A first chromosomal and nucleolar organizer regions (NORs) Analyses of Chevey's Sheetfish, Micronema cheveyi (Siluriformes, Siluridae)

Abstract

A first report on nucleolar organizer regions (NORs) and karyological analyses in the Chevey's sheetfish (Micronema cheveyi) from the Chao Phraya Basin, Thailand, was performed. The mitotic chromosome preparation was directly prepared from kidney cells of ten male and eight female specimens. Conventional staining and Ag-NOR banding techniques were applied to stain the chromosomes. The results shown that the diploid chromosome number of M. cheveyi was 2n=78 and the fundamental numbers (NF) were 96 in both sexes. The karyotype composed of 4 large metacentric, 6 large submetacentric, 10 large acrocentric, 32 medium telocentric, and 26 small telocentric chromosomes. No heteromorphic sex chromosomes were revealed. In addition, the telomeric NORs were clearly observed at the short arm adjacent to the telomere of the third chromosome pair (submetacentric chromosomes). The karyotype formula for M. cheveyi is as follows: 2n (diploid) 78=L4m+L6sm+L10a+M32t+S26t.