As soon as the stingray barb slashed through skin and muscle above her knee, Nikki Johnson-Kunz collapsed onto the deck of her family’s shrimping boat. She’d just docked and had been sorting through four hundred pounds of shrimp when she grabbed the writhing stingray to free it from the netting. The venom injected into the wound stunned her body and blurred her vision. A man strolling by raced over to help, and when she came to, she saw four of him.“The boat looked like a murder scene,” Nikki recalls as she hands over her phone to show me some gruesome photos. I feel queasy but also impressed. She then recounted how she duct-taped the wound and drove herself to a nearby emergency room. The injury…