''Tonna galea'', commonly known as the giant tun, is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of marine

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

mollusc Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...

in the family

Tonnidae The Tonnidae are a family (biology), family of medium-sized to very large sea snails, known as the tun shells. These are marine invertebrates, marine gastropod molluscs in the clade Littorinimorpha. The name ''tun'' refers to the snails' shell sh ...

(also known as the tun shells). This very large

sea snail Sea snails are slow-moving marine (ocean), marine gastropod Mollusca, molluscs, usually with visible external shells, such as whelk or abalone. They share the Taxonomic classification, taxonomic class Gastropoda with slugs, which are distinguishe ...

or tun snail is found in the

North Atlantic Ocean The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for se ...

as far as the coast of

West Africa West Africa, also known as Western Africa, is the westernmost region of Africa. The United Nations geoscheme for Africa#Western Africa, United Nations defines Western Africa as the 16 countries of Benin, Burkina Faso, Cape Verde, The Gambia, Gha ...

, in the

Mediterranean Sea The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...

and the

Caribbean Sea The Caribbean Sea is a sea of the Atlantic Ocean, North Atlantic Ocean in the tropics of the Western Hemisphere, located south of the Gulf of Mexico and southwest of the Sargasso Sea. It is bounded by the Greater Antilles to the north from Cuba ...

. The species was first described by

Carl Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...

in 1758.

Description

The ventricose shell of adult ''Tonna galea'' is very large, with an average height of . Specimens of this species have been quoted of the size of a man's head. The shell is thin and inflated, but still relatively solid and durable. The shell is almost diaphanous when young; at that time the transverse ribs of the surface are only indicated by lines of a slightly deeper tint. In terms of its weight however, the thin shell is very much lighter than the shell of most other large sea snails. The

aperture In optics, the aperture of an optical system (including a system consisting of a single lens) is the hole or opening that primarily limits light propagated through the system. More specifically, the entrance pupil as the front side image o ...

of the shell is "distinctly round" and wide. The conical

spire A spire is a tall, slender, pointed structure on top of a roof of a building or tower, especially at the summit of church steeples. A spire may have a square, circular, or polygonal plan, with a roughly conical or pyramidal shape. Spire ...

is formed of six convex, very distinct

whorl A whorl ( or ) is an individual circle, oval, volution or equivalent in a whorled pattern, which consists of a spiral or multiple concentric objects (including circles, ovals and arcs). In nature File:Photograph and axial plane floral diagra ...

s, loaded externally with wide, flat, slightly raised ribs, separated by narrow and superficial furrows. The whorls of the spire are isolated by a deep channeled suture. The

body whorl The body whorl is part of the morphology (biology), morphology of the gastropod shell, shell in those gastropod mollusks that possess a coiled shell. The term is also sometimes used in a similar way to describe the shell of a cephalopod mollusk ...

is rounded and very ventricose. The

is large, subovate, colored interiorly with reddish, and marked with transverse ribs corresponding to the furrows without. The outer

lip The lips are a horizontal pair of soft appendages attached to the jaws and are the most visible part of the mouth of many animals, including humans. Mammal lips are soft, movable and serve to facilitate the ingestion of food (e.g. sucklin ...

is dilated, undulated, tinged with black, or a deep brown upon the edge. The inner lip is whitish, spread out in a very thin plate upon the belly of the body whorl. The

columella Lucius Junius Moderatus Columella (, Arabic: ) was a prominent Roman writer on agriculture in the Roman Empire. His in twelve volumes has been completely preserved and forms an important source on Roman agriculture and ancient Roman cuisin ...

is smooth, polished, and forms at the left of the umbilicus a thick rib, marked by transverse striae, which terminates at the emargination of the base. The external surface of this shell is of a uniform reddish fawn color ; nevertheless the ribs are varied with wide spots or irregular brown and white blotches which are very remarkable.Kiener (1840). General species and iconography of recent shells : comprising the Massena Museum, the collection of Lamarck, the collection of the Museum of Natural History, and the recent discoveries of travellers; Boston :W.D. Ticknor,1837
(described as ''Dolium olearium'') The animal is of a clear brownish red, without spots, and its tentacles are encircled, towards the point, with a wide reddish-brown ring. The foot beneath is of a dark violet, with the edge embroidered with deep brown. ''Tonna galea'' possess large

salivary gland The salivary glands in many vertebrates including mammals are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands ( parotid, submandibular, and sublingual), as well as hundreds of min ...

s. The structure of these glands was first described and detailed by Heinrich Weber in 1927. Furthermore, the giant tun is also a

luminescent Luminescence is a spontaneous emission of radiation from an electronically or vibrationally excited species not in thermal equilibrium with its environment. A luminescent object emits ''cold light'' in contrast to incandescence, where an objec ...

species; this is an extremely rare characteristic among the

prosobranch Prosobranchia was a large Taxonomy (biology), taxonomic Class (biology), subclass of sea snails, land snails and freshwater snails. This taxon of gastropods dates back to the 1920s. It has however been proven to be polyphyly, polyphyletic (consis ...

gastropods. The animal gives off light that is green-white in colour when it traverses through the water with its foot "well-extended".

Distribution and habitat

This large sea snail is found in the

(specifically the

Canary Islands The Canary Islands (; ) or Canaries are an archipelago in the Atlantic Ocean and the southernmost Autonomous communities of Spain, Autonomous Community of Spain. They are located in the northwest of Africa, with the closest point to the cont ...

and

Madeira Madeira ( ; ), officially the Autonomous Region of Madeira (), is an autonomous Regions of Portugal, autonomous region of Portugal. It is an archipelago situated in the North Atlantic Ocean, in the region of Macaronesia, just under north of ...

