Production of androgenetic, triploid and tetraploid hybrids from the interspecific hybridization of female Japanese crucian carp and male blunt snout bream

Distant hybridization occurs widely in fishes and is a useful strategy to produce different ploidy offsprings. In this study, we obtained androgenetic blunt snout bream (2n = 48, ADBSB), triploid hybrids (3n = 124, 3nJB) and tetraploid hybrids (4n = 148, 4nJB) from the hybridization of two species from different subfamilies: Carassius cuvieri (♀, 2n = 100, JCC) and Megalobrama amblycephala (♂, 2n = 48, BSB). The ploidy levels of ADBSB, 3nJB and 4nJB hybrids were confirmed by counting chromosomal numbers, forming chromosomal karyotype, and measuring DNA content. In the phenotypes and reproductive traits, 3nJB and 4nJB exhibited significantly divergences from JCC and BSB, but ADBSB took after BSB. Fluorescence in situ hybridization (FISH) and 5S rDNA analyses revealed that the genetic traits of the offsprings compared with those of their parents. This is the first report on the coexistence in vertebrates of viable androgenetic, triploid and tetraploid hybrids being produced by crossing JCC and BSB. The formation of the different ploidy offspring is great significance in both evolution and fish genetic breeding and it also provides a good model for studying the genomic variation in the first generation of interspecific hybrids.