Queen conch facts for kids
Quick facts for kids Lobatus gigas |
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| Shell of Lobatus gigas (ventral view) | |
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| Shell of Lobatus gigas (dorsal view) | |
| Scientific classification | |
| Kingdom: | |
| Phylum: | |
| Class: | |
| (unranked): |
clade Caenogastropoda
clade Hypsogastropoda clade Littorinimorpha |
| Family: |
Strombidae
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| Genus: |
Lobatus
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| Species: |
L. gigas
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| Binomial name | |
| Lobatus gigas (Linnaeus, 1758)
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| Synonyms | |
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Strombus gigas Linnaeus, 1758 |
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Lobatus gigas , commonly known as the queen conch, is a species of large edible sea snail, a marine gastropod mollusc in the family of true conches, the Strombidae. This species is one of the largest molluscs native to the tropical northwestern Atlantic, from Bermuda to Brazil, reaching up to 35.2 centimetres (13.9 in) in shell length.
Contents
Anatomy
Shell
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The mature shell is typically 15–31 centimetres (5.9–12.2 in) in length, while the maximum reported size is 35.2 centimetres (13.9 in). The shell is very solid and heavy, with 9 to 11 whorls and a widely flaring and thickened outer lip. Although this notch is not as well developed as elsewhere in the family, the shell feature is nonetheless visible in an adult dextral (normal right-handed) specimen, as a secondary anterior indentation in the lip, to the right of the siphonal canal (viewed ventrally). The animal's left eyestalk protrudes through this notch.
The spire is a protruding part of the shell that includes all of the whorls except the largest and final whorl (known as the body whorl). It is usually more elongated than in other strombid snails, such as the closely related and larger goliath conch, Lobatus goliath that is endemic to Brazil. In L. gigas, the glossy finish or glaze around the aperture of the adult shell is primarily in pale shades of pink. It may show a cream, peach or yellow colouration, but it can also sometimes be tinged with a deep magenta, shading almost to red. The periostracum, a layer of protein (conchiolin) that is the outermost part of the shell surface, is thin and a pale brown or tan colour.
The overall shell morphology of L. gigas is not solely determined by the animal's genes; environmental conditions such as location, diet, temperature and depth, and biological interactions such as predation, can greatly affect it. Juvenile conches develop heavier shells when exposed to predators. Conches also develop wider and thicker shells with fewer but longer spines in deeper water.
The shells of juvenile queen conches are strikingly different in appearance from those of the adults. Noticeable is the complete absence of a flared outer lip; juvenile shells have a simple sharp lip, which gives the shell a conical or biconic outline. In Florida, juvenile queen conches are known as "rollers", because wave action very easily rolls their shells, whereas it is nearly impossible to roll an adult specimen, due to its shell's weight and asymmetric profile. Subadult shells have a thin flared lip that continues to increase in thickness until death.
Conch shells are about 95% calcium carbonate and 5% organic matter.
Historic illustrations
Index Testarum Conchyliorum (published in 1742 by the Italian physician and malacologist Niccolò Gualtieri) contains three illustrations of adult shells from different perspectives. The knobbed spire and the flaring outer lip, with its somewhat wing-like contour expanding out from the last whorl, is a striking feature of these images. The shells are shown as if balancing on the edge of the lip and/or the apex; this was presumably done for artistic reasons as these shells cannot balance like this.
One of the most prized shell publications of the 19th century, a series of books titled Illustrations conchyliologiques ou description et figures de toutes les coquilles connues, vivantes et fossiles (published by the French naturalist Jean-Charles Chenu from 1842 to 1853), contains illustrations of both adult and juvenile L. gigas shells and one uncoloured drawing depicting some of the animal's soft parts. Almost forty years later, a colored illustration from the Manual of Conchology (published in 1885 by the American malacologist George Washington Tryon) shows a dorsal view of a small juvenile shell with its typical brown and white patterning.
Soft parts
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Many details about the anatomy of Lobatus gigas were not well known until Colin Little's 1965 general study. In 2005, R. L. Simone gave a detailed anatomical description. L. gigas has a long extensible snout with two eyestalks (also known as ommatophores) that originate from its base. The tip of each eyestalk contains a large, well-developed lensed eye, with a black pupil and a yellow iris and a small slightly posterior sensory tentacle. Amputated eyes completely regenerate. Inside the mouth of the animal is a radula (a tough ribbon covered in rows of microscopic teeth) of the taenioglossan type. Both the snout and the eyestalks show dark spotting in the exposed areas. The mantle is darkly coloured in the anterior region, fading to light gray at the posterior end, while the mantle collar is commonly orange. The siphon is also orange or yellow. When the soft parts of the animal are removed from the shell, several organs are distinguishable externally, including the kidney, the nephiridial gland, the pericardium, the genital glands, stomach, style sac and the digestive gland.
