A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians have a larval phase of their life cycle; the larva's appearance is very different from the adult form including different unique structures and organs that do not occur in the adult form. Their diet may be different. Larvae are adapted to environments separate from adults. For example, some larvae such as tadpoles live exclusively in aquatic environments, but can live outside water as adult frogs. By living in a distinct environment, larvae may be given shelter from predators and reduce competition for resources with the adult population. Animals in the larval stage will consume food to fuel their transition into the adult form. In some species like barnacles, adults are immobile but their larvae are mobile, use their mobile larval form to distribute themselves; some larvae are dependent on adults to feed them. In many eusocial Hymenoptera species, the larvae are fed by female workers.
In Ropalidia marginata the males are capable of feeding larvae but they are much less efficient, spending more time and getting less food to the larvae. The larvae of some species do not develop further into the adult form; this is a type of neoteny. It is a misunderstanding; this could be the case, but the larval stage has evolved secondarily, as in insects. In these cases the larval form may differ more than the adult form from the group's common origin. Within Insects, only Endopterygotes show different types of larvae. Several classifications have been suggested by many entomologists, following classification is based on Antonio Berlese classification in 1913. There are four main types of endopterygote larvae types: Apodous larvae – no legs at all and are poorly sclerotized. Based on sclerotization, three apodous forms are recognized. Eucephalous – with well sclerotized head capsule. Found in Nematocera and Cerambycidae families. Hemicephalus – with a reduced head capsule, retractable in to the thorax.
Found in Tipulidae and Brachycera families. Acephalus – without head capsule. Found in Cyclorrhapha Protopod larvae – larva have many different forms and unlike a normal insect form, they hatch from eggs which contains little yolk. Ex. first instar larvae of parasitic hymenoptera. Polypod larvae – known as eruciform larvae, these larva have abdominal prolegs, in addition to usual thoracic legs, they poorly sclerotized and inactive. They live in close contact with the food. Best example is caterpillars of lepidopterans. Oligopod larvae – have well developed head capsule and mouthparts are similar to the adult, but without compound eyes, they have six legs. No abdominal prolegs. Two types can be seen: Campodeiform – well sclerotized, dorso-ventrally flattened body. Long legged predators with prognathous mouthparts.. Scarabeiform – poorly sclerotized, flat thorax and abdomen. Short legged and inactive burrowing forms.. Crustacean larvae Ichthyoplankton Spawn Non-larval animal juvenile stages and other life cycle stages: In Porifera: olynthus, gemmule In Cnidaria: ephyra, strobila, hydranth, medusa In Mollusca: paralarva, young cephalopods In Platyhelminthes: hydatid cyst In Bryozoa: avicularium In Acanthocephala: cystacanth In Insecta: Nymphs and naiads, immature forms in hemimetabolous insects Subimago, a juvenile that resembles the adult in Ephemeroptera Instar, intermediate between each ecdysis Pupa and chrysalis, intermediate stages between larva and imago Protozoan life cycle stages Apicomplexan life cycle Algal life cycle stages: Codiolum-phase Conchocelis-phase Marine larval ecology Media related to Larvae at Wikimedia Commons The dictionary definition of larva at Wiktionary Arenas-Mena, C.
Indirect development, transdifferentiation and the macroregulatory evolution of metazoans. Philosophical Transactions of the Royal Society B: Biological Sciences. Feb 27, 2010 Vol.365 no.1540 653-669 Brusca, R. C. & Brusca, G. J.. Invertebrates. Sunderland, Mass.: Sinauer Associates. Hall, B. K. & Wake, M. H. eds.. The Origin and Evolution of Larval Forms. San Diego: Academic Press. Leis, J. M. & Carson-Ewart, B. M. eds.. The Larvae of Indo-Pacific Coastal Fishes. An Identification Guide to Marine Fish Larvae. Fauna Malesiana handbooks, vol. 2. Brill, Leiden. Minelli, A.. The larva. In: Perspectives in Animal Phylogeny and Evolution. Oxford University Press. P. 160-170. Link. Shanks, A. L.. An Identification Guide to the Larval Marine Invertebrates of the Pacific Northwest. Oregon State University Press, Corvallis. 256 pp. Smith, D. & Johnson, K. B.. A Guide to Marine Coastal Plankton and Marine Invertebrate Larvae. Kendall/Hunt Plublishing Company. Stanwell-Smith, D. Hood, A. & Peck, L. S.. A field guide to the pelagic invertebrates larvae of the maritime Antarctic.
