Anguispira alternata

Geographic Range

Anguispira alternata , a land snail commonly called the flamed disc, is native to the Nearctic region. It is found as far north as New Brunswick, Canada, south to northern Florida, and west to northeastern Texas, Kansas and western Minnesota. Additional collections have been recorded further west, in Oregon, Alberta, and central Saskatchewan.

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Flamed discs are terrestrial snails found in a variety of habitats. These include forests, weedy roadsides, and along railroads, as well as gardens or vacant lots in urban areas. They are usually found around logs, hollow trees, and rocks in wooded areas. Flamed discs are a temperate climate species, although they can tolerate temperatures as low as -14°C.

• Habitat Regions
• temperate temperate
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest

• Other Habitat Features
• urban urban
• suburban suburban

Physical Description

Flamed discs are medium-sized snails, typically ranging from 17-25 mm in diameter. Shells average 20 mm wide and 12 mm tall, and so are considered to have a depressed helicoform shape (width greater than height). Shell coloration is pale yellow to brown, with irregular reddish-brown and brown blotches on the upper surface and reddish-brown streaks on the lower surface. These snails' shells have 5 1/2 to 6 whorls, with smooth embryonic whorls, and an umbilicus measuring almost a third of its width. There is a noticeable opening at bottom of the shell (within the whorls). The rest of the shell has ridges which diminish at the base of the shell and it is strongly angular peripherally. The aperature has an thin, unexpanded lip.

As stylommatophorans (belonging to the unranked clade Stylommatophora ), flamed discs have two pairs of tentacles, with eyes at the tips of the upper tentacles. Head and eye peduncles can be a light slatish-color, while body coloration may be brown to brownish black. Body color is typically duller during the late summer. The foot is somewhat wide and short, and can be whitish. These snails produce mucus that may be reddish in color.

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike

Development

Generally, land snails deposit their eggs in moist areas, secreting a substance to make egg masses stick to substrate or burying them in shallow holes (1.5 to 2.5 cm in depth). In captivity, eggs have measured 2 to 3 mm in diameter. Time to hatching depends on environmental conditions such as moisture and temperature; typically, land snails hatch within 30 to 45 days. Shells under 5 mm in diameter are much more fragile than larger ones, and because of this, most mortalities occur before snails reach this size. Some studies have indicated that young grow rapidly during their first summer, attaining near-adult sizes by the fall.

Reproduction

Stylommatophoran land snails are hermaphroditic. Although they usually mate with other snails, they may also self-fertilize. Mating partners may be located by following their mucus trails. After a courtship ritual, typically lasting at least a few hours, snails copulate. One snail will mount the shell of the other; each snail inserts spermatophores into the other using a penis. Each will produce fertilized eggs.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

Land snails generally breed during the warmer months of the year, and rain may increase mating. In a laboratory setting, individuals of this species require exposure to low temperatures before they will reproduce, indicating that reproduction is linked to the end of hibernation at the end of colder winter months. Sexual maturity is likely reached when the lip forms on the shell aperture. In cooler or drier areas, growth, and therefore time to sexual maturity, is slower than in warmer, moist areas; populations in Iowa have been noted to reach maturity in their second or third summers of life; in these same populations, sperm were not released by a snail until its shell reached 9 mm in diameter, and snails did not deposit eggs before reaching 13 mm in diameter. In captivity, individuals are noted to lay 2-25 eggs per season, but may lay as many as 40.

After fertilization, land snails lay eggs in leaf litter, typically at a depth of 1.5-2.5 cm and usually in moist areas. One study noted a higher number of juveniles found during the summer, indicating that eggs were fertilized and hatched in the spring.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• simultaneous hermaphrodite
• sexual sexual
• fertilization fertilization
  • internal internal
• oviparous oviparous

Land snails leave their eggs after depositing them; there is no parental care.

• Parental Investment
• no parental involvement
• pre-fertilization
  • provisioning

Lifespan/Longevity

The lifespan of this species is unknown.

Behavior

Flamed discs are commonly found climbing or at the bases of trees (commonly Arbor vitae , spruce, or in one population, American beech ( Fagus grandifolia )) at night, likely seeking food. They have been observed creating burrows by using the foot to move loose soil, then dragging their shells into the newly made depression.

In Kansas, flamed discs were observed living in groups ranging from 16 to 75 snails per square foot, burrowing together to overwinter; young and juvenile snails are often found in large groups as well. In the fall, these snails reduce their water content (aestivate) and evacuate their guts as a survival aid in cold temperatures, forming an epiphram near the bend of the shell's body whorl.

• Key Behaviors
• arboreal arboreal
• terricolous
• nocturnal nocturnal
• motile motile
• sedentary sedentary
• hibernation hibernation
• aestivation
• solitary solitary
• colonial colonial

Home Range

One study estimated the home range of flamed discs to be about 40 square meters.

Communication and Perception

Generally, land snails leave mucus trails that are used as a form of communication. The mucus allows the snails to detect members of their own species as well as others, through olfaction. Some land snails may grow more slowly when exposed to mucus trails of their own species.

The upper tentacles of stylommatophoran species are light and chemosensitive. They may use olfactory gradients in still air to locate food items. Eyes, located at the top of the tentacles, can detect light, as well as general forms at night. The anterior tentacles are chemosensory and the labia detect both touch and chemicals. Repeated experiments with flamed discs found that these snails will change their behavior when a barrier to food is encountered.

• Communication Channels
• visual visual
• tactile tactile
• chemical chemical

• Other Communication Modes
• scent marks scent marks

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

Food Habits

Flamed discs mainly use olfactory gradients to find food. They feed on decaying plant material and fungi. Since they are often found in trees, they also likely graze on bark-dwelling algae. Cannibalism of eggs by adults has been observed. The radula, a toothed feeding organ, is used to scrape or grind food.

• Primary Diet
• herbivore herbivore
  • algivore
• mycophage mycophage
• detritivore detritivore

• Animal Foods
• eggs

• Plant Foods
• leaves
• roots and tubers
• wood, bark, or stems
• bryophytes
• lichens
• algae

• Other Foods
• fungus
• detritus detritus

Predation

Specific predators are not known for this species, but in general, land snails are preyed on by lampyrid beetle larvae or other insects, birds, rodents, and small mammals, particularly chipmunks, voles and shrews. They are also prey to carnivorous land snails.

Ecosystem Roles

Land snails in general disperse spores or seeds, and are important in breaking down the detritus in forests. Flamed discs may serve as intermediate hosts for some species of trematodes and nematodes.

• Ecosystem Impact
• disperses seeds

Economic Importance for Humans: Positive

While flamed discs do not provide any known benefits specifically, land snails play an important role in breaking down forest detritus, helping to keep these ecosystems healthy and in balance.

Economic Importance for Humans: Negative

Although they may serve as intermediate hosts to parasites which later live in small mammals, flamed discs do not pose any significant threats to humans.

Conservation Status

Flamed discs have not been evaluated by the International Union for the Conservation of Nature and Natural Resources, and hold no special conservation status.

Additional Links

Encyclopedia of Life

BioKIDS Critter Catalog

Contributors

Renee Mulcrone (author), Special Projects, Jeremy Wright (editor), University of Michigan-Ann Arbor.

References

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