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Lobatus gigas

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Title: Lobatus gigas  
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Lobatus gigas

Lobatus gigas
Large sea snail with yellowish shell and protruding eyestalks, with green seagrass on a sandy bottom
A live subadult individual of Lobatus gigas, in situ surrounded by turtle grass
Colored drawing of large sea snail, soft parts protruding, showing snout, eyestalks and foot with claw-shaped operculum
A dorsal view of an adult individual of L. gigas from Chenu, 1844
CITES Appendix II (CITES)
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Clade: Caenogastropoda
Clade: Hypsogastropoda
Clade: Littorinimorpha
Family: Strombidae
Genus: Lobatus
Species: L. gigas
Binomial name
Lobatus gigas
(Linnaeus, 1758)
Synonyms[1]

Strombus gigas Linnaeus, 1758[2]
Strombus lucifer Linnaeus, 1758
Eustrombus gigas (Linnaeus, 1758)[3]
Pyramea lucifer (Linnaeus, 1758)
Strombus samba Clench, 1937[4]
Strombus horridus Smith, 1940[5]
Strombus verrilli McGinty, 1946[6]
Strombus canaliculatus Burry, 1949[7]
Strombus pahayokee Petuch, 1994[8]

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. L. gigas is closely related to the goliath conch, Lobatus goliath, a species endemic to Brazil, as well as the rooster conch, Lobatus gallus.

The queen conch is herbivorous and lives in seagrass beds, although its exact habitat varies by development stage. The adult animal has a very large, solid and heavy shell, with knob-like spines on the shoulder, a flared thick, outer lip and a characteristic pink-coloured aperture (opening). The flared lip is absent in younger specimens. The external anatomy of the soft parts of L. gigas is similar to that of other snails in its family; it has a long snout, two eyestalks with well-developed eyes, additional sensory tentacles, a strong foot and a corneous, sickle-shaped operculum.

The shell and soft parts of living L. gigas serve as a home to several different kinds of commensal animals, including slipper snails, porcelain crabs and cardinalfish. Its parasites include coccidians. The queen conch is hunted and eaten by several species of large predatory sea snails, and also by starfish, crustaceans and vertebrates (fish, sea turtles and humans). Its shell is sold as a souvenir and used as a decorative object. Historically, Native Americans and indigenous Caribbean peoples used parts of the shell to create various tools.

International trade in queen conch is regulated under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) agreement, in which it is listed as Strombus gigas. This species is not endangered in the Caribbean as a whole, but is commercially threatened in numerous areas, largely due to extreme overfishing.

Contents

  • Taxonomy and etymology 1
    • History 1.1
    • Phylogeny 1.2
    • Common names 1.3
    • Shell 1.4
      • Historic illustrations 1.4.1
    • Soft parts 1.5
    • Foot/locomotion 1.6
  • Life cycle 2
  • Ecology 3
    • Distribution 3.1
    • Habitat 3.2
    • Diet 3.3
    • Interactions 3.4
  • Human uses 4
  • Status 5
    • Threats 5.1
    • Conservation 5.2
  • References 6
  • Further reading 7
  • External links 8

Taxonomy and etymology

An antique-looking illustration, numbered 321, showing a large, apparently left-handed, sea snail shell with knobs on the shoulders of the whorls
For a number of years during the 20th century, this very early illustration was designated as the neotype of this species: a figure of L. 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.[9]

History

The queen conch was originally described from a shell in 1758 by Swedish naturalist and taxonomist Carl Linnaeus, who originated the system of binomial nomenclature.[2] Linnaeus named the species Strombus gigas, which remained the accepted name for over 200 years. Linnaeus did not mention a specific locality for this species, giving only "America" as the type locality.[10] The specific name is the ancient Greek word gigas (γίγας), which means "giant", referring to the large size of this snail compared with almost all other gastropod molluscs.[11] Strombus lucifer, which was considered to be a synonym much later, was also described by Linnaeus in Systema Naturae.[2]

