Laevistrombus canarium

The English common name of L. canarium, "dog conch", is a calque of the Malay. In the Malay Peninsula, the species is known by the Malay name siput gonggong, where siput means "snail" and gonggong is an onomatopoetic word for a dog's bark.[2][8][9]

A 1742 illustration from Index Testarum Conchyliorum, showing abapertural (left) and apertural (right) views of an adult dog conch shell

The first published depictions of the shell of this species appeared in 1681 in the earliest book solely about sea shells, Recreatio mentis et oculi in observatione animalium testaceorum (Refreshment of the mind and the eye in the observation of shell-bearing animals) by Italian scholar Filippo Buonanni.[10][11] The species was shown in the 1742 Index Testarum Conchyliorum, quae adservantur in Museo Nicolai Gualtieri (List of the shells of shellfish which are preserved in the museum of Niccolò Gualtieri) by Italian physician and malacologist Niccolò Gualtieri. In both books, the morphology of an adult shell was shown from different perspectives.[11]

In 1758, the dog conch was formally described and named Strombus canarium by Swedish naturalist and taxonomist Carl Linnaeus, who originated the system of binomial nomenclature. The specific name of this taxon, canarium, is derived from the Latin canis (dog).[12] The original description given by Linnaeus in his book, Systema Naturae, is in Latin: "S. testae labro rotundato brevi retuso, spiraque laevi." This can be translated as "Strombus with a shell having a retuse, short, rounded lip, and a smooth spire". Linnaeus did not mention a specific locality in his original description, giving only Eastern Asia as the area in which the species is found.[4]

The taxon Laevistrombus was introduced in the literature as a subgenus of Strombus by Tetsuaki Kira (1955) in the third printing of the first edition of Coloured Illustrations of the Shells of Japan. It comprised two species, Strombus (Laevistrombus) canarium and Strombus (L.) isabella Lamarck, 1822. No type specimen was designated, and Kira gave no formal description or statement of differentiation, as required by the ICZN code to validate the name. In a later version of the book, Laevistrombus was elevated to genus level, but a description was still lacking. Rüdiger Bieler and Richard Petit (1996) considered it a nomen nudum, and the authorship was transferred to Robert Tucker Abbott (1960), who had provided a proper description and illustrations of Laevistrombus and specified a type species, Strombus canarium L., in the first volume of his monograph Indo-Pacific Mollusca.[13][14][15] The currently accepted combination, Laevistrombus canarium, was proposed by Jack John Sepkoski Jr. (2002), who elevated Laevistrombus to genus level based on palaeontological data.[16]

The synonyms are other binomial names that were given over time to this taxon by authors who were unaware that the specimens they were describing belonged to a species already described by Linnaeus; in some cases, local variations in colour and form may have misled these authors into thinking they had a different species. Strombus vanicorensis is a subsequent, changed spelling of Strombus vanikorensis by one of the original authors.[1][2] Some disagreement is seen in the literature as to whether or not this taxon and the similar-looking Laevistrombus turturella are actually separate species. Leo Man In 'T Veld and Koenraad de Turck (1998) considered that L. canarium and L. turturella are distinct (yet sympatric) species, based mainly on the shell morphology and a radula comparison.[3] However, when Zaidi Che Cob reviewed a number of Strombus species in 2009, examining both shell characters and anatomical data including details of the genitalia, operculum, and radula, he concluded that L. turturella was simply a morphotype, and therefore a synonym of L. canarium.[2]

L. canarium comprises at least two known subspecies; one is the nominate subspecies L. c. canarium and the other is L. c. guidoi.[17] L. c. guidoi distinguishes itself from the other subspecies by its solid white colour, the outline of the posterior canal, and a more prominent posteriorly protruding outer lip. The presence of a freely protruding lip at the posterior portion of the columella is also a distinctive character.[3]

In 2006, Latiolais and colleagues proposed a cladogram (tree of descent) that attempts to show the phylogenetic relationships of 34 species within the family Strombidae. The authors analysed 31 species in the genus Strombus (including S. canarium) 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 protein-coding gene regions. In this proposed phylogeny S. (L.) canarium, Strombus vittatus (a synonym for Doxander vittatus)[21] and Strombus epidromis (Labiostrombus epidromis)[22] are closely related, and appear to share a common ancestor.[20]

L. canarium is native to the coastal waters of the Indo-Pacific region.[23] Its westernmost distribution is India, including Andhra Pradesh, Tamil Nadu (Gulf of Mannar, Tuticorin, Rameswaram), and the Andamans.[24] It occurs in Sri Lanka (Eastern province, Trincomalee), Thailand, Borneo (Brunei, Sabah), Indonesia (Moluccas, Saparua) and the Philippines (Cebu Island, Polillo Islands, Palawan). It is also found further east in Melanesia, including Yos Sudarso Bay in New Guinea, Papua New Guinea, Malaita and Guadalcanal in the Solomon Islands, New Caledonia, Kioa Island in Fiji, and New Hebrides. The species is known to occur in Queensland, Australia, and north to Vietnam, Taiwan, and southern Japan.[1][3]

Detailed information is available about its distribution in the Straits of Johor area and some other parts of Malaysia, where it has been reported from the Tanjung Adang Shoal, Merambong Shoal, Tanjung Bin, Tanjung Surat, Tanjung Buai and Pasir Gogok in the Johor Straits, Pulau Tinggi, Pulau Besar and Pulau Sibu, in eastern Johor, Port Dickson and Teluk Kemang in Negeri Sembilan, Pulau Pangkor, Pulau Langkawi and Cape Rachado.

