19 Jun, 06:50
A single point separated the sides as a hard-fought 5th-8th place play-off finished in France's favour at Stade Henri Desgrange on Tuesday night. Check out some photos from Ireland's fourth IRB Junior World Championsip match.
A student of medicine, the 23-year-old lock was also selected for the Pumas' end of year tour to Europe in 2008.
Commenting on the signing, Leinster team manager Guy Easterby said: "Mariano has made a real impression for Argentina since his senior international debut and we are pleased to have secured his signature as cover until the end of January.
"Obviously both Leo (Cullen) and Kevin (McLaughlin) will each miss a significant part of the early half of the season, so it is great that we have been able to cover them with a quality player."