Natural Autotetraploid and Chromosomal Characteristics in the Subfamily Botiinae (Cypriniformes, Cobitinae) from Northeast Thailand

抄録

Here we report natural autotetraploid and chromosomal characteristics in the subfamily Botiinae from Northeast Thailand. Kidney cell samples were taken from tiger botia (Syncrossus helodes), red-finned loach (Yasuhikotakai modesta), silver botia (Y. lecontei) and skunk botia (Y. morleti). The mitotic chromosome preparation was prepared directly from kidney cells. Conventional staining and Ag-NOR banding techniques were applied to stain the chromosomes. The results showed that the tetraploid chromosome numbers of S. helodes, Y. modesta, Y. lecontei and Y. morleti were 4n (natural autotetraploid)=100 for all species, and the fundamental numbers (NF) were 122 for all species. The presences of metacentric, submetacentric, and telocentric chromosomes were 12-10-78 for all species. No cytologically distinguishable sex chromosome was observed. The nucleolar organizer regions (NORs) were observed at the region adjacent to the short arms of a pair of submetacentric chromosome for all species. These results show the evolutionary relationship between species of loach fish from Thailand. The karyotype formula was deduced as:
S. helodes (4n=100): L₈^m+L₄^sm+M₄^m+M₄^sm+M₂₆^t+S₂^sm+S₅₂^t
Y. modesta (4n=100): L₁₀^m+L₈^sm+L₂₂^t+M₂^m+M₂^sm+M₅₀^t+S₆^t
Y. lecontei (4n=100): L₁₀^m+L₈^sm+L₂₂^t+M₂^m+M₂^sm+M₅₀^t+S₆^t
Y. morleti (4n=100): L₁₂^m+L₁₀^sm+L₆₆^t+M₁₂^t