When conditions are less than ideal, parasites produce more sons than daughters thus facilitating the spread of malaria, researchers at Edinburgh University have found.
According to them, by understanding the family planning strategy of these parasites, ways can be found to stop the spread of malaria
They said that finding out when the parasites are likely to favour producing one sex over the other could help in the development of anti-malarial drugs and vaccines.
Parasites transmit malaria by producing offspring inside a mosquito.
Parasites, which are sucked up into a mosquito from infected blood while it is having a meal, have 20 minutes to reproduce.
The female single-celled organism turns into an egg and the male splits up into eight sperm.
But when conditions are harsh inside the mosquito's gut, parasites adjust their production of males and females accordingly to maximise their reproduction.
Then, the parasite offspring moves to the mouth of the mosquito and when it next takes a meal they are injected into the next human via its saliva.
The researchers said it showed how malaria parasites were more sophisticated than previously thought.
They can respond to changes in their social situation and environment, something that is traditionally associated with more complex animals such as insects, birds and mammals.
Usually, malaria parasites will tend to produce more daughters than sons, because all the females are expected to find a mate.
But in unfavourable conditions, for example when under attack from a person's immune system, or when competition to breed is high among the parasites, it is beneficial to have more sons, to boost the overall chance of their genes being passed on.
"We have long suspected that malaria parasites adjust their production of males and females to ensure their spread, and we have now shown that this is the case," BBC quoted Dr Sarah Reece, of the University of Edinburgh's School of Biological Sciences, who led the study, as stating in the journal Nature.
"We hope that by understanding the family planning strategy of these parasites, ways can be found to stop the spread of malaria," she added.
The study is published in the journal Nature.