British Antarctic Survey, Cambridge. Thyssen, P. J.. Keys for Identification of Immature Insects. In: Amendt, J. et al.. Current Concepts in Forensic Entomology, chapter 2, pp. 25–42. Springer: Dordrecht
Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, it is the characteristic arrangement and number of teeth in a given species at a given age; that is, the number and morpho-physiology of the teeth of an animal. Animals whose teeth are all of the same type, such as most non-mammalian vertebrates, are said to have homodont dentition, whereas those whose teeth differ morphologically are said to have heterodont dentition; the dentition of animals with two successions of teeth is referred to as diphyodont, while the dentition of animals with only one set of teeth throughout life is monophyodont. The dentition of animals in which the teeth are continuously discarded and replaced throughout life is termed polyphyodont; the dentition of animals in which the teeth are set in sockets in the jawbones is termed thecodont. The evolutionary origin of the vertebrate dentition remains contentious. Current theories suggest either an "outside-in" or "inside-out" evolutionary origin to teeth, with the dentition arising from odontodes on the skin surface moving into the mouth, or vice versa.
Despite this debate, it is accepted that vertebrate teeth are homologous to the dermal denticles found on the skin of basal Gnathostomes. Since the origin of teeth some 450mya, the vertebrate dentition has diversified within the reptiles and fish: however most of these groups continue to possess a long row of pointed or sharp-sided, undifferentiated teeth that are replaceable; the mammalian pattern is different. The teeth in the upper and lower jaws in mammals have evolved a close-fitting relationship such that they operate together as a unit. "They'occlude'", that is, the chewing surfaces of the teeth are so constructed that the upper and lower teeth are able to fit together, crushing, grinding or tearing the food caught between."All mammals except the monotremes, the xenarthrans, the pangolins, the cetaceans have up to four distinct types of teeth, with a maximum number for each. These are the incisor, the canine, the premolar, the molar; the incisors occupy the front of the tooth row in lower jaws.
They are flat, chisel-shaped teeth that meet in an edge-to-edge bite. Their function is cutting, slicing, or gnawing food into manageable pieces that fit into the mouth for further chewing; the canines are behind the incisors. In many mammals, the canines are pointed, tusk-shaped teeth, projecting beyond the level of the other teeth. In carnivores, they are offensive weapons for bringing down prey. In other mammals such as some primates, they are used to split open hard surfaced food; the premolars and molars are at the back of the mouth. Depending on the particular mammal and its diet, these two kinds of teeth prepare pieces of food to be swallowed by grinding, shearing, or crushing; the specialised teeth—incisors, canines and molars—are found in the same order in every mammal. In many mammals the infants have a set of teeth that are replaced by adult teeth; these are called primary teeth, baby teeth or milk teeth. Animals that have two sets of teeth, one followed by the other, are said to be diphyodont.
The dental formula for milk teeth is the same as for adult teeth except that the molars are missing. Because every mammal's teeth are specialised for different functions, many mammal groups have lost teeth not needed in their adaptation. Tooth form has undergone evolutionary modification as a result of natural selection for specialised feeding or other adaptations. Over time, different mammal groups have evolved distinct dental features, both in the number and type of teeth, in the shape and size of the chewing surface; the number of teeth of each type is written as a dental formula for one side of the mouth, or quadrant, with the upper and lower teeth shown on separate rows. The number of teeth in a mouth is twice that listed. In each set, incisors are indicated first, canines second, premolars third, molars, giving I:C:P:M. So for example, the formula 220.127.116.11 for upper teeth indicates 2 incisors, 1 canine, 2 premolars, 3 molars on one side of the upper mouth. The deciduous dental formula is notated in lowercase lettering preceded by the letter d: for example: di:dc:dp.
