Arion ater group: Arion rufus

Family

Arionidae

Species

Arion rufus Linnaeus, 1758

Common name

Chocolate arion, European red slug

Description

This slugSlug:
A snail that either does not possess a shell or has one that is very reduced (no definite coiling) or internal.
belongs to a species complex that can only be differentiated by dissecting the genitaliaGenitalia:
The reproductive structures of an animal. May refer to either male or female structure.
. There are three species in this complex (Arion ater group): Arion ater, A. rufus and A. vulgaris. These slugs species range from 75-180 mm in length at maturity. They may be dark brown, black, orange or reddish in color. They are large and bulky with long, course tuberclesTubercles:
An enlarged or raised region on the body of a slug. The shape of this structure is very variable. (See also tubercle)
on the side and back. The juveniles of these species have an even wider range of colors and can be distinguished from mature adults by the presence of lateral stripes. Juveniles of the Arion ater-complex may be confused with adults of other Arion species.  The contracted body of this species is bell-shaped. The sole of the foot may be black or tripartiteTripartite:
Having three distinct section/regions.
(pale with a black vertical line down the center). The footFoot:
The muscular organ on the undersurface of the body of a mollusc upon which the animal rests or uses to crawl.
fringe may possess any of the following colors with vertical black bands: red, orange, yellow or grey. The mucus of this slugSlug:
A snail that either does not possess a shell or has one that is very reduced (no definite coiling) or internal.
group is colorless and they lack a keelKeel:
Also known as the carina. This is a longitudinal ridge that runs dorsally along the apex of the tail of the animal.
. Molecular techniques can also be used to identify members of this group.

Genitalic characters used to distinguish the three species:

Arion ater: genitaliaGenitalia:
The reproductive structures of an animal. May refer to either male or female structure.
with a slender symmetrical atriumAtrium:
Opening or passage of the genitalia. OR Region for the reception of gametes.
.

Arion rufus: genitaliaGenitalia:
The reproductive structures of an animal. May refer to either male or female structure.
with large, thick asymmetricalAsymmetrical:
Not even on both sides of a usually central axis.
atrium.

Arion vulgaris: genitaliaGenitalia:
The reproductive structures of an animal. May refer to either male or female structure.
with a short, abbreviated atriumAtrium:
Opening or passage of the genitalia. OR Region for the reception of gametes.
.

Native range

Western and Southern Europe

Distribution

North America:

• U. S.: California, Maine, Michigan, New York, Oregon, Washington, Wisconsin 
• Canada: British Columbia, Newfoundland, Quebec, Ontario

Europe

Ecology

These plant pests are often found in disturbed sites. This includes gardens, greenhouses and campgrounds. This omnivore’s diet includes living and dead plant material, fungi, feces and carrion. It is most damaging to ornamental, vegetable (e.g., strawberry, sunflower, potato, cabbage, parsley, bean) and fodder crops (e.g., clover) from seedlings to fully mature plants. The mating season lasts from summer through early autumn. If disturbed, an individual from the Arion ater-complex will contract its body, often twisting it and rocking side to side. It has been noted that both Arion ater and A. rufus will interbreed. This interbreeding behavior has not been recorded for Arion vulgaris. A. vulgaris has the potential to live up to one year and can lay up to 400 eggs in a single summer. These eggs often hatch within just 3.5-5 weeks.

Synonyms

• Limax rufus Linnaeus, 1758
• Arion ater of authors, not Linnaeus, 1758.
• Arion empiricorum Férussac, 1819 pars.

References

Anderson 2005; Cowie et al. 2009; Forsyth 2004; Grimm et al. 2009; Horsák 2004; Kantor et al. 2009; Koztowski 2005; Roth and Sadeghian 2006; Weidema 2006