Analysis of the banding patterns of Seriola aureovittata

Chromosome banding pattern study is a useful tool in exploring evolutionary mechanisms of fish because it provides basic information on the banding number, size and morphology of chromosomes. Up to now, there has been no report on chromosome banding patterns in fishes. In order to understand the morphological characteristics of chromosome banding pattern and germplasm resources of Seriola aureovittata, we injected phytohemagglutinin (PHA) and colchicine, collected all the head kidney cells of one-year-old fish artificially bred from wild broodstock along the Dalian coast of China. The chromosomal division phase was prepared by low osmotic treatment, Kano's liquid fixation, air drying and Giemsa staining. We used different methods to deal with these three patterns. We investigated the banding features and morphological characteristics of multiple chromosomes banding pattern (C-banding, G-banding and Ag-NORs). Results show that (1) All of the 48 chromosomes have C-banding. The C-banding of S. aureovittata were located mainly in the centromere regions of chromosomes. The 2nd, 4th, 5th, 16th, 18th and 19th pairs of chromosomes show positive C-banding in the terminal region. However, chromosomes do not show entire positive and middle C-banding. According to the length of the C- band, the amount of heterochromatin calculated is 31.53%. (2)The Ag-NORs polymorphisms were specific in this fish. The silver staining pots were 1-2 in interphase nucleus. The number of Ag-NORs was mostly 2. A pair of nucleolar organizer regions was found on the 5th pair of chromosomes in the terminal region. (3) The size and location of G-banding are same in homologous chromosomes, but they are not same in the non-homologous chromosomes. Every chromosome has different amounts of darkly stained and faintly stained bands. There is no entire chromosome showing darkly stained or faintly stained G-banding. The 24 pairs of chromosomes have different G-banding features in the quantity, size, location and depth of staining; Statistics showed that there were 118 G bands in the chromosome of S. aureovittata, including 70 positive bands and 48 negative bands. The study of banding pattern of chromosomes can be used to understand the law of genetic variation, genetic composition, development mechanism and genetic mechanism of sex. It also has important reference value for determining the number of the genome, the origin of the species, the relationship of each other, the status of evolution, and the classification of the organisms.