Snail

A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name snail is also used for most of the members of the molluscan class Gastropoda that have a coiled shell that is large enough for the animal to retract completely into. When the word "snail" is used in this most general sense, it includes not just land snails but also numerous species of sea snails and freshwater snails. Gastropods that naturally lack a shell, or have only an internal shell, are mostly called slugs, and land snails that have only a very small shell (that they cannot retract into) are often called semi-slugs.

Snails have considerable human relevance, including as food items, as pests, as vectors of disease, and their shells are used as decorative objects and are incorporated into jewelry. The snail has also had some cultural significance, and has been used as a metaphor.

Snail
Grapevinesnail 01
Helix pomatia, a species of land snail
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Epiphragma einer Weinbergschnecke
Helix pomatia sealed in its shell with a calcareous epiphragm

Overview

Video of snails (most likely Natica chemnitzi and Cerithium stercusmuscaram) feeding on the sea floor in the Gulf of California, Puerto Peñasco, Mexico, 50 sec
Video of snail after rain, 31 sec

Snails that respire using a lung belong to the group Pulmonata. As traditionally defined, the Pulmonata were found to be polyphyletic in a molecular study per Jörger et al., dating from 2010.[1] But snails with gills also form a polyphyletic group; in other words, snails with lungs and snails with gills form a number of taxonomic groups that are not necessarily more closely related to each other than they are related to some other groups.

Both snails that have lungs and snails that have gills have diversified so widely over geological time that a few species with gills can be found on land and numerous species with lungs can be found in freshwater. Even a few marine species have lungs.

Snails can be found in a very wide range of environments, including ditches, deserts, and the abyssal depths of the sea. Although land snails may be more familiar to laymen, marine snails constitute the majority of snail species, and have much greater diversity and a greater biomass. Numerous kinds of snail can also be found in fresh water.

Most snails have thousands of microscopic tooth-like structures located on a banded ribbon-like tongue called a radula. The radula works like a file, ripping food into small pieces. Many snails are herbivorous, eating plants or rasping algae from surfaces with their radulae, though a few land species and many marine species are omnivores or predatory carnivores. Snails cannot absorb colored pigments when eating paper or cardboard so their feces are also colored.[2]

Several species of the genus Achatina and related genera are known as giant African land snails; some grow to 15 in (38 cm) from snout to tail, and weigh 1 kg (2 lb).[3] The largest living species of sea snail is Syrinx aruanus; its shell can measure up to 90 cm (35 in) in length, and the whole animal with the shell can weigh up to 18 kg (40 lb).

Snail moving on a wet ground
Snail moving across leaves.

The snail Lymnaea makes decisions by using only two types of neuron: one deciding whether the snail is hungry, and the other deciding whether there is food in the vicinity.[4]

The largest known land gastropod is the African giant snail Achatina achatina, the largest recorded specimen of which measured 39.3 centimetres (15.5 in) from snout to tail when fully extended, with a shell length of 27.3 cm (10.7 in) in December 1978. It weighed exactly 900 g (2 lb). Named Gee Geronimo, this snail was owned by Christopher Hudson (1955–79) of Hove, East Sussex, UK, and was collected in Sierra Leone in June 1976.[5]

Slugs

Gastropods that lack a conspicuous shell are commonly called slugs rather than snails.[6] Some species of slug have a red shell, some have only an internal vestige that serves mainly as a calcium repository, and others have no shell at all. Other than that there is little morphological difference between slugs and snails. There are however important differences in habitats and behavior.

A shell-less animal is much more maneuverable and compressible, so even quite large land slugs can take advantage of habitats or retreats with very little space, retreats that would be inaccessible to a similar-sized snail. Slugs squeeze themselves into confined spaces such as under loose bark on trees or under stone slabs, logs or wooden boards lying on the ground. In such retreats they are in less danger from either predators or desiccation, and often those also are suitable places for laying their eggs.

