マウスの成長と繁殖に及ぼす飼育密度の影響IV同じ容積: 異る密度 (異る密度におけるinbrebsとhybridsの比較)

Abstract

Inbred mice (ss-strain and dd-strain) and their F1 (ss x dd-F1 and dd x ss-F1) were fed under high and low denisities of breeding and their growth and ability of reproduction were compared each other among these groups.In bodily growth, the hybrids grew better than the inbreds regardless the population density. The inbreds showed better growth under lower density of feeding, however the hybrids showed little inequality in growth by different population density.The age of saturation in day in female mice under low breeding density was younger in ss-strain of mice than that in dd-strain, however little differenfwas found between the inbreds and hybrids in the age of maturation. Under high population density, the dd-strain female mice showed earlier maturation than ss-strain. These findings probably suggest that the ss-strain mice are more keenly sensitive to the change in population density. The hybrids always showed earlier maturation than the inbreds. Under different densi-ty of feeding, the inbreds generally matured earlier under low density, the hybrids showed little difference in this respect. The hybrids matured earlier even under high population density than the inbreds fed under low density.The litter size generally tended to be larger in hybrids, whatever populatin density was. The total weight of a litter also showed the same tendency. The avarage weight of newborne of inbreds was found larger than that of hybrids under lower population density, whereas it was smaller under higher population.