HOME

TheInfoList



OR:

Slug, or land slug, is a
common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often con ...
for any apparently shell-less terrestrial
gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...
mollusc Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...
. The word ''slug'' is also often used as part of the common name of any gastropod mollusc that has no shell, a very reduced shell, or only a small internal shell, particularly
sea slug Sea slug is a common name for some Marine biology, marine invertebrates with varying levels of resemblance to terrestrial Slug, slugs. Most creatures known as sea slugs are gastropods, i.e. they are Sea snail, sea snails (marine gastropod moll ...
s and semi-slugs (this is in contrast to the common name ''
snail A snail is a shelled gastropod. The name is most often applied to land snails, terrestrial molluscs, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class Gas ...
'', which applies to gastropods that have a coiled shell large enough that they can fully retract their soft parts into it). Various taxonomic families of land slugs form part of several quite different evolutionary lineages, which also include snails. Thus, the various families of slugs are not closely related, despite the superficial similarity in overall body form. The shell-less condition has arisen many times independently as an example of
convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last comm ...
, and thus the category "slug" is
polyphyletic A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...
.


Taxonomy

Of the six orders of Pulmonata, two – the Onchidiacea and Soleolifera – solely comprise slugs. A third group, the
Sigmurethra Sigmurethra is a taxonomic category of air-breathing land snails and slugs, terrestrial pulmonate gastropod molluscs. This is an informal group which includes most land snails and slugs. The two strong synapomorphies of Sigmurethra are a long ...
, contains various clades of snails, semi-slugs (i.e. snails whose shells are too small for them to retract fully into), and slugs. The taxonomy of this group is in the process of being revised in light of DNA sequencing. Research suggests that pulmonates are paraphyletic and basal to the opisthobranchs, which are a terminal branch of the tree. The family Ellobiidae are also polyphyletic. *Subinfraorder Orthurethra **Superfamily Achatinelloidea Gulick, 1873 **Superfamily Cochlicopoidea Pilsbry, 1900 **Superfamily Partuloidea Pilsbry, 1900 **Superfamily
Pupilloidea Pupilloidea is a superfamily of small and very small air-breathing land snails, terrestrial gastropods in the infraorder '' Pupilloidei''. They are diverse in morphology, habitat, and ecological roles. Description They are characterized by the ...
Turton, 1831 *Subinfraorder
Sigmurethra Sigmurethra is a taxonomic category of air-breathing land snails and slugs, terrestrial pulmonate gastropod molluscs. This is an informal group which includes most land snails and slugs. The two strong synapomorphies of Sigmurethra are a long ...
**Superfamily Acavoidea Pilsbry, 1895 **Superfamily Achatinoidea Swainson, 1840 **Superfamily Aillyoidea Baker, 1960 **Superfamily Arionoidea J.E. Gray in Turnton, 1840 **Superfamily Athoracophoroidea ***Family Athoracophoridae **Superfamily Orthalicoidea ***Subfamily Bulimulinae **Superfamily Camaenoidea Pilsbry, 1895 **Superfamily Clausilioidea Mörch, 1864 **Superfamily Dyakioidea Gude & Woodward, 1921 **Superfamily Gastrodontoidea Tryon, 1866 **Superfamily
Helicoidea Helicoidea is a Taxonomy (biology), taxonomic Taxonomic rank, superfamily of air-breathing land snails, terrestrial molluscs, terrestrial pulmonate gastropod mollusks in the order (taxonomy), order Stylommatophora. Taxonomy 2017 taxonomy and l ...
Rafinesque, 1815 **Superfamily Helixarionoidea Bourguignat, 1877 **Superfamily Limacoidea Rafinesque, 1815 **Superfamily Oleacinoidea H. & A. Adams, 1855 **Superfamily Orthalicoidea Albers-Martens, 1860 **Superfamily Plectopylidoidea Moellendorf, 1900 **Superfamily Polygyroidea Pilsbry, 1894 **Superfamily Punctoidea Morse, 1864 **Superfamily Rhytidoidea Pilsbry, 1893 ***Family Rhytididae **Superfamily Sagdidoidera Pilsbry, 1895 **Superfamily Staffordioidea Thiele, 1931 **Superfamily Streptaxoidea J.E. Gray, 1806 **Superfamily Strophocheiloidea Thiele, 1926 **Superfamily Parmacelloidea **Superfamily Zonitoidea Mörch, 1864 **Superfamily Quijotoidea Jesús Ortea and Juan José Bacallado, 2016 ***Family Quijotidae


