First documented occurrences
Arsenal Harbor (Venice Lagoon), Venice, Italy. Colonies observed on September 23, 2010. Colonies collected on January 26 and on June 12 and 22, 2012 by Davide Tagliapietra and colleagues; identified as Didemnum vexillum by Gretchen Lambert.
Tagliapietra, D., Keppel, E., Sigovini, M, and Lambert, G., 2012, First record of the colonial ascidian Didemnum vexillum Kott, 2002 in the Mediterranean: Lagoon of Venice (Italy): Bioinvasions Records v. 1 (in press). [link to pdf file]
First anecdotal occurrence
Observed in November 2007 on a wooden navigation piling on the western side of the Lido de Pallestrina, an island that separates the Venice Lagoon from the Adriatic Sea (45 deg 17.166 min N, 12 deg 18.133 min E). Source as above.