In the first half of the 20th century, the type material for the species was thought to have been lost; in other words, the shell on which Linnaeus based his original description and which would very likely have been in his own collection, was apparently missing, which created a problem for taxonomists. To remedy this, in 1941 a neotype of this species was designated by the American malacologists William J. Clench and R. Tucker Abbott. In this case, the neotype was not an actual shell or whole specimen, but a figure from a 1684 book Recreatio mentis, et occuli, published 23 years before Linnaeus was born by the Italian scholar Filippo Buonanni. This was the first book that was solely about seashells.[10][12][13][14] In 1953 the Swedish malacologist Nils Hjalmar Odhner searched the Linnaean Collection at Uppsala University and discovered the missing type shell, thereby invalidating Clench and Abbott's neotype designation.[15]

Strombidae's taxonomy was extensively revised in the 2000s and a few subgenera, including Eustrombus, were elevated to genus level by some authors.[16][17][18] Petuch[3] and Petuch and Roberts[19] recombined this species as Eustrombus gigas, and Landau and collaborators (2008) recombined it as Lobatus gigas.[18]

Phylogeny

Strombidae

Terebellum terebellum



Canarium urceus



Conomurex luhuanus



Tricornis raninus



Lambis lambis



Strombus



Eustrombus


Aliger








A simplified version of the phylogeny and relationships of Strombidae according to Simone (2005)[16]



 






Strombus gallus


Strombus gigas



Strombus costatus




Strombus raninus


Strombus peruvianus




Strombus galeatus



Strombus latus






Strombus pugilis


Strombus alatus



Strombus gracilior



Strombus granulatus






Phylogeny and relationships of Eastern Pacific and Atlantic Strombus species, according to Latiolais et al. (2006)[17]

The phylogenetic relationships among the Strombidae were mainly formed by Simone (2005)[16] and Latiolais (2006),[17] using two distinct methods. Simone proposed a cladogram (a tree of descent) based on an extensive morpho-anatomical analysis of representatives of Aporrhaidae, Strombidae, Xenophoridae and Struthiolariidae, which included L. gigas (there referred to as Eustrombus gigas).[16]

With the exception of Lambis and Terebellum, the remaining taxa were previously allocated in the genus Strombus, including L. gigas. However, according to Simone, only Strombus gracilior, Strombus alatus and Strombus pugilis, the type species, remained within Strombus, as they constituted a distinct group based on at least five synapomorphies (traits that are shared by two or more taxa and their most recent common ancestor).[16] The remaining taxa were previously considered subgenera and were elevated to genus level by Simone. Genus Eustrombus (now considered a synonym of Lobatus[20]), in this case, included Eustrombus gigas (now considered a synonym of Lobatus gigas) and Eustrombus goliath (= Lobatus goliath), which were thus considered closely related.[16]

In a different approach, Latiolais and colleagues (2006) proposed another cladogram that attempts to show the phylogenetic relationships of 34 species within the family Strombidae. The authors analysed 31 Strombus species, including Lobatus gigas (there referred to as Strombus gigas), and three species in the allied genus Lambis. The cladogram was based on DNA sequences of both nuclear histone H3 and mitochondrial cytochrome-c oxidase I (COI) protein-coding gene regions. In this proposed phylogeny, Strombus gigas and Strombus gallus (= Lobatus gallus) are closely related and appear to share a common ancestor.[17]

Common names

Common names include "queen conch" and "pink conch" in English, caracol rosa and caracol rosado in Mexico, caracol de pala, cobo, botuto and guarura in Venezuela, caracol reina, lambí in the Dominican Republic,[21][22][23][24][25] and carrucho in Puerto Rico.[26]

sm== Anatomy ==

Shell

A queen conch shell is shown from five different perspectives
Five different views of an adult shell of L. gigas: abapertural (upper left), lateral (center), apertural (upper right), apical (lower left) and basal (lower right). The lip of this shell has been filed down or cut down artificially, a common practice in the shell trade.

