シロネズミにおける性比の季節的変動

概要

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The present paper gives some numerical data concerning seasonal variations of the sex-ratio obtained in nine strains of laboratory rats. The data were derived from a total of 1017 litters containing 6587 individuals. In annexed tables, the sex-ratios shown as the number of males to each 100 females are arranged in relation to seasons of birth. The results are outlined as follows : 1). Monthly variations of the sex-ratio in nine strains of rats are as shown in Table 1 and Figure 1. The monthly differences in the ratio can not be considered as statistically important. 2). Sex-ratio shows a significant variation according to four seasons (102.9 in spring, 101.0 in summer, 94.7 in autumn, and 109.8 in winter)(Table 2). 3). Out of the nine strains under consideration, Wistar-strain, Fischer-344-strain, Long-Evans-strain, and Gifu-agouti-strain, showed each a characteristic variation in the sex-ratio (Tables 3-6, Figure 2). 4). No correlation was obtained between the sex-ratio and litter-size (Table 7). It is likely that seasonal variations of the sex-ratio seem to be caused by both genetical and environmental factors.
1963-02-15