gh FATNESS OF MOTHERS, SONS AND DUAGHTERS

It’s common knowledge that an expectant mother is to eat well during pregnancy. But not everybody knows that mother’s fatness tells differently on her sons and daughters. This data was received by specialists of the Institute of Taxonomy and Ecology of Animals, Siberian Branch, Russian Academy of Sciences, when making experiments on water voles (Arvicola terrestris).

It is of great interest for scientists to evaluate the influence of a mother’s physical state during pregnancy and breast feeding on the posterity growth, health and life interval. The researchers have investigated the issue on vole mice from the institute vivarium. The researchers regularly weighed females and compared the received results with theoretically expected body weight. The researchers traced the fate of 257 rodents born in the course of the experiment.

Since the first days of pregnancy, female voles begin to accumulate fat. They spend it during lactation (feeding the posterity). During feeding, fat serves as an additional source not only of energy but also of water, for which the feeding female is in acute need. The more well-fed a female is at the point of coupling, the more fat it will be able to accumulate. Fat is accumulated in special fat depots of the womb, ovaries and kidneys, but does not hang in folds on the sides and the belly.

It has turned out that a mother’s fatness has a positive effect on her daughters’ body weight throughout the entire life, but it influences the sons’ body weight only till their ten-week age. The father’s body weight also tells on them but only till the age of three weeks. Such difference is not surprising: the mother’s contribution into infants’ growth and feeding is immeasurably larger. The fatter the mother is, the more milk it would have and the more nutritious the milk would be. Therefore, the fat females’ infants grow quicker.

Physical conditions of the mother influence not only offsprings’ dimensions. Daughters of fat voles enter propagation more often than daughters of lean mothers. Reproductive success of sons does not depend on the mother’s fatness, but the life interval does. The vole males whose mother’s fatness was below the average during pregnancy but above the average during lactation live longer than all others.

But fatness is not the only key factor for voles. The calendar month of their birth impacts the posterity growth. The babies born early in the propagation season (which begins in March) develop quicker during the first months of life and preserve this advantage in the adult state. The litter size is also of importance. Sons are born small in a big litter, but the number of babies in a litter does not influence the daughters’ dimensions. Apparently, development conditions in a big litter are less favorable for males than for females, which is shown already during the fetal life. When young voles begin to feed independently, negative impact of a big litter tells on the dimensions of all babies, but the difference is not evident in an elder age. Besides, a numerous litter reduces the life span of sons, but not that of daughters. The more “boys” are in the litter, the smaller they are and the bigger sparse daughters are.

Physical state of the mother’s organism is very important for continuation of the genus. It influences the body weight, readiness for propagation and offsprings’ life span. This influence depends on the babies’ sex. Individual regularities discovered by the Novosibirsk researchers are also inherent to some other mammal species. There is a probability that they are also true for human beings.

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