An adult queen conch shell with the lip completely intact
Abapertural (left) and apertural (right) views of a beachworn and slightly bleached-out juvenile shell of L. gigas

The mature shell is typically 15–31 centimetres (5.9–12.2 in) in length,[27][28] while the maximum reported size is 35.2 centimetres (13.9 in).[1][14][29] 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,[14] 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.[14][26][30][31]

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.[14] 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.[28][30][31]

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.[32][33] Juvenile conches develop heavier shells when exposed to predators. Conches also develop wider and thicker shells with fewer but longer spines in deeper water.[33]

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.[34][35][36]

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

  • "Queen Conch Factsheet". Waitt Institute. Retrieved 2015-06-08. 
  • ARKive – (Strombus gigas)images and movies of the queen conch
  • Strombus gigasAnimal Diversity Web:
  • Strombus gigas at the National Center for Biotechnology Information
  • Microdocs: Life cycle of the conch
  • Bermuda Department of Conservation Services (includes Queen Conch Recovery Plan)

External links

  • Coomans H.E. (1965). "Shells and shell objects from an Indian site on Magueyes Island, Puerto Rico". Caribbean Journal of Science 5(1–2): 15–23. PDF.
  • Spade, D.J.; Griffitt, R.J.; Liu, L.; Brown-Peterson, N.J.; Kroll, K.J.; et al. (2010). "Queen Conch (Strombus gigas) Testis Regresses during the Reproductive Season at Nearshore Sites in the Florida Keys".   Category:CS1 maint: Explicit use of et al.)
  • Stoner, A.W.; Waite, J.M. (1991). "Trophic biology of Strombus gigas in nursery habitats: diets and food sources in seagrass meadows".  

