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Anguispira alternata

By Renee Mulcrone

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. ("Anguispira alternata", 2003; Hubricht, 1985)

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. (Burch and Jung, 1988; Hubricht, 1985; Riddle and Miller, 1988)

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. (Baker, 1939; Burch and Jung, 1988; Pilsbry, 1948)

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. ("The International Union for the Conservation of Nature and Natural Resources", 2013; Baker, 1939; Burch and Jung, 1988; Pilsbry, 1948)

  • Sexual Dimorphism
  • sexes alike
  • Range length
    17 to 25 mm
    0.67 to 0.98 in

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. ("Carnegie Museum of Natural History", 2013; Burch and Pearce, 1990; Douglas, 1963; Elwell and Ulmer, 1971; Tompa, 1984)

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. (Asami, et al., 1998; Burch and Pearce, 1990; Tompa, 1984)

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. ("Carnegie Museum of Natural History", 2013; Burch and Pearce, 1990; Douglas, 1963; Elwell and Ulmer, 1971; Perez and Cordiero, 2008; Tompa, 1984)

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. ("Carnegie Museum of Natural History", 2013; Burch and Pearce, 1990; Douglas, 1963; Elwell and Ulmer, 1971; Tompa, 1984)

  • Breeding interval
    Flamed discs breed yearly.
  • Breeding season
    Flamed discs breed during the warmer months of the year.
  • Range number of offspring
    2 to 25
  • Average number of offspring
    40
  • Range gestation period
    30 to 45 days
  • Range age at sexual or reproductive maturity (female)
    2 to 3 years
  • Range age at sexual or reproductive maturity (male)
    2 to 3 years

Land snails leave their eggs after depositing them; there is no parental care. ("Anguispira alternata", 2003; "Carnegie Museum of Natural History", 2013)

  • 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. ("Carnegie Museum of Natural History", 2013; Douglas, 1963; Elwell and Ulmer, 1971; Hotopp, 2005; Pearce, 1990; Perez and Cordiero, 2008; Riddle, 1981)

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. (Douglas, 1963; Elwell and Ulmer, 1971)

  • Average territory size
    40 m^2

Home Range

One study estimated the home range of flamed discs to be about 40 square meters. (Pearce, 1990)

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. ("Carnegie Museum of Natural History", 2013; Atkinson, 2003; Atkinson, 2013; Pearce, 1997)

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. (Atkinson, 2003; Atkinson, 2013; Nordsieck, 2011; Shearer and Atkinson, 2001)

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. ("Carnegie Museum of Natural History", 2013; Atkinson, 2003; Burch and Pearce, 1990; Elwell and Ulmer, 1971; Hotopp, 2005; Perez and Cordiero, 2008; Shearer and Atkinson, 2001)

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

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. (Burch and Pearce, 1990; Elwell and Ulmer, 1971; Painter, 2013)

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. ("Carnegie Museum of Natural History", 2013; Barger, 2012; Burch and Jung, 1988; Burch and Pearce, 1990; MDNR wildlife diseases laboratory, 2013)

  • Ecosystem Impact
  • disperses seeds
Commensal/Parasitic Species

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. (Burch and Pearce, 1990)

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. (MDNR wildlife diseases laboratory, 2013)

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. ("The International Union for the Conservation of Nature and Natural Resources", 2013)

Contributors

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

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

detritivore

an animal that mainly eats decomposed plants and/or animals

detritus

particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

herbivore

An animal that eats mainly plants or parts of plants.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

internal fertilization

fertilization takes place within the female's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

mycophage

an animal that mainly eats fungus

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

suburban

living in residential areas on the outskirts of large cities or towns.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

visual

uses sight to communicate

References

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2013. "Carnegie Museum of Natural History" (On-line). Virginia land snails: Anguispira alternata (Say, 1816). Accessed November 25, 2013 at http://www.carnegiemnh.org/science/default.aspx?id=19014.

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Appel, D. 2008. "Anguispira alternata (Say)" (On-line). Accessed May 11, 2013 at https://bioweb.uwlax.edu/bio210/2011/appel_doug/index.htm.

Asami, T., R. Cowie, K. Ohbayashi. 1998. Evolution of mirror images by sexually asymmetric mating behavior in hermaphroditic snails. The American Naturalist, 152/2: 225-236. Accessed November 25, 2013 at http://www.jstor.org.proxy.lib.umich.edu/stable/10.1086/286163.

