Marine Invertebrate of the Week: Violet Snail

Every so often you might notice little purple shells washed up on the beach, usually during strong on-shore winds.  The common name for these animals is Violet Snails (Janthina spp.).  There are actually three different species, all purple in color, with three different styles of shell: Common, Dwarf, and Globular style.  They each secrete a bubble raft that they use to float on the surface of the open ocean, and they also secrete a purple dye when disturbed.  What’s unique about these snails is what they eat.  They prey upon Portuguese Man-O-War, Blue Buttons, and By-the-Wind Sailors.  If you’re a shell collector, beware that these shells are paper thin and very fragile.

Janthina spp. preying on Porpita pacifica

Portuguese Man-O-War (Physalia physalis)

Blue Button (Porpita pacifica)

By-the-Wind Sailor (Velella velella)

Bubble Float of Janthina spp.

Relative size of Janthina spp.