Malaria, Sea Grapes, and Kidney Stones: A Tale of Parasites Lost

If you're looking for a gang of vicious killers, look no further than the Apicomplexans. These single-celled protozoans cause death and destruction across the animal kingdom. They infect everything from butterflies to people. Their diseases include Texas Cattle Fever, toxoplasmosis, and the scourge that makes Plasmodium the baddest Apicomplexan of them all, malaria. Scientists have named 6,000 apicomplexans, but they estimate there may be anywhere between 1.2 and 10 million species waiting to be identified. Every apicomplexan they'd studied so far is equipped with the same fearsome weaponry. Their cells are shaped like teardrops, and at the pointed end they have a ring of tubes, like the chambers on a revolver. When an apicomplexan prepares to invade a cell, it points those chambers at its prospective host and fires a set of molecules that grab the cell's surface and stretch it open so that the apicomplexan can slide in. Apicomplexans inherited their weaponry from their common ancestor, which lived several hundred million years ago, and they've thrived as pathogens ever since. Yet in the midst of this brutal dynasty, scientists have now discovered a peacemaker. For the first time, they've found an apicomplexan that bestows a biochemical gift to its host essential for survival.