Friday Parasite: Making an Escape
The horsehair worm Spinochordodes tellinii gets a lot of press because it’s one of those insidious host-manipulating parasites that fascinates people even as it grosses them out. The worm’s larvae live inside of grasshoppers, but adult worms are free-living and aquatic. Unfortunately, grasshoppers are definitely not known for their swimming ability, leaving the worm in a bit of a fix – how to get into a body of water to mature and mate when your host shows no inclination to take you there? The answer? Mind control. S. tellinii leaves nothing to chance: taking control of the grasshopper’s brain, making it look for a body of water and jump into it, thus drowning the host but freeing the worm.
But this behavior sometimes leads to another problem for the worm: thrashing, drowning grasshoppers can attract predators before the worm has freed itself. If the dying host gets eaten, the hairworm can get swallowed up too. If it acts fast, it can use the same escape behavior that would have taken it out of the grasshopper to get out of a fish or a frog, squirming its way out of gills, mouth, or nostrils. But the clock is ticking – if the process takes more than 5 minutes, it’s curtains for the hairworm.
Source (& image from)
Ponton, F. et al. 2006. Parasite survives predation on its host. Nature 440: 756.








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