Slugs as a group are far from monophyletic; biologically speaking "slug" is a term of convenience with little taxonomic significance. The reduction or loss of the shell has evolved many times independently within several very different lineages of gastropods. The various taxa of land and sea gastropods with slug morphology occur within numerous higher taxonomic groups of shelled species; such independent slug taxa are not in general closely related to one another.

Human relevance

Snail-wiki-120-Zachi-Evenor
Helix aspersa – garden snail

Land snails are known as an agricultural and garden pest but some species are an edible delicacy and occasionally household pets.

In agriculture

There are a variety of snail-control measures that gardeners and farmers use in an attempt to reduce damage to valuable plants. Traditional pesticides are still used, as are many less toxic control options such as concentrated garlic or wormwood solutions. Copper metal is also a snail repellent, and thus a copper band around the trunk of a tree will prevent snails from climbing up and reaching the foliage and fruit. Placing crushed egg shells on the soil around garden plants can also deter snails from coming to the plants.

The decollate snail (Rumina decollata) will capture and eat garden snails, and because of this it has sometimes been introduced as a biological pest control agent. However, this is not without problems, as the decollate snail is just as likely to attack and devour other gastropods that may represent a valuable part of the native fauna of the region.

As food

In French cuisine, edible snails are served for instance in Escargot à la Bourguignonne. The practice of rearing snails for food is known as heliciculture. For purposes of cultivation, the snails are kept in a dark place in a wired cage with dry straw or dry wood. Coppiced wine-grape vines are often used for this purpose. During the rainy period, the snails come out of hibernation and release most of their mucus onto the dry wood/straw. The snails are then prepared for cooking. Their texture when cooked is slightly chewy.

As well as being relished as gourmet food, several species of land snails provide an easily harvested source of protein to many people in poor communities around the world. Many land snails are valuable because they can feed on a wide range of agricultural wastes, such as shed leaves in banana plantations. In some countries, giant African land snails are produced commercially for food.

Land snails, freshwater snails and sea snails are all eaten in a number of countries (principally Spain, Philippines, Morocco, Nigeria, Algeria, Cameroon, France, Italy, Portugal, Greece, Bulgaria, Belgium, Vietnam, Laos, Cambodia, Cyprus, Ghana, Malta, Terai of Nepal, China, Northeast India states such as Manipur, Tripura and parts of the United States). In certain parts of the world, snails are fried. For example, in Indonesia, they are fried as satay, a dish known as sate kakul. The eggs of certain snail species are eaten in a fashion similar to the way caviar is eaten.

In Bulgaria, snails are traditionally cooked in an oven with rice or fried in a pan with vegetable oil and red paprika powder. Before they are used for those dishes, however, they are thoroughly boiled in hot water (for up to 90 minutes) and manually extracted from their shells. The two species most commonly used for food in the country are Helix lucorum and Helix pomatia.

Famine food

Snails and slug species that are not normally eaten in certain areas have occasionally been used as famine food in historical times. A history of Scotland written in the 1800s recounts a description of various snails and their use as food items in times of plague.[7]

Cosmetic

Skin creams derived from Helix aspersa snails are sold for use on wrinkles, scars, dry skin, and acne. A research study suggested that secretions produced under stress by Helix aspersa might facilitate regeneration of wounded tissue.[8]

Cultural depictions

Csigabiga
Snail sculpture

Symbolism

Because of its slowness, the snail has traditionally been seen as a symbol of laziness. In Christian culture, it has been used as a symbol of the deadly sin of sloth.[9][10] Psalms 58:8 uses snail slime as a metaphorical punishment. In Mayan mythology, the snail is associated with sexual desire, being personified by the god Uayeb.[11]

Divination and other religious uses

Mochesnail
Land snails (Scutalus sp.) on a Moche pot, 200 AD, Larco Museum Collection, Lima, Peru

Snails were widely noted and used in divination.[9] The Greek poet Hesiod wrote that snails signified the time to harvest by climbing the stalks, while the Aztec moon god Tecciztecatl bore a snail shell on his back. This symbolised rebirth; the snail's penchant for appearing and disappearing was analogised with the moon.[12]

Love darts and Cupid

Monachoides vicinus dart lateral
The use of love darts by the land snail Monachoides vicinus is a form of sexual selection

Professor Ronald Chase of McGill University in Montreal has suggested the ancient myth of Cupid's arrows might be based on early observations of the love dart behavior of the land snail species Helix aspersa.[13]

Metaphor

In contemporary speech, the expression "a snail's pace" is often used to describe a slow, inefficient process. The phrase "snail mail" is used to mean regular postal service delivery of paper messages as opposed to the delivery of email, which can be virtually instantaneous.

