Purple Sea Snail, Violet Snail, Ianthina Snail
Phylum: Mollusca, Class: Gastropoda, Order: Littorinimorpha, Family: Epitoniidae (formerly Janthinidae), Genus: Janthina, Species: Janthina janthina · Epitoniidae (Wentletrap and Violet Snail family) · Gastropod (univalve); whole shell with a globose, helical spiral shape.
Species
Janthina janthina
Shell Type
Gastropod (univalve); whole shell with a globose, helical spiral shape.
Family
Epitoniidae (Wentletrap and Violet Snail family)
Size
Approximately 15-25mm (0.6-1.0 inches). This specimen is a typical adult size; the species usually ranges from 10mm to nearly 40mm.
Color & Pattern
Distinctive bicolor violet-purple. The underside (base) is a deep, rich violet, while the spire and upper surface are a pale lavender or lavender-gray. This is a natural counter-shading adaptation for its pelagic life.
Rarity
Uncommon (beach-found); while biologically common in the open ocean, the shells are extremely fragile and often shatter before reaching the shore, making intact specimens a lucky find.
Habitat
Pelagic/Neustonic; lives on the ocean surface in tropical and warm temperate waters, floating via a bubble raft.
Geographic Range
Circumtropical and subtropical; found worldwide in the warm currents of the Atlantic, Pacific, and Indian Oceans. Often washes up on beaches after storms.
Description
A beautiful, thin-walled, and lightweight shell with a globose shape and a short spire. The shell is remarkably fragile, designed for buoyancy rather than protection from predators. It features fine growth lines and a large, wide aperture with a simple, thin outer lip. The striking purple coloration is its most famous trait.
Key Features
Paper-thin structure, globose helical shape, and the unique dual-tone purple coloration (darker on bottom, lighter on top) which is reversed compared to most snails due to its upside-down floating position.
Collector Value
Low to Moderate ($5-$25 USD). While not expensive, they are highly desirable for their color and the difficulty of finding them unbroken on beaches. They are prized additions to 'shelf' collections because of their vivid hue.
Condition Notes
The shell appears remarkably intact for the species, lacking major chips on the fragile outer lip. The color remains vivid, qualifying it for a 'Fine' to 'Gem' collectibility grade depending on the hidden aperture condition.
Interesting Facts
The living snail builds a 'bubble raft' by trapping air in mucus with its foot to stay afloat. They are blind and spend their entire lives at the surface, where they prey on jellyfish like the Portuguese Man o' War (Physalia physalis) and Velella velella.
Ecological Role
Specialized predator of pleustonic cnidarians (surface-floating jellyfish). They help control populations of stinging siphonophores. They have no conservation protection but are sensitive to ocean plastic pollution.
Similar Species
Janthina globosa (rounder, more inflated) and Janthina exigua (smaller, with deeper sutures and more prominent ribs).
Beach Finding Tips
Look for them after strong onshore winds or tropical storms, particularly among rafts of 'blue bottle' jellyfish or Velella velella (By-the-wind sailors) that have washed ashore. Check the high-tide drift line carefully.