PRODUCTION OF VIABLE HAPLOID OREOCHROMIS-MOSSAMBICUS GYNOGENS USING UV-IRRADIATED SPERM

Haploid and homozygous diploid mitotic gynogens of Oreochromis mossamb icus were successfully produced using UV-irradiated sperm. Optimum UV- irradiation duration required for the production of 100% haploid was 1 0 min. Irradiation for more than 15 min caused loss of motility in spe rm. Normal homozygous diploid mitotic gynogens were produced by heat s hocking 70 min old activated haploid eggs. Haploids had 22 chromosomes , including a large subtelocentric chromosome; diploid mitotic gynogen s had 44 chromosomes, including a pair of large subtelocentric chromos omes. Ratio of nuclear volume of haploid fish RBCs to diploid RBCs was 0.53:1, whereas that of relative DNA content was 0.4:1. Haploids were viable; however, they suffered from characteristic syndromes like poo rly developed retina, twisted edematous body and curved tail. There wa s also a reduction in the number of vertebrae in the caudal region of haploids; only 4-5% eventually survived. These observations indicate t hat the syndrome characters and the lower rate of survival in haploid O. mossambicus may be more due to the absence of normal genes in pairs in homologous or heterologous chromosomes rather than due to the pres ence of lethal genes. (C) 1993 Wiley-Liss, Inc.