Slug, or land slug, is a
common name for any apparently shell-less
terrestrial
Terrestrial refers to things related to land or the planet Earth.
Terrestrial may also refer to:
* Terrestrial animal, an animal that lives on land opposed to living in water, or sometimes an animal that lives on or near the ground, as opposed to ...
gastropod mollusc. 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 invertebrates with varying levels of resemblance to terrestrial slugs. Most creatures known as sea slugs are gastropods, i.e. they are sea snails (marine gastropod mollusks) that over evolutionary time ...
s and
semislugs (this is in contrast to the common name ''
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 G ...
'', 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 a superficial similarity in the 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 com ...
, and thus the category "slug" is
polyphyletic
A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of conver ...
.
Taxonomy
Of the six orders of
Pulmonata, two – the
Onchidiacea and
Soleolifera – solely comprise slugs. A third family, the
Sigmurethra, 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.
It appears that pulmonates are paraphyletic and basal to the
opisthobranchs, which are a terminal branch of the tree. The family
Ellobiidae
Ellobiidae, common name the hollow-shelled snails, is a family of small air-breathing land snails, terrestrial pulmonate gastropod mollusks in the clade Eupulmonata.Bouchet, P. (2012). Ellobiidae. Accessed through: World Register of Marine Spe ...
are also polyphyletic.
*Subinfraorder
Orthurethra
**Superfamily
Achatinelloidea Gulick, 1873
**Superfamily
Cochlicopoidea
Pupilloidea is a superfamily of small and very small air-breathing land snails, terrestrial gastropod mollusks in the infraorder ''Pupilloidei'' .
Taxonomy
This superfamily contains the following families:
* Achatinellidae Gulick, 1873
* Agar ...
Pilsbry, 1900
**Superfamily
Partuloidea
Pupilloidea is a superfamily of small and very small air-breathing land snails, terrestrial gastropod mollusks in the infraorder ''Pupilloidei'' .
Taxonomy
This superfamily contains the following families:
* Achatinellidae Gulick, 1873
* Agar ...
Pilsbry, 1900
**Superfamily
Pupilloidea
Pupilloidea is a superfamily of small and very small air-breathing land snails, terrestrial gastropod mollusks in the infraorder ''Pupilloidei'' .
Taxonomy
This superfamily contains the following families:
* Achatinellidae Gulick, 1873
* A ...
Turton, 1831
*Subinfraorder
Sigmurethra
**Superfamily
Acavoidea Pilsbry, 1895
**Superfamily
Achatinoidea
The Achatinoidea are a superfamily of air-breathing land snails and slugs, terrestrial gastropod mollusks in the informal group Sigmurethra.
2005 taxonomy
According to taxonomy of the Gastropoda by Bouchet & Rocroi, 2005 there are four fami ...
Swainson, 1840
**Superfamily
Aillyoidea Baker, 1960
**Superfamily
Arionoidea J.E. Gray in Turnton, 1840
**Superfamily
Athoracophoroidea
***Family
Athoracophoridae
Athoracophoridae, common name the leaf-veined slugs, are a family of air-breathing land slugs, terrestrial pulmonate gastropod mollusks in the infraorder Stylommatophora, the stalk-eyed snails and slugs. Many of the species have an attractive p ...
**Superfamily
Orthalicoidea
The Orthalicoidea are a superfamily of air-breathing land snails, terrestrial gastropod mollusks in the infraorder Orthalicoidei of the suborder HelicinaMolluscaBase eds. (2021). MolluscaBase. Simpulopsidae Schileyko, 1999. Accessed through: W ...
***Subfamily
Bulimulinae
**Superfamily
Camaenoidea Pilsbry, 1895
**Superfamily
Clausilioidea Mörch, 1864
**Superfamily
Dyakioidea Gude & Woodward, 1921
**Superfamily
Gastrodontoidea Tryon, 1866
**Superfamily
Helicoidea Rafinesque
Constantine Samuel Rafinesque-Schmaltz (; October 22, 1783September 18, 1840) was a French 19th-century polymath born near Constantinople in the Ottoman Empire and self-educated in France. He traveled as a young man in the United States, ultimat ...
