A new geographical record of Polycera hedgpethi Er. Marcus, 1964 (Nudibranchia: Polyceridae) and evidence of its established presence in the Mediterranean Sea, with a review of its geographical distribution

This article reports the first record of the Nudibranch Polycera hedgpethi in the Lagoon of Venice (Italy), as well as its established presence in the Mediterranean Sea after its first record in 1986 in lake Fusaro (Naples). In less than 50 years P. hedgpethi has spread throughout the world's temperate and subtropical waters, preferring protected coastal environments and other semi-enclosed coastal water bodies such as ports, harbours and lagoons. Shipping is the most likely vector. The species distribution shows a temperate-subtropical range, at about 7-45 degrees of latitude both North and South. Polycera hedgpethi was collected during a survey in 2009 and its presence confirmed for the following two years. All individuals collected were found attached to the bryozoan Bugula neritina, to which it is linked trophically, suggesting a determined pattern of distribution. The present finding is the northernmost record for the species.