Chromosomal study on Zagros pupfish (Aphanius vladykovi)

BACKGROUND: Zagros Pupfish (Aphanius vladykovi) is a native fish of Iran which is found in basins of Chahar Mahal & Bakhtiari province. OBJECTIVES: In this study, the chromosome number and karyotype of Zagros Pupfish were investigated. METHODS: To obtain metaphase chromosome spreads in vivo, 1.2-5.4g fish were injected intraperitoneally by 0.1-0.15 mg/g of 1% colchicine and were humanely killed after being incubated in a well-aerated tank for 4-5 hours at 22-23oC. Hematopoietic, testis or ovary, gill, spleen and liver tissues were isolated from the fish and were fixed with cold Carnoy's solution after being hypotonized in 0.075M KCl. Chromosome spreads were prepared by either splashing of cell suspension or stamping of whole tissues onto slides. Slides were then stained by 10% Giemsa followed by microscopic observation. Suitable metaphase plates were digitally microphotographed and chromosomes were counted and karyotyped. RESULTS: Diploid chromosome number ranged from 42 to 49 with the modal number (2n) of 48. Based on the prepared karyotype, chromosome formula for this species was 12st+36a/t and the number of chromosome arms (FN) was calculated 60. No heteromorphic sex chromosomes could be recognized in this species. CONCLUSIONS: The diploid chromosome number of Zagros Pupfish is similar to other species of the same genus so far investigated.