Differenze nella life history di tre popolazioni di Ophryotrocha japonica (Polychaeta: Dorvilleidae).

This paper examines the life history and demography of three populations of Ophryotrocha japonica an alien species that for until 2001 had only been reported in harbour environments along the Asian and American coasts of the Pacific. The populations analysed came from the Italian harbors of Leghorn and Ravenna and from the brackish Mar Piccolo of Taranto. The three strains are inter-fertile both with one another and with their Pacific counterparts. Notwithstanding among populations were found morphological, reproductive and demographic differences. In Leghorn and Taranto populations there is a sort of sexual dimorphism based on body size that is not present in the Ravenna strain. The most important differences concern the reproductive characteristics. Indeed, fecundity, eggs size and reproductive investment varies greatly between populations. The differences in the life history determine very important consequences for the demography and fitness of the populations, and may depend on the species’ adaptation to different environment or may be the result of independent introduction from different localities or at different times.