An animal's dentition for either deciduous or permanent teeth can thus be expressed as a dental formula, written in the form of a fraction, which can be written as I. C. P. MI. C. P. M, or I. C. P. M / I. C. P. M. For example, the following formulae show the deciduous and usual permanent dentition of all catarrhine primates, including humans: Deciduous: / × 2 = 20; this can be written as di2.dc1.dm2di2.dc1.dm2. Superscript and subscript denote upper and lower jaw, i.e. do not indicate mathematical operations. The dashes in the formula are not mathematical operators, but spacers.'d' denotes deciduous teeth. Another annotation is 18.104.22.168.1.0.2, if the fact that it pertains to deciduous teeth is stated, per examples found in some texts such as The Ca
OCLC Online Computer Library Center, Incorporated d/b/a OCLC is an American nonprofit cooperative organization "dedicated to the public purposes of furthering access to the world's information and reducing information costs". It was founded in 1967 as the Ohio College Library Center. OCLC and its member libraries cooperatively produce and maintain WorldCat, the largest online public access catalog in the world. OCLC is funded by the fees that libraries have to pay for its services. OCLC maintains the Dewey Decimal Classification system. OCLC began in 1967, as the Ohio College Library Center, through a collaboration of university presidents, vice presidents, library directors who wanted to create a cooperative computerized network for libraries in the state of Ohio; the group first met on July 5, 1967 on the campus of the Ohio State University to sign the articles of incorporation for the nonprofit organization, hired Frederick G. Kilgour, a former Yale University medical school librarian, to design the shared cataloging system.
Kilgour wished to merge the latest information storage and retrieval system of the time, the computer, with the oldest, the library. The plan was to merge the catalogs of Ohio libraries electronically through a computer network and database to streamline operations, control costs, increase efficiency in library management, bringing libraries together to cooperatively keep track of the world's information in order to best serve researchers and scholars; the first library to do online cataloging through OCLC was the Alden Library at Ohio University on August 26, 1971. This was the first online cataloging by any library worldwide. Membership in OCLC is based on use of services and contribution of data. Between 1967 and 1977, OCLC membership was limited to institutions in Ohio, but in 1978, a new governance structure was established that allowed institutions from other states to join. In 2002, the governance structure was again modified to accommodate participation from outside the United States.
As OCLC expanded services in the United States outside Ohio, it relied on establishing strategic partnerships with "networks", organizations that provided training and marketing services. By 2008, there were 15 independent United States regional service providers. OCLC networks played a key role in OCLC governance, with networks electing delegates to serve on the OCLC Members Council. During 2008, OCLC commissioned two studies to look at distribution channels. In early 2009, OCLC negotiated new contracts with the former networks and opened a centralized support center. OCLC provides bibliographic and full-text information to anyone. OCLC and its member libraries cooperatively produce and maintain WorldCat—the OCLC Online Union Catalog, the largest online public access catalog in the world. WorldCat has holding records from private libraries worldwide; the Open WorldCat program, launched in late 2003, exposed a subset of WorldCat records to Web users via popular Internet search and bookselling sites.
In October 2005, the OCLC technical staff began a wiki project, WikiD, allowing readers to add commentary and structured-field information associated with any WorldCat record. WikiD was phased out; the Online Computer Library Center acquired the trademark and copyrights associated with the Dewey Decimal Classification System when it bought Forest Press in 1988. A browser for books with their Dewey Decimal Classifications was available until July 2013; until August 2009, when it was sold to Backstage Library Works, OCLC owned a preservation microfilm and digitization operation called the OCLC Preservation Service Center, with its principal office in Bethlehem, Pennsylvania. The reference management service QuestionPoint provides libraries with tools to communicate with users; this around-the-clock reference service is provided by a cooperative of participating global libraries. Starting in 1971, OCLC produced catalog cards for members alongside its shared online catalog. OCLC commercially sells software, such as CONTENTdm for managing digital collections.
