This study is the first work on the reproductive biology of lessepsian bivalve Fulvia fragilis. Monthly and bimonthly samplings were made in the period from April 2006 to October 2007, at the Bay of Tunis (northern Tunisia). From histological preparations of gonad, a gametogenic scale was drawn up based on eight stages: sexual rest; initiation of gametogenesis; advanced gametogenesis; ripe; partial spawning; advanced spawning; restoration; and spent. After examination of gonad preparations, F. fragilis appeared to be a simultaneous hermaphrodite species. Spawning was continuous all along the year, scarce in winter and with peaks during the rest of the year. The spawning peaks were positively correlated with the rise of the sea surface temperature and the nutrient availability. Furthermore, the presence of oocytes surrounded by spermatozoa in female and male follicles and in male gonoducts was observed. Self-fertilization may occur in this species. High summer mortalities probably due to the combination of vulnerability of the bivalve in response to the reproductive effort and high temperature stress were recorded. The F. fragilis reproduction strategy explains the success of its installation on the Tunisian coast.

A large number of Red Sea species are colonizing the eastern Mediterranean Sea after the opening of the sea-level Suez Canal in 1869, mainly following the Levantine and Anatolian coasts and then spreading westwards, at least in part, by shipping transport of larvae, juveniles, or adult specimens. Two of them are Cerithium scabridum and Fulvia fragilis, well established along the Italian coasts, where new large and stable populations have formed. Some other species, such as Anadara demiri, were accidentally introduced through shipping in our seas and have found good conditions to survive and develop. New distributional and ecological data about these alien molluscs are given and all the species found in association are listed to improve understanding of their living biocoenosis. The presence of a further lessepsian mollusc and of an intentionally introduced species, Brachidontes pharaonis and Ruditapes philippinarum, was also confirmed respectively from Vibo Valentia harbour and from the Gulf of Naples and the Gulf of Taranto. The nomenclature used is based on the CLEMAM Database (last research on 9 January 2008).