The term true conchs, being a common name, does not have an exact meaning. It may refer generally to any of the Strombidae but sometimes is used more specifically to include only Strombus and Lambis or just Strombus itself.
|Three shells of three species in the family Strombidae: lower left Laevistrombus turturella, upper center Lambis lambis, lower right Euprotomus aurisdianae|
Strombid gastropods live mainly in tropical and subtropical waters. These animals are widespread in the Indo-West Pacific, where most species and genera occur. Nearly forty of the living species that used to belong to the genus Strombus can be found in the Indo-Pacific region. They also occur in the eastern Pacific and Western Atlantic, and a single species can be found on the African Atlantic coast. Six species of strombids are found in the wider Caribbean region, including the queen conch Lobatus gigas, the goliath conch Lobatus goliath, the hawk-wing conch Lobatus raninus, the rooster tail conch Lobatus gallus, the milk conch Lobatus costatus, the West Indian fighting conch Strombus pugilis and the Florida fighting conch Strombus alatus. Until recently, all of these species were placed in the genus Strombus, but now many species are being moved into new genera.
Strombids have long eye stalks. The shell of a strombid has a long and narrow aperture and a siphonal canal. The shell margin has an indentation near the anterior end which accommodates one of the eye stalks. This indentation is called a strombid or stromboid notch. The stromboid notch may be more or less conspicuous, depending on the species. The shell of most species in this family grow a flared lip upon reaching sexual maturity, and they lay eggs in long, gelatinous strands. The genera Strombus and Lambis have many similarities between them, both anatomical and reproductive, though their shells show some conspicuous differences.
Strombid were widely accepted as carnivores by several authors in the 19th century, an erroneous concept that persisted for several decades into the first half of the 20th century. This ideology was probably born in the writings of Lamarck, who classified strombids alongside other supposedly carnivorous snails, and was copied in this by subsequent authors. However, the many claims of those authors were never supported by the observation of animals feeding in their natural habitat. Nowadays, strombids are known to be specialized herbivores and occasional detritivores. They are usually associated with shallow water reefs and seagrass meadows.
Unlike most snails, which glide slowly across the substrate on their foot, strombid gastropods have a characteristic means of locomotion, using their pointed, sickle-shaped, horny operculum to propel themselves forward in a so-called leaping motion.
Burrowing behaviour, in which an individual sinks itself entirely or partially into the substrate, is also frequent among strombid gastropods. The burrowing process itself, which involves distinct sequential movements and sometimes complex behaviours, is very characteristic of each species. Usually, large strombid gastropods such as the queen conch Eustrombus gigas and the spider conch Lambis lambis, do not bury themselves, except during their juvenile stage. On the other hand, smaller species such as the dog conch Strombus canarium and Strombus epidromis may bury themselves even after adulthood, though this is not an absolute rule.
For a long time all conchs and their allies (the strombids) were classified in only two genera, namely Strombus and Lambis. This classification can still be found in many textbooks and on websites on the internet. Based on molecular phylogeny as well as a well-known fossil record, both genera have been subdivided into several new genera by different authors.
The family Strombidae actually comprises several genera (extinct genera are marked with a dagger †), including:
|Phylogeny and relationships of Strombidae according to Simone (2005)|
The phylogenetic relationships among the Strombidae have been mainly accessed in two different occasions, using two distinct methods. In a 2005 monograph, Simone proposed a cladogram (a tree of descent) based on an extensive morpho-anatomical analysis of representatives of Aporrhaidae, Strombidae, Xenophoridae and Struthiolariidae. In his analysis, Simone recognized Strombidae as a monophyletic taxon supported by 13 synapomorphies (traits that are shared by two or more taxa and their most recent common ancestor), comprising at least eight distinct genera. He considered the genus Terebellum as the most basal taxon, distinguished from the remaining strombids by 13 synapomorphies, including a rounded foot. Though the genus Tibia was left out of the analysis, Simone regarded it as probably closely related to Terebellum, apparently due to some well known morphological similarities between them. With the exception of Lambis, the remaining taxa were previously allocated within the genus Strombus. 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. The remaining taxa were previously considered as subgenera, and were elevated to genus level by Simone in the end of his analysis. The genus Eustrombus (now considered a synonym of Lobatus), in this case, included Eustrombus gigas (now considered a synonym of Lobatus gigas) and Eustrombus goliath (= Lobatus goliath); similarly, the genus Aliger included Aliger costatus (= Lobatus costatus) and Aliger gallus (= Lobatus gallus).
