Black slug
Encyclopedia
The black slug also known as black arion, European black slug, or large black slug, scientific name Arion ater, is a species of large land slug, a terrestrial
slug
in the family
Arionidae
, the roundback slugs.
is reached at about 2.5 cm.
The color of the black slug is generally black, but the colouration is very variable and this slug can even be white. The general trend is for a darker pigmentation the farther north the species is found. The classification of brown-coloured and rust-coloured "black" slugs is somewhat disputed; the brown variation is sometimes considered to be a separate species, Arion rufus (Red Slug
). Young specimens of black slug do have a brown colour, which is later lost if and when the slug changes color to the mature state.
The slug covers itself in a thick foul-tasting mucus
which serves as both protection against predators as well as a measure to keep moist. It is somewhat difficult to wash off.
Like other members of the family Arionidae, the black slug has a pneumostome
(breathing hole) on the right side of its mantle
through which it breathes
. This mantle is the part which in snails secretes a shell, and in this species of slug the mantle contains a resilient protective structure of calcareous granules.
(including Britain
) and the Pacific Northwest
.
This species has not yet become established in the USA, but it is considered to represent a potentially serious threat as a pest, an invasive species
which could negatively effect agriculture, natural ecosystems, human health or commerce. Therefore it has been suggested that this species be given top national quarantine
significance in the USA.
exposure to sunlight. It is omnivorous
, eating carrion
, fungi, and vegetation
(living and decaying). The slug prefers moist conditions, such as lawn
s, making it an unwelcome sight for homeowners. This moist environment is essential for the terrestrial locomotion of the slug to function.
Like all other species of the Arionidae
family, the black slug is a hermaphrodite
, meaning it can fertilize itself if needed, although a mate is preferred. After mating
, the slug lays eggs
about 5 mm in diameter. The favoured location for eggs is a dark, cold, damp place such as a compost heap.
In the past two decades, its mating with the non-native (at northern latitudes) pest species Arion vulgaris (or Spanish slug
) has resulted in a more resilient hybrid exhibiting increased tolerance to cold.
The mucus of the slug is highly distasteful to many animals. However, this slug does have some natural predators, including the hedgehog
, badger
, shrew
, mole
, mouse
, frog
, toad
, snake
, carnivorous beetle
, and some bird
s. When picked up or touched, the black slug will contract to a hemispherical shape and begin to rock from side to side. This defensive behaviour confuses predators, and is unique in the Arionidae family.
to lubricate wooden axle
-trees or carts in Sweden. This use is documented since at least the 18th century.
Terrestrial locomotion in animals
Terrestrial locomotion has evolved as animals adapted from aquatic to terrestrial environments. Locomotion on land raises different problems than that on water, with reduced friction being replaced by the effects of gravity....
slug
Slug
Slug is a common name that is normally applied to any gastropod mollusc that lacks a shell, has a very reduced shell, or has a small internal shell...
in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Arionidae
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 roundback slugs.
Description
The size of the slug varies from 10 to 15 cm. MaturitySexual maturity
Sexual maturity is the age or stage when an organism can reproduce. It is sometimes considered synonymous with adulthood, though the two are distinct...
is reached at about 2.5 cm.
The color of the black slug is generally black, but the colouration is very variable and this slug can even be white. The general trend is for a darker pigmentation the farther north the species is found. The classification of brown-coloured and rust-coloured "black" slugs is somewhat disputed; the brown variation is sometimes considered to be a separate species, Arion rufus (Red Slug
Red Slug
The red slug, also known as the chocolate arion or the European red slug, Arion rufus, is a large land slug, a terrestrial pulmonate gastropod mollusk in the family Arionidae, the roundback slugs....
). Young specimens of black slug do have a brown colour, which is later lost if and when the slug changes color to the mature state.
The slug covers itself in a thick foul-tasting mucus
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...
which serves as both protection against predators as well as a measure to keep moist. It is somewhat difficult to wash off.
Like other members of the family Arionidae, the black slug has a pneumostome
Pneumostome
The pneumostome is a feature of the external body anatomy of an air-breathing land slug or land snail. It is a part of the respiratory system of gastropods....
(breathing hole) on the right side of its mantle
Mantle (mollusc)
The mantle is a significant part of the anatomy of molluscs: it is the dorsal body wall which covers the visceral mass and usually protrudes in the form of flaps well beyond the visceral mass itself.In many, but by no means all, species of molluscs, the epidermis of the mantle secretes...
through which it breathes
Gas exchange
Gas exchange is a process in biology where gases contained in an organism and atmosphere transfer or exchange. In human gas-exchange, gases contained in the blood of human bodies exchange with gases contained in the atmosphere. Human gas-exchange occurs in the lungs...
. This mantle is the part which in snails secretes a shell, and in this species of slug the mantle contains a resilient protective structure of calcareous granules.
Distribution
This species is found in northern EuropeNorthern Europe
Northern Europe is the northern part or region of Europe. Northern Europe typically refers to the seven countries in the northern part of the European subcontinent which includes Denmark, Estonia, Latvia, Lithuania, Norway, Finland and Sweden...
(including Britain
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
) and the Pacific Northwest
Pacific Northwest
The Pacific Northwest is a region in northwestern North America, bounded by the Pacific Ocean to the west and, loosely, by the Rocky Mountains on the east. Definitions of the region vary and there is no commonly agreed upon boundary, even among Pacific Northwesterners. A common concept of the...
.
