PARASITOLOGY

Give and Take

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Science  14 Feb 2003:
Vol. 299, Issue 5609, pp. 979-981
DOI: 10.1126/science.299.5609.979e

Parasitoid wasps lay eggs within the bodies of insects, and when the larvae hatch, they consume the insect from within and kill it. These kinds of wasps are exploited as biocontrol agents, but even easily visible parasitoid targets, such as aphids, are not sitting ducks. Oliver et al. have shown that some secondary bacterial symbionts protect pea aphids against the ravages of parasitoid attack. They exposed aphids, inoculated with three different secondary symbionts, to adult wasps. Two of the secondary symbiont types killed 25 to 41% of the developing parasitoid larvae a few days after oviposition. These aphids continued to reproduce and transmit the protective symbionts to their daughters, hence maintaining the symbiont population. But it's not a perfect partnership, as there seems to be a cost borne from pathogenic effects of the symbionts that ultimately compromises aphid fecundity and longevity. — CA

Proc. Natl. Acad. Sci. U.S.A.100, 1803 (2003).

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