Abstract
In the Mediterranean Sea, Polylabris tubicirrus (Monogenea, Polyopisthocotylea) is found only on breams of the genus Diplodus : D. sargus, D. annularis, D. vulgaris. The discovery of this parasite on farmed gilt head sea breams (Sparus aurata) raises the problem of the enlargement of the host range of a parasite under artificial conditions of confinement, and of the potential danger this type of transfer can involve.