Further reading

  1. ^ a b c Rosenberg, G. (2009). Eustrombus gigas (Linnaeus, 1758). Malacolog Version 4.1.1: A Database of Western Atlantic Marine Mollusca. Retrieved 27 September 2009.
  2. ^ a b c Linnaeus, C. (1758). Systema Naturae, 10th ed., vol. 1. 824 pp. Laurentii Salvii: Holmiae (Stockholm, Sweden). p. 745.
  3. ^ a b Petuch, E.J. (2004). Cenozoic Seas: The view from Eastern North America. CRC Press. pp. 1–308.  
  4. ^ Clench, W. J. (1937). "Descriptions of new land and marine shells from the Bahama Islands." Proceedings of the New England Zoölogical Club 16: 17–26, pl. 1. (Stated date: 5 February 1937.) On pages 18–21, plate 1 figure 1.
  5. ^ Smith, M. (1940). World Wide Seashells: illustrations, geographical range and other data covering more than sixteen hundred species and sub-species of molluscs (1 ed.). Lantana, Florida: Tropical Photographic Laboratory. pp. 131, 139. 
  6. ^ McGinty, T. L. (1946). "A new Florida Strombus, S. gigas verrilli". The Nautilus 60: 46–48, plates. 5–6: plate 5, figs. 2–3; plate 6, figs. 7–8.
  7. ^ Burry, L. A. (1949). Shell Notes (Lantana, Florida: Frank Lyman) 2: 106–109. 
  8. ^ Petuch, E. J. (1994). Atlas of Florida Fossil Shells. Chicago Spectrum Press: Evanston, Illinois., xii + 394 pp., 100 pls. On page 82, plate 20: figure c.
  9. ^ Allmon, W. D. (2007). "The evolution of accuracy in natural history illustration: reversal of printed illustrations of snails and crabs in pre-Linnaean works suggests indifference to morphological detail". Archives of natural history 34 (1): 174–191.  
  10. ^ a b Clench, W.J.; Abbott, R.T. (1941). "The genus Strombus in the Western Atlantic". Johnsonia 1 (1): 1–16. 
  11. ^ Brown, R. W. (1954). Composition of Scientific Words (PDF). Baltimore, Maryland, USA: Published by the author. p. 367. 
  12. ^ Robertson, R. (2012). "Buonanni's Chiocciole (1681)". Digital Collections from the Ewell Sale Stewart Library and Archives. The Academy of Natural Sciences of Drexel University, Philadelphia, USA. Retrieved 20 December 2012. 
  13. ^ Buonanni, F. (1684). Recreatio mentis, et oculi in observatione animalium testaceorum Italico sermone primum proposita ... nunc ... Latine oblata centum additis testaceorum iconibus. Romae, Ex typographia Varesii. pp. 531–532. 
  14. ^ a b c d e f g h i Moscatelli, R. (1987). The superfamily Strombacea from Western Atlantic. São Paulo, Brazil: Antonio A. Nanô & Filho Ltda. pp. 53–60. 
  15. ^ Wallin, L. (2001). Catalogue of type specimens 4: Linnaean specimens (PDF). Uppsala, Sweden: Uppsala University Museum of Evolution Zoology section (UUZM). pp. 1–128. 
  16. ^ a b c d e f g h Simone, L. R.L. (2005). "Comparative morphological study of representatives of the three families of Stromboidea and the Xenophoroidea (Mollusca, Caenogastropoda), with an assessment of their phylogeny" (PDF). Arquivos de Zoologia (São Paulo: Museu de Zoologia – USP) 37 (2): 178–180.  
  17. ^ a b c d e Latiolais, J.M.; Taylor, M.S; Roy, K. & Hellberg, M.E. (2006). "A molecular phylogenetic analysis of strombid gastropod morphological diversity" (PDF). Molecular Phylogenetics and Evolution (Elsevier) 41 (2): 436–444.  
  18. ^ a b Landau, B.M.; Kronenberg G.C.; Herbert, G. S. (2008). "A large new species of Lobatus (Gastropoda: Strombidae) from the neogene of the Dominican Republic, with notes on the genus". The Veliger (Santa Barbara: California Malacozoological Society, Inc.) 50 (1): 31–38.  
  19. ^ Petuch, E.J.; Roberts, C.E. (2007). The geology of the Everglades and adjacent areas. Boca Raton, Florida: CRC Press, Taylor & Francis Group. pp. 1–212.  
  20. ^ Swainson, 1837Lobatus .  Retrieved through: World Register of Marine Species on 5 December 2012.
  21. ^ Rodríguez, B.; Posada, J.; Posada, J. (1994). "Revisión histórica de la pesquería del botuto o guarura (Strombus gigas L.) y el alcance de su programa de manejo en el Parque Nacional Archipiélago de Los Roques, Venezuela". In Appeldoorn R.; Rodríguez, B. Queen conch biology, fisheries and mariculture. Caracas, Venezuela: Fundación Cientifica Los Roques. pp. 13–24. 
  22. ^ Buitriago, J. (1983). L)"Strombus gigas"Cria en cautiverio, del huevo al adulto, del botuto (. Memoria Sociedad de Ciencias Naturales La Salle 43: 29–39. 
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  25. ^ Posada, J.M.; Ivan, M.R. & Nemeth, M. (1999). , (Gastropoda) in shallow waters of the Jaragua National Park, Dominican Republic"Strombus Gigas"Occurrence, abundance, and length frequency distribution of queen conch, (PDF).  
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  28. ^ a b c Warmke, G.L.; Abbott, R. T. (1975). Caribbean Seashells. Dover Publications, Inc. p. 88.  
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  44. ^ Berg, C.J. (1975). "Behavior and ecology of conch (superfamily Strombacea) on a deep subtidal algal plain". Bulletin of Marine Science 25 (3): 307–317. abstract.
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  80. ^ Appendices I, II and III. cites.org website. Retrieved 4 July 2009.
  81. ^ NOAA Fisheries Office of International Affairs website: CITES. Retrieved 4 July 2009.
  82. ^ "Standing Committee Recommendations". CITES Official Documents No 2003/057. 2003. Retrieved 16 April 2010. 
  83. ^ "Vedas Vigentes en el Territorio Colombiano". Instituto Colombiano Agropecuario (Official Website). Ministerio de Agricultura y Desarrollo Rural, Colombia. Retrieved 19 October 2015. 