, 1815
**Superfamily
Helixarionoidea Bourguignat, 1877
**Superfamily
Limacoidea Rafinesque
Constantine Samuel Rafinesque-Schmaltz (; October 22, 1783September 18, 1840) was a French 19th-century polymath born near Constantinople in the Ottoman Empire and self-educated in France. He traveled as a young man in the United States, ultimat ...
, 1815
**Superfamily
Oleacinoidea H. & A. Adams, 1855
**Superfamily
Orthalicoidea
The Orthalicoidea are a superfamily of air-breathing land snails, terrestrial gastropod mollusks in the infraorder Orthalicoidei of the suborder HelicinaMolluscaBase eds. (2021). MolluscaBase. Simpulopsidae Schileyko, 1999. Accessed through: W ...
Albers-Martens, 1860
**Superfamily
Plectopylidoidea Moellendorf, 1900
**Superfamily
Polygyroidea Pilsbry, 1894
**Superfamily
Punctoidea
Punctoidea is a superfamily of air-breathing land snails and slugs, terrestrial pulmonate gastropod mollusks in the informal group Sigmurethra.
Taxonomy
The superfamily Punctoidea is classified within the clade Stylommatophora within the clade ...
Morse, 1864
**Superfamily
Rhytidoidea
The Rhytidoidea are a superfamily of air-breathing land snails and slugs, terrestrial gastropod mollusks in the suborder Helicina. MolluscaBase eds. (2021). MolluscaBase. Rhytidoidea Pilsbry, 1893. Accessed through: World Register of Marine Spec ...
Pilsbry, 1893
***Family
Rhytididae
Rhytididae is a taxonomic family of medium-sized predatory air-breathing land snails, carnivorous terrestrial pulmonate gastropod molluscs in the superfamily Rhytidoidea. MolluscaBase eds. (2020). MolluscaBase. Rhytididae Pilsbry, 1893. Acces ...
**Superfamily
Sagdidoidera Pilsbry, 1895
**Superfamily
Staffordioidea Thiele, 1931
**Superfamily
Streptaxoidea
Streptaxoidea is a superfamily of air-breathing land snails, terrestrial pulmonate gastropod mollusks in the suborder Achatinina of the order Stylommatophora.
Taxonomy
2005 taxonomy
There have been recognized the only family Streptaxidae wi ...
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
Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 te ...
sensing and has eyespots at the ends, while the lower pair provides the
sense of smell
The sense of smell, or olfaction, is the special sense through which smells (or odors) are perceived. The sense of smell has many functions, including detecting desirable foods, hazards, and pheromones, and plays a role in taste.
In humans, ...
. Both pairs are retractable.
* Mantle: On top of the slug, behind the head, is the saddle-shaped ''
mantle,'' and under this are the genital opening and anus. On one side (almost always the right hand side) of the mantle is a
respiratory
The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies gre ...
opening, which is easy to see when open, but difficult to see when closed. This opening is known as the
pneumostome
The pneumostome or breathing pore is a respiratory opening of the external body anatomy of an air-breathing land slug or land snail. It is a part of the respiratory system of gastropods.
It is an opening in the right side of the mantle of a ...
.
* Tail: The part of a slug behind the mantle is called the 'tail'.
* Keel: Some species of slugs, for example ''
Tandonia budapestensis'', have a prominent ridge running over their back along the middle of the tail (sometimes along the whole tail, sometimes only the final part). This ridge is called a 'keel'.
* 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
Muscle contraction is the activation of tension-generating sites within muscle cells. In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in muscle length, such as ...
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 and mucous cells. It ...
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
Philomycidae are a family of air-breathing land slugs (snails without shells or with only shell remnants). They are terrestrial pulmonate gastropod mollusks in the superfamily Arionoidea (according to the taxonomy of the Gastropoda by Bouc ...
,
Onchidiidae and
Veronicellidae
The Veronicellidae, also known by their common name the leatherleaf slugs, are a family of pulmonate terrestrial slugs.
The herbivorous molluscs occur mainly in the tropical and subtropical areas of America, Asia and Africa.
They act as intermed ...
lack shells.
