Observations of parthenogenetic rotifers demonstrated that they, like many other species, the age of the mother negatively affects fitness and reproductive success of offspring. The pressure of natural selection on the descendants of the old females does not reach a sufficient level to weed out the genes responsible for this effect. According to the researchers, the findings of which are outlined in the journal PNAS, they created the model can be used to study species that have aging mother does not reduce the success of her children.
The older the mother, the less likely that her offspring will be healthy, live long and achieve reproductive success. This regularity was observed for many species of animals, including humans. However, natural selection for some reason does not deprive females of venerable age, of the ability to reproduce.
To understand this paradox has decided the team of biologists led by Christina Hernandez (Christina M. Hernández) from the Oceanographic Institute in woods hole. As a model organism they chose the rotifer Brachionus manjavacas is a tiny aquatic invertebrate. These creatures can reproduce asexually and sometimes form a population composed exclusively of parthenogenetic females. Each of them within ten days gives rise to 25-30 major daughters. This is no maternal care rotifers do not show.
Scientists tracked the lives of several generations of parthenogenetic rotifers in the lab, and analyzed the results using sophisticated demographic models. The first observations have confirmed that the age of mothers is negatively correlated with offspring survival and reduces his chances of successful reproduction. Daughter old females laid fewer eggs even at a young age, which negatively affected the entire population. The genetic mechanisms that underlie this pattern remain unknown.
The effect of ageing of mothers, which was shown in rotifers ideal for laboratory and in models. Most notably he was in the simulation, where they maintain a low birth rate. In the laboratory and in the simulation with low survivability, the influence of maternal age across the population offset. The reason is the demographic structure: in both cases nearly all species were represented by young mothers and their offspring.
The researchers also found that, although the descendants of the older females and worse adapted to life, the pressure of natural selection has been reduced. This means that they are not eliminated quite rapidly from the population was eliminated genetic variants responsible for the effects of aging mothers.
Although the work was undertaken on a single species, the authors believe that their model can be used for other animals, making amendments to their demographic structure and characteristics of maternal care. It is particularly interesting to apply it to species in which aging females did not reduce the viability and reproductive success of offspring. These include, for example, include bony fish (Teleostei): their quality and the number of sweeps of the calf increases with age females. Some species, caring for offspring, also can avoid the effects of aging mothers.
The age of the mother is not the only factor responsible for the survival of the offspring. For example, in humans the important role played by the level of education. As shown by a recent study, the lower it is, the higher the risk of child death in the first year of life, and is governed by this relationship is insufficient weight at birth and the earliest term of pregnancy at the time of delivery
Sergey Knee High