Arion subfuscus

Geographic Range

Arion subfuscus is native to the Paleartic (Beyer and Saari, 1978) and has been introduced to northeastern North America, where it ranges from eastern Canada to South Carolina, and as far west as Indiana. In Europe its range has expanded to include the northwestern, central, and eastern regions (Pinceel et al. 2005).

• Biogeographic Regions
• nearctic nearctic
  • introduced introduced
• palearctic palearctic
  • native native

• Other Geographic Terms
• holarctic holarctic

Habitat

Habitat use by the terrestrial gastropod Arion subfuscus varies seasonally. In fall A. subfuscus can be found foraging in moist plant debris and small crevices in the soil. As winter approaches, it usually moves deeper into the soil, returning to the leaf litter in spring. In summer A. subfuscus must find adequate shelter to prevent desiccation (Beyer and Saari 1978).

• Habitat Regions
• temperate temperate

• Terrestrial Biomes
• forest forest

• Other Habitat Features
• urban urban
• suburban suburban
• agricultural agricultural

Physical Description

Arion subfuscus is a terrestrial slug. Like most slugs A. subfuscus has a tough body covered in mucus and lacks a visible shell. A. subfuscus individuals will have one of four color groups: reddish brown, black, orange or yellow, and lateral or mantle bands may or may not be present (Beyer and Saari, 359).

Arion subfuscus is a pulmonate gastropod and thus lacks gills but instead has a lung developed from the mantle cavity. The lung is open to the outside by a small pore called the pneumostome, which permits air exchange but limits water loss. The mantle sits on top of the body and lung. Internal shells are very reduced and present only as calcareous grains under the rear part of the mantle (Nichols, Cooke and Whiteley, 62).

• Other Physical Features
• ectothermic ectothermic
• bilateral symmetry bilateral symmetry
• polymorphic polymorphic

Development

Arion subfuscus generally has an annual life cycle where eggs hatch in autumn and adults die in summer. This can vary, however, depending on geographical location and habitat (Beyer and Saari 1978). Adults lay eggs which hatch directly into small juvenile slugs. The slugs grow slowly during the first few months, followed by rapid growth resulting in sexual maturity. During the period of rapid growth, the hermaphrodite gland becomes enlarged and the ratio of gland weight to body weight reaches a maximum as body weight reaches a maximum in the spermatozoon stage. During the reproductive stage, body weight remains constant but the hermaphrodite gland decreases in size as the slugs move into post-reproductive phase (Barker 1991).

Reproduction

Arion subfuscus is hermaphroditic and can both self- and cross-fertilize, depending on the conditions and habitat stability (McCraken and Selander 1980).

During copulation slugs exchange sperm through their protruding genitalia. Fertilization is internal, and several days after mating the slug will lay hundreds of eggs in the soil. Most adult slugs die soon after breeding and there is no parental care (Barker 1991).

In Arion and other genera, some individuals engage in apophallation: during sperm transfer male genitalia can become entangled. In such a case, the slugs may bite off each others penises to free themselves. Following apophallation the slug effectively becomes a female and never regains male functioning.

• Key Reproductive Features
• semelparous semelparous
• seasonal breeding seasonal breeding
• simultaneous hermaphrodite
• sexual sexual
• fertilization fertilization
  • internal internal
• oviparous oviparous
• sperm-storing sperm-storing
• delayed fertilization delayed fertilization

Species such as A. subfuscus that belong to genus Arion lay their eggs in clusters in the soil. Although the eggs are left alone and there is no parental care, the eggs are chemically protected by a diterpene called miriamin. This chemical is a caustive agent that prevents the eggs from being eaten or damaged (Schroeder et al. 1999).

• Parental Investment
• no parental involvement
• pre-hatching/birth
  • protecting

Lifespan/Longevity

A. subfuscus is an annual species with a lifespan ranging from 8-12 months. Arion slugs generally hatch sometime between autumn and winter. They typically undergo a period of slow growth during winter followed by a period of rapid growth culminating in reproductive maturity. Slugs usually die post reproduction, but this can vary depending on the conditions and geographical location (Barker 1991).

Behavior

Arion subfuscus utilizes a muscular “foot” to creep slowly through vegetation and litter. A. subfuscus is most active during dusk or night to avoid desiccation(Beyer and Sarri 1977).

• Key Behaviors
• terricolous
• nocturnal nocturnal
• crepuscular crepuscular
• sedentary sedentary

Home Range

Home range is relatively confined because of its generalist feeding habits and avoidance of dessication (Beyer and Saari 1978).

Communication and Perception

In general terrestrial gastropods have poor ability to perceive objects by vision, and have little or no auditory perception. The primary sense used in perception is smell. The olfactory organs on a slug are located at the tips of the tentacles. The 4 tentacles can regenerate if they are removed and the olfactory organ will regenerate with it. Slugs also have chemoreceptors to detect toxins. The chemoreceptors are located on the lips. They eyes of the slugs are not primarily for vision. They are thought to be used to perceive light and to set its circadian rhythm (Barker, 2001).

