Two types of gynogenetic blunt snout bream derived from different sperm

Blunt snout bream (Megalobrama amblycephala, 2n = 48, BSB) is an important fish species with great commercial value but has a shortcoming in hypoxia tolerance. Gynogenesis is an effective way to obtain improved BSB with a higher ability to tolerate hypoxia. In this study, BSB eggs were activated by UV-irradiated sperm of koi carp (Cyprinus carpio haematopterus, 2n = 100, KOC) and topmouth culter (Erythroculter ilishaeformis, 2n = 48, TC), respectively. Following cold shock to double the chromosomes, two types of gynogenetic BSB (abbreviated as GBSB-K and GBSB-T) were obtained. Comparative analyses regarding the morphological characteristics, DNA content and chromosome number showed no significant difference among BSB, GBSB-K and GBSB-T (p > 0.05). However, the results of microsatellites (Cca15-K, Cca15-T) revealed that paternal DNA fragments were detected in GBSB-K and GBSB-T. These special DNA fragments were valuable molecular markers to distinguish gynogenetic BSB from BSB. Furthermore, the experimental results showed that GBSB-K and GBSB-T showed obviously higher hypoxia-tolerant ability than BSB (p < 0.05). Both KOC and TC were effective stimuli to induce gynogenesis of BSB and to form the hybrid effect. Factors including cold shock, barely living irradiated sperm and the allo-sperm hybrid effect potentially produce stronger gynogenetic BSB with greater hypoxia-tolerance ability. The formation of the two types of gynogenetic BSB derived from the two types of allo-sperm is of great significance in fish genetic breeding.