The Float-making Barnacle (Dosima fascicularis), is a specialised pleustonic goose barnacle species. It hangs downwards from the water surface, held up by a float of its own construction, and is carried along by ocean currents.
As an adult, D. fascicularis lives attached to a float made either of natural flotsam or of a cement it secretes itself, which has a texture like that of expanded polystyrene foam. It is the only barnacle to produce its own gas-filled float. The cyprid larvae are planktonic, and must attach to a float for metamorphosis into the adult form, but the adults are eventually capable of using their own float, sometimes forming aggregations of many individuals attached to a single float. Among the floats used by adult buoy barnacles are seaweeds , plastic debris, driftwood, feathers, cuttlefish bone, they have even been known to colonise the backs of turtles. It is a fugitive species, which can be out-competed by other barnacle species, and relies on being able to colonise surfaces and reproduce quickly; after settling on a float, D. fascicularis can reproduce within 45 days. D. fascicularis appears to be increasing in abundance as a result of anthropogenic marine debris accumulating in the sea.This source of floats was of "minor importance" in 1974.
D. fascicularis has a cosmopolitan distribution, with a preference for temperate seas, having been found at latitudes from 71° North off Siberia to 57° South near Cape Horn. Groups have been observed journeying from Japan to the Hawaiian Islands in the Pacific Ocean, and sometimes wash up on westerly beaches in the British Isles. It is not normally found in the Mediterranean Sea, but may have begun to colonise there from the Atlantic Ocean.