Physiology
Slugs' bodies are made up mostly of water and, without a full-sized shell, their soft tissues are prone to
desiccation. They must generate protective mucus to survive. Many species are most active just after rain because of the moist ground. In drier conditions, they hide in damp places such as under
tree bark, fallen
logs, rocks and man-made structures, such as
planters, to help retain body moisture.
Like all other gastropods, they undergo
torsion
Torsion may refer to:
Science
* Torsion (mechanics), the twisting of an object due to an applied torque
* Torsion of spacetime, the field used in Einstein–Cartan theory and
** Alternatives to general relativity
* Torsion angle, in chemistry
Bi ...
(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
The pneumostome or breathing pore is a respiratory opening of the external body anatomy of an air-breathing land slug or land snail. It is a part of the respiratory system of gastropods.
It is an opening in the right side of the mantle of a ...
, 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 and mucous cells. It ...
: 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 or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substan ...
. 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 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
hermaphrodites, 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. A few days later, the slugs lay approximately thirty eggs in a hole in the ground, or beneath the cover of an object such as a fallen log.
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.
Ecology
Slugs play an important role in the
ecosystem
An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...
by eating decaying plant material and
fungi
A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...
.
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,
lichens
A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.[mushrooms
A mushroom or toadstool is the fleshy, spore-bearing fruiting body of a fungus, typically produced above ground, on soil, or on its food source. ''Toadstool'' generally denotes one poisonous to humans.
The standard for the name "mushroom" is ...]
, and even
carrion.
Some slugs are
predator
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...
s and eat other slugs and
snails
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 Gastro ...
, or
earthworm
An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; and they usually have setae on all segments. T ...
s.
Slugs can feed on a wide variety of
vegetables
Vegetables are parts of plants that are consumed by humans or other animals as food. The original meaning is still commonly used and is applied to plants collectively to refer to all edible plant matter, including the flowers, fruits, stems ...
and
herbs, including flowers such as
petunia
''Petunia'' is 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 ''petun'', meaning "tobacco," from a Tupi–Guarani language. A tende ...
s,
chrysanthemums,
daisies,
lobelia
''Lobelia'' () is a genus of flowering plants comprising 415 species, with a subcosmopolitan distribution primarily in tropical to warm temperate regions of the world, a few species extending into cooler temperate regions.Huxley, A., ed. (1992 ...
,
lilies
''Lilium'' () is a genus of herbaceous flowering plants growing from bulbs, all with large prominent flowers. They are the true lilies. Lilies are a group of flowering plants which are important in culture and literature in much of the world. M ...
,
daffodils,
narcissus,
gentians,
primroses,
tuberous begonias,
hollyhocks,
irises, 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 ]fungivore
Fungivory or mycophagy is the process of organisms consuming fungi. Many different organisms have been recorded to gain their energy from consuming fungi, including birds, mammals, insects, plants, amoebas, gastropods, nematodes, bacteria and oth ...
s. It is the case in the Philomycidae
Philomycidae are a family of air-breathing land slugs (snails without shells or with only shell remnants). They are terrestrial pulmonate gastropod mollusks in the superfamily Arionoidea (according to the taxonomy of the Gastropoda by Bouc ...
(e. g. ''Philomycus carolinianus
''Philomycus carolinianus'', common name the Carolina mantleslug, is a species of land slug, a terrestrial gastropod mollusk in the family Philomycidae.
Anatomy
These slugs create and use love dart
A love dart (also known as a gypsobelu ...
'' and '' Phylomicus flexuolaris'') and '' Ariolimacidae'' ('' Ariolimax californianus''), which respectively feed on slime molds ( myxomycetes) and mushrooms (basidiomycetes
Basidiomycota () is one of two large 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. More specifically, Ba ...
).[ Species of mushroom producing fungi used as food source by slugs include milk-caps, '' Lactarius'' spp., the oyster mushroom, '']Pleurotus ostreatus
''Pleurotus ostreatus'', the oyster mushroom, oyster fungus, or hiratake, is a common edible mushroom. It was first cultivated in Germany as a subsistence measure during World War I and is now grown commercially around the world for food. It is ...
