Development of rainbow trout microsatellite markers from repeat enriched libraries.

The efficiency of developing polymorphic microsatellite markers from 2 repeat enriched libraries was evaluated. Thirty-six polymorphic microsatellite markers were developed for rainbow trout, 27 of which were informative in a mapping family. The ability of each marker to amplify genomic DNA from other salmonids was also observed.

Genetics of size and growth rate through sexual maturity in freshwater-reared coho salmon (Oncorhynchus kisutch).

Genetic parameters of size through sexual maturity have been relatively unexplored for Pacific salmon. In this study, individually tagged coho salmon were raised in freshwater, and the heritabilities of size and growth rate were estimated at several intervals between 13 and 24 months of age (spawning). Heritability estimates for size were moderate to high from 13 to 19 months of age, ranging from 0.36 to 0.50, and lower from 21 months to spawning at 24 months, ranging from 0.17 to 0.32. Heritabilities of specific growth rates estimated over 3-month intervals were moderate from 16 to 21 months of age, ranging from 0.21 to 0.34. Genetic and phenotypic correlations between sizes measured at different ages were moderate to high, ranging from about 0.7 to 1.0. Correlations between growth rate and size indicated that the larger fish were the fastest growing between 16 and 19 months of age and were slower growing between 19 and 21 months of age.

Genetic Consequences of Blocking Polar Body I with Cytochalasin B in Fertilized Eggs of the Pacific Oyster, Crassostrea gigas: I. Ploidy of Resultant Embryos.

The effect of blocking polar body I (PB1) with cytochalasin B (CB) on the ploidy of embryos was studied in the Pacific oyster, Crassostrea gigas. To block the release of PB1, fertilized eggs were treated with CB (1.0 µg/ml) for 15 min beginning at 5 min post-fertilization at 25°C. The CB treatment and its control were repeated in three crosses. Ploidy of 8-h-old embryos was determined with karyological analysis. In control groups, the majority of the cells (89.3%) had a diploid number of 20 chromosomes, although spontaneous haploids (0.7%), triploids (1.3%) and aneuploids (8.7%) were also encountered. In CB-treated groups, only 4.5% of the cells remained as diploid, and the majority were either triploid (15.6%), tetraploid (19.4%) or aneuploid (57.6%). Despite variation among the three crosses, contingency Chi-square analysis showed that the occurrence of triploids, tetraploids and aneuploids had a significant (P = 0.0001) dependence on the CB treatment. The majority of the aneuploids fell into two groups containing either 23-25 or 35-37 chromosomes. The production of triploids, tetraploids and aneuploids in specific distributions suggests that blocking PB1 complicates subsequent chromosome segregation.

Genetic Consequences of Blocking Polar Body I with Cytochalasin B in Fertilized Eggs of the Pacific Oyster, Crassostrea gigas: II. Segregation of Chromosomes.

The effect of blocking polar body I (PB1) with cytochalasin B (CB) on subsequent chromosome segregation was studied in fertilized eggs of the Pacific oyster, Crassostrea gigas. To block the release of PB1, fertilized eggs were treated with CB (1.0 µg/ml) for 15 min beginning at 5 min post-fertilization at 25{deg}C. Chromosome segregation in both control and CB-treated eggs was analyzed with an acetic orcein stain. In untreated eggs, ten maternal tetrad chromosomes went through meiosis I and II, and released two polar bodies, reaching a haploid number of 10 chromatids. In CB-treated eggs, meiosis I proceeded normally and produced two groups of dyads, ten in each group. However, blocking PB1 dramatically changed chromosome segregation in meiosis II. In the majority of the treated eggs (68%), the two groups of dyads from meiosis I entered meiosis II through a "tripolar segregation", although two other types of segregation, namely "united bipolar" (7%) and "separated bipolar" (12%) were also observed. After anaphase II, chromatids at the peripheral pole were released as polar body II (PB2). The release of two sets of chromatids as PB2 through either a united bipolar or a separated bipolar segregation resulted in the formation of meiosis I triploids (14%). The release of one set of chromatids as PB2 from an unmixed tripolar or a separated bipolar segregation formed meiosis I tetraploids (20%). Aneuploids (56%) were produced, primarily when the two groups of dyads from meiosis I united or overlapped before entering the tripolar segregation.

Changes in the hemoglobin system of the coho salmon Oncorhynchus kisutch during smoltification and triiodothyronine and propylthiouracil treatment.

Three electrophoretically separable forms of blood hemoglobin were found in fry of coho salmon (Oncorhynchus kisutch). Ten hemoglobin forms were found in juvenile and adult salmon. Treatment of yearling salmon with triiodothyronine (T3) at 12 ppm in the diet accelerated the increase in concentration of adult forms of hemoglobin, while treatment with T3 at 4 ppm had no effect. Dietary propylthiouracil (1.5 or 5 mg/g) reduced the increases in adult forms of hemoglobin during smoltification. These results implicate thyroid hormones in the expression of adult forms of hemoglobin during the parr to smolt transformation of juvenile salmon.