Description

The external anatomy of a slug includes the following: * Tentacles: Like other pulmonate land gastropods, the majority of land slugs have two pairs of 'feelers' or ''tentacles'' on their head. The upper pair is light-sensing and has eyespots at the ends, while the lower pair provides the sense of smell. Both pairs are retractable in stylommatophoran slugs, but contractile in veronicellid slugs. * Mantle: On top of the slug, behind the head, is the saddle-shaped '' mantle''. In stylommatophoran slugs, on the right-hand side of the mantle is a respiratory opening, the pneumostome, which is easier to see when open; also on the right side at the front are the genital opening and anus. Veronicellid slugs have a mantle covering the whole dorsal part of the body, they have no respiratory opening, and the anus opens posteriorly. * Tail: The part of a slug behind the mantle is called the 'tail'. * Keel: Some species of slugs, for example ''
Tandonia budapestensis ''Tandonia budapestensis'' is a species of air-breathing, keel (slug), keeled, land slug, a shell-less terrestrial molluscs, terrestrial gastropod mollusks in the family Milacidae.Marshall, B. (2014). Tandonia budapestensis (Hazay, 1880). Accesse ...
'', have a prominent ridge running over their back along the middle of the tail (sometimes along the whole tail, sometimes only the posterior part). * Foot: The bottom side of a slug, which is flat, is called the 'foot'. Like almost all gastropods, a slug moves by rhythmic waves of muscular contraction on the underside of its foot. It simultaneously secretes a layer of
mucus Mucus (, ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both Serous fluid, serous and muc ...
that it travels on, which helps prevent damage to the foot tissues. Around the edge of the foot in some slugs is a structure called the 'foot fringe'. * Vestigial shell: Most slugs retain a remnant of their shell, which is usually internalized. This organ generally serves as storage for calcium salts, often in conjunction with the digestive glands. An internal shell is present in the Limacidae and Parmacellidae. Adult Philomycidae, Onchidiidae and Veronicellidae lack shells.


Physiology

Slugs' bodies are made up mostly of water and, without a full-sized shell, their soft tissues are prone to
desiccation Desiccation is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container. The ...
. They must generate protective mucus to survive. Many species are most active following rainfall or during nighttime since there is increased moisture on the ground. In drier conditions, they hide in damp places such as under
tree bark Bark is the outermost layer of stems and roots of woody plants. Plants with bark include trees, woody vines, and shrubs. Bark refers to all the tissues outside the vascular cambium and is a nontechnical term. It overlays the wood and consist ...
, fallen logs, rocks and manmade structures, such as planters, to help retain body moisture. Like all other gastropods, they undergo torsion (a 180° twisting of the internal organs) during development. Internally, slug anatomy clearly shows the effects of this rotation—but externally, the bodies of slugs appear more or less symmetrical, except the pneumostome, which is on one side of the animal, normally the right-hand side. Slugs produce two types of
mucus Mucus (, ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both Serous fluid, serous and muc ...
: one is thin and watery, and the other thick and sticky. Both kinds are
hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption (chemistry), absorption or adsorption from the surrounding Natural environment, environment, which is usually at normal or room temperature. If water mol ...
. The thin mucus spreads from the foot's centre to its edges, whereas the thick mucus spreads from front to back. Slugs also produce thick mucus that coats the whole body of the animal. The mucus secreted by the foot contains fibres that help prevent the slug from slipping down vertical surfaces. The "
slime Slime or slimy may refer to: Science and technology Biology * Slime coat, the coating of mucus covering the body of all fish * Slime mold, an informal name for several eukaryotic organisms * Biofilm, or slime, a syntrophic community of micr ...
trail" a slug leaves behind has some secondary effects: other slugs coming across a slime trail can recognise the slime trail as produced by one of the same species, which is useful in finding a mate. Following a slime trail is also part of the hunting behaviour of some carnivorous slugs. Body mucus provides some protection against predators, as it can make the slug hard to pick up and hold by a bird's beak, for example, or the mucus itself can be distasteful. Some slugs can also produce very sticky mucus which can incapacitate predators and can trap them within the secretion. Some species of slug, such as '' Limax maximus'', secrete slime cords to suspend a pair during copulation.


