''Janthina globosa'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

holoplankton Holoplankton are organisms that are planktic (they live in the water column and cannot swim against a current) for their entire life cycle. Holoplankton can be contrasted with meroplankton, which are planktic organisms that spend part of their lif ...

sea snail Sea snail is a common name for slow-moving marine gastropod molluscs, usually with visible external shells, such as whelk or abalone. They share the taxonomic class Gastropoda with slugs, which are distinguished from snails primarily by the ...

, a

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...

in the family

Epitoniidae Wentletraps are small, often white, very high-spired, predatory or ectoparasitic sea snails, marine gastropod mollusks in the family Epitoniidae.Gofas, S. (2010). Epitoniidae. In: Bouchet, P.; Gofas, S.; Rosenberg, G. (2010) World Marine Mollu ...

, the violet snails or purple storm snails.MolluscaBase (2019). MolluscaBase. Janthina globosa Swainson, 1822. Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=214493 on 2019-10-09

Anatomy and Morphology

''Janthina globosa'', commonly referred to as the violet snail, is a neustonic organism characterized by its thin, fragile purple shell and large size The maximum recorded

shell Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses ** Thin-shell structure Science Biology * Seashell, a hard ou ...

length is 38.5 mm.Welch J. J. (2010). "The "Island Rule" and Deep-Sea Gastropods: Re-Examining the Evidence". '' PLoS ONE'' 5(1): e8776. . Females normally grow to larger sizes than males, making it easy to distinguish between the sexes. ''Janthina globosa'' has a glossy shell, characterized by four symmetrical spirals evenly spaced on its shell. Inside its shell lives the organism itself. Protected by its hard outer shell, ''Janthina globosa'' has a soft body with forked cephalic tentacles on its belly, used for many different things like locomotion and receiving sensory input. Its unique purple color serves to camouflage itself in its environment and also serves as an efficient means of obtaining food, making it a better predator. It and many other members of the ''Janthina'' genera have an epipodium that is thought to help with balance in the water (Wilson and Wilson, 1956, 301).

Feeding and Preferred Prey

It secretes a purple dye (the same dye that gives it its purple color) to paralyze its prey, allowing it to eat its target without much of a fight. Although ''Janthina globosa'' seems like a harmless snail, it is an incredibly successful predator. Its most popular prey, based on scientific observation, seems to be

Velella ''Velella'' is a monospecific genus of hydrozoa in the Porpitidae family. Its only known species is ''Velella velella'', a cosmopolitan free-floating hydrozoan that lives on the surface of the open ocean. It is commonly known by the names sea raf ...

(Wilson and Wilson, 1956, 301) ''.'' Although scientists have observed that ''Velella'' is its favored prey option, upon gut analysis it seems that ''Janthina globosa'' will eat just about anything, even exhibiting cannibalistic behaviors by eating members of its own species. ''Velella'' has stinging

nematocysts A cnidocyte (also known as a cnidoblast or nematocyte) is an explosive cell containing one large secretory organelle called a cnidocyst (also known as a cnida () or nematocyst) that can deliver a sting to other organisms. The presence of this c ...

that they use to defend themselves and to capture prey. ''Janthina globosa'' are able to tolerate the poison excreted from ''Velella’s'' nematocysts, making them an easy target for predation by ''Janthina globosa''. Unlike many other marine animals, ''Janthina globosa’s'' diet does not change too much as it matures. ''Janthina globosa'' seems to prefer larger ''Velella'' over smaller bodied ''Velella'' due to the availability of more soft tissue to eat as compared to the smaller members of that species. Since ''Velella'' is their preferred prey, ''Janthina globosa'' will appear in places it is not normally found if there is a large amount of ''Velella'' prey to consume. This makes the population size of ''Velella'' a good predictor of ''Janthina globosa'' location and population size (Deudero S, Pinnegar J, Polunin N. 2002).

Distribution and Habitat

Four other species that fall in the genera ''Janthina'' can be found in the Mediterranean Sea (along with ''Janthina globosa)'' but they are also found between these latitudes: 50°N and 40°S. If conditions permit it, these snails can be found outside these latitudes. Strandings of this species and others of its genera are also due to wave and current movements (F. Betti et al 2017). Minimum recorded depth is 0 m. Maximum recorded depth is .

Taxonomy

''Janthina globosa'' was first captured in 1822 off the

Gulf of Antalya The Gulf of Antalya ( tr, Antalya Körfezi) is a large bay of the northern Levantine Sea, in the eastern Mediterranean Sea south of Antalya Province, Turkey. It includes some of the main seaside resorts of Turkey, also known as the "Turkish Riviera ...

in the Northeastern part of the Mediterranean Sea (Teker S, Gökoğlu M , Julian D. 2017). The oldest fossil of the ''Janthina'' genera was found on

Santa Maria Island Santa Maria () is an island in the Eastern Group, Azores, eastern group of the Azores archipelago (south of the island of São Miguel Island, São Miguel) and the southernmost island in the Azores. The island is known for its white sand beaches, ...

in the Atlantic, but the earliest record of ''Janthina globosa'' specifically is unclear, despite its long fossil record (Record of the Australian Museum, 2017, 142). Many other species fall in the genera ''Janthina''. ''J. globosa'' most likely evolved from the species ''J. krejcii'', but it looks more like ''J. pallida'' (Record of the Australian Museum, 2017, 160-161). It is thought that ''Janthina globosa'' was used as a source of purple dye for clothes in ancient times.

