Janthina
Encyclopedia
Janthina is a genus
of small to medium-sized pelagic or planktonic sea snail
s, marine
gastropod molluscs in the family
Janthinidae
, commonly known as the "purple snails" or the "violet shells".
larvae, however, actively swim in the water column.
The adult snails prey upon (and live near to) one of several species of pelagic animals loosely known as jellyfish. More specifically they eat the medusae of free-swimming Cnidaria
, in particular the genus known as "by-the-wind sailors", Velella
.
The snails are able to float securely because they create a raft of clear chitin
around air bubbles formed near the ocean surface. They anchor to this raft using their foot. The snails do not have an operculum
.
These snails are frequently washed ashore during storms.
The common names for this genus derive from the light purple or violet color of the shells and the violet-colored bodies. The other genus in the family, Recluzia
, has olive-tan colored shells.
s of just a few species which have world-wide distributions in tropical waters. Experts disagree about some details of the synonymy.
Species within the genus Janthina include:
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of small to medium-sized pelagic or planktonic sea snail
Snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...
s, marine
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
gastropod molluscs in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Janthinidae
Janthinidae
Janthinidae, common name the purple snails or violet snails, are a family of pelagic sea snails, marine gastropod mollusks in the informal group Ptenoglossa of the clade Hypsogastropoda....
, commonly known as the "purple snails" or the "violet shells".
Description
These snails are pelagic and live at the surface of the ocean. Adult snails may not be capable of swimming, and die when they are detached from their rafts; Janthina janthinaJanthina janthina
Janthina janthina, common name the common purple snail, is a species of holoplanktonic sea snail, a marine gastropod mollusk in the family Janthinidae, the violet snails or purple storm snails.-Distribution:...
larvae, however, actively swim in the water column.
The adult snails prey upon (and live near to) one of several species of pelagic animals loosely known as jellyfish. More specifically they eat the medusae of free-swimming Cnidaria
Cnidaria
Cnidaria is a phylum containing over 9,000 species of animals found exclusively in aquatic and mostly marine environments. Their distinguishing feature is cnidocytes, specialized cells that they use mainly for capturing prey. Their bodies consist of mesoglea, a non-living jelly-like substance,...
, in particular the genus known as "by-the-wind sailors", Velella
Velella
Velella is a genus of free-floating hydrozoans that lives on the surface of the open ocean, worldwide, and is commonly known by the names by-the-wind sailor, purple sail, little sail, or simply Velella...
.
The snails are able to float securely because they create a raft of clear chitin
Chitin
Chitin n is a long-chain polymer of a N-acetylglucosamine, a derivative of glucose, and is found in many places throughout the natural world...
around air bubbles formed near the ocean surface. They anchor to this raft using their foot. The snails do not have an operculum
Operculum (gastropod)
The operculum, meaning little lid, is a corneous or calcareous anatomical structure which exists in many groups of sea snails and freshwater snails, and also in a few groups of land snails...
.
These snails are frequently washed ashore during storms.
The common names for this genus derive from the light purple or violet color of the shells and the violet-colored bodies. The other genus in the family, Recluzia
Recluzia
Recluzia is a genus of small to medium-sized pelagic or planktonic sea snails, marine gastropod molluscs in the family Janthinidae.-Species:* Recluzia annamitica Wattebled, 1886* Recluzia jehennei Petit, 1853...
, has olive-tan colored shells.
Species
This genus has accumulated a very large number of species names over the centuries. Most of the names that have been given are in fact synonymSynonym
Synonyms are different words with almost identical or similar meanings. Words that are synonyms are said to be synonymous, and the state of being a synonym is called synonymy. The word comes from Ancient Greek syn and onoma . The words car and automobile are synonyms...
s of just a few species which have world-wide distributions in tropical waters. Experts disagree about some details of the synonymy.
Species within the genus Janthina include:
- Janthina exiguaJanthina exiguaJanthina exigua, also known as the dwarf janthina, is a species of small holoplanktonic sea snail, a marine gastropod mollusk in the family Janthinidae, the violet snails or purple storm snails.- Distribution :...
Lamarck, 1816 - dwarf janthina - Janthina globosaJanthina globosaJanthina globosa is a species of holoplanktonic sea snail, a marine gastropod mollusk in the family Janthinidae, the violet snails or purple storm snails.- External links :*...
Swainson, 1822 - Janthina janthinaJanthina janthinaJanthina janthina, common name the common purple snail, is a species of holoplanktonic sea snail, a marine gastropod mollusk in the family Janthinidae, the violet snails or purple storm snails.-Distribution:...
(Linnaeus, 1758) - Janthina pallidaJanthina pallidaJanthina pallida, also known as the pale janthina, is a species of holoplanktonic sea snail, a marine gastropod mollusk in the family Janthinidae, the violet snails or purple storm snails....
W. Thompson, 1840 - Janthina umbilicataJanthina umbilicataJanthina umbilicata, also known as the elongate janthina, is a species of holoplanktonic sea snail, a marine gastropod mollusk in the family Janthinidae, the violet snails or purple storm snails....
d'Orbigny, 1841