#9 THE CLAWED FROG – Xenopus laevis
Warty, slimy and somewhat dead-looking, the African clawed frog Xenopus laevis is a truly unlikely hero. The frogs are popular primarily for their tractability—large eggs and embryos are ideal for microsurgery—but also because of a historical quirk. In the 1930s scientists discovered that female Xenopus ovulate when injected with the urine from a pregnant woman, a feature that made egg harvesting convenient. More recently, the frogs have inspired a new kind of visual test for banned performance enhancing drugs: drugs bind to receptors in their skin, triggering a color switch.
