A new type of triploid fish derived from the diploid hybrid crucian carp (♀) × autotetraploid fish (♂)

Based on the allodiploid lineage (WR, 2n ​= ​100, F1–F5) of white crucian carp (Carassius cuvieri, WCC, 2n ​= ​100) (♀) ​× ​red crucian carp (Carassius auratus red var., RCC, 2n ​= ​100) (♂) and the diploid hybrid fish (WR-II, 2n ​= ​100) derived from WR-F1 (♀) ​× ​WCC (♂), in this research, we obtain a new type of triploid fish (WR-III) by the distant hybridization of WR-II (♀) and autotetraploid fish (4nAU, 4n ​= ​200) (♂). We investigate the morphological traits, chromosomal numbers, DNA content, growth rates and 5S rDNA in the WR-III. The results show that the WR-III is triploid fish with 150 chromosomes and they have no barbel and have a gray body color. All the measurable traits of WR-III show hybrid characteristics; and there is a significant difference in the body length/body height between WR-III and 4nAU, which indicating that WR-III has a smaller head and higher body compared with 4nAU; furthermore, the WR-III has a fast growth rate, the average body weights of eight months old WR-III is 487g. The 5s rDNA of the WR-III inherits the 5s rDNA of its parents and has some mutant bases or chimeric sequences, which revealed heredity, variability and heterozygosity in WR-III. The successful production of this triploid fish is of great significance in fish genetic breeding.