'' and the penny bun, ''Boletus edulis
''Boletus edulis'' (English: cep, penny bun, porcino or porcini) is a basidiomycete fungus, and the type species of the genus ''Boletus''. Widely distributed in the Northern Hemisphere across Europe, Asia, and North America, it does not occu ...
''. Other species pertaining to different genera, such as ''Agaricus
''Agaricus'' is a genus of mushrooms containing both edible and poisonous species, with over 400 members worldwide and possibly again as many disputed or newly-discovered species. The genus includes the common ("button") mushroom ('' Agaricus bi ...
'', '' Pleurocybella'' and ''Russula
''Russula'' is a very large genus composed of around 750 worldwide species of ectomycorrhizal mushrooms. They are typically common, fairly large, and brightly colored – making them one of the most recognizable genera among mycologists and mushr ...
'', 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. Moreover, in other cases, whole mushrooms can be eaten, without any selection or bias towards ]ontogenetic
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 egg to adult. The term can also be used to refer to the st ...
stages.[
]
Predators
Slugs are preyed upon by various vertebrates
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () (chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with c ...
and invertebrates
Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordat ...
. The predation of slugs has been the subject of studies for at least a century. Because some species of slugs are considered agricultural pest
A pest is any animal or plant harmful to humans or human concerns. The term is particularly used for creatures that damage crops, livestock, and forestry or cause a nuisance to people, especially in their homes. Humans have modified the environ ...
s, research investments have been made to comprehend and investigate potential predators. This is a necessary knowledge to establish biological control strategies.[
]
Vertebrates
Slugs are preyed upon by virtually every major vertebrate group. With many examples among reptiles, birds, mammals
Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur o ...
, amphibians and fish
Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of ...
, 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 European species of salmonid fish that has been widely introduced into suitable environments globally. It includes purely freshwater populations, referred to as the riverine ecotype, ''Salmo trutta'' morph ...
''), 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
''Bufo'' is a genus of true toads in the amphibian family Bufonidae. As traditionally defined, it was a wastebasket genus containing a large number of toads from much of the world, but following taxonomic reviews most of these have been moved t ...
'' (e. g. '' Bufo marinus'') and '' Ceratophrys''.[
Reptiles that feed on slugs include mainly ]snake
Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes . Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more j ...
s and lizards.[ Some ]colubrid
Colubridae (, commonly known as colubrids , from la, coluber, 'snake') is a family of snakes. With 249 genera, it is the largest snake family. The earliest species of the family date back to the Oligocene epoch. Colubrid snakes are found on ev ...
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
''Dipsas'' is a genus of nonvenomous New World snakes in the subfamily Dipsadinae of the family Colubridae. The genus ''Sibynomorphus'' has been moved here. The genus ''Dipsas'' are as known as snail-eater.
Geographic range
Species in the genus ...
''/''Sibynomorphus
''Dipsas'' is a genus of nonvenomous New World snakes in the subfamily Dipsadinae of the family Colubridae. The genus ''Sibynomorphus'' has been moved here. The genus ''Dipsas'' are as known as snail-eater.
Geographic range
Species in the genus ...
'' (e.g. '' Sibynomorphus 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
''Tiliqua rugosa'', most commonly known as the shingleback lizard or bobtail lizard, is a short-tailed, slow-moving species of blue-tongued skink (genus ''Tiliqua'') endemic to Australia. It is commonly known as the shingleback or sleepy lizard ...
''), the she-oak skink (''Cyclodomorphus casuarinae
The she-oak skink (''Cyclodomorphus casuarinae'') is a large, long-tailed, snake-like skink endemic to Tasmania, Australia. It is viviparous
Among animals, viviparity is development of the embryo inside the body of the parent. This is opp ...
'') and the common lizard (''Zootoca vivipara
The viviparous lizard, or common lizard, (''Zootoca vivipara'', formerly ''Lacerta vivipara''), is a Eurasian lizard. It lives farther north than any other species of non-marine reptile, and is named for the fact that it is viviparous, meaning it ...
'').
