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Add To Calendar 25/02/2016 14:15:0025/02/2016 14:35:00America/ChicagoAquaculture 2016REPRODUCTIVE ABILITY OF SECOND GENERATION KOI X GOLDFISH HYBRID MALES AND RESULTS OF THEIR CROSSES WITH HYBRID FEMALES   Concorde AThe World Aquaculture Societyjohnc@was.orgfalseanrl65yqlzh3g1q0dme13067DD/MM/YYYY


Jeffrey L. Warner*, Boris Gomelsky, and Thomas A. Delomas
Aquaculture Research Center
Kentucky State University
Frankfort, KY 40601

Previous studies have shown that F1 hybrid females between koi carp (Cyprinus carpio) and goldfish (Carassius auratus) produce diploid eggs due to a transformation of meiosis. Hybrid F1 males are typically sterile, but a single fertile male, which produced diploid spermatozoa, was found. This F1 male was crossed with F1 hybrid females for the production of F2 hybrids. F2 progenies consisted mostly (81-97%) of diploids but aneuploid and tetraploid fish occurred in F2 with low frequencies. Analysis of microsatellite DNA markers showed that diploid males repeated the genotype of the parent F1 male while diploid females repeated the genotypes of the parent F1 females. On this basis, it was suggested that diploid males and females in F2 resulted respectively from spontaneous androgenesis and spontaneous gynogenesis.

The purpose of the present study was to investigate the reproductive ability of diploid F2 males. Thirty three from 185 (18%) investigated 2-year-old F2 males released sperm. Flow cytometric analysis showed that spermatozoa produced by F2 males were diploid. Four F2 hybrid males were crossed with F1 hybrid females. A total of three progenies were raised and analyzed; progenies 1 and 2 were obtained by separate crossings of individual males while the offspring from two other males were combined in one progeny (progeny 3). Results of flow cytometric analysis of juveniles from these progenies are presented in Table 1. Most fish (from 82.5% to 99.6%) were diploid while the rest of the fish were aneuploid with ploidy ranges of 2.1n-2.2n and 3.1n-3.4n.

The results of the present study show that the reproductive ability of F2 males was similar to the reproductive ability demonstrated earlier by the fertile F1 male. Like the F1 male, F2 males produced diploid spermatozoa. Fish ploidy distributions in progenies obtained by crossing F2 males with F1 females were similar to ones obtained before by crossing the F1 male with females of the same category. It is remarkable that almost 20% of F2 males were able to produce sperm. This increase in reproductive capacity of F2 males as compared with F1 males could be predicted since based on previous data all of the F2 males inherited the genotype of the fertile F1 male.

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