Alien seaweed is aquarium escapee.

New genetic tests confirm what biologists had long suspected: Aggressive alien algae blanketing ever larger patches of the Mediterranean seafloor (SN: 7/4/98, p. 8) appear to be clones of specimens in several major aquariums--and demonstrably different from any wild members of their species. This Caulerpa taxifolia appears to be so genetically distinct from its brethren elsewhere in the wild that it likely constitutes a new strain, European researchers say.

Olivier Jousson of the Marseille Center for Oceanology in France and his coworkers deciphered a characteristic stretch of the DNA sequence from 18 separate specimens of the species: 2 from the Caribbean; 1 from Japan; 10 from the Mediterranean; 4 from public aquariums around the world, including one in Hawaii; and 1 from an aquarium shop in Geneva. They also sequenced the same genetic span from four other species of wild Caulerpa.

In the Oct. 22 Marine Ecology Progress Series, Jousson's team reports that its analyses "revealed the presence of a striking similarity between all of the Mediterranean and aquarium C taxifolia." Asked to elaborate, the Marseille Center's team leader, Charles E Boudouresque, told Science News that the analyzed DNA sequences in all 14 plants in the Mediterranean and aquariums are identical and likely trace to a common aquarium source. His team has since found the identical seaweed in two more aquarium shops, suggesting the alga is still being sold in the aquarium trade despite calls for bans (see following story).