Physalia physalis (Linnaeus, 1758)
Common in the Solitary Islands Marine Park. Found throughout the Indian and Pacific oceans.
Drifts on the ocean surface trailing a long tentacle which it uses to catch plankton, small fish and crustaceans.
Physalia physalis is not a single animal but consists of colonies of four specialized polyps and medusoids (tentacled heads) that drift on the surface of the oceans. Bouyancy is provided by the blue coloured gas-filled bladder, and a long tentacle containing venomous nematocysts measuring up to 3m trails underneath. With strong on shore winds, thousands of individuals sometimes become stranded on beaches, where their toxic nematocysts can remain potent even dried in the wind and sun. May cause intense pain to swimmers but not known to cause fatalities. Predators are known to include Loggerhead and Leatherback turtles and the Common Violet Snail, Janthina janthina. The float may reach 150mm but 75 to 100mm in length is more common.