|Phylogeny and relationships of Strombidae according to Latiolais (2006)|
A different approach, this time based on sequences of nuclear histone H3 and mitochondrial cytochrome-c oxidase I (COI) genes was proposed by Latiolais and colleagues in a 2006 paper. The analysis included 32 strombid species that used to, or still belong in the genus Strombus and Lambis.
Several species belonging to numerous genera among Strombidae are considered economically important. Used as food, fishing bait, tools or simply as decoration, some strombid snail species have been used in human culture for centuries.
Aliger is a genus of sea snails, marine gastropod mollusks in the family Strombidae, the true conchs.Aliger has become a synonym of Lobatus Swainson, 1837Canarium wilsonorum
Canarium wilsonorum is a species of sea snail, a marine gastropod mollusk in the family Strombidae, the true conchs.Conch
is a common name that is applied to a number of different medium to large-sized shells. The term generally applies to large snails whose shell has a high spire and a noticeable siphonal canal (in other words, the shell comes to a noticeable point at both ends).
In North America, a conch is often identified as a queen conch, indigenous to the waters of The Bahamas. Queen conchs are valued for seafood, and are also used as fish bait.The group of conchs that are sometimes referred to as "true conchs" are marine gastropod molluscs in the family Strombidae, specifically in the genus Strombus and other closely related genera. For example, see Lobatus gigas, the queen conch, and Laevistrombus canarium, the dog conch.
Many other species are also often called "conch", but are not at all closely related to the family Strombidae, including Melongena species (family Melongenidae), and the horse conch Triplofusus papillosus (family Fasciolariidae). Species commonly referred to as conchs also include the sacred chank or more correctly shankha shell (Turbinella pyrum) and other Turbinella species in the family Turbinellidae.Conomurex decorus
Conomurex decorus, common name : the Mauritian Conch, is a species of sea snail, a marine gastropod mollusk in the family Strombidae, the true conchs.Harpago chiragra
Harpago chiragra, common name the Chiragra spider conch, is a species of very large sea snail, a marine gastropod mollusk in the family Strombidae, the true conchs.Labiostrombus epidromis
Labiostrombus epidromis, common name the swan conch, is a species of sea snail, a marine gastropod mollusk in the family Strombidae, the true conchs.Laevistrombus canarium
Laevistrombus canarium (commonly known as the dog conch or by its better-known synonym, Strombus canarium) is a species of edible sea snail, a marine gastropod mollusc in the family Strombidae (true conches). Known from illustrations in books dating from the late 17th century, L. canarium is an Indo-Pacific species occurring from India and Sri Lanka to Melanesia, Australia and southern Japan. The shell of adult individuals is coloured from light yellowish-brown to golden to grey. It has a characteristic inflated body whorl, a flared, thick outer lip and a shallow stromboid notch. The shell is valued as an ornament, and because it is heavy and compact it is also often used as a sinker for fishing nets.
The external anatomy of the soft parts of this species is similar to that of other strombid snails. The animal has an elongate snout, thin eyestalks with well-developed eyes and sensory tentacles, and a narrow, strong foot with a sickle-shaped operculum. A molecular analysis conducted in 2006 based on DNA sequences of histone and mitochondrial genes demonstrated that Laevistrombus canarium, Doxander vittatus and Labiostrombus epidromis are closely related species. The dog conch exhibits behaviours common among Strombidae, including burrowing and a characteristic leaping form of locomotion. The former behaviour, however, involves movement sequences unique to this species.