Atkinson, J. 2013. "Michigan State University Snail Laboratory" (On-line). Accessed May 15, 2013 at https://www.msu.edu/~atkinso9/.

Atkinson, J. 2003. Foraging strategy switch in detour behavior of the land snail Anguispira alternata (Say). Invertebrate Biology, 122/4: 326-333. Accessed August 19, 2013 at http://www.jstor.org/stable/3227069.

Baker, F. 1939. Fieldbook of Illinois land snails, Illinois Natural History Survey Manual 2. Urbana, Illinois: Illinois Natural History Survey.

Barger, M. 2012. Life span of cercariae of Postharmostomum helicis (Trematoda: Brachylaimidae) under different temperatures and relative humidity. Comparative Parasitology, 79/2: 169=172.

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Burch, J., T. Pearce. 1990. Terrestrial gastropoda. Pp. 201-310 in D Dindal, ed. Soil Biology Guide. New York: John Wiley and Sons.

Douglas, C. 1963. Population analyses, variation and behavior of Anguispira alternata alternata. Transactions of the Kansas Academy of Science, 66/2: 186-194. Accessed October 31, 2013 at http://www.jstor.org/stable/3626559.

Elwell, A., M. Ulmer. 1971. Notes on the biology of Anguispira alternata. Malacologia, 11/1: 199-215. Accessed November 26, 2013 at http://archive.org/stream/malacologia111971inst/malacologia111971inst_djvu.txt.

Hotopp, K. 2005. "Anguispira alternata (Say, 1816)" (On-line). Pennsylvania land snails. Accessed April 14, 2013 at http://www.carnegiemnh.org/science/default.aspx?id=16811.

Hubricht, L. 1985. The distributions of the native land mollusks of the Eastern United States. Fieldiana, Zoology New Series, 24: 1-191. Accessed August 19, 2013 at http://archive.org/stream/distributionsofn24hubr#page/n3/mode/2up.

MDNR wildlife diseases laboratory, 2013. "Brainworm (meningeal worm)" (On-line). Michigan Department of Natural Resources. Accessed May 11, 2013 at http://www.michigan.gov/dnr/0,4570,7-153-10370_12150_12220-26502--,00.html.

Nordsieck, R. 2011. "The eyes of snails" (On-line). The living world of mollusks. Accessed May 10, 2013 at http://www.molluscs.at/gastropoda/index.html?/gastropoda/morphology/eyes.html.

Painter, T. 2013. "Disc cannibal snail (Haplotrema concavum)" (On-line). Study of Northern Virginia Ecology. Accessed December 06, 2013 at http://www.fcps.edu/islandcreekes/ecology/disc_cannibal_snail.htm.

Pearce, T. 1990. Spool and line technique tracing field movements of terrestrial snails. Walkerana, 4/12: 307-316.

Pearce, T. 1997. Interference and resource competition in two land snails: adults inhibit conspecific juvenile growth in field and laboratory. Journal of Molluscan Studies, 63: 389-399. Accessed October 31, 2013 at http://mollus.oxfordjournals.org/content/63/3/389.full.pdf.

Perez, K., J. Cordiero. 2008. A guide for terrestrial gastropod identification. American Malacological Society: Terrestrial gastropod identification workshop, 1: 1-73. Accessed November 26, 2013 at http://www.uwlax.edu/biology/faculty/perez/Perez/PerezLab/Research/Publications/AMS_Workbook_KEP_FINAL.pdf.

Pilsbry, H. 1948. Land mollusca of North America (North of Mexico). Monographs of the Academy of Natural Sciences of Philadelphias, 3: 1-1113.

Riddle, W. 1981. Cold hardiness in the woodland snail, Anguispira alternata (Say) (Endodontidae). Journal of Thermal Biology, 6: 117-121.

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Shearer, A., J. Atkinson. 2001. Comparative analysis of food-finding behavior of an herbivorous and carnivorous land snail. Invertebrate Biology, 120/3: 199-205. Accessed October 31, 2013 at http://www.jstor.org/stable/3227244.

Tompa, A. 1984. Land snails (Stylommatophora). Pp. 47-139 in A Tompa, N Verdonk, J van den Biggelaar, eds. The Mollusca, Vol. 7, reproduction. London: Academic Press, Inc.

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