Reproduction

Slugs are
hermaphrodite A hermaphrodite () is a sexually reproducing organism that produces both male and female gametes. Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic. The individuals of many ...
s, having both female and male reproductive organs. Once a slug has located a mate, they encircle each other and sperm is exchanged through their protruded genitalia. Apophallation has been reported only in some species of banana slug ('' Ariolimax'') and one species of '' Deroceras''. In the banana slugs, the penis sometimes becomes trapped inside the body of the partner. Apophallation allows the slugs to separate themselves by one or both of the slugs chewing off the other's or its own penis. Once the penis has been discarded, banana slugs are still able to mate using only the female parts of the reproductive system. In a temperate climate, slugs usually live one year outdoors. In greenhouses, many adult slugs may live for more than one year.


Ecology

Slugs play an important role in the
ecosystem An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...
by eating decaying plant material and
fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
. Most carnivorous slugs on occasion also eat dead specimens of their own kind.


Feeding habits

Most species of slugs are generalists, feeding on a broad spectrum of organic materials, including leaves from living plants,
lichen A lichen ( , ) is a hybrid colony (biology), colony of algae or cyanobacteria living symbiotically among hypha, filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualism (biology), m ...
s,
mushroom A mushroom or toadstool is the fleshy, spore-bearing Sporocarp (fungi), fruiting body of a fungus, typically produced above ground on soil or another food source. ''Toadstool'' generally refers to a poisonous mushroom. The standard for the n ...
s, and even
carrion Carrion (), also known as a carcass, is the decaying flesh of dead animals. Overview Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters (or scavengers) include crows, vultures ...
. Some slugs are
predator Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...
s and eat other slugs and
snail A snail is a shelled gastropod. The name is most often applied to land snails, terrestrial molluscs, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class Gas ...
s, or
earthworm An earthworm is a soil-dwelling terrestrial invertebrate that belongs to the phylum Annelida. The term is the common name for the largest members of the class (or subclass, depending on the author) Oligochaeta. In classical systems, they we ...
s. Slugs can feed on a wide variety of
vegetable Vegetables are edible parts of plants that are consumed by humans or other animals as food. This original meaning is still commonly used, and is applied to plants collectively to refer to all edible plant matter, including edible flower, flo ...
s and herbs, including flowers such as
petunia ''Petunia'' is a genus of 20 species of flowering plants of South American origin. The popular flower of the same name derived its epithet from the French, which took the word , 'tobacco', from a Tupi–Guarani language. A tender perennial plan ...
s,
chrysanthemum Chrysanthemums ( ), sometimes called mums or chrysanths, are flowering plants in the Asteraceae family. They are native to East Asia and northeastern Europe. Most species originate from East Asia, and the center of diversity is in China. Co ...
s, daisies, lobelia, lilies,
dahlia ''Dahlia'' ( , ) is a genus of bushy, tuberous, herbaceous perennial plants native to Mexico and Central America. Dahlias are members of the Asteraceae (synonym name: Compositae) family of dicotyledonous plants, its relatives include the sun ...
s, narcissus, gentians, primroses, tuberous begonias, hollyhocks, marigolds, and fruits such as strawberries. They also feed on carrots, peas, apples, and cabbage that are offered as a sole food source. Slugs from different families are fungivores. It is the case in the Philomycidae (e. g. '' Philomycus carolinianus'' and '' Phylomicus flexuolaris'') and '' Ariolimacidae'' ('' Ariolimax californianus''), which respectively feed on slime molds ( myxomycetes) and mushrooms (
basidiomycetes Basidiomycota () is one of two large division (mycology), divisions that, together with the Ascomycota, constitute the subkingdom Dikarya (often referred to as the "higher fungi") within the kingdom Fungi. Members are known as basidiomycetes. Mor ...
). Species of mushroom producing fungi used as food source by slugs include milk-caps (''
Lactarius ''Lactarius'' is a genus of mushroom-producing, ectomycorrhizal fungi, containing several Edible mushroom, edible species. The species of the genus, common name, commonly known as milk-caps, are characterized by the milky fluid ("latex") they ex ...
'' spp.), the oyster mushroom ('' Pleurotus ostreatus'') and the penny bun (''
Boletus edulis ''Boletus edulis'' (English: cep, penny bun, porcino) is a basidiomycete fungus, and the type species of the genus ''Boletus''. It is prized as an edible mushroom. The fungus produces Basidiospore, spore-bearing basidiocarp, fruit bodies ...
''). Other genera such as '' Agaricus'', '' Pleurocybella'' and '' Russula'' are also eaten by slugs. Slime molds used as food source by slugs include '' Stemonitis axifera'' and '' Symphytocarpus flaccidus''. Some slugs are selective towards certain parts or developmental stages of the fungi they eat, though this is very variable. Depending on the species and other factors, slugs eat only fungi at specific stages of development. In other cases, whole mushrooms can be eaten, without any selection or bias towards ontogenetic stages.