In Indonesian mythology

Dewi Sekartaji Keong Emas
Dewi Sekartaji as Keong Emas

Keong Emas (Javanese and Indonesian for Golden Snail) is a popular Javanese folklore about a princess magically transformed and contained in a golden snail shell. The folklore is a part of popular Javanese Panji cycle telling the stories about the prince Panji Asmoro Bangun (also known as Raden Inu Kertapati) and his consort, princess Dewi Sekartaji (also known as Dewi Chandra Kirana).

Textiles

Certain varieties of snails, notably the family Muricidae, produce a secretion that is a color-fast natural dye. The ancient Tyrian purple was made in this way as were other purple and blue dyes.[14][15][16] The extreme expense of extracting this secretion is sufficient quantities limited its use to the very wealthy. It is such dyes as these that led to certain shades of purple and blue being associated with royalty and wealth.[17]

See also

References

  1. ^ Jörger, Katharina M; Stöger, Isabella; Kano, Yasunori; Fukuda, Hiroshi; Knebelsberger, Thomas; Schrödl, Michael (2010). "On the origin of Acochlidia and other enigmatic euthyneuran gastropods, with implications for the systematics of Heterobranchia". BMC Evolutionary Biology. 10 (1): 323. doi:10.1186/1471-2148-10-323. PMC 3087543. PMID 20973994.
  2. ^ "Floor tiles made of coloured snail poo by Lieske Schreuder - design". 26 November 2013. Retrieved 29 March 2018.
  3. ^ Fredericks, Anthony D. (2010). How Long Things Live & How They Live As Long As They Do. Stackpole Books. p. 73. ISBN 9780811736220. Retrieved 19 June 2012.
  4. ^ Crossley, Michael; Staras, Kevin; Kemenes, György (3 June 2016). "A two-neuron system for adaptive goal-directed decision-making in Lymnaea". Nature Communications. 7: 11793. Bibcode:2016NatCo...711793C. doi:10.1038/ncomms11793. PMC 4895806. PMID 27257106.
  5. ^ "Largest Snail". Guinness World Records. Retrieved 17 December 2016.
  6. ^ "Slug vs Snail - Difference and Comparison - Diffen". Retrieved 29 March 2018.
  7. ^ Chambers, Robert (1858). Domestic annals of Scotland, from the reformation to the revolution. W. & R. Chambers. (Also quoted here.
  8. ^ Brieva, A.; Philips, N.; Tejedor, R.; Guerrero, A.; Pivel, J. P.; Alonso-Lebrero, J. L.; Gonzalez, S. (January 2008). "Molecular basis for the regenerative properties of a secretion of the mollusk Cryptomphalus aspersa". Skin Pharmacology and Physiology. 21 (1): 15–21. doi:10.1159/000109084. ISSN 1660-5527. PMID 17912020.
  9. ^ a b de Vries, Ad (1976). Dictionary of Symbols and Imagery. Amsterdam: North-Holland Publishing Company. p. 430. ISBN 978-0-7204-8021-4.
  10. ^ Tresidder, Jack (2006). Symbols and Their Meanings. New York: Barnes & Noble. p. 41. ISBN 978-0-7607-8164-7.
  11. ^ Susan Milbrath, Star Gods of the Maya: Astronomy in Art, Folklore, and Calendars, University of Texas Press, 01/01/2010
  12. ^ Cooper, J. C. (1992). Symbolic and Mythological Animals. London: Aquarian Press. p. 213. ISBN 978-1-85538-118-6.
  13. ^ Mayell, Hillary (February 13, 2004). "Lovebirds and Love Darts: The Wild World of Mating". news.national-geographic.com. National Geographic Society. Retrieved 2010-02-21.
  14. ^ Ziderman, I. I. (1986). "Purple dye made from shellfish in antiquity". Review of Progress in Coloration. 16: 46–52. ISSN 1472-3581.
  15. ^ Biggam, Carole P. (March 2006). "Whelks and purple dye in Anglo-Saxon England" (PDF). The Archeo+Malacology Group Newsletter (9).
  16. ^ Moorey, Peter (1999). Ancient Mesopotamian Materials and Industries: The Archaeological Evidence. Winona Lake, Indiana: Eisenbrauns. p. 138. ISBN 978-1-57506-042-2.
  17. ^ Nuttall, Zelia (1909). "A Curious Survival in Mexico of the Use of the Purpura Shell-fish for Dyeing". In Boas, Franz. Putnam Anniversary Volume. Anthropological Essays Presented to Fredrick Ward Putnam in Honor of his Seventieth Birthday, by his Friends and Associates. New York: G. E. Stechert & Co. pp. 368–384. LCCN 10011191.