Birds that prey upon slugs include common blackbirds ('' Turdus merula''), starling
Starlings are small to medium-sized passerine birds in the family Sturnidae. The Sturnidae are named for the genus '' Sturnus'', which in turn comes from the Latin word for starling, ''sturnus''. Many Asian species, particularly the larger ones, ...
s (''Sturnus vulgaris
The common starling or European starling (''Sturnus vulgaris''), also known simply as the starling in Great Britain and Ireland, is a medium-sized passerine bird in the starling family, Sturnidae. It is about long and has glossy black plumage ...
''), rooks ('' Corvus frugilegus''), jackdaw
Jackdaws are two species of bird in the genus ''Coloeus'' closely related to, but generally smaller than, the crows and ravens (''Corvus''). ''Coloeus'' is sometimes treated as a subgenus of ''Corvus'', including by the IUCN.Madge & Burn (1994) ...
s ('' Corvus monedula''), owl
Owls are birds from the order Strigiformes (), which includes over 200 species of mostly solitary and nocturnal birds of prey typified by an upright stance, a large, broad head, binocular vision, binaural hearing, sharp talons, and feathers a ...
s, vulture
A vulture is a bird of prey that scavenges on carrion. There are 23 extant species of vulture (including Condors). Old World vultures include 16 living species native to Europe, Africa, and Asia; New World vultures are restricted to North and ...
s and duck
Duck is the common name for numerous species of waterfowl in the family Anatidae. Ducks are generally smaller and shorter-necked than swans and geese, which are members of the same family. Divided among several subfamilies, they are a form ...
s. Studies on slug predation also cite fieldfare
The fieldfare (''Turdus pilaris'') is a member of the thrush family Turdidae. It breeds in woodland and scrub in northern Europe and across the Palearctic. It is strongly migratory, with many northern birds moving south during the winter. It i ...
s (feeding on '' Deroceras reticulatum''), redwing
The redwing (''Turdus iliacus'') is a bird in the thrush family, Turdidae, native to Europe and the Palearctic, slightly smaller than the related song thrush.
Taxonomy and systematics
This species was first described by Carl Linnaeus in h ...
s (feeding on ''Limax
''Limax'' is a genus of air-breathing land slugs in the terrestrial pulmonate gastropod mollusk family Limacidae.
The generic name ''Limax'' literally means "slug".
Some species, such as the leopard slug (''L. maximus'') and the tawny garden ...
'' and '' Arion''), thrushes
The thrushes are a passerine bird family, Turdidae, with a worldwide distribution. The family was once much larger before biologists reclassified the former subfamily Saxicolinae, which includes the chats and European robins, as Old World flyca ...
(on ''Limax
''Limax'' is a genus of air-breathing land slugs in the terrestrial pulmonate gastropod mollusk family Limacidae.
The generic name ''Limax'' literally means "slug".
Some species, such as the leopard slug (''L. maximus'') and the tawny garden ...
'' and '' Arion ater''), red grouse (on '' Deroceras'' and '' Arion hortensis''), game bird
Galliformes is an order of heavy-bodied ground-feeding birds that includes turkeys, chickens, quail, and other landfowl. Gallinaceous birds, as they are called, are important in their ecosystems as seed dispersers and predators, and are ofte ...
s, wryneck
The wrynecks (genus ''Jynx'') are a small but distinctive group of small Old World woodpeckers. ''Jynx'' is from the Ancient Greek ''iunx'', the Eurasian wryneck.
These birds get their English name from their ability to turn their heads almos ...
s (on '' Limax flavus''), rock dove
The rock dove, rock pigeon, or common pigeon ( also ; ''Columba livia'') is a member of the bird family Columbidae (doves and pigeons). In common usage, it is often simply referred to as the "pigeon".
The domestic pigeon (''Columba livia domes ...
s and charadriiform birds as slug predators.
Mammals that eat slugs include foxes, badger
Badgers are short-legged omnivores in the family Mustelidae (which also includes the otters, wolverines, martens, minks, polecats, weasels, and ferrets). Badgers are a polyphyletic rather than a natural taxonomic grouping, being united by ...
s and hedgehog
A hedgehog is a spiny mammal of the subfamily Erinaceinae, in the eulipotyphlan family Erinaceidae. There are seventeen species of hedgehog in five genera found throughout parts of Europe, Asia, and Africa, and in New Zealand by introductio ...