Predators

Slugs are preyed upon by various
vertebrate Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...
s and
invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...
s. The predation of slugs has been the subject of studies for at least a century. Because some species of slugs are considered agricultural pests, research investments have been made to discover and investigate potential predators in order to establish biological control strategies.


Vertebrates

Slugs are preyed upon by virtually every major vertebrate group. With many examples among
reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology), orders: Testudines, Crocodilia, Squamata, and Rhynchocepha ...
s,
bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...
s,
mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...
s,
amphibian Amphibians are ectothermic, anamniote, anamniotic, tetrapod, four-limbed vertebrate animals that constitute the class (biology), class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all Tetrapod, tetrapods, but excl ...
s and
fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...
, vertebrates can occasionally feed on, or be specialised predators of, slugs. Fish that feed on slugs include the brown trout (''
Salmo trutta The brown trout (''Salmo trutta'') is a species of salmonid ray-finned fish and the most widely distributed species of the genus ''Salmo'', endemic to most of Europe, West Asia and parts of North Africa, and has been widely introduced species, in ...
''), which occasionally feeds on '' Arion circumscriptus'', an '' arionid'' slug. Similarly, the shortjaw kokopu ('' Galaxias postvectis'') includes slugs in its diet. Amphibians such as frogs and toads have long been regarded as important predators of slugs. Among them are species in the genus '' Bufo'', '' Rhinella'' and '' Ceratophrys''. Reptiles that feed on slugs include mainly
snake Snakes are elongated limbless reptiles of the suborder Serpentes (). Cladistically squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales much like other members of the group. Many species of snakes have s ...
s and
lizard Lizard is the common name used for all Squamata, squamate reptiles other than snakes (and to a lesser extent amphisbaenians), encompassing over 7,000 species, ranging across all continents except Antarctica, as well as most Island#Oceanic isla ...
s. Some
colubrid Colubridae (, commonly known as colubrids , from , 'snake') is a family of snakes. With 249 genera, it is the largest snake family. The earliest fossil species of the family date back to the Late Eocene epoch, with earlier origins suspected. Colu ...
snakes are known predators of slugs. Coastal populations of the garter snake, '' Thamnophis elegans'', have a specialised diet consisting of slugs, such as '' Ariolimax'', while inland populations have a generalized diet. One of its congeners, the Northwestern garter snake ('' Thamnophis ordinoides''), is not a specialized predator of slugs but occasionally feeds on them. The redbelly snake ('' Storeria occipitomaculata'') and the brown snake ('' Storeria dekayi'') feed mainly but not solely on slugs, while some species in the genus '' Dipsas'' (e.g. '' Dipsas neuwiedi'') and the common slug eater snake ('' Duberria lutrix''), are exclusively slug eaters. Several lizards include slugs in their diet. This is the case in the slowworm ('' Anguis fragilis''), the bobtail lizard ('' Tiliqua rugosa''), the she-oak skink ('' Cyclodomorphus casuarinae''), and the common lizard ('' Zootoca vivipara''). Birds that prey upon slugs include