External links

Cancellariidae

Cancellariidae, common name the nutmeg snails or nutmeg shells, are a family of small to medium-large sea snails, marine gastropod mollusks in the clade Neogastropoda. Some of the shells of the species in this family resemble a nutmeg seed.

Cancellariidae is the only family in the superfamily Cancellarioidea.

Cinnamon roll

A cinnamon roll (also cinnamon bun, cinnamon swirl, and cinnamon snail) is a sweet roll served commonly in Northern Europe and North America. In Denmark, it is known as Kanelsnegl; 'cinnamon snail' and is a form of wienerbrød ('Vienna Bread'). Its main ingredients are flour, cinnamon, sugar, and butter, which provide a robust and sweet flavor.

Columella (gastropod)

The columella (meaning "little column") or (in older texts) pillar is a central anatomical feature of a coiled snail shell, a gastropod shell. The columella is often only clearly visible as a structure when the shell is broken, sliced in half vertically, or viewed as an X-ray image.

The columella runs from the apex of the shell to the midpoint of the undersurface of the shell, or the tip of the siphonal canal in those shells which have a siphonal canal. If a snail shell is visualized as a cone of shelly material which is wrapped around a central axis, then the columella more or less coincides spatially with the central axis of the shell. In the case of shells that have an umbilicus, the columella is a hollow structure.

The columella of some groups of gastropod shells can have a number of plications or folds (the columellar fold, plaits or plicae), which are usually visible when looking to the inner lip into the aperture of the shell. These folds can be wide or narrow, prominent or subtle. These features of the columella are often useful in identifying the family, genus, or species of the gastropod.

The surface of the columella is called the columellar wall. The columellar callus is a smooth, calcareous thickening, secreted by the mantle, extending over the columellar area. The columellar lip, the visible part of the columella, is the lower part of the inner lip and is situated near the axis of coiling. A columellar tooth is a raised projection on the inner lip of a columella in the direction of the aperture.

Cone snail

Cone snails, cone shells, or cones are common names for a large group of small to large-sized extremely venomous

predatory sea snails, marine gastropod molluscs.Until fairly recently, over 600 species of cone snails were all classified under one genus, Conus, in one family, the Conidae. However, in recent years, it was suggested that cone snails should occupy only a subfamily that should be split into a very large number of genera. A 2014 paper attempted to stabilize a newer classification of the group, significantly reducing the number of new genera but keeping a fairly large number of subgenera. Although the taxonomy has changed significantly several times during recent years, in the current (2015) version of the taxonomy of these snails and their close relatives, cone snails once again compose the entire family Conidae.

Geologically speaking, fossils of cone snails are known from the Eocene to the Holocene epochs. Cone snail species have shells that are shaped more or less like geometric cones. Many species have colorful patterning on the shell surface. Cone snails are almost all tropical in distribution.