), the

, the

, and in the waters off the coast of

Angola Angola, officially the Republic of Angola, is a country on the west-Central Africa, central coast of Southern Africa. It is the second-largest Portuguese-speaking world, Portuguese-speaking (Lusophone) country in both total area and List of c ...

Cape Verde Cape Verde or Cabo Verde, officially the Republic of Cabo Verde, is an island country and archipelagic state of West Africa in the central Atlantic Ocean, consisting of ten volcanic islands with a combined land area of about . These islands ...

and

. The preferred habitat for this species is

seabed The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as seabeds. The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...

s that are muddy or sandy with

seagrass Seagrasses are the only flowering plants which grow in marine (ocean), marine environments. There are about 60 species of fully marine seagrasses which belong to four Family (biology), families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and ...

beds. In the Mediterranean, these snails are typically found at depths ranging from just beneath the surface to . ''Tonna galea'' has been placed on Annex II of both the

Berne Convention on the Conservation of European Wildlife and Natural Habitats Bern (), or Berne (), ; ; ; . is the '' de facto'' capital of Switzerland, referred to as the " federal city".; ; ; . According to the Swiss constitution, the Swiss Confederation intentionally has no "capital", but Bern has governmental i ...

and the Protocol of the

Barcelona Convention The Convention for the Protection of the Marine Environment and the Coastal Region of the Mediterranean, originally the Convention for Protection of the Mediterranean Sea against Pollution,

Ecology

Information on the biology and life history of ''Tonna galea'' is scarce, due to the fact that the species has only rarely been studied. It is

carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose nutrition and energy requirements are met by consumption of animal tissues (mainly mu ...

, and utilizes its two

proboscis A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular arthropod mouthparts, mouthparts used for feeding and sucking. In vertebrates, a pr ...

es—located on top of its head—to envelop its prey, which primarily consists of

sea cucumber Sea cucumbers are echinoderms from the class (biology), class Holothuroidea ( ). They are benthic marine animals found on the sea floor worldwide, and the number of known holothuroid species worldwide is about 1,786, with the greatest number be ...

s. To a lesser extent it also feeds on

sea urchin Sea urchins or urchins () are echinoderms in the class (biology), class Echinoidea. About 950 species live on the seabed, inhabiting all oceans and depth zones from the intertidal zone to deep seas of . They typically have a globular body cove ...

starfish Starfish or sea stars are Star polygon, star-shaped echinoderms belonging to the class (biology), class Asteroidea (). Common usage frequently finds these names being also applied to brittle star, ophiuroids, which are correctly referred to ...

. fish,

bivalves Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed by a calcified exoskeleton consis ...

and

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

s. As a

defense mechanism In psychoanalytic theory, defence mechanisms are unconscious psychological processes that protect the self from anxiety-producing thoughts and feelings related to internal conflicts and external stressors. According to this theory, healthy ...

, the snail will squirt its highly-acidic saliva when disturbed. This contains approximately 2–5%

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...

, which is used to kill its prey. The presence of this acid was recorded by

Franz Hermann Troschel Franz Hermann Troschel (10 October 1810 – 6 November 1882) was a German zoologist born in Spandau. He studied mathematics and natural history at the University of Berlin, where he was awarded his doctorate in 1834.Beolens, Bo; Watkins, Michael; G ...

in 1854.

List of synonyms

This is a list of all the various scientific names that have been applied to this species over time. * ''Buccinum galea'' Linnaeus, 1758 (original combination) * ''Buccinum olearium'' Linnaeus, 1758 * ''Cadium galea'' (Linnaeus, 1758) * ''Cadus galea'' (Linnaeus, 1758) * ''Dolium (Dolium) galea'' (Linnaeus, 1758) * ''Dolium (Dolium) galea antillarum'' (Mörch, 1877) * ''Dolium (Dolium) galea'' var. ''brasiliana'' (Mörch, 1877) * ''Dolium (Dolium) galea'' var. ''epidermata'' (de Gregorio, 1884) * ''Dolium (Dolium) galea'' var. ''spirintrorsum'' (de Gregorio, 1884) * ''Dolium (Dolium) galea'' var. ''tardina'' (de Gregorio, 1884) * ''Dolium antillarum'' Mörch, 1877 * ''Dolium antillarum'' var. ''brasiliana'' Mörch, 1877 * ''Dolium epidermata'' de Gregorio, 1884 * ''Dolium galea'' (Linnaeus, 1758) * ''Dolium galea'' var. ''epidermata'' de Gregorio, 1884 * ''Dolium galea'' var. ''spirintrorsa'' de Gregorio, 1884 * ''Dolium galea'' var. ''spirintrorsum'' de Gregorio, 1884 * ''Dolium galea'' var. ''tardina'' de Gregorio, 1884 * ''Dolium galeatum'' Locard, 1886 * † ''Dolium modjokasriense'' Martin, 1899 * ''Dolium tardina'' de Gregorio, 1884 * ''Dolium tenue'' Menke, 1830 * ''Tonna (Tonna) galea'' (Linnaeus, 1758) * ''Tonna (Tonna) galea brasiliana'' (Mörch, 1877) * ''Tonna (Tonna) galea galea'' (Linnaeus, 1758) * ''Tonna galea abbotti'' Macsotay & Campos, 2001 * ''Tonna galea brasiliana'' (Mörch, 1877) * ''Tonna olearium'' (Linnaeus, 1758)

References

External links

* {{taxonbar, from=Q1548480 Tonnidae Molluscs of the Atlantic Ocean Molluscs of the Mediterranean Sea Gastropods described in 1758 Taxa named by Carl Linnaeus