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Do You Know what a Buoy Barnacle is?

Dosima fascicularis, the
buoy barnacle, is “the
most 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 pellets of tar,
seaweeds, plastic debris, driftwood, feathers, cranberries,
cuttlefish bone, the “by-the-wind-sailor” Velella velella,
seagrass leaves, Styrofoam, seeds, and even apples;
they have even been known to colonise the backs of
turtles and the sea snake Pelamis platurus. 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.
Compliments of & Nico Opperman – photography

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