Induced gynogenesis in autotetraploids derived from Carassius auratus red var. (♀) × Megalobrama amblycephala (♂)

Autotetraploids fish (4nRR) (4n = 200, AAAA) were resulted from the whole-genome duplication of Carassius auratus red var. (RCC) (2n = 100, AA). Following activation by UV-irradiated Megalobrama amblycephala (BSB) sperm, the autodiploid eggs (2n = 100, AA) of 4nRR females developed into all-female autodiploid gynogenetic offspring (G1) (2n = 100, AA) without chromosome doubling treatment, indicating an XXXX genotype of the female autotetraploids. Compared with 4nRR and RCC, G1 individuals matured after 2 years, suggesting obviously delayed maturity. Tetraploid offspring (4nRG) (4n = 200) were also produced by crossing G1 females with male autotetraploids, suggesting that G1 individuals can produce unreduced eggs (2n = 100). After activation by UV-irradiated BSB sperm, the fertilized eggs of G1 females developed into a second generation of autodiploid gynogenetic offspring (G2) (2n = 100, AA) without chromosome doubling treatment. The diploid gametes are an important gamete source for the production of polyploid fish and the establishment of a diploid gynogenetic clone line, which will be useful for genetic analyses and breeding.