Foot/locomotion
The species has a large and powerful foot with brown spots and markings towards the edge, but is white nearer to the visceral hump that stays inside the shell and accommodates internal organs. The base of the anterior end of the foot has a distinct groove, which contains the opening of the pedal gland. Attached to the posterior end of the foot for about one third of its length is the dark brown, corneous, sickle-shaped operculum, which is reinforced by a distinct central rib. The base of the posterior two-thirds of the animal's foot is rounded; only the anterior third touches the ground during locomotion. The columella, the central pillar within the shell, serves as the attachment point for the white columellar muscle. Contraction of this strong muscle allows the animal's soft parts to shelter in the shell in response to undesirable stimuli.
Lobatus gigas has an unusual means of locomotion, first described in 1922 by George Howard Parker (1864–1955). The animal first fixes the posterior end of the foot by thrusting the point of the sickle-shaped operculum into the substrate, then it extends the foot in a forward direction, lifting and throwing the shell forward in a so-called leaping motion. This way of moving is considered to resemble that of pole vaulting, making L. gigas a good climber even of vertical concrete surfaces. This leaping locomotion may help prevent predators from following the snail's chemical traces, which would otherwise leave a continuous trail on the substrate.
Life cycle
Lobatus gigas is gonochoristic, which means each individual snail is either distinctly male or distinctly female. Females are usually larger than males in natural populations, with both sexes existing in similar proportion. After internal fertilization, the females lay eggs in gelatinous strings, which can be as long as 75 feet (23 m). These are layered on patches of bare sand or seagrass. The sticky surface of these long egg strings allows them to coil and agglutinate, mixing with the surrounding sand to form compact egg masses, the shape of which is defined by the anterior portion of the outer lip of the female's shell while they are layered. Each one of the egg masses may have been fertilized by multiple males. The number of eggs per egg mass varies greatly depending on environmental conditions such as food availability and temperature. Commonly, females produce 8–9 egg masses per season, each containing 180,000–460,000 eggs, but numbers can be as high as 750,000 eggs. L. gigas females may spawn multiple times during the reproductive season, which lasts from March to October, with activity peaks occurring from July to September.
Queen conch embryos hatch 3–5 days after spawning. At the moment of hatching, the protoconch (embryonic shell) is translucent and has a creamy, off-white background color with small, pustulate markings. This coloration is different from other Caribbean Lobatus, such as Lobatus raninus and Lobatus costatus, which have unpigmented embryonic shells. Afterwards, the emerging two-lobed veliger (a larval form common to various marine and fresh-water gastropod and bivalve mollusks) spend several days developing in the plankton, feeding primarily on phytoplankton. Metamorphosis occurs some 16–40 days from the hatching, when the fully grown protoconch is about 1.2 mm high. After the metamorphosis, L. gigas individuals spend the rest of their lives in the benthic zone (on or in the sediment surface), usually remaining buried during their first year of life. The queen conch reaches sexual maturity at approximately 3 to 4 years of age, reaching a shell length of nearly 180 mm and weighing up to 5 pounds. Individuals may usually live up to 7 years, though in deeper waters their lifespan may reach 20–30 years and maximum lifetime estimates reach 40 years. It is believed that the mortality rate tends to be lower in matured conchs due to their thickened shell, but it could be substantially higher for juveniles. Estimates have demonstrated that its mortality rate decreases as its size increases and can also vary due to habitat, season and other factors.
Distribution
Lobatus gigas is native to the tropical Western Atlantic coasts of North and Central America. It lives in the greater Caribbean tropical zone.
Aruba, of the Netherlands Antilles; Barbados; all of the islands and cays of the Bahamas; Belize; Bermuda; North and northeastern regions of Brazil (though this is contested by some authors); Old Providence Island in Colombia; Costa Rica; the Dominican Republic; Panama; Swan Islands in Honduras; Jamaica; Martinique; Alacran Reef, Campeche, Cayos Arcas and Quintana Roo, in Mexico; Puerto Rico; Saint Barthélemy; Mustique and Grenada in the Grenadines; Pinar del Río, North Havana Province, North Matanzas, Villa Clara, Cienfuegos, Holguín, Santiago de Cuba and Guantánamo, in the Turks and Caicos Islands and Cuba; South Carolina, Florida, including East Florida, West Florida, the Florida Keys and the Flower Garden Banks National Marine Sanctuary, in the United States; Carabobo, Falcon, Gulf of Venezuela, Las Aves archipelago, Los Roques archipelago, Los Testigos Islands and Sucre in Venezuela; St. Croix in the Virgin Islands.
