Cytogenetic Characterization of Myers' silver rasbora (Rasbora myersi), in Mun River, Surin Province

Abstract

The karyotype and standardized idiogram of Myers' silver rasbora (Rasbora myersi), collected from the Mun River, Ta Tum District, Surin Province, were examined. The fish were sexed, and 10 males and 10 females were selected for the study. Chromosomes were prepared using the direct method, and chromosome staining was performed using the conventional staining technique and the Ag-NOR banding technique. The results showed that the diploid number of Myers' Silver Rasbora was 2n = 50 and the fundamental number (NF) was 90 in both males and females. The types of metaphase chromosomes were as follows: 4 large metacentric, 4 medium metacentric, 6 large submetacentric, 6 medium submetacentric, 8 large acrocentric, 10 medium acrocentric, 2 small acrocentric, 2 large telocentric, 4 medium telocentric and 4 small telocentric. However, no of strange sized chromosomes related to sex were observed. The region adjacent to the telomere of the short arm of chromosome pair 5 showed clearly observable nucleolar organizer regions (NORs). The karyotype formula of Myers' Silver Rasbora is as follows: 2n (50) = L^m₄+L^sm₆+L^a₈+L^t₂+M^m₄+M^sm₆+M^a₁₀+M^t₄+S^a₂+S^t₄