Because all cone snails are venomous and capable of "stinging" humans, live ones should never be handled, as their venomous sting will occur without warning and can be fatal. The species most dangerous to humans are the larger cones, which prey on small bottom-dwelling fish; the smaller species mostly hunt and eat marine worms. Cone snails use a hypodermic needle–like modified radula tooth and a venom gland to attack and paralyze their prey before engulfing it. The tooth, which is sometimes likened to a dart or a harpoon, is barbed and can be extended some distance out from the head of the snail, at the end of the proboscis.

Cone snail venoms are mainly peptides. The venoms contain many different toxins that vary in their effects; some are extremely toxic. The sting of small cones is no worse than a bee sting, but the sting of a few of the larger species of tropical cone snails can be serious, occasionally even fatal to humans. Cone snail venom is showing great promise as a source of new, medically important substances.

Cornu aspersum

Cornu aspersum, known by the common name garden snail, is a species of land snail. As such it is a terrestrial pulmonate gastropod mollusc in the family Helicidae, which includes some of the most commonly familiar land snails. Of all terrestrial molluscs, this species may well be the most widely known. In English texts it was classified under the name Helix aspersa for over two centuries, but the prevailing classification now places it in the genus Cornu.

Cornu aspersum is native to the Mediterranean area and Western Europe, but whether deliberately or accidentally, humans have spread it to temperate and subtropical areas worldwide. The snail is relished as a food item in some areas, but it is also widely regarded as a pest in gardens and in agriculture, especially in regions where it has been introduced accidentally, and where snails are not usually considered to be a menu item.

Escargot

Escargots, IPA: [ɛs.kaʁ.ɡo], (French for snails) are a delicacy consisting of cooked edible land snails. They are often served as an hors d'oeuvre and consumed by the French people, as well as people from Portugal, Sardinia, and Spain. They are also a typical of the cuisines of Crete, and Greece, as well as such North African countries as Algeria and Morocco. The word escargot is also sometimes applied to living examples of those species which are commonly eaten in this way. In British English, the menu item is usually referred to simply as snails.

Freshwater snail

Freshwater snails are gastropod mollusks which live in freshwater. There are many different families. They are found throughout the world in various habitats, ranging from ephemeral pools to the largest lakes, and from small seeps and springs to major rivers. The great majority of freshwater gastropods have a shell, with very few exceptions. Some groups of snails that live in freshwater respire using gills, whereas other groups need to reach the surface to breathe air. In addition, some are amphibious and have both gills and a lung (e.g. Ampullariidae). Most feed on algae, but many are detritivors and some are filter feeders.

According to a 2008 review of the taxonomy, there are about 4,000 species of freshwater gastropods (3,795-3,972).At least 33–38 independent lineages of gastropods have successfully colonized freshwater environments. It is not possible to quantify the exact number of these lineages yet, because they have yet to be clarified within the Cerithioidea. From six to eight of these independent lineages occur in North America.

Gastropod shell

The gastropod shell is part of the body of a gastropod or snail, a kind of mollusc. The shell is an exoskeleton, which protects from predators, mechanical damage, and dehydration, but also serves for muscle attachment and calcium storage. Some gastropods appear shell-less (slugs) but may have a remnant within the mantle, or the shell is reduced such that the body cannot be retracted within (semi-slug). Some snails also possess an operculum that seals the opening of the shell, known as the aperture, which provides further protection. The study of mollusc shells is known as conchology. The biological study of gastropods, and other molluscs in general, is malacology. Shell morphology terms vary by species group. An excellent source for terminology of the gastropod shell is "How to Know the Eastern Land Snails" by John B. Burch now freely available at the Hathi Trust Digital Library.

Gastropoda

The gastropods (), more commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca, called Gastropoda. This class comprises snails and slugs from saltwater, from freshwater, and from the land. There are many thousands of species of sea snails and slugs, as well as freshwater snails, freshwater limpets, and land snails and slugs.