This article incorporates public domain text (a public domain work of the United States Government) from the reference.[52]

References

This species has been mentioned in the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) since 1985.[33] In 1992 the United States proposed queen conch for listing in CITES Appendix II, making queen conch the first large-scale fisheries product to be regulated by CITES (as Strombus gigas).[52][80][81] In 1995 CITES began reviewing the biological and trade status of the queen conch under its "Significant Trade Review" process. These reviews are undertaken to address concerns about trade levels in an Appendix II species. Based on the 2003 review,[66] CITES recommended that all countries prohibit importation from Honduras, Haiti and the Dominican Republic, according to Standing Committee Recommendations.[82] Queen conch meat continues to be available from other Caribbean countries, including Jamaica and Turks and Caicos, which operate well-managed queen conch fisheries.[52] For conservation reasons, the Government of Colombia currently bans the commercialisation, and consumption, of the conch between the months of June and October.[83]

The queen conch fishery is usually managed under the regulations of individual nations. In the United States all taking of queen conch is prohibited in Florida and in adjacent Federal waters. No international regional fishery management organization exists for the whole Caribbean area, but in places such as Puerto Rico and the Virgin Islands, queen conch is regulated under the auspices of the Caribbean Fishery Management Council (CFMC).[52] In 2014, the Parties to the Convention for the Protection and Development of the Marine Environment of the Wider Caribbean Region (Cartagena Convention) included queen conch in Annex III of its Protocol Concerning Specially Protected Areas and Wildlife (SPAW Protocol). Species included in the Annex III require special measures to be taken to ensure their protection and recovery, and their use is authorised and regulated accordingly.[78][79]

Conservation

Within the conch fisheries, one of the threats to sustainability stems from the fact that there is almost as much meat in large juveniles as there is in adults, but only adult conchs can reproduce, and thus sustain a population.[65] In many places where adult conchs have become rare due to overfishing, larger juveniles and subadults are taken before they ever mate.[65][76] On a number of islands, subadults provide the majority of the harvest.[77] Lobatus gigas abundance is declining throughout its range as a result of overfishing and poaching. Trade from many Caribbean countries such as Antigua and Barbuda, Honduras, Haiti and the Dominican Republic is known or thought to be unsustainable.[76] As of 2001, queen conch populations in at least 15 Caribbean countries and states were overfished and/or overexploited.[76] Illegal harvest, including fishing in foreign waters and subsequent illegal international trade, is a common problem in the region.[52] The Caribbean "International Queen Conch Initiative" is an international attempt at managing this species.[54]

The island of Anegada, British Virgin Islands, a heap consisting of thousands of queen conch shells discarded after their flesh was taken for human consumption

Threats

Status

Very rarely (about 1 in 10,000 conchs),[27] a conch pearl may be found within the mantle.[27][35] Though they occur in a range of colors corresponding to the colors of the interior of the shell, pink specimens are the most valuable.[75] These pearls are considered semi-precious,[14] and a popular tourist curio.[55] 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.[75]

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.[42] In contemporary times, queen conch shells are mainly utilized in handicraft. Shells are made into cameos, bracelets and lamps,[55][71] and traditionally as doorstops or decorations by families of seafaring men.[71] The shell continues to be popular as a decorative object, though its export is now regulated and restricted by the CITES agreement.[27] In modern culture, queen conch shells are often represented in everyday objects such as coins[70][72] and stamps.[73][74]

