Summary Chromosomal characteristics of nucleolar organizer regions/NORs and karyological analysis of the Tokay gecko (Gekko gecko) from Khon Kaen Province, northeast Thailand was studied. Gecko chromosome preparations were conducted by squash technique from bone marrow and testis. Conventional staining and Ag-NOR banding techniques were applied to stain the chromosome with Giemsa s solution. The results showed that the number of diploid chromosomes is 2n=38, while the fundamental number (NF) is 50 in both males and females. The types of chromosomes were 2 large metacentric, 4 large submetacentric, 4 large telocentric, 6 medium telocentric, 4 small metacentric, 2 small acrocentric, and 16 small telocentric chromosomes. NORs are located at the secondary constriction to the telomere on long arm of the largest telocentric chromosome pair 4. There are no sex differences in karyotypes between males and females. We found that during metaphase I the homologous chromosomes showed synapsis, which can be defined as 19 ring bivalents and 19 haploid chromosomes (n=19) at metaphase II as a diploid species. The karyotype formula is as follows:2n (38)

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: m sm a t t 4 6 10 32 26

Chromosome and morphometric analyses of the croslet horseshoe bat (Rhinolophus coelophyllus) and least horseshoe bat (R. pusillus) from Northeast of Thailand were studied. Bat chromosome preparations were conducted by squash technique from bone marrow and testis. Conventional staining and Ag-NOR banding techniques were applied to stain the chromosomes. The results showed that the diploid chromosome number of R. coelophyllus and R. pusillus were 2n=62, and the fundamental number (NF) were 64 in both species. The types of autosomes observed were 26 large telocentric, 12 medium telocentric, and 22 small telocentric chromosomes in R. coelophyllus and R. pusillus. The X-chromosome was a largest acrocentric chromosome and the Y-chromosome was a small acrocentric chromosome in both species. NORs are located at the secondary constriction near the centromere on the long arm of the large acrocentric chromosome pair 13 in R. coelophyllus and R. pusillus. We found that during metaphase I the homologous chromosomes showed synapsis, which can be defined as 31 bivalents. Six external morphological characters were measured as well as 13 cranial and dental measurements. The karyotype formulae were as follows: t t t 26 12 22 t t t 26 12 22

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