Compared to most other gastropods, L. canarium has an unusual means of locomotion that is common only among the Strombidae. This curious series of maneuvers was originally described by American zoologist George Howard Parker in 1922. The animal initially fixes the posterior end of the foot by thrusting the point of its sickle-shaped operculum into the substrate. Then, it extends its foot forward, lifting the shell and throws it ahead in a motion that has been described as "leaping".[19][25]

Burrowing behaviour, in which an individual sinks itself entirely (or partially) into the substrate, is frequent among strombid gastropods.[26] The burrowing behaviour of L. canarium consists of a series of movements characteristic of the species. There are three consecutive movements: first is probing, where the animal pushes the anterior portion of the foot into the substrate to gain a hold; next is shovelling, where it pushes the substrate with its long, extensible proboscis. Retraction is the final movement, where it moves the shell along an anterior-posterior axis to settle the substrate around it. Once burrowed, part of the dorsal shell is usually still visible (although the ventral surface and the animal's soft parts are buried).[26]

The escape response in gastropods—the perception of stimuli (for example, the presence of a predator nearby) and a subsequent escape motion—is a frequent target of behavioural studies.[27] In gastropods, the perception of environmental chemical stimuli originating, for example, from food or other organisms is possibly mediated by sensory organs such as the osphradium.[28] In the case of L. canarium, the perception of a predator can occur through chemoreception or vision (a well-developed sense in strombid gastropods).[27][29] The presence of a predator can significantly alter the movement pattern of L. canarium, inducing an increase in the frequency of leaps.[27]

The dog conch lives on muddy sand bottoms among algae and seagrass beds on insular and continental shores. It usually prefers major islands and continental coasts rather than the shores of small islands, although this is not an absolute rule.[1][30] L. canarium prefers areas of mixed seagrasses (with a predominance of Halophila), and also prefers sediment with high levels of organic matter.[31] This conch avoids environments with a high density of Enhalus acoroides, a large seagrass native to coastal waters of the Indo-Pacific.[31][32] The dog conch can be found in littoral and sublittoral zones, from shallow water to a depth of 55 m (180 ft).[1] It is normally found in large colonies,[19] and is usually abundant wherever it occurs.[33]

One known predator of the dog conch is the cloth-of-gold cone snail, Conus textile.

During the 19th century, strombid gastropods were believed to be carnivores. This erroneous conception was based on the writings of French naturalist Jean Baptiste Lamarck, whose classification scheme grouped strombids with carnivorous sea snails.[34] Subsequent studies have refuted the concept, proving beyond doubt that strombid gastropods are herbivorous animals.[34] In common with other Strombidae, Laevistrombus canarium is known to be a herbivore,[33] feeding on algae and occasionally detritus.[1]

Many carnivorous marine gastropods are known predators of L. canarium, including the volutes Cymbiola nobilis and Melo melo and the cone snail (Conus textile).[27] The dog conch is also preyed upon by vertebrates. These include the crab-eating macaque, Macaca fascicularis, an opportunistic predator that scours intertidal environments.[35] Humans are one of the dog conch's main predators, subjecting the species to intensive fishing and exploitation.[1][23] Empty shells of L. canarium are often occupied by the land hermit crab Coenobita violascens.[36]

L. canarium is often parasitized by protists of the phylum Apicomplexa, which are common mollusk parasites.[37][38] The coccidian parasites that infect L. canarium belong to the genus Pseudoklossia. These spore-forming, single-celled microorganisms[39] infest the hosts' kidney cells, and the digestive ducts and tubules of its digestive gland.[37]

Structural diagram of a tributyltin (TBT) compound. Organic tin compounds such as TBT can cause imposex in gastropods.

The flesh of the dog conch is edible. It is a staple food for locals living along the seashore, and is fished in many parts of Southeast Asia.[23] Despite their ornamental value,[1][41] L. canarium shells are traditionally used by local fishermen as sinkers for fishing nets.[1] Studies from 2008 to 2009 indicate that L. canarium has been overexploited and overfished in many areas; malacologists and ecologists have recommended reducing exploitation rates to maintain its availability as a natural resource.[23] Finding large dog-conch individuals has become an increasingly difficult task in several regions where this species occurs.[42] Initiatives in the southern Thailand province of Phuket intend to increase depleted natural stocks of L. canarium by reintroducing cultured animals in local seagrass beds. Fishermen are encouraged not to collect younger, smaller individuals that have not yet reproduced.[42]

L. canarium is a local delicacy in the Malay Peninsula. Dog conchs are boiled with lemongrass and can be eaten with white rice.

Dog conchs served in a seafood restaurant near Johor Bahru, Malaysia

Imposex has recently been detected in L. canarium.[43] Imposex is the development of male sex organs in female animals exposed to man-made organic tin compounds, such as tributyltin (TBT). It has negative consequences for several species of sea snails, ranging from sterility in some individuals to the extinction of entire populations.[44] Tin compounds are biocidal antifouling agents mixed into paints to prevent marine encrustations on boats and ships. High concentrations of these compounds are commonly present in seawater near shipyards and docking areas, exposing nearby marine life to harmful effects.[43][44] In a 2011 paper, Cob and colleagues found that imposex rates are high in dog conch populations near Malaysian ports; however, the researchers could not detect any cases of sterility in affected females. The authors concluded that females of L. canarium often develop a penis when seawater contains organotin compounds, but the phenomenon does not cause sterility in this species. The ability of the dog conch to survive despite imposex makes this species a suitable local bioindicator for organotin pollution.[43]

• Media related to Laevistrombus canarium at Wikimedia Commons
• "Laevistrombus canarium". Gastropods.com. Retrieved 23 March 2011.