The class Gastropoda contains a vast total of named species, second only to the insects in overall number. The fossil history of this class goes back to the Late Cambrian. As of 2017, 721 families of gastropods are known, of which 245 are extinct and appear only in the fossil record, while 476 are currently extant with or without a fossil record.Gastropoda (previously known as univalves and sometimes spelled "Gasteropoda") are a major part of the phylum Mollusca, and are the most highly diversified class in the phylum, with 65,000 to 80,000 living snail and slug species. The anatomy, behavior, feeding, and reproductive adaptations of gastropods vary significantly from one clade or group to another. Therefore, it is difficult to state many generalities for all gastropods.

The class Gastropoda has an extraordinary diversification of habitats. Representatives live in gardens, woodland, deserts, and on mountains; in small ditches, great rivers and lakes; in estuaries, mudflats, the rocky intertidal, the sandy subtidal, in the abyssal depths of the oceans including the hydrothermal vents, and numerous other ecological niches, including parasitic ones.

Although the name "snail" can be, and often is, applied to all the members of this class, commonly this word means only those species with an external shell big enough that the soft parts can withdraw completely into it. Those gastropods without a shell, and those with only a very reduced or internal shell, are usually known as slugs; those with a shell into which they can partly but not completely withdraw are termed semi-slugs.

The marine shelled species of gastropod include species such as abalone, conches, periwinkles, whelks, and numerous other sea snails that produce seashells that are coiled in the adult stage—though in some, the coiling may not be very visible, for example in cowries. In a number of families of species, such as all the various limpets, the shell is coiled only in the larval stage, and is a simple conical structure after that.

Helix pomatia

Helix pomatia, common names the Roman snail, Burgundy snail, edible snail or escargot, is a species of large, edible, air-breathing land snail, a pulmonate gastropod terrestrial mollusc in the family Helicidae. It is a European species. In the English language it is called by the French name escargot when used in cooking (escargot simply means 'snail'). Although this species is highly prized as a food, it is difficult to cultivate and rarely farmed commercially.

Land snail

A land snail is any of the numerous species of snail that live on land, as opposed to sea snails and freshwater snails. Land snail is the common name for terrestrial gastropod mollusks that have shells (those without shells are known as slugs). However, it is not always easy to say which species are terrestrial, because some are more or less amphibious between land and fresh water, and others are relatively amphibious between land and salt water.

The majority of land snails are pulmonates. That is, they have a lung and breathe air. A minority, however, belong to much more ancient lineages whose anatomy includes a gill and an operculum. Many of these operculate land snails live in habitats or microhabitats that are sometimes (or often) damp or wet, such as in moss.

Land snails have a strong muscular foot; they use mucus to enable them to crawl over rough surfaces and to keep their soft bodies from drying out. Like other mollusks, land snails have a mantle, and they have one or two pairs of tentacles on their head. Their internal anatomy includes a radula and a primitive brain.

In terms of reproduction, all known species of land snails are hermaphrodites (they have a full set of organs of both sexes) and most lay clutches of eggs in the soil. Tiny snails hatch out of the egg with a small shell in place, and the shell grows spirally as the soft parts gradually increase in size. Most land snails have shells that are right-handed in their coiling.

A wide range of different vertebrate and invertebrate animals prey on land snails. They are used as food by humans in various cultures worldwide, and are raised on farms in some areas for use as food.

List of SpongeBob SquarePants characters

The characters in the American animated television series SpongeBob SquarePants were created by artist, animator, and former marine biologist Stephen Hillenburg. The series chronicles the adventures of the title character and his various friends in the fictional underwater city of Bikini Bottom. Most characters are anthropomorphic sea creatures based on real-life species. Many of the characters' designs originated in an unpublished educational comic book titled The Intertidal Zone, which Hillenburg created in 1989.

SpongeBob SquarePants features the voices of Tom Kenny, Bill Fagerbakke, Rodger Bumpass, Clancy Brown, Mr. Lawrence, Jill Talley, Carolyn Lawrence, Mary Jo Catlett and Lori Alan. Most one-off and background characters are voiced by Dee Bradley Baker, Sirena Irwin, Bob Joles, Mark Fite and Thomas F. Wilson. In addition to the series' regular cast, various celebrities from a wide range of professions have voiced guest characters and recurring roles.

