Simplify the following text for a Grade 12 native English-speaking person.
Original: After graduation he moved to St Petersburg ( then called Leningrad ) , and studied under Yuri Filipchenko , who had a Drosophila lab .
Simplified: He then moved to Leningrad , Russia , to study under Yuri Filipchenko , where a Drosophila melanogaster lab had been established .