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Janthina

Janthina is a genus of small to medium-sized pelagic or planktonic sea snails that belongs to the family Epitoniidae. Species in this genus occur worldwide in tropical, subtropical and warm seas.

The common names for this genus derive from the light purple or violet color of the shells and the violet-colored bodies. The other genera in the family, Recluzia, has olive-tan colored shells.

Description

They are small to medium sized and their shells and bodies often have a light purple to violet coloration. These snails do not have an operculum.

Behavior

This genus exhibits hermaphroditism meaning that they produce both male and female gametes.

These snails are frequently washed ashore during storms.

Raft

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. Adult snails may not be capable of swimming, and die when they are detached from their rafts; Janthina janthina larvae, however, actively swim in the water column. The evolution of their rafts start with the proto-janthinid ancestor which was benthic with females tethering egg masses with associated males. Then these eggs become buoyant.

Diet

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, they feed on the genus Velella (by-the-wind sailor) however some species, such as J. janthina, feed on it along with other jellyfishes such as Physalia physalis (Portuguese man o' war) while other species such as J. pallida prey solely on Velella.

Species

<div align=center> The five extant species of the genus Janthina

</div align=center>

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 synonyms 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:

Species brought into synonymy:
  • Janthina affinis <small>Reeve, 1858</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina africana <small>Reeve, 1858</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina alba <small>Anton, 1838</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina balteata <small>Reeve, 1858</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina bicolor <small> Menke, 1828</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina bicolor <small>O. G. Costa, 1830</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina bifida <small>Nuttall, 1850</small>: synonym of Janthina exigua <small>Lamarck, 1816</small>
  • Janthina britannica <small>Forbes & Hanley, 1853</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina capreolata <small>Montrouzier, 1860</small>: synonym of Janthina exigua <small>Lamarck, 1816</small>
  • Janthina carpenteri <small>Mörch, 1860</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina casta <small>Reeve, 1858</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina coeruleata <small>Reeve, 1858</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina communis <small>Lamarck, 1822</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina contorta <small>Carpenter, 1857</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina costae <small>Mörch, 1860</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina decollata <small>Carpenter, 1857</small>: synonym of Janthina globosa <small>Swainson, 1822</small>
  • Janthina depressa <small>Reeve, 1858</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina elongata [sic]: synonym of Janthina globosa <small>Swainson, 1822</small>
  • Janthina fibula <small>Reeve, 1858</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina fragilis <small>Lamarck, 1801</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina globosa <small>Blainville, 1822:</small> synonym of Janthina umbilicata <small>d'Orbigny, 1840</small>
  • Janthina grandis <small>Reeve, 1858</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina incisa <small>Philippi, 1848</small>: synonym of Janthina exigua <small>Lamarck, 1816</small>
  • Janthina involuta <small>Reeve, 1858</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina iricolor <small>Reeve, 1858</small>: synonym of Janthina globosa <small>Swainson, 1822</small>
  • Janthina jehennei <small>(Petit de la Saussaye, 1853)</small>: synonym of Recluzia jehennei <small>Petit de la Saussaye, 1853</small>
  • Janthina laeta <small>Monterosato, 1884</small>: synonym of Janthina pallida <small>W. Thompson, 1840</small>
  • Janthina megastoma <small>A. Adams, 1861</small>: synonym of Janthina umbilicata <small>d'Orbigny, 1840</small>
  • Janthina nana <small>Gray, 1842</small>: synonym of Janthina globosa <small>Swainson, 1822</small>
  • Janthina nitens <small>Menke, 1828</small>: synonym of Janthina globosa <small>Swainson, 1822</small>
  • Janthina nitida <small> A. Adams, 1861</small>: synonym of Janthina exigua <small>Lamarck, 1816</small>
  • Janthina orbignyi <small>Mörch, 1860</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina patula <small>Philippi, 1844</small>: synonym of Janthina pallida <small>W. Thompson, 1840</small>
  • Janthina payraudeaui <small>Locard, 1900</small>: synonym of Janthina globosa <small>Swainson, 1822</small>
  • Janthina penicephela <small>Peron, 1824</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina planispirata <small> A. Adams & Reeve, 1848</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina prolongata <small>Blainville, 1822</small>: synonym of Janthina globosa <small>Swainson, 1822</small>
  • Janthina rosea <small>Anton, 1838</small>: synonym of Janthina pallida <small>W. Thompson, 1840</small>
  • Janthina roseala <small>Reeve, 1858</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina roseola <small>Reeve, 1858</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina rotundata <small>Dillwyn, 1840</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina smithiae <small>Reeve, 1858</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina splendens <small>Monterosato, 1884</small>: synonym of Janthina globosa <small>Swainson, 1822</small>
  • Janthina striata <small>Montrouzier, 1860</small>: synonym of Janthina exigua <small>Lamarck, 1816</small>
  • Janthina striolata<small> A. Adams & Reeve, 1848</small>: synonym of Janthina pallida <small>W. Thompson, 1840</small>
  • Janthina striulata <small>Carpenter, 1857</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina trochoidea <small>Reeve, 1858</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina vinsoni <small>Deshayes, 1863</small>: synonym of Janthina exigua <small>Lamarck, 1816</small>
  • Janthina violacea <small>Röding, 1798</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>
  • Janthina vulgaris <small>Gray, 1847</small>: synonym of Janthina janthina <small>(Linnaeus, 1758)</small>

References

  • Laursen, D. 1953. The genus Ianthina: A monograph. Dana Report 38: 1-40, pl. 1

External links