Horizon 1 1 17 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES Cytogenetic and Genome Research 83-88 Ancestral karyotype Hapalomys delacouri Muridae Rattus norvegicus Zoo-FISH 2012 fdi:010086629 ENG Cytogenetic and Genome Research 1424-8581 ISI:000301173900001 2 10.1159/000335286 https://www.documentation.ird.fr/hor/fdi:010086629 https://www.documentation.ird.fr/intranet/publi/2022-12/010086629.pdf 136 Horizon (IRD) We report on the construction of a comparative chromosome map between the emblematic laboratory rat, Rattus norvegicus (RNO), and Delacour's Marmoset rat, Hapalomys delacouri (HDE), based on cross-species fluorescence in situ hybridization with R. norvegicus painting probes. Sixteen R. norvegicus chromosomes (RNO 3-6, 8, 10-15, 17-20, and X) were retained in their entirety (as a conserved block or as a single chromosome) in the H. delacouri genome. The remaining 5 R. norvegicus chromosomes (RNO 1, 2, 7, 9, and 16) produced 2 signals in the H. delacouri karyotype. Our analysis allowed the detection of an X-autosome translocation between RNO X and 11 that occurred convergently in an unrelated species, Bandicota savilei, and a single B chromosome that accounts for the 2n = 48 karyotype observed in this specimen. In total, the rat chromosome paints revealed 27 segments of conserved synteny in H. delacouri. The analysis showed 7 NOR bearing pairs in H. delacouri (HDE 1, 3, 6, 7, 8, 10, and 13) and the occurrence of an interstitial telomeric signal at the centromeric regions of 8 H. delacouri chromosomes (HDE 3, 10, 11, 12, 13, 16, 19, and 22). These data, together with published comparative maps, enabled a revision of the previously postulated murine ancestral condition suggesting that it probably comprised a wholly acrocentric karyotype with 2n = 46-50. 080 ; 020 UR022 Afrique du Sud