Production of clonal founders in the European sea bass, Dicentrarchus labrax L., by mitotic gynogenesis

Reproduction by mitotic gynogenesis was carried out in European sea bass, Dicentrarchus labrax L., by fertilizing eggs from three normal and one meiotic gynogenetic females with UV-irradiated sperm. The haploid chromosome set was then doubled by applying a pressure shock at 81 or 91 MPa for 4 min at the time of the onset of the first cleavage furrow in order to obtain four progenies of mitotic gynogenetic double haploid (G2N) fish. Haploids, tetraploids and normal diploids were also produced as controls. Survival of G2N prelarvae was 7-18% of that of normal diploids. The diploid status of G2Ns was verified by flow cytometry, while maternal chromosome inheritance was confirmed by unilocus analysis of six microsatellites amplified by hexaplex PCR and by the precocious death of haploid controls. Two progenies were found to be completely homozygous for the heterozygous maternal microsatellite alleles while, in the other two progenies, only 92% and 95% of the fish were fully homozygous, as 7 fishes were heterozygous at one locus, 6 at two, and I at three loci. Similar small percentages of triploid fish were found within the corresponding tetraploid controls. No increment of heterozygous or triploid fish was observed in successive samplings. In the most numerous progeny, 100 fish have been raised for 2 years and some of them are essentially of normal appearance. In these G2Ns, 16 double haplotypes were found on the basis of the 6 microsatellite loci analyzed. The possible use of G2Ns as clonal founders for sex control and performance improvement is discussed. (c) 2005 Elsevier B.V. All rights reserved.