common blackbird The common blackbird (''Turdus merula'') is a species of true thrush. It is also called the Eurasian blackbird (especially in North America, to distinguish it from the unrelated New World blackbirds), or simply the blackbird. It breeds in Europ ...
s ('' Turdus merula''),
starling Starlings are small to medium-sized passerine (perching) birds known for the often dark, glossy iridescent sheen of their plumage; their complex vocalizations including mimicking; and their distinctive, often elaborate swarming behavior, know ...
s ('' Sturnus vulgaris''), rooks ('' Corvus frugilegus''),
jackdaw Jackdaws are two species of bird in the genus ''Coloeus'' closely related to, but generally smaller than, crows and ravens ('' Corvus''). They have a blackish crown, wings, and tail, with the rest of their plumage paler.Madge & Burn (1994) 136� ...
s ('' Corvus monedula''), owls, vultures, and
duck Duck is the common name for numerous species of waterfowl in the family (biology), family Anatidae. Ducks are generally smaller and shorter-necked than swans and goose, geese, which are members of the same family. Divided among several subfam ...
s. Studies on slug predation also cite fieldfares (feeding on '' Deroceras reticulatum''), redwings (feeding on '' Limax'' and '' Arion''), thrushes (on '' Limax'' and '' Arion ater''),
red grouse The red grouse (''Lagopus scotica'') is a medium-sized bird of the grouse family which is found in Calluna, heather moorland in Great Britain and Ireland. It was formerly classified as a subspecies of the willow ptarmigan (''Lagopus lagopus'') ...
(on '' Deroceras'' and '' Arion hortensis''), game birds, wrynecks (on '' Limax flavus''),
rock dove The rock dove (''Columba livia''), also sometimes known as "rock pigeon" or "common pigeon", is a member of the bird family Columbidae (doves and pigeons). In common usage, it is often simply referred to as the "pigeon", although the rock dov ...
s, and charadriiform birds as slug predators. Mammals that eat slugs include foxes,
badger Badgers are medium-sized short-legged omnivores in the superfamily Musteloidea. Badgers are a polyphyletic rather than a natural taxonomic grouping, being united by their squat bodies and adaptions for fossorial activity rather than by the ...
s, and
hedgehog A hedgehog is a spiny mammal of the subfamily Erinaceinae, in the eulipotyphlan family Erinaceidae. There are 17 species of hedgehog in five genera found throughout parts of Europe, Asia, and Africa, and in New Zealand by introduction. The ...
s.


Invertebrates

Beetles in the family
Carabidae Ground beetles are a large, cosmopolitan family of beetles, the Carabidae, with more than 40,000 species worldwide, around 2,000 of which are found in North America and 2,700 in Europe. As of 2015, it is one of the 10 most species-rich animal ...
, such as '' Carabus violaceus'' and '' Pterostichus melanarius'', are known to feed on slugs. Ants are a common predator of slugs; some ant species are deterred by the slug's mucus coating, while others such as driver ants will roll the slug in dirt to absorb its mucus.