Very early 20th century painting of a young girl holding a shell of this species up to the light and looking into it
Shell of this species featured in an 1902 painting by Frank Weston Benson

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.[27][68] In Mesoamerican history, Aztecs used the shell as part of jewelry mosaics such as the double-headed serpent.[69] The Aztecs also believed that the sound of trumpets made from queen conch shells represented divine manifestations, and used them in religious ceremonies.[70] 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.[70] 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.[64]

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.[27][42][55][65] In 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).[52][55] L. gigas is among the most important fishery resources in the Caribbean: its harvest value was US$30 million in 1992,[33] increasing to $60 million in 2003.[66] 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.[66] 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.[67]

Four queen conch shells, all have a hole in the spire of the shell
Four subadult shells of Lobatus gigas from Nevis, all having been fished and showing the cut in the spire. This cut is used to sever the columellar muscle allowing the soft parts to slide out.[64]

Human uses

L. gigas is a prey species for several carnivorous gastropod mollusks, including the apple murex Phyllonotus pomum, the horse conch Pleuroploca gigantea, the lamp shell Turbinella angulata, the moon snails Natica spp. and Polinices spp., the muricid snail Murex margaritensis, the trumpet triton Charonia variegata and the tulip snail Fasciolaria tulipa.[14][27][62] Crustaceans are also conch predators, such as the blue crab Callinectes sapidus, the box crab Calappa gallus, the giant hermit crab Petrochirus diogenes, the spiny lobster Panulirus argus and others.[27][62] Sea stars, vertebrates, including fish (such as the permit Trachinotus falcatus[63] and the porcupine fish Diodon hystrix), loggerhead sea turtles (Caretta caretta) and humans also dine on the queen conch.[27][62]

[60] A few different animals establish

Interactions

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.[58] In common with other Strombidae,[17] Lobatus gigas is a specialized herbivore,[28] that feeds on macroalgae (including red algae, such as species of Gracilaria and Hypnea),[36] seagrass[55] and unicellular algae, intermittently also feeding on algal detritus.[58][59] The green macroalgae Batophora oerstedii is one of its preferred foods.[31]

Diet

Lobatus gigas lives at depths from 0.3–18 m[31] to 25–35 m.[29][49] Its depth range is limited by the distribution of seagrass and algae cover. In heavily exploited areas, the queen conch is more abundant in the deepest range.[49] The queen conch lives in seagrass meadows and on sandy substrate,[45] usually in association with turtle grass (species of the genus Thalassia, specifically Thalassia testudinum[34] and also Syringodium sp.)[32] and manatee grass (Cymodocea sp.).[55] Juveniles inhabit shallow, inshore seagrass meadows, while adults favor deeper algal plains and seagrass meadows.[31][56] The critical nursery habitats for juvenile individuals are defined by a series of characteristics, including tidal circulation and macroalgal production, which together enable high rates of recruitment and survival.[57] L. gigas is typically found in distinct aggregates that may contain several thousand individuals.[33]

Habitat

Lobatus gigas is native to the tropical Western Atlantic coasts of North and Central America in the greater Caribbean tropical zone.[31] Although the species undoubtedly occurs in other places, this species has been recorded within the scientific literature as occurring, in:[1][53][54] Aruba, (Netherlands Antilles); Barbados; the Bahamas; Belize; Bermuda; North and northeastern regions of Brazil (though this is contested);[14] 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, with the Florida Keys and Flower Garden Banks National Marine Sanctuary, in the United States; Carabobo, Falcon, Gulf of Venezuela, Los Roques archipelago, Los Testigos Islands and Sucre in Venezuela; St. Croix in the Virgin Islands.