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 fami ...
, such as ''Carabus violaceus
''Carabus violaceus'', sometimes called the violet ground beetle, or the rain beetle is a nocturnal species of a beetle, from the family Carabidae.
Description
The violet ground beetle is a non-shiny, black beetle that has violet or indigo edge ...
'' and '' Pterostichus melanarius'', are known to feed on slugs.
Parasites and parasitoids
Slugs are parasitised by several organisms, including acari
Mites are small arachnids (eight-legged arthropods). Mites span two large orders of arachnids, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari, but genetic analysis does not show clear evid ...
and a wide variety of nematodes.[ The slug mite, '' Riccardoella limacum'', is known to parasitise several dozen species of molluscs, including many slugs, such as '' Agriolimax agrestis'', '' Arianta arbustrum'', '' Arion ater'', '' Arion hortensis'', '' Limax maximus'', '' Milax budapestensis'', '' Milax gagates'', and '' Milax 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 mammals are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands ( parotid, submandibular, and sublingual), as well as hundreds of minor salivary glands. Salivary gl ...
and rectum 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
''Angiostrongylus cantonensis'' is a parasitic nematode (roundworm) that causes angiostrongyliasis, the most common cause of eosinophilic meningitis in Southeast Asia and the Pacific Basin. The nematode commonly resides in the pulmonary arteries ...
'', a meningitis-causing nematode, have larval stages that can only live in molluscs, including slugs, such as '' Limax maximus''.
Insects such as dipterans are known parasitoids 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 egg to adult. The term can also be used to refer to the s ...
. Some species of blow-flies (Calliphoridae
The Calliphoridae (commonly known as blow flies, blow-flies, carrion flies, bluebottles, greenbottles, or cluster flies) are a family of insects in the order Diptera, with almost 1,900 known species. The maggot larvae, often used as fishing ba ...
) in the genus ''Melinda
Melinda is a feminine given name.
Etymology
The modern name ''Melinda'' is a combination of "Mel" with the suffix "-inda". "Mel" can be derived from names such as Melanie meaning "dark, black" in Greek, or from Melissa (μέλισσα) meaning ...
'' are known parasitoids of Arionidae, Limacidae and Philomycidae
Philomycidae are a family of air-breathing land slugs (snails without shells or with only shell remnants). They are terrestrial pulmonate gastropod mollusks in the superfamily Arionoidea (according to the taxonomy of the Gastropoda by Bouc ...
. 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 to the wing. This behaviour is a source of one of thei ...
, specially those in the genus ''Megaselia
''Megaselia'' is a genus of flies in the family Phoridae.
See also
* List of Megaselia species
This is a list of 1675 species in '' Megaselia'', a genus of scuttle flies in the family Phoridae.
''Megaselia'' species
A
* ''Megaselia abaliena ...
'', are parasitoids of Agriolimacidae
''Agriolimacidae'' is a family of small and medium-sized land slugs, or shell-less snails, terrestrial pulmonate gastropod mollusks.
Distribution
Distribution of Limacidae is Holarctic, this include: Nearctic, western Palearctic and eastern Pal ...
, including many species of '' Deroceras''. House flies in the family Muscidae
Muscidae are a family of flies found in the superfamily Muscoidea.
Muscidae, some of which are commonly known as house flies or stable flies due to their synanthropy, are worldwide in distribution and contain almost 4,000 described species i ...
, 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. 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
Autotomy (from the Greek ''auto-'', "self-" and ''tome'', "severing", αὐτοτομία) or self-amputation, is the behaviour whereby an animal sheds or discards one or more of its own appendages, usually as a self-defense mechanism to elude ...
) 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 organis ...
s and individuals from other species when competing for resources. This aggressiveness is also influenced by seasonality
In time series data, seasonality is the presence of variations 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 a ...
, because the availability of resources such as shelter and food may be compromised due to climatic
Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorological ...
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 wasp ...
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 have been found to cause process issues resulting in increased energy and chemical use.
