Abstract
Biuve fulvipunctata (Baba 1938) is an Indo-West Pacific sea slug that was first described in Japan. Its striking coloration, particularly the distinctive W-shaped white mark on its cephalic shield, makes it easily recognizable and hard to miss. Reported as a non-indigenous species (NIS) in the Mediterranean Sea, it is hypothesized to be introduced via shipping and ballast water. Since its first sighting in 1959, it has spread across the eastern, central, and western Mediterranean Basin. In Libya, it has been observed in the western regions over a three-year period, from January to September, often in association with the brown alga, Colpomenia sp. and Hydroclathrus clathratus (C. Agardh) M.Howe, 1920, and the bryozoan Amathia verticillata (Delle Chiaje, Napoli: Fratelli Fernandes (vol. 1), and Società Tipografica, 1822). This study documents the first record of B. fulvipunctata in Libya and describes previously unreported aspects of the mating behaviour, including mating constellation, rivalry, and mating strategies.