Since they arrived in the Great Lakes in the 1980s, two species of mussels the size of pistachios have spread to hundreds of lakes and rivers in 34 states and have done vast economic and ecological damage. These silent invaders, the quagga and zebra mussels, have disrupted ecosystems by devouring phytoplankton, the foundation of the aquatic food web, and have clogged the water intakes and pipes of cities and towns, power plants, factories and even irrigated golf courses. Now the mussels may have met their match: Daniel P. Molloy, an emeritus biologist at the New York State Museum in Albany...