Sensational female responses can be triggered by the activation of a diverse set of genes from sex, including immunity, libido, altered fertility, and eating and sleep patterns.

A team of researchers from the University of East Anglia set out to determine the response female fruit flies (Drosophila melanogaster) have to mating.

The findings, published in Proceedings of the Royal Society B, indicated that semen consists of a single protein which generates a variety of responses in numerous genes in females, which appears evident at different instances and in different areas of their bodies after mating.

The discovery in the flies, the authors suggest, may be similar to responses in many animals, where semen is inserted into the female’s body while having sex.

According to research earlier this year in PLoS Biology, neurodegenerative disorders that occur in both fruit flies and humans are caused by mutations in the same gene, showing that it is plausible that humans may experience the same effect during sex that fruit flies do with the activation of genes.

Scientists have been aware that males pass on seminal fluid proteins to their partner while mating, impacting their feeding, sleep patterns, immunity, egg laying, sexual receptivity, and water balance.

Professor Tracey Chapman, from UEA’s school of Biological Sciences and head author, said:

“We tested here the effects of one enigmatic seminal fluid protein, known as the ‘sex peptide’, and found it to change the expression of a remarkable array of many genes in females- both across time and in different parts of the body.”

Researchers identified significant changes to genes linked to:

  • early embryogenesis
  • egg development
  • nutrient sensing
  • behavior
  • phototransduction– the pathways by which they see

This demonstrated that females’ behavior and reproductive system is affected by a direct and global influence of males. In other words, the semen protein is a ‘master regulator’.

These effects could possibly be found across many species, the team pointed out.

Chapman added:

“An additional and intriguing twist is that the effects of semen proteins can favor the interests of males whilst generating costs in females, resulting in sexual conflict.

For example, there can be a tug-of-war, where males employ semen proteins to ensure that females make a large investment in the current brood- even if that doesn’t suit the longer term interests of females.”

Written by Sarah Glynn