page_title: Black slug
section_title: Ecology
hierarchical_section_title: Black slug / Ecology
caption_attribution_description: English: The flexible invertebrate Arion ater (Arionidae) with slimy trail, a big black slug, had just crept out of daytime hideout, photogenically extending her feelers. On bended knees I struggled to put the camera [red-eye-reduction ON etc.] into an appropriate position closing up on the head of the tough and flexible, sluggishly bending primeval. The flashlight reflexions of the surrounding bright sands have given a tasty colour to the orange-brown coaster of the black 'liquorice' ... Photo was taken when the dawn began to arrive. Under a cloudy sky at 20.06 pm (MEZ), - immediately before the sunset.
context_page_description: The black slug Arion ater L. is a large terrestrial gastropod mollusk in the family Arionidae, the round back slugs. Land slugs lack shells like other terrestrial mollusks. Without such shells, slugs produce unappetizing mucus, that may also contain toxins—to deter predators. Terrestrial slugs produce two other forms of mucus that facilitate locomotion and prevent death from drying. Such mollusks are hermaphroditic. Slugs most often function as decomposers but are also often omnivores. Arion ater is one such slug, decomposing organic matter, preying on other organisms, and consuming vegetative matter including agricultural crops. Native to Europe, the black slug is an invasive species in Australia, Canada, and the United States.
context_section_description: The black slug is mainly nocturnal and avoids exposure to sunlight, although in introduced areas, it has been observed to be active all parts of the day and night. It is omnivorous, eating carrion, fungi, animal feces, algae, lichen, and vegetation (living or decaying). These slugs prefer to eat on cloudy days or at night when temperatures are above 10 degrees Celsius. Mucus-production necessitates moist habitats, such as among leaf-litter, mosses, or fallen trees. Consequently, the black slug becomes most active after rainfall. A 1976 study compared black slug assimilation rates to that of similar slugs in the UK. The study determined the black slug feeds at similar rates to other European slugs (in terms of biomass), suggesting the black slug is an equally important decomposer/consumer in forest systems. The study theorized these high assimilation rates might result from abundant enzymes in slug digestive systems: amylase, invertase, cellulase, xylanase, and chitinase. The last might be especially indicative of how these slugs can consume large quantities of fungi such as Armillaria mellea. Microbiota within black slug digestive systems produce these enzymes—such as the bacteria that produce cellulose—enabling the slugs to break down lignocellulose. A recent study further explored Arion ater’s gut microbiome and discovered the black slug to have far more bacteria within its gut than did neighboring, northern European insects, including members of the orders Coleoptera, Isoptera, Orthoptera, and Diptera. This study learned the black slug’s gut microbiome to be functional at a wide range of temperatures and pH levels, and its results suggest that the mycobacterial culture may be uniform throughout the black slug’s gut and that Gammaproteobacteria composes most of this culture. This study contrasted its results to studies of North American black slugs that presented higher levels of cellulolytic activity at a narrower pH range. In summary, Arion ater can digest diverse food material such as cellulose because gut bacteria produce digestive enzymes.
  As decomposers/consumers, slugs engage an important niche, contributing to ecosystem health. A 2005 study looked at another Arion slug species and concluded slugs may promote plant biodiversity. This study suggested that slugs promote plant—especially forb—species diversity and that slugs support annual plant species’ fitness, reducing rates of successional change. Additionally, slugs help disperse seeds and spores through their waste, and slugs facilitate nutrient cycling by being an omnivorous consumer (especially a decomposer) and by leaving behind their mucus, which also facilitates decomposition.
  Slugs are common agricultural and horticultural pests. They consume abundant vegetative matter, especially seedlings. Additionally, many people find slugs to be unsightly.
  Most animals prefer not to prey upon the black slugs because of the taste of its mucus and because this mucus can make them slippery and consequently difficult to capture; however, this slug does have some natural predators, including the hedgehog, badger, shrew, mole, mouse, frog, toad, snake, carnivorous beetle, and some birds. When picked up or touched, the black slug will contract to a hemispherical shape and begin to rock from side to side. This defensive behavior confuses predators, and is unique in the family Arionidae.
caption: A black slug on the move.
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