Fruit flies force young to booze to kill parasites

Fruit flies force their young to drink alcohol to protect them against deadly parasitic infections, a new study has found.
When fruit flies sense parasitic wasps in their environment, they lay their eggs in an alcohol-soaked piece of fermenting fruit, essentially forcing their larvae to consume booze as a drug to combat the deadly wasps.
"The adult flies actually anticipate an infection risk to their children, and then they medicate them by depositing them in alcohol," said Todd Schlenke, the evolutionary geneticist whose lab carried the research.
According to the study led by Balint Zacsoh, an Emory University graduate, the larvae of the common fruit fly, Drosophila melanogaster, eat the rot, or fungi and bacteria, that grows on overripe, fermenting fruit.
 

They have evolved a certain amount of resistance to the toxic effects of the alcohol levels in their natural habitat, which can range up to 15 per cent.

Tiny, endoparasitoid wasps are major killers of fruit flies. The wasps inject their eggs inside the fruit fly larvae, along with venom that aims to suppress their hosts' cellular immune response.
Earlier study by Schlenke's lab showed how fruit fly larvae infected with wasps prefer to eat food high in alcohol, according to the study published in the journal Science.
This behaviour greatly improves the survival rate of the fruit flies because they have evolved high tolerance of the toxic effects of the alcohol, but the wasps have not.

"The fruit fly larvae raise their blood alcohol levels, so that the wasps living in their blood will suffer," Schlenke said in a statement.
For the latest study, the researchers asked whether the fruit fly parents could sense when their children were at risk for infection, and whether they then sought out alcohol to prophylactically medicate them.
Adult female fruit flies were released in one mesh cage with parasitic wasps and another mesh cage with no wasps. Both cages had two petri dishes containing yeast, the nourishment for lab-raised fruit flies and their larvae.
The yeast in one of the petri dishes was mixed with 6 per cent alcohol, while the yeast in the other dish was alcohol free. After 24 hours, the petri dishes were removed and the researchers counted the eggs that the fruit flies had laid.

The results were dramatic. In the mesh cage with parasitic wasps, 90 per cent of the eggs laid were in the dish containing alcohol. In the cage with no wasps, only 40 per cent of the eggs were in the alcohol dish.