"I'm delighted and proud to have received the call-up to the squad," said Ryder.

"First and foremost, my focus is on helping Glasgow Warriors win tomorrow's massive Heineken Cup match in Bath, but I'm really looking forward to joining up with the rest of the Scotland squad, putting in a lot of hard work and challenging for a place."

Ryder could now win his first Scotland cap in the opening game of the tournament against England having worn the Red Rose at age-grade level.

The former Saracens star represented England from U16 upwards but qualifies for Scotland through his Glaswegian father, Paul.

Ryder joined Glasgow in August 2010 on a two-month loan deal but signed a permanent contract later that season.

He has since made 29 appearances in the RaboDirect PRO12 and a further six in the Heineken Cup and has also worn Scotland colours at A level.

The 6ft 5in, 18st 6lb forward impressed for Scotland's second string in the wins over Italy A and the USA last term and will now hope to be given the chance to make the step up to the senior XV against the country of his birth on February 4 or against Wales in Cardiff eight days later.

"It's a blow for Fraser but I've always stressed the importance of performing on Scotland A duty and consistently for your club. Tom has done this and deserves this chance," added Scotland head coach Andy Robinson.