Standardized Karyotype and Idiogram of Titan Triggerfish, Balistoides viridescens (Tetraodontiformes, Balistidae) in Thailand

Abstract

The standardized karyotype and idiogram of the titan triggerfish, Balistoides viridescens (Bloch & Schneider 1801) from Phuket Province, Thailand, were obtained from the present study. Kidney cell samples were taken from five male and five female fish. The mitotic chromosome preparations were conducted directly from the kidney cells. Conventional staining and Ag-NOR banding techniques were applied to stain the chromosomes. The results indicated that the diploid chromosome number of B. viridescens was 2n=44, and the fundamental number (NF) was 60 in both sexes. The chromosome types consist of 2 large metacentric, 4 large acrocentric, 2 large telocentric, 8 medium acrocentric, 10 medium telocentric, 2 small acrocentric, and 16 small telocentric chromosomes. No strange-sized chromosomes related to sex was observed. The region adjacent to the subtelomeric of short arm of chromosome pair 3 showed clearly observable secondary constriction/NORs. The karyotype formula for B. viridescens is as follows:
2n (diploid) 44=L^m₂+L^a₄+L^t₂+M^a₈+M^t₁₀+S^a₂+S^t₁₆