A Canadian insurer will be making changes at the top.

Donald Guloien, who has worked for Manulife Financial Corp., Toronto, for 28 years, will succeed Dominic D’Alessandro as president and chief executive May 7, 2009, the company says.

D’Alessandro, who has led Manulife since 1994, will be retiring, the company says.

Guloien is now senior executive vice president and chief investment officer at Manulife.

Manulife also says John D. DesPrez III, who also has been a senior executive vice president, will become chief operating officer.

DesPrez will be responsible for insurance and wealth management operations in Canada, the United States, Asia and Japan, Manulife says.

DesPrez will continue to be president of the company’s John Hancock Financial Services, Manulife says.