Defending Pro12 champions Connacht suffered a shock defeat in the opening round of the 2016-17 season as they were humbled 41-5 by Glasgow Warriors.
The Irish side lifted the title for the first time in May, but their defence got off to a shaky start as Glasgow ran in five tries - including two for Tommy Seymour - to exact some revenge for last season's semi-final defeat.
Seymour opened the scoring after 11 minutes and added his second before the break, Glasgow scoring 33 unanswered points to romp to victory.
Stuart Hogg, Tim Swinson and Sean Lamont all crossed for the visitors, Henry Pyrgos and Rory Clegg adding the rest with the boot.
Ten points from Tyler Bleyendaal helped Munster claim victory on the opening day as they recorded a 23-13 victory against Scarlets.
The Munster fly-half kicked his side to victory at Parc y Scarlets, with scores from James Cronin and Ronan O'Mahony completing a good win in a clash between the two sides who finished just outside the top four last season.
Scarlets struggled to convert their chances and Munster - who gave a debut to Rassie Erasmus - made them pay.
Steven Shingler was Edinburgh's tormentor in-chief as Cardiff Blues opened their campaign with a 34-16 win.
A tight opening half saw only four points between the two sides, but the second 40 belonged to Cardiff, who ran away with proceedings.
Converted tries from Nick Williams and Tomos Williams came after Shingler had racked up 15 points as the Blues earned a bonus point.