The show's characters have received positive critical reception and attention from celebrities. They have made frequent appearances in media outside of the television show, including a theatrical film series and many video games. The characters have also been referenced and parodied throughout popular culture. The title character SpongeBob became a merchandising icon during the height of the show's second season and has seen continued commercial popularity.

Mollusca

Mollusca is the second largest phylum of invertebrate animals. The members are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is estimated between 60,000 and 100,000 additional species.Molluscs are the largest marine phylum, comprising about 23% of all the named marine organisms. Numerous molluscs also live in freshwater and terrestrial habitats. They are highly diverse, not just in size and in anatomical structure, but also in behaviour and in habitat. The phylum is typically divided into 8 or 9 taxonomic classes, of which two are entirely extinct. Cephalopod molluscs, such as squid, cuttlefish and octopus, are among the most neurologically advanced of all invertebrates—and either the giant squid or the colossal squid is the largest known invertebrate species. The gastropods (snails and slugs) are by far the most numerous molluscs and account for 80% of the total classified species.

The three most universal features defining modern molluscs are a mantle with a significant cavity used for breathing and excretion, the presence of a radula (except for bivalves), and the structure of the nervous system. Other than these common elements, molluscs express great morphological diversity, so many textbooks base their descriptions on a "hypothetical ancestral mollusc" (see image below). This has a single, "limpet-like" shell on top, which is made of proteins and chitin reinforced with calcium carbonate, and is secreted by a mantle covering the whole upper surface. The underside of the animal consists of a single muscular "foot". Although molluscs are coelomates, the coelom tends to be small.

The main body cavity is a hemocoel through which blood circulates; as such, their circulatory systems are mainly open. The "generalized" mollusc's feeding system consists of a rasping "tongue", the radula, and a complex digestive system in which exuded mucus and microscopic, muscle-powered "hairs" called cilia play various important roles. The generalized mollusc has two paired nerve cords, or three in bivalves. The brain, in species that have one, encircles the esophagus. Most molluscs have eyes, and all have sensors to detect chemicals, vibrations, and touch. The simplest type of molluscan reproductive system relies on external fertilization, but more complex variations occur. All produce eggs, from which may emerge trochophore larvae, more complex veliger larvae, or miniature adults. The coelomic cavity is reduced. They have an open circulatory system and kidney-like organs for excretion.

Good evidence exists for the appearance of gastropods, cephalopods and bivalves in the Cambrian period, 541 to 485.4 million years ago. However, the evolutionary history both of molluscs' emergence from the ancestral Lophotrochozoa and of their diversification into the well-known living and fossil forms are still subjects of vigorous debate among scientists.

Molluscs have been and still are an important food source for anatomically modern humans. There is a risk of food poisoning from toxins which can accumulate in certain molluscs under specific conditions, however, and because of this, many countries have regulations to reduce this risk. Molluscs have, for centuries, also been the source of important luxury goods, notably pearls, mother of pearl, Tyrian purple dye, and sea silk. Their shells have also been used as money in some preindustrial societies.

Mollusc species can also represent hazards or pests for human activities. The bite of the blue-ringed octopus is often fatal, and that of Octopus apollyon causes inflammation that can last for over a month. Stings from a few species of large tropical cone shells can also kill, but their sophisticated, though easily produced, venoms have become important tools in neurological research. Schistosomiasis (also known as bilharzia, bilharziosis or snail fever) is transmitted to humans via water snail hosts, and affects about 200 million people. Snails and slugs can also be serious agricultural pests, and accidental or deliberate introduction of some snail species into new environments has seriously damaged some ecosystems.

Muricidae

Muricidae is a large and varied taxonomic family of small to large predatory sea snails, marine gastropod mollusks, commonly known as murex snails or rock snails. With about 1,600 living species, the Muricidae represent almost 10% of the Neogastropoda. Additionally, 1,200 fossil species have been recognized. Numerous subfamilies are recognized, although experts disagree about the subfamily divisions and the definitions of the genera.