It offers the bibliographic discovery system WorldCat Discovery, which allows for library patrons to use a single search interface to access an institution's catalog, database subscriptions and more. OCLC has been conducting research for the library community for more than 30 years. In accordance with its mission, OCLC makes its research outcomes known through various publications; these publications, including journal articles, reports and presentations, are available through the organization's website. OCLC Publications – Research articles from various journals including Code4Lib Journal, OCLC Research, Reference & User Services Quarterly, College & Research Libraries News, Art Libraries Journal, National Education Association Newsletter; the most recent publications are displayed first, all archived resources, starting in 1970, are available. Membership Reports – A number of significant reports on topics ranging from virtual reference in libraries to perceptions about library funding. Newsletters – Current and archived newsletters for the library and archive community.
Presentations – Presentations from both guest speakers and OCLC research from conferences and other events. The presentations are organized into five categories: Conference presentations, Dewey presentations, Distinguished Seminar Series, Guest presentations, Research staff
Carnivora is a diverse scrotiferan order that includes over 280 species of placental mammals. Its members are formally referred to as carnivorans, whereas the word "carnivore" can refer to any meat-eating organism. Carnivorans are the most diverse in size of any mammalian order, ranging from the least weasel, at as little as 25 g and 11 cm, to the polar bear, which can weigh up to 1,000 kg, to the southern elephant seal, whose adult males weigh up to 5,000 kg and measure up to 6.7 m in length. Carnivorans have teeth and claws adapted for catching and eating other animals. Many hunt in are social animals, giving them an advantage over larger prey; some carnivorans, such as cats and pinnipeds, depend on meat for their nutrition. Others, such as raccoons and bears, are more omnivorous, depending on the habitat; the giant panda is a herbivore, but feeds on fish and insects. The polar bear subsists on seals. Carnivorans are split into two suborders: Caniformia. Carnivorans all share the same arrangement of teeth in which the last upper premolar and the first lower molar have blade-like enamel crowns that work together as carnassial teeth to shear meat.
Carnivorans have had this arrangement for over 60 million years with many adaptions, these dental adaptions help identify carnivoran species and groupings of species. Carnivorans evolved in North America out of members of the family Miacidae about 42 million years ago, they soon split into dog-like forms. Their molecular phylogeny shows the extant Carnivora are a monophyletic group, the crown group of the Carnivoramorpha. Most carnivorans are terrestrial; the last premolar of the upper jaw and first molar of the lower are termed the carnassials or sectorial teeth. These blade-like teeth occlude with a scissor-like action for shredding meat. Carnassials are most developed in the Felidae and the least developed in the Ursidae. Carnivorans have two conical canines in each jaw; the only two exceptions to this are the sea otter, which has four incisors in the lower jaw, the sloth bear, which has four incisors in the upper jaw. The number of molars and premolars is variable between carnivoran species, but all teeth are rooted and are diphyodont.
Incisors are retained by carnivorans and the third incisor is large and sharp. Carnivorans have either four or five digits on each foot, with the first digit on the forepaws known as the dew claw, being vestigial in most species and absent in some; the superfamily Canoidea – Canidae, Mustelidae, Ursidae, Otariidae and Phocidae and the extinct family Amphicyonidae – are characterized by having nonchambered or chambered auditory bullae, nonretractable claws, a well-developed baculum. Most species are rather plain in coloration, lacking the flashy spotted or rosetted coats like many species of felids and viverrids have; this is because Canoidea tend to range in the temperate and subarctic biomes, although Mustelidae and Procyonidae have a few tropical species. Most are terrestrial. All families except the Canidae and a few species of Mustelidae are plantigrade. Diet is varied and most tend to be omnivorous to some degree, thus the carnassial teeth are less specialized. Canoidea have more molars in an elongated skull.
The superfamily Feloidea – Felidae, Herpestidae, Hyaenidae and Eupleridae, as well as the extinct family Nimravidae – have spotted, rosetted or striped coats, tend to be more brilliantly colored than their Canoidean counterparts. This is because these species tend to range in tropical habitats, although a few species do inhabit temperate and subarctic habitats. Many are arboreal or semiarboreal, the majority are digitigrade. Diet tends to be more carnivorous in the family Felidae, they have fewer teeth and shorter skulls, with much more specialized carnassials meant for shearing meat. Feliformia claws are retractile, or semiretractile; the terminal phalanx, with the claw attached, folds back in the forefoot into a sheath by the outer side of the middle phalanx of the digit, is retained in this position when at rest by a strong elastic ligament. In the hindfoot, the terminal joint or phalanx is retracted on to the top, not the side of the middle phalanx. Deep flexor muscles straighten the terminal phalanges, so the claws protrude from their sheaths, the soft "velvety" paw becomes converted into a formidable weapon.
