Yosida T H
Cytogenet Cell Genet. 1977;19(5):262-72. doi: 10.1159/000130819.
F1 hybrids between the Asian type (2n=42) and Ceylonese type black rats (2n=40) invariably showed 41 chromosomes, while those between the Oceanian type (2n=38) and the Ceylonese type usually showed 39 chromosomes. Twelve F2 hybrids (three litters) were obtained only from the latter combination. Among them, the karyotypes of nine rats were successfully analyzed. They were segregated into the Oceanian type (three rats) and the F1 type (six rats). No Ceylonese type was obtained. From the results of fertility testing in F1 hybrids between these three variants, the Oceanian type is assumed to be more closely related to the Ceylonese type than the Asian type. This coincided well with the results of karyotypic evolution of these geographic variants. Among the nine F2 hybrids examined, one female consistently showed 37 chromosomes with one X chromosome. This XO female appeared to be a normal female and to have been a sporadic natural occurrence.
亚洲型（2n = 42）与锡兰型黑鼠（2n = 40）之间的F1杂种总是显示41条染色体，而大洋洲型（2n = 38）与锡兰型之间的F1杂种通常显示39条染色体。仅从后一种组合中获得了12只F2杂种（三窝）。其中，成功分析了9只大鼠的核型。它们被分为大洋洲型（3只大鼠）和F1型（6只大鼠）。未获得锡兰型。根据这三个变种之间F1杂种的育性测试结果，推测大洋洲型与锡兰型的关系比与亚洲型的关系更密切。这与这些地理变种的核型进化结果非常吻合。在所检查的9只F2杂种中，有一只雌性始终显示37条染色体和一条X染色体。这只XO雌性似乎是正常雌性，是偶发的自然现象。