Behavior

This species lives its life upside down attached to air bubbles that it made itself, forming a self-made float. These air bubbles are produced by a specialized organ called the propodium. This organ sucks air from above the surface of the water to create a bubble. It then coats it with a covering of mucus before adding it to the bottom of the float. It is further adhered to the float with more mucus to ensure it is secure. This bubble making process has been timed and it took one organism of the ''Janthina'' genera about a minute to completely form one bubble (Wilson and Wilson, 1956, 300). This mechanism of staying afloat is almost entirely unique to the ''Janthina'' genera, with the one exception being the ''Recluzia''. ''Janthina globosa'' is not restricted to living in the open ocean; they can also live in enclosed bays if the weather conditions allow them to.

Reproduction

''Janthina globosa'' is hermaphroditic and reproduces sexually. This means that it does not stay as the sex that it was at birth but begins life as a male, and then exhibits a cycle of

protandry Sequential hermaphroditism (called dichogamy in botany) is a type of hermaphroditism that occurs in many fish, gastropods, and plants. Sequential hermaphroditism occurs when the individual changes its sex at some point in its life. In particular, ...

, where it morphs into a female in order to reproduce. It does this by laying pale pink eggs on the underside of its float, where they stay attached until they hatch later on in their development (Wilson and Wilson, 1956, 302).

Gallery

References

* Laursen, D. 1953. T''he genus Ianthina: A monograph''. Dana Report 38: 1-40, pl. 1. * Spencer, H.G., Marshall, B.A. & Willan, R.C. (2009). ''Checklist of New Zealand living Mollusca''. Pp 196-219. in: Gordon, D.P. (ed.) New Zealand inventory of biodiversity. Volume one. Kingdom Animalia: Radiata, Lophotrochozoa, Deuterostomia. Canterbury University Press, Christchurch. * Crnčević M, Cetinić AB. 2016. The violet snail Janthina janthina (Linnaeus, 1578) (Mollusca: Gastropoda) is around the Croatian Adriatic island of Lokrum again. Natura Croatica, 25(2):327-330. * Deudero S, Pinnegar J, Polunin N. 2002. Insights into fish host-parasite trophic relationships revealed by stable isotope analysis. Diseases of Aquatic Organisms. 52:77-86. * F. Betti, G. Bavestrello, M. Bo, M. Coppari, F. Enrichetti, M. Manuele & R. Cattaneo-Vietti (2017) Exceptional strandings of the purple snail ''Janthina pallida'' Thompson, 1840 (Gastropoda: Epitoniidae) and first record of an alien goose barnacle along the Ligurian coast (western Mediterranean Sea), The European Zoological Journal, 84:1,488-495, DOI: 10.1080/24750263.2017.1379562 * Teker S, Gökoğlu M , Julian D. 2017. First Record of Janthina globosa Swainson, 1822 (Mollusca, Gastropoda) and Prostheceraeus giesbrechtii Lang, 1884 (Platyhelminthes) in the Gulf of Antalya. Natural and Engineering Sciences, 2(1): 6-10. * The Author, 2017. Journal compilation © Australian Museum, Sydney, 2017 Records of the Australian Museum (2017) Vol. 69, issue number 3, pp. 119–222. ISSN 0067-1975 (print), ISSN 2201-4349 (online) https://doi.org/10.3853/j.2201-4349.69.2017.1666 * Wilson, D. P., and M. A. Wilson. 1956. A contribution to the biology of Ianthina janthina (L.). Journal of the Marine Biological Association of the United Kingdom 35: 291–305. https://doi.org/10.1017/S0025315400010146

External links

Gary Rosenberg's Malacolog 4.1.1 info on this species

Swainson, W. (1820-1823). Zoological Illustrations, or, original figures and descriptions of new, rare, or interesting animals, selected chiefly from the classes of ornithology, entomology, and conchology, and arranged on the principles of Cuvier and other modern zoologists. London: Baldwin, Cradock & Joe; Strand: W. Wood. (Vol. 1-3)

Menke, K. T. (1828). Synopsis methodica molluscorum generum omnium et specierum earum, quae in Museo Menkeano adservantur; cum synonymia critica et novarum specierum diagnosibus. XII + 91 pp

Blainville H.M.D. de. (1822). Janthine, Janthina. pp. 148-155, in: Dictonnaire des Sciences Naturelles (F. Cuvier, ed.), vol. 24. Levrault, Strasbourg & Le Normant, Paris

Monterosato T. A. (di) (1884). Nomenclatura generica e specifica di alcune conchiglie mediterranee. Palermo, Virzi, 152 pp.

Locard_A._&_Caziot_E._(1900-1901)._Les_coquilles_marines_des_côtes_de_Corse._Annales_de_la_Société_Linnéenne_de_Lyon,_46:_193-274_[1900
_47:_1-80,_159-291.html" ;"title="900">Locard A. & Caziot E. (1900-1901). Les coquilles marines des côtes de Corse. Annales de la Société Linnéenne de Lyon, 46: 193-274 [1900
47: 1-80, 159-291">900">Locard A. & Caziot E. (1900-1901). Les coquilles marines des côtes de Corse. Annales de la Société Linnéenne de Lyon, 46: 193-274 [1900
47: 1-80, 159-291
Philippi R.A. (1844). Enumeratio molluscorum Siciliae cum viventium tum in tellure tertiaria fossilium, quae in itinere suo observavit. Vol. 2. Halle [Halis Saxorum
Eduard Anton. iv + 303 pp., pls 13-28]
Beu A.G. (2017). Evolution of Janthina and Recluzia (Mollusca: Gastropoda: Epitoniidae). Records of the Australian Museum. 69(3): 119-222
Epitoniidae Gastropods described in 1822 {{Caenogastropoda-stub