The habitual retraction of the claws preserves their points from wear. The superfamily Pinnipedia, now considered to be part of Caniformia, are medium to large aquatic mammals. Being homeothermic marine mammals, pinni
Eutheria is one of two mammalian clades with extant members that diverged in the Early Cretaceous or the Late Jurassic. Except for the Virginia opossum, from North America, a metatherian, all post-Miocene mammals indigenous to Europe, Africa and North America north of Mexico are eutherians. Extant eutherians, their last common ancestor, all extinct descendants of that ancestor are members of Placentalia. Eutherians are distinguished from noneutherians by various phenotypic traits of the feet, ankles and teeth. All extant eutherians lack epipubic bones; this allows for expansion of the abdomen during pregnancy. The oldest-known eutherian species is Juramaia sinensis, dated at 161 million years ago from the Jurassic in China. Eutheria was named in 1872 by Theodore Gill. Distinguishing features are: an enlarged malleolus at the bottom of the tibia, the larger of the two shin bones the joint between the first metatarsal bone and the entocuneiform bone in the foot is offset farther back than the joint between the second metatarsal and middle cuneiform bones—in metatherians these joints are level with each other various features of jaws and teeth Eutheria contains several extinct genera as well as larger groups, many with complicated taxonomic histories still not understood.
Members of the Adapisoriculidae and Leptictida have been placed within the out-dated placental group Insectivora, while Zhelestids have been considered primitive ungulates. However, more recent studies have suggested these enigmatic taxa represent stem group eutherians, more basal to Placentalia; the weakly favoured cladogram favours Boreoeuthearia as a basal Eutherian clade as sister to the Atlantogenata
Animals are multicellular eukaryotic organisms that form the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, grow from a hollow sphere of cells, the blastula, during embryonic development. Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million animal species in total. Animals range in length from 8.5 millionths of a metre to 33.6 metres and have complex interactions with each other and their environments, forming intricate food webs. The category includes humans, but in colloquial use the term animal refers only to non-human animals; the study of non-human animals is known as zoology. Most living animal species are in the Bilateria, a clade whose members have a bilaterally symmetric body plan; the Bilateria include the protostomes—in which many groups of invertebrates are found, such as nematodes and molluscs—and the deuterostomes, containing the echinoderms and chordates.
Life forms interpreted. Many modern animal phyla became established in the fossil record as marine species during the Cambrian explosion which began around 542 million years ago. 6,331 groups of genes common to all living animals have been identified. Aristotle divided animals into those with those without. Carl Linnaeus created the first hierarchical biological classification for animals in 1758 with his Systema Naturae, which Jean-Baptiste Lamarck expanded into 14 phyla by 1809. In 1874, Ernst Haeckel divided the animal kingdom into the multicellular Metazoa and the Protozoa, single-celled organisms no longer considered animals. In modern times, the biological classification of animals relies on advanced techniques, such as molecular phylogenetics, which are effective at demonstrating the evolutionary relationships between animal taxa. Humans make use of many other animal species for food, including meat and eggs. Dogs have been used in hunting, while many aquatic animals are hunted for sport.
Non-human animals have appeared in art from the earliest times and are featured in mythology and religion. The word "animal" comes from the Latin animalis, having soul or living being; the biological definition includes all members of the kingdom Animalia. In colloquial usage, as a consequence of anthropocentrism, the term animal is sometimes used nonscientifically to refer only to non-human animals. Animals have several characteristics. Animals are eukaryotic and multicellular, unlike bacteria, which are prokaryotic, unlike protists, which are eukaryotic but unicellular. Unlike plants and algae, which produce their own nutrients animals are heterotrophic, feeding on organic material and digesting it internally. With few exceptions, animals breathe oxygen and respire aerobically. All animals are motile during at least part of their life cycle, but some animals, such as sponges, corals and barnacles become sessile; the blastula is a stage in embryonic development, unique to most animals, allowing cells to be differentiated into specialised tissues and organs.