Parasites and parasitoids

Slugs are parasitised by several organisms, including
acari Mites are small arachnids (eight-legged arthropods) of two large orders, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari. However, most recent genetic analyses do not recover the two as ea ...
and a wide variety of
nematode The nematodes ( or ; ; ), roundworms or eelworms constitute the phylum Nematoda. Species in the phylum inhabit a broad range of environments. Most species are free-living, feeding on microorganisms, but many are parasitic. Parasitic worms (h ...
s. The slug mite, '' Riccardoella limacum'', is known to parasitise several dozen species of molluscs, including many slugs, such as '' Deroceras reticulatum'', '' Arianta arbustorum'', '' Arion ater'', '' Arion hortensis'', '' Limax maximus'', ''
Tandonia budapestensis ''Tandonia budapestensis'' is a species of air-breathing, keel (slug), keeled, land slug, a shell-less terrestrial molluscs, terrestrial gastropod mollusks in the family Milacidae.Marshall, B. (2014). Tandonia budapestensis (Hazay, 1880). Accesse ...
'', '' Milax gagates'', and '' Tandonia sowerbyi''. ''R. limacum'' can often be seen swarming about their host's body, and live in its respiratory cavity. Several species of nematodes are known to parasitise slugs. The nematode worms '' Agfa flexilis'' and '' Angiostoma limacis'' respectively live in the
salivary glands The salivary glands in many vertebrates including mammals are exocrine glands that produce saliva through a system of Duct (anatomy), ducts. Humans have three paired major salivary glands (Parotid gland, parotid, Submandibular gland, submandibula ...
and
rectum The rectum (: rectums or recta) is the final straight portion of the large intestine in humans and some other mammals, and the gut in others. Before expulsion through the anus or cloaca, the rectum stores the feces temporarily. The adult ...
of '' Limax maximus''. Taylor J. W. (1902). Part 8, pages 1–52
''Monograph of the land and freshwater Mollusca of the British Isles. Testacellidae. Limacidae. Arionidae''
Taylor Brothers, Leeds. Introductio
page XV.
page
34
��52.
Species of widely known medical importance pertaining to the genus '' Angiostrongylus'' are also parasites of slugs. Both '' Angiostrongylus costaricensis'' and '' Angiostrongylus cantonensis'', a
meningitis Meningitis is acute or chronic inflammation of the protective membranes covering the brain and spinal cord, collectively called the meninges. The most common symptoms are fever, intense headache, vomiting and neck stiffness and occasion ...
-causing nematode, have larval stages that can only live in molluscs, including slugs, such as '' Limax maximus''. Insects such as dipterans are known
parasitoid In evolutionary ecology, a parasitoid is an organism that lives in close association with its host (biology), host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionarily stable str ...
s of molluscs. To complete their development, many dipterans use slugs as hosts during their
ontogeny Ontogeny (also ontogenesis) is the origination and development of an organism (both physical and psychological, e.g., moral development), usually from the time of fertilization of the ovum, egg to adult. The term can also be used to refer to t ...
. Some species of blow-flies ( Calliphoridae) in the genus '' Melinda'' are known parasitoids of Arionidae, Limacidae and Philomycidae. Flies in the family
Phoridae The Phoridae are a family of small, hump-backed flies resembling fruit flies. Phorid flies can often be identified by their escape habit of running rapidly across a surface rather than taking flight. This behaviour is a source of one of their al ...
, specially those in the genus '' Megaselia'', are parasitoids of Agriolimacidae, including many species of '' Deroceras''. House flies in the family Muscidae, mainly those in the genus '' Sarcophaga'', are facultative parasitoids of Arionidae.


