Emerald Cockroach Wasp sanitizes prey
A new study has revealed the parasitic Emerald Cockroach Wasp (Ampulex compressa) has developed its own method of food hygiene. In much the same way as humans go to great lengths to ensure food safety, by washing hands, refrigerating and pasteurising, this wasp sanitizes its prey using a combination of antimicrobial liquids.
Female Emerald Cockroach Wasps attach an egg to the leg of an American Cockroach (Periplaneta americana) when reproducing. When the egg hatches, the larva bores a hole into the insect and moves inside, where it feeds on the internal organs of the cockroach. A cocoon is then spun within the carcass, and eventually an adult wasp emerges.
However, the unsanitary living conditions of the cockroach means that many bacteria, viruses and fungi pollute the young wasp's food supply, threatening its survival. Lead author of the study Gudrun Herzner, of the Institute of Zoology at the University of Regensburg, wanted to investigate exactly how these wasp larvae protected themselves from the contamination of their food source.
"It was clear that a species that feeds on these cockroaches had to protect its food and ... itself from foodborne illnesses," says Herzner. "This [environment] was a good place to look for antimicrobial defense mechanisms."
Herzner and her team collected droplets of the liquid that is secreted when the larvae inhabit their hosts. Analysis of the liquid revealed a combination of the chemicals mullein and micromolide. These were found to be effective antimicrobial agents against bacteria commonly found on American cockroaches. Herzner's study is the first to find this combination of chemicals in one source.
"It seems that it's exactly this mixture [that gives] broad-spectrum protection from different kinds of bacteria" Herzner said.
The strategy used by the wasp larvae also prevents the development of bacterial resistance, in a similar way to the use of combination antibiotics in humans. The wasps "virtually soak their cockroaches in these antimicrobial secretions [to] sanitize the cockroach" Herzner adds.
Jim Whitfield, professor of entomology at the University of Illinois comments that the wasp larva's method of defence is quite unique:
"Normally the adult female wasp produces the compounds that protect the offspring, and not the larva itself. In this case, it sounds like it's the larva that produces it," he said.
It is even thought that this combination of antimicrobial agents could one day be used in human antibiotics and food safety techniques. Micromolide has already been identified as a promising lead for protecting against the microbe that causes TB. Herzner adds that there could be other agents out there that are even more powerful than those produced by the wasp larva:
"Evolution might still be working to make an even better combination [for defence]."
Herzner's findings will be published this week in Proceedings of the National Academy of Sciences.
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