As control measures, baits are commonly used in both agriculture and the garden. In recent years, iron phosphate Iron phosphate may refer to:
* Iron(II) phosphate
* Iron(III) phosphate
Iron(III) phosphate, also ferric phosphate, is the inorganic compound with the formula Fe PO4. Several related materials are known, including four polymorphs of FePO4 and ...
baits have emerged and are preferred over the more toxic metaldehyde
Metaldehyde is an organic compound with the formula (C8H16O4). It is used as a pesticide against slugs, snails, and other gastropods. It is the cyclic tetramer of acetaldehyde.
Production and properties
Metaldehyde is flammable, toxic if ing ...
, 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 beer traps, diatomaceous earth, 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 from a region of high water potential (region of lower solute concentration) to a region of low water potential (region o ...
but this is not used for agricultural control as soil salinity is detrimental to crops. Conservation tillage
Tillage is the agricultural preparation of soil by mechanical agitation of various types, such as digging, stirring, and overturning. Examples of human-powered tilling methods using hand tools include shoveling, picking, mattock work, hoei ...
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, which has numerous uses.
Traditional unfermented food uses of soybeans include soy milk, from which tofu a ...
in the US to be more severely affected under low till because this increases organic matter, thus providing food and shelter.[ .]
In a few rare cases, humans have developed ''Angiostrongylus cantonensis
''Angiostrongylus cantonensis'' is a parasitic nematode (roundworm) that causes angiostrongyliasis, the most common cause of eosinophilic meningitis in Southeast Asia and the Pacific Basin. The nematode commonly resides in the pulmonary arteries ...
''-induced meningitis 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. It is most often grown as a leaf vegetable, but sometimes for its stem and seeds. Lettuce is most often used for salads, although it is also seen in other kinds of food, ...
), or improperly cooked slugs (for use in recipes requiring larger slugs such as banana slug
Banana slugs are North American terrestrial slugs comprising the genus ''Ariolimax''. MolluscaBase eds. (2021). MolluscaBase. Ariolimax Mörch, 1859. Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p= ...
s), 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
The ''Medical Journal of Australia'' is a peer-reviewed medical journal published 22 times a year. It is the official journal of the Australian Medical Association, published by Wiley on behalf of the Australasian Medical Publishing Company.
The ...
'' 179 (8): 430–431.
Gallery
Image:Mating Great Grey Slug 4124.jpg, '' Limax maximus'' mating
Image:Black-velvet leatherleaf slug (belocaulus angustipes).jpg, '' Belocaulus angustipes'' mating; note the white penis extending to the reproduction pore on the underside of the smaller slug
Image:Arion vulgaris eating.jpg, '' Arion vulgaris'' feeding
Image:Ghost Slug adult.jpg, The ghost slug (''Selenochlamys ysbryda'')
Image:Amanita amerimuscaria 126174.jpg, A banana slug
Banana slugs are North American terrestrial slugs comprising the genus ''Ariolimax''. MolluscaBase eds. (2021). MolluscaBase. Ariolimax Mörch, 1859. Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p= ...
eating a fly agaric, '' Amanita muscaria''
Image:Ambigolimax Slug ഒച്ച് from Calicut Kerala.jpg, '' Ambigolimax'' from Kozhikode
Kozhikode (), also known in English as Calicut, is a city along the Malabar Coast in the state of Kerala in India. It has a corporation limit population of 609,224 and a metropolitan population of more than 2 million, making it the second l ...
, Kerala, India
Image:Slug climbing garden bucket.jpg, Slug climbing up a garden bucket in Oklahoma
See also
* 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 G ...
* Sea slug
Sea slug is a common name for some marine invertebrates with varying levels of resemblance to terrestrial slugs. Most creatures known as sea slugs are gastropods, i.e. they are sea snails (marine gastropod mollusks) that over evolutionary time ...
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 land-grant research university in Gainesville, Florida. It is a senior member of the State University System of Florida, traces its origins to 1853, and has operated continuously on its ...
IFAS
{{Authority control
Stylommatophora
Gastropod anatomy
Articles containing video clips
Mollusc common names
Paraphyletic groups