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 contra ...
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 ...
s and
semislug
Semi-slugs, also spelled semislugs, are land gastropods whose shells are too small for them to retract into, but not quite vestigial. The shell of some semi-slugs may not be easily visible on casual inspection, because the shell may be covere ...
s (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
Pulmonata or pulmonates, is an informal group (previously an order, and before that a subclass) of snails and slugs characterized by the ability to breathe air, by virtue of having a pallial lung instead of a gill, or gills. The group include ...
, two – the
Onchidiacea and
Soleolifera – solely comprise slugs. A third family, 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 p ...
, 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 opisthobranch
Opisthobranchs () is now an informal name for a large and diverse group of specialized complex gastropods which used to be united in the subclass Opisthobranchia. That taxon is no longer considered to represent a monophyletic grouping.
Euopis ...
s, 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 Sp ...
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
* Agard ...
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
* Ag ...
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 p ...
**Superfamily Acavoidea
The Acavoidea are a taxonomic superfamily of air-breathing land snails and slugs, terrestrial pulmonate gastropod mollusks in the informal group Sigmurethra.
This taxonomy was based on the study by Nordsieck, published in 1986.
Taxonomy
Familie ...
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
Aillyidae is a family of air-breathing land snails, terrestrial pulmonate gastropod mollusks in the informal group Sigmurethra.
Aillyidae is the only family in the superfamily Aillyoidea.
This family and the genus is named in honor of Swedis ...
Baker, 1960
**Superfamily Arionoidea
Arionoidea is a taxonomic group, superfamily of air-breathing land slugs, shell-less terrestrial pulmonate gastropod mollusks.
Families
Families within the superfamily Arionoidea include:
* Arionidae
* Anadenidae
* Ariolimacidae
* Binneyidae ...
J.E. Gray in Turnton, 1840
**Superfamily Athoracophoroidea
***Family Athoracophoridae
**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: ...
***Subfamily Bulimulinae
**Superfamily Camaenoidea Pilsbry, 1895
**Superfamily Clausilioidea Mörch, 1864
**Superfamily Dyakioidea Gude & Woodward, 1921
**Superfamily Gastrodontoidea
Gastrodontoidea is a taxonomic superfamily of air-breathing land snails, terrestrial pulmonate gastropod mollusks in the limacoid clade.
Taxonomy
According to the taxonomy of the Gastropoda (Bouchet & Rocroi, 2005), families in this superfamily ...
Tryon, 1866
**Superfamily Helicoidea
Helicoidea is a taxonomic superfamily of air-breathing land snails, terrestrial pulmonate gastropod mollusks in the clade Stylommatophora.
Taxonomy 2005 taxonomy
There are 19 families within the superfamily Helicoidea according to the taxonom ...
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
Limacoidea is a Taxonomy (biology), taxonomic Taxonomic rank, superfamily of medium-sized to large, air-breathing land slugs and snails. They are Terrestrial molluscs, terrestrial pulmonate gastropod mollusc, mollusks in the infraorder Stylommatop ...
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: ...
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 th ...
Morse, 1864
**Superfamily Rhytidoidea 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 Thiele is a German-language surname.
Geographical distribution
As of 2014, 78.0% of all known bearers of the surname ''Thiele'' were residents of Germany, 10.9% of the United States, 2.3% of Australia, 2.0% of Brazil, 1.0% of Canada and 1.0% of Sou ...
, 1931
**Superfamily Streptaxoidea J.E. Gray, 1806
**Superfamily Strophocheiloidea Thiele Thiele is a German-language surname.
Geographical distribution
As of 2014, 78.0% of all known bearers of the surname ''Thiele'' were residents of Germany, 10.9% of the United States, 2.3% of Australia, 2.0% of Brazil, 1.0% of Canada and 1.0% of Sou ...
, 1926
**Superfamily Parmacelloidea
**Superfamily Zonitoidea Mörch, 1864
**Superfamily Quijotoidea Jesús Ortea and Juan José Bacallado, 2016
***Family Quijotidae
''Quijote'' is a monotypic genus
In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In ...
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, it ...
. 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 ...
.
* 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
Limacidae, also known by their common name the keelback slugs, are a taxonomic family of medium-sized to very large, air-breathing land slugs, terrestrial pulmonate gastropod molluscs in the superfamily Limacoidea.
Distribution
The distributi ...
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 Bouch ...
,[ ]Onchidiidae
Onchidiidae are a family of small, air-breathing sea (and land) slugs. They are shell-less marine (except for 2 species)preview pulmonate gastropod molluscs. Onchidiidae is the only family within the superfamily Onchidioidea.
These animals are ...
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 interm ...
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. ...
. 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
Bark is the outermost layers 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 consis ...
, fallen logs, rocks and man-made structures, such as planters
Planters Nut & Chocolate Company is an American snack food company now owned by Hormel Foods. Planters is best known for its processed nuts and for the Mr. Peanut icon that symbolizes them. Mr. Peanut was created by grade schooler Antonio Genti ...
