No abstract

No abstract

No abstract

No abstract

Diploid gynogenetic fry of rainbow trout, Salmo guirdnui, were produced by treating eggs activated by UV-irradiated sperm with hydrostatic pressure. Treatments for 10 min at 40 min after activation with 55 000 kPa (8000 psi) pressure resulted in high hatching rates and yields of heterozygous diploid gynogenomes of up to 8 1 Yo. Attempts to produce homozygous diploid gynogenomes by the suppression of the first mitotic division of the eggs failed.Ether treatment alone did not induce diploid gynogenesis.

SUMMARYGenetic analysis was performed on five enzyme systems (G3PDH; GPI-A; GPI-B; PGM; MDH-A) in plaice (Pleuronectes plotessa) collected in spawning condition from the North Sea. Conventional crosses, induced gynogenesis and induced triploidy were performed. The data conclusively demonstrated the inheritance of isozymes by co-dominant alleles at individual loci for each system. No linkage was observed but tests did not include MDII nor the possibility of linkage between G3PDH and GPI-A. Some anomalous segregation ratios were observed, particularly a deficiency of heterozygotes for GPI-A, but the data were largely in conformity with Mendelian expectations. At the PGM locus, five independent anomalous individuals were scored and interpreted as mutations with a mutation rate of 11 x 1 0' per gamete. Recombination with the centromere was assessed and induced triploidy and cross-over values of4l per cent for PGM, 19 per cent for MDH-A and 9 per cent for GPI-B were derived on the assumption of complete interference. Amongst the parent fish, genotypic and phenotypic frequencies were largely consistent with the expectations of the Hardy-Weinberg Law, and allelic frequencies were not significantly different between year of collection or location of collection ground.

Diploid gynogenesis in rainbow trout eggs was induced by a heat shock applied after fertilization with UV irradiated sperm. Survivals were high when the heat treatment was given soon after fertilization at times corresponding to the completion of egg meiosis but were low at all other times. Increases in survival occurred, however, when the heat treatment was given at 4 h 30 min and 5 h after fertilization, with an incubation temperature of 10" C, and at 9 h after fertilization, with an incubation temperature of 5" C. Electrophoretic analysis at three enzyme loci demonstrated a significant increase in homozygous offspring from eggs given these later heat treatments when compared to offspring from eggs treated between 40 and 70 min after fertilization, again with an incubation temperature of lo" C. There was still a significant frequency of heterozygotes in these groups, however, probably of spontaneous origin via diploidization during meiosis. No tetraploid alevins were observed after normal fertilization and attempted suppression of first mitosis.

No abstract