyo type, including both sex chromosomes. Since early meiosis is reported to be normal without any visible inversion loops of the synaptonemal c omplex, the observed chromosomal rearrangements would lead to heterosy napsis and, therefore, leave a large fraction of the male black muntja c karyotype balanced between the two sexes.