Bizarre snail that swims like a flying insect
Snails usually lumber along on their single fleshy foot; but not sea butterflies (Limacina helicina). These tiny marine molluscs gently flit around their Arctic water homes propelled by fleshy wings that protrude out of the shell opening. But little was known about how they move through water. "Most zooplankton swim with a drag-based paddling technique," explains David Murphy from the Georgia Institute of Technology, USA, and even though one of Murphy's thesis advisors - Jeannette Yen - had filmed one of the enigmatic snails swimming while it was attached to a wire in 2003, it had not been possible to observe how fluid flowed around the animals to explain how they move. So, when Murphy built a new 3D system to visualise fluid movements around minute animals, Yen and Don Webster were keen to test more sea butterflies as they swam freely to discover more about their exotic mode of...