(Photo : Image by Mohamed Nuzrath from Pixabay)

From animal species to species, there are significant differences in the fundamental biological process of reproduction. Sometimes, males and females among these animal species evolve creative strategies to pursue their interest in these mating interactions.

Some studies have been carried out for quite some time in small species like fruit fly Drosophila melanogaster, whereby the seminal fluid of the male gives protein to the female, which leads to radical changes in her behavior after the actual mating and in the processes occurring inside her body.

There will be an increase in her activity due to the protein in her and a reduction in her sexual receptivity and stimulation of her immune system.

For some time, scientists know that such processes are not particularly beneficial for both sexes. That is why researchers from Germany and Switzerland have now taken a closer look at which mechanisms change evolutionarily when there are no conflicts of interest between the sexes, and when the competition between males is eliminated.

The researchers got the result that male flies produce fewer proteins in their seminal fluid, which changes the behavior of the females. This result indicates that male flies mainly manipulate their partners to increase their chances in the reproductive competition. The side effect of it is that most times, females have health disadvantages.

Evolutionary biologist and research team leader at the University of Munster, Claudia Fricke, said that with the current study, they confirmed a theory that has existed for a long time. The team has published their research in the journal PNAS (Proceedings of the National Academy of Sciences).

For the background and methods of their study, the researchers arranged the individual pairs of flies to live in a monogamous way over many generations for them to determine the extent to which the different interests pursued by each sex play a role in the evolution of fruit flies. This manner of living was contrary to their usual mode of reproduction.

Each day, only one male and one female mated as they ruled out any chance for antagonistic interactions among potential partners. The only offspring the male gained were the eggs the female could only lay.

As for the second group, they have five males, and five females mated freely with one another. It was a perfectly normal polygamous lifestyle for these insects which naturally created competition - both between males and between females with the scope for antagonistic interactions. However, the entire population for both groups was equal.

In their further tests, the scientists read out the expression of genes of female fruit flies after mating. In the brain and abdomen of the female, the structures that have the responsibility of reproduction and any changes in behavior, they measure the expression of genes essential for reproduction. Their discovery indicated that these genes are far less expressed in the female who lived a monogamous life.

The researchers hope to identify in their subsequent studies further genes that play a role in this process both in female and male fruit flies.