Photo by Alessandro Catenazzi

From National Geographic News comes this:

Once the parasitic crustaceans enter the gills of a tadpole victim, they feed off the tadpole's tissues until male and female parasites mate. The male dies soon after. Meanwhile the fertilized female bores her way partially out of the tadpole.

Yes, and then the tadpole develops into a small, weak frog possibly with no hind legs or missing an eye or otherwise deformed. The NGN briefing summarizes a report just published in the journal Copeia about this parasitic copepod, Lernaea cyprinacea , which has proliferated in the overwarm waters of South Fork Eel River and wormed its way into Foothill Yellow-legged frogs, Rana boylii .