All animals are composed of cells, surrounded by a characteristic extracellular matrix composed of collagen and elastic glycoproteins. During development, the animal extracellular matrix forms a flexible framework upon which cells can move about and be reorganised, making the formation of complex structures possible; this may be calcified, forming structures such as shells and spicules. In contrast, the cells of other multicellular organisms are held in place by cell walls, so develop by progressive growth. Animal cells uniquely possess the cell junctions called tight junctions, gap junctions, desmosomes. With few exceptions—in particular, the sponges and placozoans—animal bodies are differentiated into tissues; these include muscles, which enable locomotion, nerve tissues, which transmit signals and coordinate the body. There is an internal digestive chamber with either one opening or two openings. Nearly all animals make use of some form of sexual reproduction, they produce haploid gametes by meiosis.
These fuse to form zygotes, which develop via mitosis into a hollow sphere, called a blastula. In sponges, blastula larvae swim to a new location, attach to the seabed, develop into a new sponge. In most other groups, the blastula undergoes more complicated rearrangement, it first invaginates to form a gastrula with a digestive chamber and two separate germ layers, an external ectoderm and an internal endoderm. In most cases, a third germ layer, the mesoderm develops between them; these germ layers differentiate to form tissues and organs. Repeated instances of mating with a close relative during sexual reproduction leads to inbreeding depression within a population due to the increased prevalence of harmful recessive traits. Animals have evolved numerous mechanisms for avoiding close inbreeding. In some species, such as the splendid fairywren, females benefit by mating with multiple males, thus producing more offspring of higher genetic quality; some animals are capable of asexual reproduction, which results
A snail is, in loose terms, a shelled gastropod. The name is most applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name snail is used for most of the members of the molluscan class Gastropoda that have a coiled shell, large enough for the animal to retract into; when the word "snail" is used in this most general sense, it includes not just land snails but numerous species of sea snails and freshwater snails. Gastropods that lack a shell, or have only an internal shell, are called slugs, land snails that have only a small shell are called semi-slugs. Snails have considerable human relevance, including as food items, as pests, as vectors of disease, their shells are used as decorative objects and are incorporated into jewelry; the snail has had some cultural significance, has been used as a metaphor. 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.
But snails with gills form a polyphyletic group. Both snails that have lungs and snails that have gills have diversified so over geological time that a few species with gills can be found on land and numerous species with lungs can be found in freshwater. A few marine species have lungs. Snails can be found in a wide range of environments, including ditches and the abyssal depths of the sea. Although land snails may be more familiar to laymen, marine snails constitute the majority of snail species, have much greater diversity and a greater biomass. Numerous kinds of snail can 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. 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 colored.
Several species of the genus Achatina and related genera are known as giant African land snails. The largest living species of sea snail is Syrinx aruanus; the snail Lymnaea makes decisions by using only two types of neuron: one deciding whether the snail is hungry, the other deciding whether there is food in the vicinity. The largest known land gastropod is the African giant snail Achatina achatina, the largest recorded specimen of which measured 39.3 centimetres from snout to tail when extended, with a shell length of 27.3 cm in December 1978. It weighed 900 g. Named Gee Geronimo, this snail was owned by Christopher Hudson of Hove, East Sussex, UK, was collected in Sierra Leone in June 1976. Gastropods that lack a conspicuous shell are called slugs rather than snails; some species of slug have a red shell, some have only an internal vestige that serves as a calcium repository, 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 quite large land slugs can take advantage of habitats or retreats with 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, those are suitable places for laying their eggs. Slugs as a group are far from monophyletic; the reduction or loss of the shell has evolved many times independently within several different lineages of gastropods. The various taxa of land and sea gastropods with slug morphology occur within numerous higher taxonomic groups of shelled species. Land snails are known as an agricultural and garden pest but some species are an edible delicacy and household pets. 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 a snail repellent, 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 deter snails from coming to the plants; the decollate snail will capture and eat garden snails, 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 to attack and devour other gastropods that may represent a valuable part of the native fauna of the region. 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