Many muricids have unusual shells which are considered attractive by shell collectors and by interior designers.

Olive snail

Olive snails, also known as olive shells and olives, scientific name Olividae, are a taxonomic family of medium to large predatory sea snails with smooth, shiny, elongated oval-shaped shells.The shells often show various muted but attractive colors, and may be patterned also. They are marine gastropod molluscs in the family Olividae within the main clade Neogastropoda.

Also see the Olivellidae, the dwarf olives, which were previously grouped within this family, but which now have their own family.

One Piece

One Piece (Japanese: ワンピース, Hepburn: Wan Pīsu) is a Japanese manga series written and illustrated by Eiichiro Oda. It has been serialized in Shueisha's Weekly Shōnen Jump magazine since July 22, 1997, and has been collected into 92 tankōbon volumes. The story follows the adventures of Monkey D. Luffy, a boy whose body gained the properties of rubber after unintentionally eating a Devil Fruit. With his crew of pirates, named the Straw Hat Pirates, Luffy explores the Grand Line in search of the world's ultimate treasure known as "One Piece" in order to become the next Pirate King.

The manga has been adapted into an original video animation (OVA) produced by Production I.G in 1998, and an anime series produced by Toei Animation, which began broadcasting in Japan in 1999. Additionally, Toei has developed thirteen animated feature films, one OVA and thirteen television specials. Several companies have developed various types of merchandising such as a trading card game and numerous video games. The manga series was licensed for an English language release in North America and the United Kingdom by Viz Media and in Australia by Madman Entertainment. The anime series was licensed by 4Kids Entertainment for an English-language release in North America in 2004, before the license was dropped and subsequently acquired by Funimation in 2007.

One Piece has received praise for its storytelling, art, characterization, and humor. Several volumes of the manga have broken publishing records, including the highest initial print run of any book in Japan. The official website for Eiichiro Oda's One Piece manga announced that the manga has set a Guinness World Record for "the most copies published for the same comic book series by a single author". As of March 2019, the manga has sold over 450 million copies worldwide, making it the best-selling manga series in history. It became the best-selling manga for the eleventh consecutive year in 2018.

Sciomyzidae

The family Sciomyzidae belongs to the typical flies (Brachycera) of the order Diptera. They are commonly called marsh flies, and in some cases snail-killing flies due to the food of their larvae.

Here, the Huttoninidae, Phaeomyiidae and Tetanoceridae are provisionally included in the Sciomyzidae. Particularly the latter seem to be an unequivocal part of this group and are ranked as tribe of subfamily Sciomyzinae by most modern authors, while the former two are very small lineages that may or may not stand outside the family and are provisionally ranked as subfamilies here. Whether the Salticellinae and the group around Sepedon warrant recognition as additional subfamilies or are better included in the Sciomyzinae proper is likewise not yet entirely clear. Altogether, the main point of contention is the relationship between the "Huttoninidae", "Phaeomyiidae", Sciomyzidae sensu stricto, and the Helosciomyzidae which were also once included in the Sciomyzidae.

Sciomyzidae are found in all the Ecozones but are poorly represented in the Australasian and Oceanian Regions.

Sea snail

Sea snail is a common name for snails that normally live in salt water, in other words marine gastropods. The taxonomic class Gastropoda also includes snails that live in other habitats, such as land snails and freshwater snails. Many species of sea snails are edible and exploited as food sources by humans.

Trematoda

Trematoda is a class within the phylum Platyhelminthes. It includes two groups of parasitic flatworms, known as flukes.

They are internal parasites of molluscs and vertebrates. Most trematodes have a complex life cycle with at least two hosts. The primary host, where the flukes sexually reproduce, is a vertebrate. The intermediate host, in which asexual reproduction occurs, is usually a snail.

Edible mollusks
Bivalves
Gastropods
Inkfish
Chitons
Related topics

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