Prenatal growth and development of the water vole, Arvicola amphibius (rodentia, arvicolinae)

The morphological and morphometric characteristics of water vole embryos are studied. Embryo implantation occurs on the 5th day of pregnancy. A description of the morphological features of embryonic development at different stages of pregnancy is given, with equations for embryo body weight and length revealed. The results of multiple regression analysis show that embryo weight, when considering the influence of gestational age, is negatively related to the number of live embryos. Our results complement the existing literature on the biology of mammalian development and may be useful for establishing equivalent stages of embryonic development in different species when conducting comparative studies. Morphological features of development and the embryonic growth equations can be used to determine the age of pregnancy and the calendar dates of the beginning and end of the breeding season in natural populations.