Evidence for the evolutionary origin of goldfish derived from the distant crossing of red crucian carp × common carp

BACKGROUND: Distant hybridization can generate transgressive hybrid phenotypes that lead to the formation of new populations or species with increased genetic variation. In this study, we produced an experimental hybrid goldfish (EG) by distant crossing of red crucian carp (Carassius auratus) × common carp (Cyprinus carpio) followed by gynogenesis. RESULTS: We evaluated the phenotype, ploidy level, gonadal structure, and 5S rDNA of the EG. Diploid EG possessed a high level of genetic variation, which was stably inherited. In particular, the EG combined transgressive phenotypes, including a forked tail and shortened caudal peduncle, traits that are present in common goldfish. The EG and common goldfish share a number of morphological and genetic similarities. CONCLUSIONS: Using the EG, we provide new evidence that goldfish originated from hybridization of red crucian carp × common carp.