Behavior

When attacked, slugs can contract their body, making themselves harder and more compact and more still and round. By doing this, they become firmly attached to the substrate. This, combined with the slippery mucus they produce, makes slugs more difficult for predators to grasp. The unpleasant taste of the mucus is also a deterrent. Slugs can also incapacitate predators through the production of a highly sticky and elastic mucus which can trap predators in the secretion. Some species present different response behaviors when attacked, such as the
Kerry slug The Kerry slug or Kerry spotted slug (''Geomalacus maculosus'') is a species of terrestrial, pulmonate, gastropod mollusc. It is a medium-to-large sized, air-breathing land slug in the Family (biology), family of roundback slugs, Arionidae. Ad ...
. In contrast to the general behavioral pattern, the Kerry slug retracts its head, lets go of the substrate, rolls up completely, and stays contracted in a ball-like shape. 9 pp. This is a unique feature among all the Arionidae, and among most other slugs. Some slugs can self-amputate ( autotomy) a portion of their tail to help the slug escape from a predator. Some slug species hibernate underground during the winter in temperate climates, but in other species, the adults die in the autumn. Intra- and inter-specific agonistic behavior is documented, but varies greatly among slug species. Slugs often resort to aggression, attacking both
conspecific Biological specificity is the tendency of a characteristic such as a behavior or a biochemical variation to occur in a particular species. Biochemist Linus Pauling stated that "Biological specificity is the set of characteristics of living organism ...
s and individuals from other species when competing for resources. This aggressiveness is also influenced by
seasonality In time series data, seasonality refers to the trends that occur at specific regular intervals less than a year, such as weekly, monthly, or quarterly. Seasonality may be caused by various factors, such as weather, vacation, and holidays and consi ...
, because the availability of resources such as shelter and food may be compromised due to climatic conditions. Slugs are prone to attack during the summer, when the availability of resources is reduced. During winter, the aggressive responses are substituted by a
gregarious Sociality is the degree to which individuals in an animal population tend to associate in social groups (gregariousness) and form cooperative societies. Sociality is a survival response to evolutionary pressures. For example, when a mother was ...
behavior.


Human relevance

The great majority of slug species are harmless to humans and to their interests, but a small number of species are serious pests of agriculture and horticulture. They can destroy foliage faster than plants can grow, thus killing even fairly large plants. They also feed on fruits and vegetables prior to harvest, making holes in the crop, which can make individual items unsuitable to sell for aesthetic reasons, and can make the crop more vulnerable to rot and disease. Excessive buildup of slugs within some wastewater treatment plants with inadequate screening has been found to cause process issues resulting in increased energy and chemical use. In a few rare cases, humans have developed '' Angiostrongylus cantonensis''-induced
meningitis Meningitis is acute or chronic inflammation of the protective membranes covering the brain and spinal cord, collectively called the meninges. The most common symptoms are fever, intense headache, vomiting and neck stiffness and occasion ...
from eating raw slugs. Live slugs that are accidentally eaten with improperly cleaned vegetables (such as
lettuce Lettuce (''Lactuca sativa'') is an annual plant of the family Asteraceae mostly grown as a leaf vegetable. The leaves are most often used raw in Green salad, green salads, although lettuce is also seen in other kinds of food, such as sandwiche ...
), or improperly cooked slugs (for use in recipes requiring larger slugs such as banana slugs), can act as a vector for a parasitic infection in humans.Senanayake, S. N.; Pryor, D. S.; Walker, J.; Konecny, P. (2003
"First report of human angiostrongyliasis acquired in Sydney"
. '' The Medical Journal of Australia'' 179 (8): 430–431.


