CAULERPA TAXIFOLIA IN THE NORTHWEST MEDIT ERRANEAN - INTRODUCED SPECIES OR MIGRANT FROM THE RED-SEA

Specimens of the green alga Caulerpa mexicana Sender ex Kutzing were c ollected at Messina (Sicily) and transported to Monaco in February 199 5. Five days after transplantation into aguaria, the samples began met amorphosing into typical northwest Mediterranean C. taxifolia (Vahl) C . Agardh. Accompanying metamorphosis was novel production of the sesqu iterpene secondary metabolite, caulerpenyne, which was absent in pre-m etamorphosed samples. These results support the contention that C. mex icana and C. taxifolia are ecads of a single species; the former of wh ich has existed in the eastern Mediterranean since 1939. Biogeographic dispersion of the mexicana ecad, combined with the morphogenetic tran sformation reported here, may explain the occurrence of C. taxifolia i n the northwest Mediterranean. Northwesterly migration of this species and others previously localized in the Levant Sea, such as Caulerpa r acemosa (Forsk.) J. Agardh and the seagrass Halophila stipulacea (Fors k.) Ascherson, may have been assisted by recent warming of the western Mediterranean basin.