Postnatal growth pattern of F1 hybrids of a cross between two strains of large and small musk shrews, Suncus murinus.

In our previous comparison of the postnatal growth of two laboratory strains of the musk shrew (Suncus murinus), the large shrews originating in Bangladesh (BAN strain) and the small shrews from Nagasaki, Japan (NAG strain), we found that differences in the 120-day adult body weight of the two strains (BAN: males 135.3g and females 82.0g; NAG: 52.9 and 34.2g, respectively) reflect both an approximately 2.5 times longer linear growth phase and an approximately 1.5 times higher growth rate during this phase in the BAN strain. We examined the postnatal growth (from 5 to 120 days after birth) of the F1 hybrids of a cross between the two strains and compared our findings with the above-mentioned growth data for the parent strains. A growth equation composed of linear and monomolecular functions was fitted to the growth data for the shrews. The growth trajectories of both sexes of the F1 hybrids were situated roughly midway between those of the two parent strains throughout the entire growth process. The adult body weight of the F1 shrews at 120 days of age averaged 86.0g in the males and 51.7g in the females. The growth phase lasted approximately 60 days in the males and approximately 40 days in the females of both the F1 shrews and the parent strains. The duration of the linear growth phase of the F1 hybrids (29.8 days in the males and 19.0 days in the females), however, was approximately intermediate between the parent strains (BAN: males 33.4 days and females 26.1 days; NAG: 18.8 and 13.9 days, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)