Sexual maturation of daughters depends on the mother’s body condition during pregnancy: An example of the water vole Arvicola terrestris L.

Abstract

The body condition of an animal directly depends on the amount, quality, and assimilation efficiency of available food and on the energy expenditures and may serve as a reliable criterion of both internal and external conditions favorable for the onset of reproduction. The body condition is known to determine the probability of participation in reproduction and its effectiveness [8, 11]. Unlike species that rely on stored body reserves during pregnancy and bringing up the offspring [7], females of many small nonhibernating rodents has to rearrange their energy budget during pregnancy to reach a positive balance. When the amount of energy consumed with food is insufficient to support pregnancy and lactation, the energy deficit is compensated for at the expense of metabolic reserves of the body, primarily, fat [6, 12]. Previous ecological and population studies showed that, in the water vole, the probability of pregnancy failure and the litter size depended on the energy balance. In the years when population density dropped because of reduced food supply and/or stressful situations, a higher concentration of free fatty acids was found in female blood, which testifies to the mobilization of energy substrates from the stores of fat. This was accompanied by a significantly higher frequency of embryo resorption at the postimplantation developmental stage [1]. During the perinatal period, the probability of death of the young also depends on the mother’s body condition. The female body weight after the birth of the offspring is found to exceed their body weight on the day of mating by about 10%. However, in females that display a 100% death rate of offspring, the increase in the body weight during pregnancy was significantly lower (3%) [4]. The effect of the mother’s body condition during gestation on the offspring’s postnatal development remains unstudied so far. The rate of sexual maturation is one of the most plastic parameter that is related to animal growth [5]. Analysis of the contribution of maternal factors to the variation of the rate of the daughters’ sexual maturation in the water vole Arvicola terrestris L. showed that the mother’s body condition during pregnancy had a significant effect on this characteristic. The animals used in our study were kept in a vivarium at the natural photoperiod and received food and water ad libitum. The index of body condition during gestation was defined as the difference between the logarithm of the postpartum body weight and the logarithm of the expected body weight. The logarithm of the expected body weight was calculated from the regression equation of the postpartum body weight on the body weight at mating ( R 2 = 0.81; p < 0.001):