Shannon endured a baptism of fire on their return to Energla All-Ireland League Men's Division 1A with a 39-3 defeat to Terenure College, last season's runners-up.
Signalling their intent for the season ahead, Sean Skehan's Terenure side ran in six unanswered tries at Thomond Park with debutant winger Matthew Bowen claiming the last of them.
Dylan Donnellan continued where he left off last season with a brace of tries in Clontarf's hard-fought 24-19 bonus point victory at UCD.
Cork Constitution came from nine points down to pip Young Munster 19-18, with captain Aidan Moynihan landing a 79th-minute match-winning penalty.
The Temple Hill faithful were fearing the worst when Conor Hayes crossed for his second try, moving Munsters into a 15-6 lead early in the second half.
However, Moynihan converted replacement James Murphy's try and added two penalties, the last of them cancelling out an Evan Cusack effort that had edged the Cookies back in front.
Dublin University stormed straight to the top of the table courtesy of a barnstorming eight-try display at Dooradoyle.
Tony Smeeth's youngsters, who included seven AIL debutants, ran out 50-14 winners over Garryowen with excellent out-half Aran Egan scoring a hat-trick of tries and 25 points in all.
The shock result in the top flight came on the Aviva Stadium's back pitch where Ballynahinch edged out Lansdowne in a nine-try thriller.
Out-half Greg Hutley's 72nd-minute penalty handed 'Hinch a famous 34-31 bonus point victory. George Pringle (2) and debutants Mark Best and Fergus Jemphreys, an Ireland Sevens international, shared out their tries.
In Division 1B, there was a winning start for UCC's new director of rugby, Michael Bradley. Half-backs Aaron Quirke and Andrew O'Mahony both touched down in a 36-12 bonus point triumph at Malone.
David Poff's try inside the opening minute put early leaders Old Wesley on course to beat old foes Naas 37-7. Cian Bohane's two tries helped Highfield to beat Banbridge 26-20.
Connor Owende marked his 100th AIL appearance with a try in Old Belvedere's 32-28 win over Sean Cronin's St. Mary's. Buccaneers, now coached by Eddie O'Sullivan, lost 22-20 at City of Armagh who had a try each from Ulster duo Frank Bradshaw-Ryan and James McCormick.