Abstract
BackgroundBleeker’s yellow tail (Xenocypris davidi Bleeker, YT) and topmouth culter (Culter alburnus Basilewsky, TC) are both famous and important economic freshwater fish in China. YT, a kind of omnivorous fish, has strong resistance. TC, a kind of carnivorous fish, has high-quality meat but poor resistance. Distant hybridization can integrate the advantages of both parents. There has been no previous report regarding hybrid fish derived from female YT × male TC. It is expected that hybridization of these two kinds of fish will result in F1 hybrids with improved characteristics, such as faster growth rate, stronger resistance, and high-quality meat, which are of great significance in fish genetic breeding.ResultsIn this study, we investigated the main biological characteristics of diploid hybrid fish derived from female YT × male TC. The hybrids had an intermediate number of upper lateral line scales between those for YT and TC. The hybrids were diploids with 48 chromosomes and had the same karyotype formula as their parents. The hybrids generated variations in 5S rDNA (designated class IV: 212 bp) and lost specific 5S rDNA derived from the maternal parent (designated class II: 221 bp), which might be related to hybridization. In terms of reproductive traits, all the tested female hybrids exhibited normal gonadal development, and the two-year-old F1 females produced mature eggs. However, all the tested testes of the male hybrids could not produce mature sperm. It is possible that the hybrid lineage will be established by back-crossing the fertile female hybrids and their parents.ConclusionsObtaining a fertile female hybrid fish made the creation of a new type of fish possible, which was significant in fish genetic breeding.
Highlights
Bleeker’s yellow tail (Xenocypris davidi Bleeker, YT) and topmouth culter (Culter alburnus Basilewsky, Topmouth culter (TC)) are both famous and important economic freshwater fish in China
After analysing the 5S ribosomal RNA (rRNA) genes in different ploidy-level hybrids derived from female Red crucian carp (RCC) × male TC, He et al [19] found that a paternalspecial unit lost and a novel unit was generated in the hybrid offspring
The results showed that the fertilization rate and hatching rate of the experimental group (YT (♀) × TC (♂)) was not significantly differently (P > 0.05) from those of the control groups (YT (♀) × YT (♂) and TC (♀) × TC (♂))
Summary
Molecular analysis of polymorphisms in 5S rDNA sequences The primers (5SP1 and 5SP2R) were used to amplify DNA fragments from YT, TC, and 2nYC, and the results of agarose gel electrophoresis showed that YT had three bands (approximately 200, 250, and 400 bp), TC had three bands (approximately 200, 280, and 400 bp), and 2nYC had three bands (approximately 200, 280, and 400 bp) (Fig. 3). DNA fragments of Sox genes Primers (HMG (+) and HMG (−)) were used to amplify DNA fragments from YT, TC, and 2nYC, and the results of agarose gel electrophoresis showed that there were two bands (approximately 200 and 700 bp) in YT, TC, and 2nYC (Fig. 5). All the tested testes of the male hybrids could not produce mature sperm
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