Abstract:Karyological study is a useful tool in exploring evolutionary mechanisms of fish because it provided basic information on the number, size and morphology of chromosomes. In this study we characterized the karyotype and chromosomal characteristics of the yellowtail kingfish Seriola aureovittata by examining metaphase spreads from head kidney cells of one-year-old fish artificially bred from wild broodstock in the Dalian coast of China. Chromosome samples were prepared through in vivo injection of phytohemagglutinin (PHA), olchicine-air drying technique, and Giemsa staining. A total of 80 mitotic metaphases from 21 individuals were analyzed, and 65 spreads showed 2n=48 chromosomes, which represented 81.25% of the observed metaphases. The relative size of the chromosomes in this subspecies varied from (2.50±0.23)% to (5.16±0.56)%. The long arm, short arm, and total length of the first submetacentric chromosomes were (1.81±0.09) μm, (0.87±0.03) μm, and (2.68±0.09) μm respectively. Two pairs of subtelocentric chromosomes were found in this subspecies. The length of their short arms was (0.55±0.04) μm and (0.39±0.06) μm, and that of the long arms was (2.10±0.06) μm and (1.87±0.07) μm. The diploid consisted of 4 submetacentric, 6 subtelocentric, and 38 telocentric chromosomes, and the fundamental number of chromosome arms was 54. The first pair of chromosomes had secondary constriction and satellite. The karyotype formula for this species was determined to be 2n=48 = 6sm + 4st + 38t. The total haploid chromosome length was approximately 51.97 μm. The fact that S. aureovittata has 3 pairs of submetacentric and 2 pairs of subtelocentric chromosomes distinguishes this species from other previously reported Seriola species. The comparison of karyotypes suggested that S. aureovittata might belong to an advanced and specific evolutionary group. Our study promoted the understanding of the specific karyotype evolution of the genus Seriola, and provided information on the polyploidy manipulation, hybridization, and sex control.
