Aphids saved from gruesome death by virus-infected bacteria

http://www.eurekalert.org/pub_releases/2009-08/uoa-asf081909.php

Public release date: 20-Aug-2009
Contact: Mari N. Jensen
University of Arizona

IMAGE: A parasitoid wasp, Aphidius ervi, stalks pea aphids so she can lay eggs in them. The wasp is a tad bigger than 0.01 inches long.
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The term "beneficial virus" sounds like an oxymoron.

But for pea aphids under attack by parasitic wasps, carrying infected bacteria is the difference between life and a slow death, according to new research.

The wasps lay eggs inside the aphids, and the wasp larvae eat the living aphids from the inside out.

"A parasitoid death would be a very gruesome death," said first author Kerry M. Oliver. "It's like the movie 'Alien' where this thing grows inside of you and then ruptures out of you and kills you."

In laboratory experiments, about eighty percent of aphids carrying uninfected Hamiltonella defensa bacteria died as a result of wasp attacks.

However, most of the aphids whose H. defensa bacteria had a particular virus did survive wasp attacks.