WASHINGTON, Sept. 1 -- The Center for Biological Diversity, Tucson, Arizona, has submitted a public comment letter to the U.S. Fish and Wildlife Service urging the agency to move swiftly to protect the Barrens darter as an endangered species. The letter, representing 1.8 million members, highlights the urgent need for critical habitat designation for this fish, which is native to the Barrens Plateau in central Tennessee. In the letter, the Center emphasizes that the Barrens darter's survival is more ST