Comparative Studies on Chromosoes of 3 Subspecies of Tupaia belangeri

This paper deals with the comparison of chromosomes of 3 subspecies of Tupaia belangeri chinensis,T.b.tonquinia and T.b.yaoshanensis.All of them are distributed in the southwestern China.Their chromosomes were studed by several banding techniques (G-,C- and Ag-staining),and a technique for simultaneous exhibiting chromosome replication patterns and late replicating Y chromosome. (1) The diploid number of 3 subspecies of tree shrews (T.belangeri) are 62.There are 3 pairs of metacentrics (Nos.1-3),two large and one small;three pairs of submetacentrics (Nos.4-6),one larger than the other two;one small pair of acrocentric with a distinct secondary constriction near the middle of the long arm (No.7).Among the remaining 23 acrocentric pairs,one is outstandingly large,some (e.g No.25 and 26) have a minute arm in all these 3 subspecies.But there appeared a minute arm on Nos.10,11,27 and 29 pairs of chromosome only in T.b.tonquinia and T.b.yaoshanensis.The X chromosome is a large submetacentric,and the Y,a small acrocentric,which is similar to Nos.22-25 acrocentrics acording to size and morphology. (2)The G-banding patterns of chromosomes are similar for 3 subspecies of tree shrews.The centromeric distribution of heterochromatin has been demonstrated in all chromosome of 3 subspecies.Interstitial distribution of heterochromatin has also been demonstrated on the long arm in a largest acrocentric in 3 subspecies.The minute arms of chromosome pair 25 and 26 are heterochromatic in T.b.chinenesis.The minute arms of chromosome pair 10,11.25,27 and 29 are also heterochromtic in T.b.tonquinia and T.b.yaoshanensis.Y chromosome is completely C-band positive.Replicating bands of T.b.chinensis chromosomes are revealed by the BrdU-Giemsa technique.Y chromosome is late replicating which appears pale compared with the rest complement in the favourable metaphase. (3)Ag-NORs have been observed at the secondary constriction and terminal of the chromosome pair 3,6 and 7 in all subspecies.