Laevistrombus canarium lives on muddy and sandy bottoms, grazing on algae and detritus. It is gonochoristic and sexually dimorphic, depending on internal fertilization for spawning. Larvae of this species spend several days as plankton, undergoing a series of transformations until they reach complete metamorphosis. The maximum life span is 2 to 2.5 years. Predators of this snail include carnivorous gastropods such as cone snails and volutes. It is also a prey species for vertebrates including macaques, and also humans, who consume the soft parts in a wide variety of dishes.
The dog conch is an economically important species in the Indo-West Pacific, and several studies indicate that it may be suffering population declines due to overfishing and overexploitation. Malacologists and ecologists have recommended a reduction in its exploitation rate; initiatives in Thailand are attempting to ensure the possibility of reproduction in young-adult individuals and manage the natural populations in general. L. canarium demonstrates the imposex phenomenon, but is resistant to sterility caused by it; therefore, it has been suggested that this species might be useful as a bioindicator for organotin pollution monitoring near Malaysian ports.Lambis
Lambis is a genus of large sea snails sometimes known as spider conchs, marine gastropod mollusks in the family Strombidae, the true conch family.Lambis scorpius
Lambis scorpius, common name the scorpion conch or scorpion spider conch, is a species of large sea snail, a marine gastropod mollusk in the family Strombidae, the true conchs.Lentigo pipus
Lentigo pipus, common name : the Elegant Conch, is a species of Conch sea snail, a marine gastropod mollusk in the family Strombidae, the true conchs.Lobatus
Lobatus is a genus of very large sea snails, marine gastropod mollusks in the family Strombidae, the true conchs.Some of the species within this genus were previously placed in the genus Eustrombus.Lobatus gigas
Lobatus gigas, originally known as Strombus 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 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.Mirabilistrombus listeri
Mirabilistrombus listeri, common name the Lister's conch, is a species of sea snail, a marine gastropod mollusk in the family Strombidae, the true conchs.Persististrombus
Persististrombus is a genus of sea snails, marine gastropod mollusks in the family Strombidae, the true conchs.Persististrombus latus
Persististrombus latus, commonly known as the Bubonian Conch, is a species of sea snail, a marine gastropod mollusk in the family Strombidae, the true conchs.Rostellaria
Rostellaria is a genus of sea snails, marine gastropod mollusks in the family Strombidae, the true conchs.The genus Rostellaria has become a synonym of Tibia Röding, 1798Strombus
Strombus is a genus of medium to large sea snails, marine gastropod molluscs in the family Strombidae, which comprises the true conchs and their immediate relatives. The genus Strombus was named by Swedish Naturalist Carl Linnaeus in 1758. There were around 50 living species recognized, which vary in size from fairly small to very large. Six species live in the greater Caribbean region, including the queen conch, Strombus gigas (now usually known as Eustrombus gigas or Lobatus gigas), and the West Indian fighting conch, Strombus pugilis. However, since 2006, many species have been assigned to discrete genera. These new genera are however not yet found in most textbooks and collector's guides.
Worldwide, several of the larger species are economically important as food sources; these include the endangered queen conch which very rarely also produces a pink, gem quality pearl.
In the geological past, a much larger number of species of Strombus existed. Fossils of species within this genus have been found all over the world in sediments from Cretaceous to Quaternary (age range: 140.2 to 0.0 million years ago).Of the living species, most are in the Indian and Pacific Oceans. Many species of true conchs live on sandy bottoms among beds of sea grass in tropical waters. They eat algae and have a claw-shaped operculum.Tridentarius dentatus
Tridentarius dentatus, common name : the Toothed Conch, is a species of sea snail, a marine gastropod mollusk in the family Strombidae, the true conchs.Varicospira
Varicospira is a genus of sea snails, marine gastropod mollusks in the family Rostellariidae within the Stromboidea, the true conchs and their allies.