First Chromosome Analysis and Localization of the Nucleolar Organizer Region of Land Snail, Sarika resplendens (Stylommatophora, Ariophantidae) in Thailand

摘要

We report the first chromosome analysis and localization of the nucleolar organizer region of the land snail Sarika resplendens (Philippi 1846) in Thailand. The mitotic and meiotic chromosome preparations were carried out by directly taking samples from the ovotestis. Conventional and Ag-NOR staining techniques were applied to stain the chromosomes. The results showed that the diploid chromosome number of S. resplendens is 2n=66 and the fundamental number (NF) is 132. The karyotype has the presence of six large metacentric, two large submetacentric, 26 medium metacentric, and 32 small metacentric chromosomes. After using the Ag-NOR banding technique, one pair of nucleolar organizer regions (NORs) was observed on the long arm subtelomeric region of chromosome pair 11. We found that during metaphase I, the homologous chromosomes show synapsis, which can be defined as the formation of 33 ring bivalents, and 33 haploid chromosomes at metaphase II as diploid species. The karyotype formula of S. resplendens could be deduced as: (2n=66): L-6(m)+L-2(sm)+M-26(m)+S-32(m)