Unreduced diploid sperm from diploid hybrids and formation of a new type of tetraploid hybrid
2020
Wang, Yude | Zhang, Minghe | Tao, Suifei | Xie, Xiang | Tan, Huifang | Cao, Liu | Wang, Jing | Qin, Qinbo | Zhang, Chun | Tao, Min | Ma, Ming | Chen, Bo | Liu, Shaojun
The production of unreduced gametes is an important resource for the formation of polyploids. Here, we obtained a second generation of diploid hybrids (2nKCF₂) derived from koi carp (KOC; 2n = 100; ♀) × colored crucian carp (CCC; 2n = 100; ♂) with the unusual reproductive trait of producing unreduced diploid sperm. Compared with KOC and CCC, 2nKCF₂ had unique morphological characteristics, including a gray and golden head, golden-brown scaly outer edge, and smooth golden-yellow back. FISH and 5S rDNA analysis revealed that 2nKCF₂ not only inherited genomic DNA from their parents but also lost some parental DNA fragments. Chromosomal spreads of germ cells provided direct cytological evidence for the production of unreduced diploid sperm by male 2nKCF₂. Electron microscopy results showed that the heads of the diploid sperm generated by 2nKCF₂ were twice as large as those of the haploid sperm generated by CCC (P < 0.05), confirming that the sperm of 2nKCF₂ were diploid. A new type of tetraploid hybrid (4n = 200) was produced by crossing 2nKCF₂ males with improved female allotetraploid hybrids of red crucian carp (♀) × common carp (♂). This study provides insights into reproductive biology and aquaculture.
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