Diet
Strombid gastropods were widely accepted as carnivores by several authors in the 19th century, a concept that persisted until the first half of the 20th century. This erroneous idea originated in the writings of Jean-Baptiste Lamarck, who classified strombids with other supposedly carnivorous snails. This idea was subsequently repeated by other authors, but were not supported by observation. Subsequent studies have refuted the concept, proving beyond doubt that strombid gastropods are herbivorous animals. In common with other Strombidae, Lobatus gigas is a specialized herbivore, that feeds on macroalgae (including red algae, such as species of Gracilaria and Hypnea), seagrass and unicellular algae, intermittently also feeding on algal detritus. The green macroalgae Batophora oerstedii is one of its preferred foods.
Uses
Conch meat has been consumed for centuries and has traditionally been an important part of the diet in many islands in the West Indies and Southern Florida. It is consumed raw, marinated, minced or chopped in a wide variety of dishes, such as salads, chowder, fritters, soups, stew, pâtés and other local recipes. In both English and Spanish-speaking regions, for example in the Dominican Republic, Lobatus gigas meat is known as lambí. Although conch meat is used mainly for human consumption, it is also sometimes employed as fishing bait (usually the foot). L. gigas is among the most important fishery resources in the Caribbean: its harvest value was US$30 million in 1992, increasing to $60 million in 2003. The total annual harvest of meat of L. gigas ranged from 6,519,711 kg to 7,369,314 kg between 1993 and 1998, later production declined to 3,131,599 kg in 2001. Data about US imports shows a total of 1,832,000 kg in 1998, as compared to 387,000 kg in 2009, a nearly 80% reduction twelve years later.
Queen conch shells were used by Native Americans and Caribbean Indians in a wide variety of ways. South Florida bands (such as the Tequesta), the Carib, the Arawak and Taíno used conch shells to fabricate tools (such as knives, axe heads and chisels), jewelry, cookware and used them as blowing horns. In Mesoamerican history, Aztecs used the shell as part of jewelry mosaics such as the double-headed serpent. The Aztecs also believed that the sound of trumpets made from queen conch shells represented divine manifestations, and used them in religious ceremonies. In central Mexico, during rain ceremonies dedicated to Tlaloc, the Maya used conch shells as hand protectors (in a manner similar to boxing gloves) during combat. Ancient middens of L. gigas shells bearing round holes are considered an evidence that pre-Columbian Lucayan Indians in the Bahamas used the queen conch as a food source.
Brought by explorers, queen conch shells quickly became a popular asset in early modern Europe. In the late 17th century they were widely used as decoration over fireplace mantels and English gardens, among other places. In contemporary times, queen conch shells are mainly utilized in handicraft. Shells are made into cameos, bracelets and lamps, and traditionally as doorstops or decorations by families of seafaring men. The shell continues to be popular as a decorative object, though its export is now regulated and restricted by the CITES agreement. In modern culture, queen conch shells are often represented in everyday objects such as coins and stamps.
Very rarely (about 1 in 10,000 conchs), a conch pearl may be found within the mantle. Though they occur in a range of colors corresponding to the colors of the interior of the shell, pink specimens are the most valuable. These pearls are considered semi-precious, and a popular tourist curio. The best specimens have been used to create necklaces and earrings. A conch pearl is a non-nacreous pearl (formerly referred to by some sources as a 'calcareous concretion') which differs from most pearls that are sold as gemstones.
Research into the conch shell's unique architecture is currently under way at MIT.
Images for kids
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For a number of years during the 20th century, this very early illustration was designated as the neotype of this species: a figure of A. gigas from Recreatio mentis, et occuli (1684). The shell in the figure appears left-right reversed because of the engraving process. The original type was subsequently found, invalidating this designation.
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Five different views of an adult shell of A. gigas: abapertural (upper left), lateral (center), apertural (upper right), apical (lower left) and basal (lower right). Note: The lip of this shell has been filed down or cut down artificially, a common practice in the shell trade.
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Abapertural (left) and apertural (right) views of a beachworn and slightly bleached-out juvenile shell of A. gigas
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The shaded area of this map indicates the geographical distribution of Aliger gigas.
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Anterior view of a live individual. The eyestalk on the left is protruded through the stromboid notch, and the eyestalk on the right is protruded through the siphonal canal. The outer surface of the shell is covered by periphyton
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A horse conch, Triplofusus papillosus, feeding on A. gigas in Dry Tortugas National Park, Florida, June 2010
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The giant hermit crab, Petrochirus diogenes, inside a subadult shell of A. gigas
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On the island of Anegada, British Virgin Islands, a heap consists of thousands of empty queen conch shells, discarded after their flesh was taken for human consumption.
See also
In Spanish: Lobatus gigas para niños
