Fine-tuned manipulation
February 01, 2010
The effects of the larva are apparently due to chemical products that it introduces into the spider
A female wasp traps a spider Allocyclosa bifurca on its web and lays an egg on its abdomen. The egg grows into a larva that makes small holes in the spider’s skin so it can drink vital juices from the spider to survive.
The larva of Polysphincta gutfreundi matures and induces its host to build a modified, physically stable orb web, to which the larva then attaches its pupal cocoon. It also makes it add a linear silk to this web that may camouflage the cocoon that will turn into its killer, drinking its internal fluids until only its outer layer remains.
The effects of the larva are apparently due to chemical products that it introduces into the spider. Behavioral modification is gradual, and various behavioral effects arise in a consistent order.
William G. Eberhard, of the STRI staff, experimentally removed the larva just before it killed the spider. Then the spider’s behavior recovers gradually in exactly the reverse order. In addition, a greater delay in removing the larva leads to more pronounced and enduring behavioral changes, so the larval effects may depend on a cumulative or dose-dependent process.
Experiments like these are helpful for studying future animal behavior because the manipulations parasites make in their hosts’ behavior have “been honed by natural selection over long periods of time,” Eberhard told the blog Smithsonian Science. “Understanding how these mechanisms work promises new, exciting and potentially powerful access into determining how animal behavior is controlled.”
See Smithsonian.Com - Surprising Science
Eberhard, William G. 2010. "Recovery of spiders from the effects of parasitic wasps: Implications for fine-tuned mechanisms of manipulation." Animal Behaviour 79(2): 375-383.
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