Yosida T H, Kato H, Tsuchiya K, Moriwaki K, Ochiai Y, Monty J
Chromosoma. 1979 Oct 2;75(1):51-62. doi: 10.1007/BF00330624.
All seventeen black rats collected from Mauritius Island were characterized by having many extra small acrocentric autosomes. Their basic karyotype was of Oceanian type, because of the presence of the large metacentric M1 and M2 pairs, but chromosome numbers in 13 specimens among them were 42, those of 3 specimens 43, and those of the remaining one specimen 44. Although the Oceanian type rat had 2 small acrocentric autosomes (pair no. 13), 16 Mauritius rats had 10 small acrocentrics, and the remaining one had 8 small acrocentrics. Comparative karyotype analysis between Oceanian and Mauritius type rats showed that the extra small acrocentrics found in Mauritius rats were due to Robertsonian fission of small metacentric pairs no. 14 and 18 of the original Oceanian type rat. Only one rat with 8 small acrocentrics showed the heteromorphic pair no. 18 consisting of one metacentric and two acrocentrics. The large metacentric M1 chromosome in 13 of 17 rats examined showed homologous pair, but two of them were heteromorphic by involving one metacentric M1 and two acrocentrics. In the remaining two rats M1 chromosome was not observed, but acrocentric pairs no. 4 and 7 were included. These acrocentrics were also suggested to be originated from Robertsonian fission of the large metacentric M1 chromosome. Robertsonian fission seemed to be one of the important mechanism found in karyotype evolution.
从毛里求斯岛收集的所有17只黑鼠的特征是具有许多额外的小近端着丝粒常染色体。它们的基本核型属于大洋洲类型，因为存在大型中着丝粒M1和M2对，但其中13个标本的染色体数为42条，3个标本为43条，其余1个标本为44条。尽管大洋洲类型的大鼠有2条小近端着丝粒常染色体（第13对），但16只毛里求斯大鼠有10条小近端着丝粒染色体，其余1只大鼠有8条小近端着丝粒染色体。大洋洲型和毛里求斯型大鼠的核型比较分析表明，毛里求斯大鼠中发现的额外小近端着丝粒染色体是由于原始大洋洲型大鼠第14和18对小中着丝粒染色体的罗伯逊裂变。只有一只具有8条小近端着丝粒染色体的大鼠显示出由一条中着丝粒染色体和两条近端着丝粒染色体组成的异型第18对。在检查的17只大鼠中的13只中，大型中着丝粒M1染色体显示为同源对，但其中两只因涉及一条中着丝粒M1和两条近端着丝粒染色体而异型。在其余两只大鼠中未观察到M1染色体，但包含近端着丝粒第4和第7对。这些近端着丝粒染色体也被认为起源于大型中着丝粒M1染色体的罗伯逊裂变。罗伯逊裂变似乎是核型进化中发现的重要机制之一。
