Violet Sea-snail Shell | Mexican Shells.org

Violet Sea-snail Shell, Janthina janthina

Violet Sea-snail Shell, Janthina janthina. Shell collected at sea off the surface in the greater Los Cabos area, May 2018. Size: 2.0 cm (0.8 inches) x 1.5 cm (0.6 inches).

Violet Sea-snail Shell, Janthina janthina. Shells collected off the beach in the greater Los Barilles area, Baja California Sur, January 2024. Size: 1.8 cm (0.7 inches) to 2.0 cm (0.8 inches). Collections, photograph and identifications courtesy of Brad Murakami, Surrey, British Columbia.

Phylogeny: The Violet Sea-snail Shell, Janthina janthina (Linnaeus, 1758), is a gastropod mollusk that is a member of the Epitoniidae Family of Wentletraps and Violet Snail Shells. The genus Janthina is one of seventy-one genera in this family, and there are eight species in this genus. They are also known as the Common Purple Sea Snail Shell, the Common Janthina Shell, and the Large Violet Shell and in Mexico as Lantana Morada. The genus name Janthina comes from the Greek word meaning violet-blue. Because these shells are free-floating drifters they are considered to be a form of holoplankton. Note: taxonomy for this species is currently in flux. The order Caenogastropoda incertae sedis means that no one currently knows where this shell fits. The family was changed within the past decade from Janthinidae or Ianthinidae to Epitoniidae, with most family members not physically resembling this shell.

Description: Violet Sea-snail Shells have a globular shape and consist of six whorls. They have a fairly low spire, when compared to other purple sea snails in the region. Their exterior is smooth. The top exterior surface of the shell is purple to violet in color and the bottom is lavender to white; the interior is white. Violet Sea-snail Shells reach a maximum of 4.0 cm (1.6 inches) in diameter.

Habitat and Distribution: Violet Sea-snails live on the surface of the open sea. They are found worldwide in subtropical to tropical seas and in all Mexican waters of both the Atlantic and the Pacific Oceans. They are seldom seen, but when they are, they are usually in very large groups with most are seen after being pushed ashore by the wind.

Ecology and Behavior: Violet Sea-snails are predators that feed on zooplankton including haliobatids, hydrozoans, siphonophores, and other Janthinas, such as the Blue Button, Porpita porpita and the By-the-Wind Sailor, Velella velella. In turn they are preyed upon by sea birds, fish, sea turtles, and other pelagic mollusks are common predators for these shells. They are protandric hermaphrodites and reproduce sexually, with internal fertilization. They are ovoviviparous, with the eggs developing internally and being released as veliger larvae. Their engagement in any type of commensal, parasitic, symbiotic relationships has not been formally documented. They are known to host the Small Goose Barnacle, Lepas pectinata, as an epibiont. They construct their bubble rafts by attaching together bubbles made by the extension and contraction of their propodium. From a conservation perspective they have not been formally evaluated. However, they are fairly common with a very wide distribution and should be consider to be of Least Concern.

Synonyms: Helix janthina, Ianthina affinis, Ianthina africana, Ianthina balteata, Ianthina bicolor, Ianthina bicolor var. minor, Ianthina britannica, Ianthina caeruleata, Ianthina casta, Ianthina depressa, Ianthina fibula, Ianthina grandis, Ianthina involuta, Ianthina planispirata, Ianthina roseola, Ianthina smithiae, Ianthina striulata, Ianthina striulata var. contorta, Ianthina trochoidea, Janthina (Achates) carpenteri, Janthina (Achates) orbignyi, Janthina auriculata, Janthina bicolor, Janthina bicolor, Janthina bicolor var. conica, Janthina bicolor var. major, Janthina communis, Janthina costae, Janthina fragilis, Janthina penicephala, Janthina rotundata, Janthina violacea, and Janthina vulgaris.