Comparative studies on the DNA content from three strains of crucian carp (Carassius auratus)

In China, there are many strains of crucian carp in different area. According to genetic theory, the chromosomal numbers and DNA contents of different species can reflect the relationships among species because of invariableness of themselves. Generally, cellular DNA content was determined by Feulgen staining and micro-fluorescence dense miter. However, its manipulation is lasting and complicated by this method. In present paper, using flow cytometry ( FCM) the DNA contents of erythrocytes front red crucian carp ( Carassius auratus var. red), Pengze crucian carp ( Carassius auratus var. Pengze) and gibel carp ( Carassius auratus gibelio) were measured and comparisons between them were carried. Four live fishes from every strain were collected from Guanqiao experimental Station of Institute of Hydrobiology, the Chinese Academy of Sciences. From every experimental fish 0.5mL of blood were collected, and erythrocytes were isolated by means of precipitation. Cock red cell was served as control. After raising and PI staining, DNA contents of erythrocytes were measured by flow cytometry ( FCM, Beckman Coulter) Measuring dates were treated and assayed by microcomputer. The DNA contents of erythrocytes from red crucian carp ( Carassius auratus var. red) , pengze crucian carp ( C. auratus var pengze) and allogynogenetic crucian carp ( C. arasstus gibelio) were measured and comparisons between them were carried. Results indicated that DNA content of erythrocyte was 3.0 picograms(pg) in red crucian carp, 4.7 picograms(pg) in pengze crucian carp, and 4.8 picograms ( pg) in allogynogenetic crucian carp. Obviously, DNA content of triploid pengze crucian carp was 1.57 times of diploid red crucian carp, and content of allogynogenetic crucian carp was 1.6 times of diploid red crucian carp. Ploidy investigation of red crucian carp, pengze crucian carp and allogynogenetic crucian carp was undertaken by chromosomal number counts of mitosis metaphase of kidney cell. The result showed that chromosomal number of red crucian carp was diploidy (2n = 100), chromosomal number of Pengze crucian carp was triploidy(3n = 162) and chromosomal number of allogynogenetic crucian carp was front 156 to 162(3n = 156-162). The research revealed that there was a significantly positive correlation between DNA content and ploidy. Use of flow cytometry technique as ploidy discrimination of fish have some advantages ( convenience, rapidity, credibility) and made up some shortages of chromosomal analysis. It provided new methods and theoretical basis for checking up of quality of fish. At the same time, it can also be used as ploidy discrimination of rare freshwater and marine and introduced polyploidy fish