Toyota and Mazda's project to build a $1.6 billion joint-venture auto plant in Huntsville, Ala., has gotten complicated over one very small matter: the spring pygmy sunfish. The automakers began construction preparation work this summer at the Alabama site, which is adjacent to one of the only known habitats of the fish, a protected endangered species since 2013. An environmental group called the Center for Biological Diversity has filed suit against the U.S. Fish and Wildlife Service in U.S. District Court for the District of Columbia, claiming that the agency has failed to protect the fish from the planned construction project. State, local and regional authorities worked for years to assemble the 2,400-acre Huntsville mega-site. The legal challenge could delay construction.