Prevention

As control measures, baits are commonly used in both agriculture and the garden. In recent years, iron phosphate baits have emerged and are preferred over the more toxic metaldehyde, especially because domestic or wild animals may be exposed to the bait. The environmentally safer iron phosphate has been shown to be at least as effective as baits. Methiocarb baits are no longer widely used. Parasitic nematodes ('' Phasmarhabditis hermaphrodita'') are a commercially available biological control method that are effective against a wide range of common slug species. The nematodes are applied in water and actively seek out slugs in the soil and infect them, leading to the death of the slug. This control method is suitable for use in organic growing systems. Other slug control methods are generally ineffective on a large scale, but can be somewhat useful in small gardens. These include ,
diatomaceous earth Diatomaceous earth ( ), also known as diatomite ( ), celite, or kieselguhr, is a naturally occurring, soft, siliceous rock, siliceous sedimentary rock that can be crumbled into a fine white to off-white powder. It has a particle size ranging fr ...
, crushed eggshells, coffee grounds, and copper. Salt kills slugs by causing water to leave the body owing to
osmosis Osmosis (, ) is the spontaneous net movement or diffusion of solvent molecules through a selectively permeable membrane, selectively-permeable membrane from a region of high water potential (region of lower solute concentration) to a region of ...
but this is not used for agricultural control as high
soil salinity Soil salinity is the salt (chemistry), salt content in the soil; the process of increasing the salt content is known as salinization (also called salination in American and British English spelling differences, American English). Salts occur nat ...
is detrimental to crops. Conservation tillage worsens slug infestations. Hammond et al. 1999 find maize/corn and
soybean The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean. Soy is a staple crop, the world's most grown legume, and an important animal feed. Soy is a key source o ...
in the US to be more severely affected under low till because this increases organic matter, thus providing food and shelter. .


Gallery

File:Orange slug.jpg, '' Arion rufus'' File:Bug moving dead snail with fly 1a.jpg, A dung beetle ('' Geotrupes stercorarius'') moving a dead slug. File:Amanita amerimuscaria 126174.jpg, A
mushroom A mushroom or toadstool is the fleshy, spore-bearing Sporocarp (fungi), fruiting body of a fungus, typically produced above ground on soil or another food source. ''Toadstool'' generally refers to a poisonous mushroom. The standard for the n ...
(''
Amanita muscaria ''Amanita muscaria'', commonly known as the fly agaric or fly amanita, is a basidiomycete fungus of the genus ''Amanita''. It is a large white-lamella (mycology), gilled, white-spotted mushroom typically featuring a bright red cap covered with ...
'') being eaten by a banana slug. File:Slug damaging vegetables.jpg, Slugs eating
vegetable Vegetables are edible parts of plants that are consumed by humans or other animals as food. This original meaning is still commonly used, and is applied to plants collectively to refer to all edible plant matter, including edible flower, flo ...
s. File:Jõelähtme Parish, Harju County, Estonia - panoramio - Николай Семёнов (4).jpg, '' Limax cinereoniger'', the world's largest terrestrial slug. File:GrallariaRufocinereaSmit (cropped).jpg, An illustration by Joseph Smit of a bicolored antpitta catching a slug.


See also

*
Snail A snail is a shelled gastropod. The name is most often applied to land snails, terrestrial molluscs, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class Gas ...
*
Sea slug Sea slug is a common name for some Marine biology, marine invertebrates with varying levels of resemblance to terrestrial Slug, slugs. Most creatures known as sea slugs are gastropods, i.e. they are Sea snail, sea snails (marine gastropod moll ...


References


Further reading

*


External links

*
Slugs and Their Management.
Ohio State University Extension. * The Nature Conservancy.
Land Slugs and Snails and Their Control.
USDA Farmer's Bulletin No. 1895. Revised 1959. Hosted by th
UNT Government Documents Department
University of Florida The University of Florida (Florida or UF) is a public university, public land-grant university, land-grant research university in Gainesville, Florida, United States. It is a senior member of the State University System of Florida and a preem ...
IFAS {{Authority control Stylommatophora Gastropod anatomy Articles containing video clips Mollusc common names Polyphyletic groups