Distribution

A human hand is holding an immature queen conch shell, inside which is a very large brown hermit crab.
The giant hermit crab, Petrochirus diogenes, inside a subadult shell ofL. gigas

A sandy bottom. On it a large sea snail with a bright orange-red body and a large operculum is reaching far into the shell of a queen conch.
A horse conch, Pleuroploca gigantea, feeding on L. gigas in Dry Tortugas National Park, Florida, June 2010

Live snail (on sandy bottom) from the front, showing eyestalks protruding from two large notches in the edge of the lip of the shell, which looks
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

map showing some of the Western Atlantic Ocean and the eastern parts of North America, Central America and the north part of South America, with a shaded area over the water covering Bermuda, Florida, the Gulf of Mexico, all of the Caribbean Sea and south from there to the northern part of the Brazilian coast
The shaded area of this map indicates the geographical distribution of Lobatus gigas.

Ecology

Queen conch embryos hatch 3–5 days after spawning.[48][49] 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.[48] Afterwards, the emerging two-lobed veliger (a larval form common to various marine and fresh-water gastropod and bivalve mollusks)[50] spend several days developing in the plankton, feeding primarily on phytoplankton. Metamorphosis occurs some 16–40 days from the hatching,[33] when the fully grown protoconch is about 1.2 mm high.[45] 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.[51] 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.[26][31] Individuals may usually live up to 7 years, though in deeper waters their lifespan may reach 20–30 years[31][33][45] and maximum lifetime estimates reach 40 years.[52] 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.[51]

Lobatus gigas is gonochoristic, which means each individual snail is either distinctly male or distinctly female.[26] Females are usually larger than males in natural populations, with both sexes existing in similar proportion.[45] After internal fertilization,[33] the females lay eggs in gelatinous strings, which can be as long as 75 feet (23 m).[31] 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.[33][46] Each one of the egg masses may have been fertilized by multiple males.[46] The number of eggs per egg mass varies greatly depending on environmental conditions such as food availability and temperature.[33][46] Commonly, females produce 8–9 egg masses per season,[26][47] each containing 180,000–460,000 eggs,[31] but numbers can be as high as 750,000 eggs.[33] L. gigas females may spawn multiple times during the reproductive season,[31] which lasts from March to October, with activity peaks occurring from July to September.[26]

A dense bed of seagrass with a shell in the middle of it
A subadult individual in a seagrass bed, Rice Bay, San Salvador Island, Bahamas

Life cycle

[44].substrate This leaping locomotion may help prevent predators from following the snail's chemical traces, which would otherwise leave a continuous trail on the [43] a good climber even of vertical concrete surfaces.L. gigas making [42],pole vaulting 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 [41][40] has an unusual means of Lobatus gigas

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.[16][38] 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.[38]

Foot/locomotion

A drawing of an adult male Lobatus gigas (from Duclos in Chenu, 1844) showing the external soft parts including the spade-shaped penis on the left. Separate details show the mouth, the distal portion of the penis, and both sides of the claw-like operculum

Many details about the anatomy of Lobatus gigas were not well known until Colin Little's 1965 general study.[38] In 2005, R. L. Simone gave a detailed anatomical description.[16] L. gigas has a long extensible nephiridial gland, the pericardium, the genital glands, stomach, style sac and the digestive gland. In adult males, the penis is also visible.[38]

A stout mottled eyestalk protruding from the siphonal canal of the shell with a ringed eye at the tip of the eyestalk and a small tentacle nearby branching off of the eyestalk
At the tip of the eyestalk is the well-developed eye. Near the tip is a small sensory tentacle

Soft parts

Antique illustration of large sea snail shell with flaring lip, as viewed more or less from the apex
Adult shell, apical view, Gualtieri, 1742

Similar large shell viewed from the apertural side
Adult shell, ventral view, Gualtieri, 1742

Similar shell viewed from the side opposite the aperture
Adult shell, dorsal view, Gualtieri, 1742

shell viewed from the apertural side
Juvenile shell, Tryon, 1885

[36]

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