A New Natural Autotetraploid and Chromosomal Characteristics of Dwarf Snakehead Fish, Channa gachua (Perciformes, Channidae) in Thailand

A new natural autotetraploid and the chromosomal characteristics of the dwarf snakehead fish (Channa gachua) from Kalasin, Nong Khai, Nong Bua Lam Phu and Udon Thani Provinces (four populations) in northeast Thailand were studied. Kidney cell samples were taken from 12 male and 12 female fish. Mitotic chromosome preparations were conducted using a blood cell culture technique as well as taken directly from kidney cells. Conventional and Ag-NOR staining techniques were applied to stain the chromosomes. The results showed that the autotetraploid chromosome number of C. gachua was 4n=104, and the fundamental number (NF) was 112 in both sexes. The types of chromosomes were 4 large submetacentric, 2 large acrocentric, 16 large telocentric, 2 medium submetacentric, 68 medium telocentric and 12 small telocentric chromosomes. No strange-sized chromosomes related to sex were observed. The region adjacent to the centromere of chromosome pair 3 showed clearly observable secondary constriction (NORs). The karyotype formula for C. gachua is as follows: 4n (autotetraploid) 104=L-4(sm)+L-2(a)+L-16(t)+M-2(sm)+M-68(t)+S-12(t)