, 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
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 ...
, 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 substance ...
. 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
''Limax maximus'' (literally, "biggest slug"), known by the common names great grey slug and leopard slug, is a species of slug in the family Limacidae, the keeled slugs.Marshall, B. (2014). Limax maximus Linnaeus, 1758. Accessed through: World ...
'', secrete slime cords to suspend a pair during copulation.
Reproduction
Slugs are hermaphrodite
In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes.
Many taxonomic groups of animals (mostly invertebrates) do not have ...
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. 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
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 ...
'') 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 syst ...
by eating decaying plant material and fungi
A fungus (plural, : fungi or funguses) is any member of the group of Eukaryote, eukaryotic organisms that includes microorganisms such as yeasts and Mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified ...
.[ 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 th ...]
, and even carrion
Carrion () is the decaying flesh of dead animals, including human flesh.
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 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 ...
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 Ga ...
, 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. ...
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 edible flower, flowers, ...
and herbs
In general use, herbs are a widely distributed and widespread group of plants, excluding vegetables and other plants consumed for macronutrients, with savory or aromatic properties that are used for flavoring and garnishing food, for medicina ...
, 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, chrysanthemum
Chrysanthemums (), sometimes called mums or chrysanths, are flowering plants of the genus ''Chrysanthemum'' in the family Asteraceae. They are native to East Asia and northeastern Europe. Most species originate from East Asia and the center ...
s, 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'' is a genus of predominantly spring flowering perennial plants of the amaryllis family, Amaryllidaceae. Various common names including daffodil,The word "daffodil" is also applied to related genera such as '' Sternbergia'', ''Is ...
, narcissus, gentians, primroses, tuberous begonias, hollyhocks, irises, and fruits such as strawberries
The garden strawberry (or simply strawberry; ''Fragaria × ananassa'') is a widely grown Hybrid (biology), hybrid species of the genus ''Fragaria'', collectively known as the strawberries, which are cultivated worldwide for their fruit. The f ...
.[ 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 Bouch ...
(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 darts as part of their mating behavior. The dar ...
'' and '' Phylomicus flexuolaris'') and ''Ariolimacidae
Ariolimacidae is a family of air-breathing land slugs, terrestrial pulmonate gastropod mollusks in the superfamily Arionoidea (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005).
Subfamilies and genera
The family Ariolimac ...
'' ('' 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, Basi ...
).[ 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 species. The species of the genus, commonly known as milk-caps, are characterized by the milky fluid ("latex") they exude when cut or damaged. Like ...
'' 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 b ...
'', '' 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 mush ...
'', 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 s ...
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, wi ...
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 chordate ...
. 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
Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephali ...
, birds
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
, 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), fu ...
, amphibians
Amphibians are four-limbed and ectothermic vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arb ...
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% ...
, 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
''Galaxias'' is a genus of small freshwater fish in the family Galaxiidae, and are frequently referred to as the galaxiids. These highly adaptable fish are typically found at temperate latitudes across the Southern Hemisphere.
Galaxiids are s ...
'') 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 ...
'' (e. g. ''Bufo marinus
The cane toad (''Rhinella marina''), also known as the giant neotropical toad or marine toad, is a large, terrestrial true toad native to South and mainland Central America, but which has been introduced to various islands throughout Ocea ...
'') and ''Ceratophrys
''Ceratophrys'' is a genus of frogs in the family Ceratophryidae. They are also known as South American horned frogs as well as Pacman frogs due to their characteristic round shape and large mouth, reminiscent of the video game character Pac-M ...
''.[
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 lizard
Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia al ...
s.[ 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 ever ...
snakes are known predators of slugs. Coastal populations of the garter snake, '' Thamnophis elegans'', have a specialised diet consisting of slugs, such as ''Ariolimax
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 ...
'', 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 genu ...
'' (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 slow worm (''Anguis fragilis'') is a reptile native to western Eurasia. It is also called a deaf adder, a slowworm, a blindworm, or regionally, a long-cripple and hazelworm. These legless lizards are also sometimes called common slowworms. Th ...
''), 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 lizar ...
''), 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 where this does no ...
s (''Turdus merula
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 where this does no ...
''), 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''), rooks
Rook (''Corvus frugilegus'') is a bird of the corvid family. Rook or rooks may also refer to:
Games
*Rook (chess), a piece in chess
* Rook (card game), a trick-taking card game
Military
* Sukhoi Su-25 or Rook, a close air support aircraft
* US ...
('' 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 a ...
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 fo ...
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 ...
s (feeding on ''Deroceras reticulatum
''Deroceras reticulatum'', common names the "grey field slug" and "grey garden slug", is a species of small air-breathing land slug, a terrestrial pulmonate gastropod mollusc in the family Agriolimacidae. This species is an important agricul ...
''), 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 his ...
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 gar ...
