Three-tooth Cavoline Cavolinia tridentata
This species of sea butterfly has a small, almost transparent, spherical shell with three distinctive, posterior projections. The shell also has two slits through which large extensions of the mantle pass. These brownish “wings” are ciliated and so can create weak water currents as well as aid buoyancy. Sea butterflies are unusual among shelled mollusks in that they can live in open water. Like other members of this group, the three-tooth cavoline produces a mucus web very much larger than itself, which traps planktonic organisms, such as diatoms and the larvae of other species. It eats the web and the trapped food at intervals, then produces a new one. During their lifetime, sea butterflies change first from males into hermaphrodites and then into females.