Comparative cytogenetic studies in tree shrews (Tupaia).

Area of Science:

• Comparative genomics
• Mammalian cytogenetics
• Evolutionary biology

Background:

• Tupaia species are valuable models for mammalian evolution.
• Previous karyological studies have shown variations within the Tupaia genus.
• Understanding chromosomal relationships aids in evolutionary insights.

Purpose of the Study:

• To determine the karyotypes of Tupaia belangeri, T. chinensis, and T. glis using RBA banding.
• To compare chromosomal banding patterns and nucleolus organizer regions (NORs) among these species.
• To investigate the chromosomal basis for evolutionary divergence within the Tupaia genus.

Main Methods:

• Bromodeoxyuridine (BrdU) replication was used to obtain RBA-banded karyotypes.
• Standard cytogenetic staining techniques, including RBA banding and silver staining for NORs, were applied.
• Karyotypes were analyzed and compared across the three Tupaia species.

Main Results:

• Tupaia belangeri has a chromosome number of 2n=62, confirmed for T. chinensis.
• Identical RBA banding patterns and NOR locations were observed between T. belangeri and T. chinensis.
• Tupaia glis has a reduced chromosome number (2n=60) attributed to a Robertsonian translocation involving specific acrocentric chromosome pairs.
• Non-homoeologous chromosome pairs were identified between T. glis and T. belangeri/T. chinensis based on RBA patterns.
• T. glis possesses eight NORs, while T. belangeri and T. chinensis have four NORs each.

Conclusions:

• T. belangeri and T. chinensis exhibit significant chromosomal conservation, indicating a recent divergence or lack of reproductive isolation.
• Robertsonian translocation is the likely mechanism driving karyotypic differentiation in T. glis.
• Differences in NORs suggest distinct regulatory mechanisms or evolutionary trajectories in these species.
• Geographical isolation may play a role in the observed chromosomal similarities between T. belangeri and T. chinensis.