Apple (NASDAQ: AAPL) said that Bertrand Serlet -- senior vice president of Mac Software Engineering -- will be leaving the company and would be replaced by Craig Federighi, who is currently the vice president of Mac Software Engineering.

Serlet, who joined Apple in 1997, has been a key player involved in the definition, development and creation of Mac OS X. He succeeded Avie Tevanian to the recent position in July 2003 and has been primarily responsible for the release of Mac OS X Tiger, Leopard and Snow Leopard. As vice president of Platform Technology, Serlet managed the largest part of the Mac OS software engineering group.

Before joining Apple, Serlet spent four years at Xerox PARC, then joined NeXT in 1989. NeXT was acquired by Apple in 1996.

I've worked with Steve for 22 years and have had an incredible time developing products at both NeXT and Apple, but at this point, I want to focus less on products and more on science, said Bertrand Serlet in a statement. Craig has done a great job managing the Mac OS team for the past two years, Lion is a great release and the transition should be seamless.

Serlet's successor Federighi, who will report to Apple's CEO Steve Jobs, is also responsible for the development of Mac OS X and has been managing the Mac OS software engineering group for the past two years.

Federighi worked at NeXT, followed by Apple, and then spent a decade at Ariba where he held several roles including vice president of Internet Services and chief technology officer. He returned to Apple in 2009 to lead Mac OS X engineering.

Shares of Cupertino, California-based Apple were down $2.66 to $338.54 in Wednesday's morning trade on Nasdaq.