Purple Ocean Snail (Janthina janthina)
The Purple Sea Snail or Purple Ocean Snail has a delicate shell that grows up to 3.5 cms (1.4 inches) across and is light purple on top and dark purple below. This remarkable mollusc has adapted to life on the open ocean. It spends its life hanging from a raft made of mucous bubbles filled with gas that the snail creates and carefully maintains. This life raft of bubbles keeps the snail at the sea surface where it hunts for food. It mainly eats other ocean drifters such as Portuguese-man-of-war jellyfish, Blue Ocean Slugs and Velella.
The Janthina on its little raft of bubbles is carried wherever the wind or the ocean currents take it. Often after storms or when the wind has been consistently blowing on-shore for several days, rows of Purple Ocean Snails, Sargassum weed and other open ocean creatures can be found washed up on Bermuda’s beaches.
The closely related Pallid Janthina (Janthina pallida) is also rarely found in Bermuda. It is smaller, the shell is more highly domed and is a uniform lavender colour.
Janthina janthina shells are usually the size of a penny, but can grow up to twice that size. They are lavender on top and dark purple below.