Tiny sea snail 'swims like a bee'

By Jonathan Webb

Science reporter, BBC News

A tiny species of sea snail "flies" underwater using movements just like winged insects, according to a study.

US scientists observed the so-called sea butterfly - actually an aquatic snail - using high-speed video and flow-tracking systems.

The 3mm critter flaps its wing structures, which grow where a snail's foot would normally be, in a characteristic figure-of-eight pattern.

It also uses some of the vortex-making tricks that keep insects in the air.

"It looks like it's flying, like a very small insect," said Dr David Murphy, a mechanical engineer at Johns Hopkins University.

The study, published in the Journal of Experimental Biology, was part of his PhD research while studying at Georgia Tech.

Honorary insect

Limacina helicina is a bizarre-looking predatory mollusc which, when not displaying its swimming prowess, makes large webs of mucus to filter-feed on smaller plankton.

Its insect-like acrobatics are "a remarkable example of convergent evolution", the researchers write. In other words, the same trait has evolved more than once in completely independent lineages.

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