Strobilation in a species of Bougainvillioidea (Cnidaria, Hydrozoa)

In november 1994 several specimens of an unknown hydroid were collected in a tank of the Genoa Aquarium (Italy). The polyps, characterised by filiform tentacles around a proboscis, displayed unusual asexual reproduction, lead ing to a linear chain of three elements (strobilation) joined by alternate oro-aboral polarity. This hydroid is very similar to another, unidentified hydroid collected in 1954 in San Francisco Bay. The hydroid of the Genoa Aq uarium released free medusae characterised by four marginal tentacles, four radial canals and four oral tentacles around a tubular mouth. These featur es indicate that the species belongs to the superfamily Bougainvillioidea.