- Great Britain
- Ireland
- Sweden
- Germany
- Newfoundland
- Scandinavia
- British Columbia, Canada
This species has not yet become established in the USA, but it is considered to represent a potentially serious threat as a pest, an invasive species
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....
which could negatively effect agriculture, natural ecosystems, human health or commerce. Therefore it has been suggested that this species be given top national quarantine
Quarantine
Quarantine is compulsory isolation, typically to contain the spread of something considered dangerous, often but not always disease. The word comes from the Italian quarantena, meaning forty-day period....
significance in the USA.
Behaviour
The black slug is mainly nocturnal and avoidsPhototaxis
Phototaxis is a kind of taxis, or locomotory movement, that occurs when a whole organism moves in response to the stimulus of light. This is advantageous for phototrophic organisms as they can orient themselves most efficiently to receive light for photosynthesis...
exposure to sunlight. It is omnivorous
Omnivore
Omnivores are species that eat both plants and animals as their primary food source...
, eating carrion
Carrion
Carrion refers to the carcass of a dead animal. Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters include vultures, hawks, eagles, hyenas, Virginia Opossum, Tasmanian Devils, coyotes, Komodo dragons, and burying beetles...
, fungi, and vegetation
Vegetation
Vegetation is a general term for the plant life of a region; it refers to the ground cover provided by plants. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic characteristics. It is broader...
(living and decaying). The slug prefers moist conditions, such as lawn
Lawn
A lawn is an area of aesthetic and recreational land planted with grasses or other durable plants, which usually are maintained at a low and consistent height. Low ornamental meadows in natural landscaping styles are a contemporary option of a lawn...
s, making it an unwelcome sight for homeowners. This moist environment is essential for the terrestrial locomotion of the slug to function.
Like all other species of the Arionidae
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 :...
family, the black slug is a hermaphrodite
Hermaphrodite
In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.Many taxonomic groups of animals do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both...
, meaning it can fertilize itself if needed, although a mate is preferred. After mating
Mating
In biology, mating is the pairing of opposite-sex or hermaphroditic organisms for copulation. In social animals, it also includes the raising of their offspring. Copulation is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization...
, the slug lays eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
about 5 mm in diameter. The favoured location for eggs is a dark, cold, damp place such as a compost heap.
In the past two decades, its mating with the non-native (at northern latitudes) pest species Arion vulgaris (or Spanish slug
Spanish slug
The Spanish slug, scientific name Arion vulgaris, more commonly known in English-speaking countries under the incorrectly applied Latin name, Arion lusitanicus, is a species of air-breathing land slug, a terrestrial pulmonate gastropod mollusk in the family Arionidae, the roundback slugs.This is a...
) has resulted in a more resilient hybrid exhibiting increased tolerance to cold.
The mucus of the slug is highly distasteful to many animals. However, this slug does have some natural predators, including the hedgehog
Hedgehog
A hedgehog is any of the spiny mammals of the subfamily Erinaceinae and the order Erinaceomorpha. There are 17 species of hedgehog in five genera, found through parts of Europe, Asia, Africa, and New Zealand . There are no hedgehogs native to Australia, and no living species native to the Americas...
, badger
Badger
Badgers are short-legged omnivores in the weasel family, Mustelidae. There are nine species of badger, in three subfamilies : Melinae , Mellivorinae , and Taxideinae...
, shrew
Shrew
A shrew or shrew mouse is a small molelike mammal classified in the order Soricomorpha. True shrews are also not to be confused with West Indies shrews, treeshrews, otter shrews, or elephant shrews, which belong to different families or orders.Although its external appearance is generally that of...
, mole
Mole (animal)
Moles are small cylindrical mammals adapted to a subterranean lifestyle. They have velvety fur; tiny or invisible ears and eyes; and short, powerful limbs with large paws oriented for digging. The term is especially and most properly used for the true moles, those of the Talpidae family in the...
, mouse
Mouse
A mouse is a small mammal belonging to the order of rodents. The best known mouse species is the common house mouse . It is also a popular pet. In some places, certain kinds of field mice are also common. This rodent is eaten by large birds such as hawks and eagles...
, frog
Frog
Frogs are amphibians in the order Anura , formerly referred to as Salientia . Most frogs are characterized by a short body, webbed digits , protruding eyes and the absence of a tail...
, toad
Toad
A toad is any of a number of species of amphibians in the order Anura characterized by dry, leathery skin , short legs, and snoat-like parotoid glands...
, snake
Snake
Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...
, carnivorous beetle
Beetle
Coleoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek , koleos, "sheath"; and , pteron, "wing", thus "sheathed wing". Coleoptera contains more species than any other order, constituting almost 25% of all known life-forms...
, and some bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s. When picked up or touched, the black slug will contract to a hemispherical shape and begin to rock from side to side. This defensive behaviour confuses predators, and is unique in the Arionidae family.
Human use
Arion ater was used as greaseGrease (lubricant)
The term grease is used to describe semisolid lubricants. Although the word grease is also used to describe rendered fat of animals, in the context of lubrication, grease typically applies to a material consisting of a soap emulsified with mineral or vegetable oil...
to lubricate wooden axle
Axle
An axle is a central shaft for a rotating wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to its surroundings, with the wheels rotating around the axle. In the former case, bearings or bushings are provided at the mounting points where the axle...
-trees or carts in Sweden. This use is documented since at least the 18th century.
External links
- "European black slug", Alan Watson Featherstone, Species profile, Trees for Life website, accessed 23 July 2011