Janthina prolongata

Janthina prolongata De Blainville, 1822


This is a large, deep violet shelled pelagic snail, 2.4 cm high. It lives in the pleuston and does not have swimming fins. The dextral shell with about 4 whorls is depressed. The body whorl increases rapidly, the aperture is large and oval. There is a small keel and an faint incision in the outer aperture rim. The operculum is absent in adults. It is a carnivore which predates on relatively large floating prey animals. This species occurs in the warm waters of all oceans (Janthina prolongata 3).

Taxonomic Description

The deep violet shell is fragile, dextral and globose. The rim of the aperture, with a sinus slightly above the middle, curves regularly. The surface is relatively roughly striated with a fish-bone pattern from the middle of the whorl. The apex is well defined, the body whorl is large, the aperture is wide. A low keel is seen on all whorls. The shell is thin and translucent. The aperture is higher than wide by the long columella (Janthina prolongata, Janthina prolongata 1, Janthina prolongata 2). The operculum is absent in adults. The jaws are large, the radula is powerful and has numerous teeth, the central teeth are lacking. The species is variable, and hence an extra illustration is given here (Janthina prolongata 4, Janthina prolongata 5, Janthina prolongata 6).
Shell height up to 24 mm, aperture height up to 22 mm aperture width up to 13.5 mm.


The juveniles have a dextrally coiled shell. A special description is not available.


This species is a viviparous, protandric hermaphrodite.


This species is a carnivorous surface dweller which feeds on: Porpita,Velella, Janthinidae, Haliobatidae and Siphonophora (less preferred: Physalia). Cannibalism is found.


This species lives in the warm waters of all oceans, see the Janthina prolongata map.


Janthina prolongata De Blainville, 1849: 155.
Types and type locality not indicated.