| Popis: |
The influence of the increase of the degree of homozygosity, obtained by successive consanguine cross-breeding, on the mean weights and the variability of the weights of twelve muscles of the Japanese quail (Coturnix c. japonica) was studied in four generations of females and two generations of males. It was found that the mean weights of the twelve muscles in both sexes showed a progressive reduction in the consecutive generations of consanguine crosses, this reduction being more marked in the males than in the females. These results support the hypotheses of Haldane and Lerner that heterozygotes are at an advantage, having a more active metabolism and a greater rate of growth, because their richer biochemical system and greater number of alleles coding the enzymes enables them to benefit from their environment to a greater extent and within wider limits. The rates of decrease vary from one muscle to the other within the limits of 5.3 and 16.6%. For certain muscles there are also notable differences between males and females. Contrary to the hypothesis that could be formed at first sight, the variability in weight increases considerably, in almost all cases, when the degree of homozygosity increases. Here again quite considerable differences are found in the evolution of the variability with the degree of homozygosity, from one muscle to the other and also between the two sexes. Comparison of the mean weight of the left and right elements of the bilateral muscles shows no significant preponderance. It was found, however, that slight asymmetries observed in the different groups of different consanguinity tend to be in the same direction for a given muscle. The variability of the weights of the left and right elements does not seem to be influenced by the degree of homozygosity in the females; in the males, however, an increase in homozygosity increases the variability of the weights of the left and right elements in certain cases. The mean degree of humidity and the variability of the ratio wet weight/dry weight are not changed significantly by the degree of consanguinity in females. In the males, the variability in the degree of humidity is less in heterozygotes, an indication of their better capacity for homeostatic regulation. The reduction in the mean weights and the increase in variability as the degree of homozygosity increases shows the importance of the advantage of heterozygotes, which has a bearing on theories of the genetics of populations and their application in rearing, and particularly to selection techniques. |