'' and ''Arion
Arion (; grc-gre, Ἀρίων; fl. c. 700 BC) was a kitharode in ancient Greece, a Dionysiac poet credited with inventing the dithyramb. The islanders of Lesbos claimed him as their native son, but Arion found a patron in Periander, tyrant of ...
''), 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 flycat ...
(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 gar ...
'' and ''Arion ater
Arion (; grc-gre, Ἀρίων; fl. c. 700 BC) was a kitharode in ancient Greece, a Dionysiac poet credited with inventing the dithyramb. The islanders of Lesbos claimed him as their native son, but Arion found a patron in Periander, tyrant ...
''), red grouse
The red grouse (''Lagopus lagopus scotica'') is a medium-sized bird of the grouse family which is found in heather moorland in Great Britain and Ireland. It is usually classified as a subspecies of the willow ptarmigan but is sometimes consid ...
(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 often ...
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 almo ...
s (on ''Limax flavus
''Limacus flavus'', known commonly as the cellar slug, the yellow slug, or the tawny garden slug, is a medium to large species of air-breathing land slug, a terrestrial pulmonate gastropod mollusk in the family Limacidae.MolluscaBase (2019). ...
''), 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 ]fox
Foxes are small to medium-sized, omnivorous mammals belonging to several genera of the family Canidae. They have a flattened skull, upright, triangular ears, a pointed, slightly upturned snout, and a long bushy tail (or ''brush'').
Twelv ...
es, 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 ...
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 introduct ...
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 fam ...
, such as '' Carabus violaceus'' 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 ...
[ 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 (; grc-gre, Ἀρίων; fl. c. 700 BC) was a kitharode in ancient Greece, a Dionysiac poet credited with inventing the dithyramb. The islanders of Lesbos claimed him as their native son, but Arion found a patron in Periander, tyrant ...
'', '' Arion hortensis'', ''Limax maximus
''Limax maximus'' (literally, "biggest slug"), known by the common names great grey slug and leopard slug, is a species of slug in the family Limacidae, the keeled slugs.Marshall, B. (2014). Limax maximus Linnaeus, 1758. Accessed through: World ...
'', '' 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. Salivar ...
and rectum
The rectum is the final straight portion of the large intestine in humans and some other mammals, and the gut in others. The adult human rectum is about long, and begins at the rectosigmoid junction (the end of the sigmoid colon) at the l ...
of ''Limax maximus
''Limax maximus'' (literally, "biggest slug"), known by the common names great grey slug and leopard slug, is a species of slug in the family Limacidae, the keeled slugs.Marshall, B. (2014). Limax maximus Linnaeus, 1758. Accessed through: World ...
''.[ 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
''Angiostrongylus'' is a genus of parasitic nematode
The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-Parasitism, parasitic nematodes also k ...
'' 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, headache, and neck stiffness. Other symptoms include confusion ...
-causing nematode, have larval stages that can only live in molluscs, including slugs, such as ''Limax maximus
''Limax maximus'' (literally, "biggest slug"), known by the common names great grey slug and leopard slug, is a species of slug in the family Limacidae, the keeled slugs.Marshall, B. (2014). Limax maximus Linnaeus, 1758. Accessed through: World ...
''.[
Insects such as ]dipterans
Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced ...
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 stu ...
. 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 b ...
) in the genus '' Melinda'' are known parasitoids of Arionidae
Arionidae, common name the "roundback slugs" or "round back slugs" are a taxonomic family of air-breathing land slugs, terrestrial pulmonate gastropod mollusks in the superfamily Arionoidea.
Distribution
The distribution of this family of ...
, Limacidae
Limacidae, also known by their common name the keelback slugs, are a taxonomic family of medium-sized to very large, air-breathing land slugs, terrestrial pulmonate gastropod molluscs in the superfamily Limacoidea.
Distribution
The distributi ...
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 Bouch ...
. 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 the ...
, specially those in the genus '' Megaselia'', are parasitoids of Agriolimacidae, 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 in ...
, mainly those in the genus ''Sarcophaga
''Sarcophaga'' is a genus of true flies and the type genus of the flesh-fly family (Sarcophagidae). The members of this cosmopolitan genus are frequently known as common flesh flies.
This genus occurs essentially worldwide. These flies are gene ...
'', 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
Substrate may refer to:
Physical layers
*Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached
** Substrate (locomotion), the surface over which an organism lo ...
. 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
Arionidae, common name the "roundback slugs" or "round back slugs" are a taxonomic family of air-breathing land slugs, terrestrial pulmonate gastropod mollusks in the superfamily Arionoidea.
Distribution
The distribution of this family of ...
, 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
Hibernation is a state of minimal activity and metabolic depression undergone by some animal species. Hibernation is a seasonal heterothermy characterized by low body-temperature, slow breathing and heart-rate, and low metabolic rate. It most ...
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 organ ...
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 w ...
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
{{Short pages monitor