• Communication Channels
• chemical chemical

• Perception Channels
• visual visual
• tactile tactile
• chemical chemical

Food Habits

Arion subfuscus uses its radula to scrape and consume its food (Pearse et al., 1987). It appears to have a broad diet which includes fungi and decaying plants as major components, but also yellowed foliage, exposed plant parts, animal feces, insect larvae, dead or injured earthworms, and algae. A. subfuscus was observed foraging 6 m from the ground on tree trunks (Beyer and Sarri, 1977).

• Primary Diet
• mycophage mycophage
• detritivore detritivore

• Plant Foods
• leaves
• algae

• Other Foods
• fungus
• detritus detritus
• dung

Predation

Arion subfuscus is preyed upon by a wide variety of organisms including insects, amphibians, reptiles, birds and small mammals (Martin, 2000).

Ecosystem Roles

Arion subfuscus is an example of a generalist species and has been found living in woodlands, arable lands, edge habitats, and around human habitations. They can survive in a variety of soils and microhabitats including soil, plant litter and vegetation. As generalist herbivores, slugs could be a major factor in limiting the geographical ranges of plants (Scheidel and Bruelheide, 1999).

Because terrestrial slugs store environmental chemicals in their bodies, these toxic residues may be passed along the food chain and ultimately affect the biodiversity of an ecosystem (Martin, 2000).

Economic Importance for Humans: Positive

A. subfuscus and other slugs are potentially useful as indicators of metals and other contaminants in the environment.

• Positive Impacts
• research and education

Economic Importance for Humans: Negative

Slugs are significant agricultural pests. Given its continued growth in abundance and range, Arion subfuscus is among the most important slug pests in North America (Frank 2003).

• Negative Impacts
• crop pest

Conservation Status

A. subfuscus is not listed as endangered, threatened, vulnerable in any part of its range.

Additional Links

Encyclopedia of Life

Contributors

Kelly Amanda (author), Rutgers University, Jessica Mazzara (author), Rutgers University, Christen McCoy (author), Rutgers University, Philip Nicodemo (author), Rutgers University, David V. Howe (editor), Rutgers University, Renee Mulcrone (editor), Special Projects.

References

Barker, G. 2001. The Biology of Terrestrial Molluscs . New York, NY: CABI Publishing.

Barker, G. 1991. Biology of slugs (Agriolimacidae and Arionidae: Mollusca) in New Zealand hill country pastures. Oecologia , Vol. 85, No. 4: 581-595.

Beyer, W., D. Saari. 1978. Activity and ecological distribution of the slug, Arion subfuscus (Draparnaud) (Stylommotophora, Arionidae). American Midland Naturalist , 100/2: 359-367.

Cook, A. 1992. The function of trail following in the pulmonate slug, Limax pseudoflavus . Animal Behaviour , 43/5: 813-821.

Davison, A., C. Wade, P. Mordan, S. Chiba. 2005. Sex and darts in slugs and snails (Mollusca: Gastropoda: Stylommatophora). Journal of Zoology , 267: "329-338".

Frank, T. 2003. Influence of slug herbivory on the vegetation development in an experimental wildflower strip. Basic and Applied Ecology , 4/2: "139-147".

Leonard, J., J. Pearse, A. Harper. 2002. Comparative reproductive biology of Ariolimax californicus and A. dolichophallus . Invertebrate reproduction & development , 41/1-3: "83-93".

Martin, S. 2000. Terrestrial snails and slugs (Mollusca: Gastropoda) of Maine. Northeastern Naturalist , 7/1: 33-88.

McCraken, G., R. Selander. 1980. Self-fertilization and monogenic strains in natural populations of terrestrial slugs. Proceedings of the National Academy of Sciences of the United States , 77/1: "684-688".

Nichols, D., J. Cooke, D. Whitely. 1971. The Oxford Book of Invertebrates . London: Oxford University Press.

Pearse, V., J. Pearse, M. Buschbaum, R. Buschbaum. 1987. Living Invertebrates . California: Blackwell Scientific Publications and The Boxwood Press.

Pinceel, J., K. Jordaens, N. Van Houtte, G. Bernon, T. Backeljau. 2005. Population genetics and identity of an introduced terrestrial slug: Arion subfuscus s.l. in the north-east USA (Gastropoda, Pulmonata, Arionidae). Genetica , 125: 155-171.

Scheidel, U., H. Bruelheide. 1999. Selective slug grazing on montane meadow plants. Journal of Ecology , 87: 828-838.

Schroeder, F., A. Gonzàlez, T. Eisner, J. Meinwald. 1999. Miriamin, a defensive diterpene from the eggs of a land slug ( Arion sp. ). Proceedings of the National Academy of Sciences of the United States , 96/24: "13620-13625".