Formation and Diachronic Changes of Placental Scars in the House Shrew (Suncus murinus)

Abstract

In the present study, diachronic changes in fresh and stained placental scars of postpartum house shrews (Suncus murinus) were studied and compared with the actual number of offspring. In non- stained fresh uteri, the placental scars were barely visible externally, except in some exceptional cases. In stained uteri, placental scars were observed in all specimens, even in the oldest animals evaluated (12 months postpartum). The study estimated the number of offspring and time of parturition using the degree of staining in the scars and the change in their forms.  As the time postpartum increased, the stained placental scars became discoloured and shrank, making it difficult to distinguish between the scars from normal parturition and those that formed following halted development after implantation. Placental scars provided an invaluable method for estimating the female reproductive state in wild mammals. In captive house shrews, however, placental scars were barely detected in non- stained fresh uteri. Moreover, placental scars were observed in older animals at 12 months postpartum. It can be concluded that, it is not feasible to estimate the number of offspring or time of parturition based on placental scars in wild shrews, which are believed to undergo multiple parturitions a year.