Michael Shannon, the first and only American dancer to study with the Bolshoi Ballet Academy, was absent from the opening-night bill when the academy began its U.S. tour this week at Wolf Trap in Virginia, but he did perform the second night. The 19-year-old dancer, who is from L.A., has received a lot of attention. He was taken off the opening-night program in a last-minute change by artistic director Sophia Golovkina. “There was no reason. . . . It was just a regular casting change,” said Susan Arons, a spokeswoman for the company. Shannon is expected to dance at the troupe’s next stop in Indianapolis. The company comes to the Southland later July 25.