Koi ×Goldfish Hybrid Females Produce Triploid Progeny when Backcrossed to Koi Males

Abstract

Hybrids of koi (an ornamental variant of the common carp Cyprinus carpio) and goldfish Carassius auratus auratus were produced by artificial spawning. All 3‐year‐old F1 hybrid males examined were sterile, whereas some F1 hybrid females were fertile and produced eggs after hormonal injection. Backcross progeny were obtained by using intact koi sperm to inseminate eggs from F1 hybrid females; gynogenetic progeny were obtained by inseminating eggs from F1 hybrid females with koi sperm that was genetically inactivated by ultraviolet irradiation. Flow cytometric analysis of DNA content indicated that the backcross progeny were triploid, while the gynogenetic progeny, pure koi, pure goldfish, and F1 hybrids were all diploid. The triploidy of backcross progeny obtained without application of any treatment to the eggs demonstrates that the koi × goldfish hybrid females produce diploid eggs.

Reproductive ability of second generation ornamental (koi) carp ( Cyprinus carpio L.) × goldfish ( Carassius auratus L.) hybrids and characteristics of their offspring

“…This phenomenon was described in several interspecies F 1 fish hybrids belonging to different taxonomic groups, including Cyprinids (Cherfas, Gomelsky, Emelyanova, & Recoubratsky, 1994;Gomelsky, Schneider, & Plouffe, 2012), Salmonids (Galbreath, Adams, Wheeler, & Thorgaard, 1997;Johnson & Wright, 1986), Centrarchids (Dawley, 1987) and ricefishes (Adrianichthyidae; Shimizu, Shibata, Sakaizumi, & Yamashita, 2000). In addition, diploid gynogenetic progenies DOI: 10.1111 have been produced without any applied shocks by insemination of eggs produced by F 1 hybrid females with koi sperm genetically inactivated by UV-irradiation (Gomelsky et al, 2012). Gomelsky et al (2012) reported the production of diploid eggs by F 1 hybrid females obtained by crossing ornamental (koi) common carp (Cyprinus carpio L.) females with goldfish (Carassius auratus L.) males.…”

“…This phenomenon was described in several interspecies F 1 fish hybrids belonging to different taxonomic groups, including Cyprinids (Cherfas, Gomelsky, Emelyanova, & Recoubratsky, 1994;Gomelsky, Schneider, & Plouffe, 2012), Salmonids (Galbreath, Adams, Wheeler, & Thorgaard, 1997;Johnson & Wright, 1986), Centrarchids (Dawley, 1987) and ricefishes (Adrianichthyidae; Shimizu, Shibata, Sakaizumi, & Yamashita, 2000). This transformation is usually observed in hybrid females and results in the formation of eggs with an unreduced diploid chromosome number.…”

“…This transformation is usually observed in hybrid females and results in the formation of eggs with an unreduced diploid chromosome number. Gomelsky et al (2012) reported the production of diploid eggs by F 1 hybrid females obtained by crossing ornamental (koi) common carp (Cyprinus carpio L.) females with goldfish (Carassius auratus L.) males. Cherfas et al (1994) and Shimizu et al (2000) showed that the generation of diploid eggs by hybrid females results from the occurrence of premeiotic endomitosis (i.e., doubling of chromosomes without cytokinesis) in early oogenesis; the resulting tetraploid oocytes then undergo two normal, consecutive meiotic divisions.…”

“…In addition, diploid gynogenetic progenies DOI: 10.1111 have been produced without any applied shocks by insemination of eggs produced by F 1 hybrid females with koi sperm genetically inactivated by UV-irradiation (Gomelsky et al, 2012). Gomelsky et al (2012) reported that F 1 koi 9 goldfish hybrid males were sterile; however, one fertile F 1 male was identified later. Almost all of the gynogenetic offspring had microsatellite genotypes identical to their respective maternal genotypes.…”

Polyphyletic Origin of Ornamental Goldfish

“…The mechanism of integration of two genomes at remote hybridization is related to peculiarities of reproduction modes (bisexual reproduction and gynogenesis) and to production of different in ploidy egg cells by the goldfish C. a. auratus [24] [25]. The probability of formation of diploid hybrid forms is exemplified also by back-crossing and gynogenesis of hybrid females F 1 C. a. auratus (♀) × C. carpio "Koi" (♂) with a male "Koi" carp [26]. The recent studies showed that diverse hybrid variants of bisexual and fertile goldfishes can be obtained by combining the natural androgenesis and gynogenesis of hybrids C. auratus (red var.)…”