Aliger gigas, originally known as Strombus gigas or more recently as Lobatus gigas, commonly known as the queen conch, is a species of large 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 Caribbean Sea, and tropical northwestern Atlantic, reaching up to in shell length. A. gigas is closely related to the goliath conch, Titanostrombus goliath, a species endemic to Brazil, as well as the rooster conch, Aliger gallus.
The queen conch is herbivorous. It feeds by browsing for plant and algal material growing in the seagrass beds, and scavenging for decaying plant matter. These large sea snails typically reside in seagrass beds, which are sandy plains covered in swaying sea grass and associated with coral reefs, although the exact habitat of this species varies according to developmental age. 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 or orange aperture (opening). The outside of the queen conch is sandy colored, helping them blend in with their surroundings. The flared lip is absent in juveniles; it develops once the snail reaches reproductive age. The thicker the shell's flared lip is, the older the conch is. The external anatomy of the soft parts of A. gigas is similar to that of other snails in the family Strombidae; 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 A. gigas serve as a home to several different kinds of commensal animals, including slipper snails, porcelain crabs and a specialized species of cardinalfish known as the conchfish Astrapogon stellatus. Its parasites include coccidians. The queen conch's natural predators include several species of large predatory sea snails, octopus, starfish, crustaceans and vertebrates (fish, sea turtles, nurse sharks). It is an especially important food source for large predators like sea turtles and nurse sharks. Human capture and consumption date back into prehistory.
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 the Caribbean 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.
Taxonomy and etymology
thumb|left|alt=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 [[Type (biology)|neotype of this species: a figure of A. gigas from ' (1684). The shell in the figure appears left-right reversed because of the engraving process. The original type was subsequently found, invalidating this designation.]]
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. The specific name is the ancient Greek word ' (), which means "giant", referring to the large size of this snail compared with almost all other gastropod molluscs. Strombus lucifer, which was considered to be a synonym much later, was also described by Linnaeus in Systema Naturae.
Strombidae's taxonomy was extensively revised in the 2000s and a few subgenera, including Eustrombus, were elevated to genus level by some authors. and Petuch and Roberts recombined this species as Eustrombus gigas, and Landau and collaborators (2008) recombined it as Lobatus gigas. In 2020, it was recombined as Aliger gigas by Maxwell and colleagues, which is the current valid name according to the World Register of Marine Species.
Phylogeny
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