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Haplotrema concavum

By Renee Mulcrone

Geographic Range

Haplotrema concavum, also known as the gray-foot lancetooth snail, is found in the eastern United States and southeastern Canada. These snails range from Maine and central Ontario south to Florida's panhandle. They are found as far west as eastern Iowa and eastern Texas (with small isolated populations reported in a few areas farther west), and as far east as the coastline of the Atlantic Ocean. ("Haplotrema concavum Say, 1821", 2013; "Haplotrema concavum", 2003; Hubricht, 1985)

Habitat

Gray-foot lancetooth snails inhabit moist areas of upland woods, including river valleys with oak, elm, hickory, basswood, walnut, and pine trees. They may be found in growth such as cinnamon fern (Osmunda cinnamomea), Virginia creeper (Parthenocissus quinquefolia), bracken fern (Pteridium aquilinum), greenbrier (Smilax rotundifolia), and poison ivy (Toxicodendron radicans), as well as in forest debris and on the underside of logs. (Burch and Jung, 1988; Hubricht, 1985; Painter, 2013)

Physical Description

Gray-foot lancetooth snails are 11-21 mm in diameter, with 4 1/2 to 5 1/2 whorls. The height of an adult shell ranges from 5-10 mm. Their shells, which are whitish to greenish or yellowish in color, are glossy, smooth, and sculptured, with irregular growth and fine spiral lines. The shell shape is round or flat like a disk and the spire is depressed. The underside is widely umbilicate, with a wide opening where the shell coils. The shell opening (aperture) is oblong and crescent-shaped, with an internal layer of calcareous material. The thickened lip of the aperture is expanded at the base and the outer margin. ("Virginia land snails: Haplotrema concavum", 2013; Burch and Jung, 1988; Pilsbry, 1946)

Within the shell, gray-foot lancetooth snails have a thick, coarse epidermis, which may be checkered in appearance. Two pairs of tentacles are found on the head and the mantle edge is broad and heavy, with a large and prominent flap on the right part of the elongate neck. The radula has a few inverted v-shaped transverse rows of teeth. Other teeth are sharply pointed, the inner ones increasing and outermost decreasing in size. Most of the teeth are unicuspid and slender. (Burch and Jung, 1988; Pilsbry, 1946)

  • Sexual Dimorphism
  • sexes alike
  • Range length
    12 to 13 mm
    0.47 to 0.51 in

Development

Land snails deposit their eggs in moist areas, secreting a substance to make egg masses stick. Hatching typically occurs within 7-10 days. Time to hatching is dependent on moisture and temperature; they may reach maturity more slowly in dry areas. Maturity is usually reached once the shell aperture's outer lip has formed. ("Illinois Snails and Slugs", 2009; Burch and Pearce, 1990)

Reproduction

Land snails in the clade Stylommotophora, such as gray-foot lancetooths, are hermaphroditic. Although they usually mate with other snails, they may also self-fertilize if the sperm and eggs of one individual become mature at the same time. Mating partners may be located by following mucus trails. Land snails typically exhibit a courtship ritual before mating begins. When gray-foot lancetooth snails mate, one will mount the other with its genital pore (located on the right side of the animal) above the genital pore of the other snail. The animal on top will crawl forward and thrust its head and neck downward upon reaching its partner's aperture rim. The snail on the bottom will arch its head and neck upward, and both snails will gnaw at the other's foreparts for several minutes before extruding their copulatory organs and mating. Each snail inserts its penis into the other's vagina and both animals will lay fertilized eggs. Copulation was observed lasting for over 10 hours in one instance. (Burch and Pearce, 1990; Tompa, 1984; Webb, 1943)

Sexual maturity is likely reached when the lip at the aperture forms. In cooler or drier areas, growth is slower, so it takes longer for individuals to reach sexual maturity than in warmer, moist areas. Mating season for this species in unknown, although it is likely to be in the warmer months of the year. In captivity, individuals mated during October and January. Rain may also bring on increased mating. The average clutch size for land snails is 20 eggs. ("Illinois Snails and Slugs", 2009; Burch and Pearce, 1990; Tompa, 1984; Webb, 1943)

  • Breeding interval
    Gray-foot lancetooth snails mate multiple times a year.
  • Breeding season
    Breeding season for this species has not been clearly identified; it is likely that breeding occurs during spring and fall months.
  • Average number of offspring
    20
  • Range gestation period
    7 to 10 days

Land snails leave eggs after they are deposited; no parental care is exhibited. ("Illinois Snails and Slugs", 2009)

  • Parental Investment
  • no parental involvement

Lifespan/Longevity

The lifespan of gray-foot lancetooth snails is unknown at this time; however, it is thought that they have a lifespan of 1-2 years, which is typical of land snails. ("Haplotrema concavum", 2003)

Behavior

Light intensity, relative humidity, and temperature influence much of a land snail's behavior, since these factors affect the snail's water retention. In general, land snails are nocturnal, and more active with increased relative humidity and decreased temperature. In temperate climates, a snail may reduce its water content and form a membrane (epiphram) over the aperature as it aestivates over the winter. During dry periods, this same membrane will serve to prevent desiccation. Snails may also "lope" to avoid rough substrates or retain water. As predators, gray-foot lancetooth snails are more solitary than other land snails. (Atkinson, 2013; Burch and Pearce, 1990; Pearce, 1989)

Home Range

Home range size is unknown for this species specifically, but other land snails of a similar size have ranges of at least 40 m^2. (Pearce, 1990; Pearce, 1990)

Communication and Perception

Land snails leave mucus trails, which are used as a form of communication. The mucus allows the snails to detect their own species (to reproduce) and other species. Some land snails may grow more slowly when exposed to mucus trails of the same species. Gray-foot lancetooth snails are known to follow mucus trails of their prey. The anterior tentacles of stylommatophoran snails are chemosensitive and their labia are both touch and chemosensitive. These snails can find food in still air by following olfactory gradients. Eyes located at the tops of the tentacles can detect light and may also be used for sensing forms at night. (Atkinson, 2013; Burch and Pearce, 1990; Nordsieck, 2011)

Food Habits

Gray-foot lancetooth snails are carnivorous, feeding on other snails and chewing on dead shells to obtain calcium. Although they are known to be cannabalistic, studies have shown that these snails show a preference for young of other species, such as flamed discs (Anguispira alternata), over their own species. Younger individuals will eat the eggs of thier own and other species, but begin to consume whole snails once reaching 6-7 mm in diameter. Gray-foot lancetooth snails prefer larger prey items with softer shells, such as juvenile oval ambersnails (Novisuccinea ovalis). This species will also eat nematodes and plants. (Atkinson and Balaban, 1997; Atkinson, 1998; Hotopp, 2006; Hubricht, 1985; Painter, 2013; Shearer and Atkinson, 2001)

Gray-foot lancetooth snails will follow the slime trails of their prey. They attack smaller prey by climbing over or turning their prey's shell. When attacking larger snails, they will crawl inside their prey's shell. An attacked snail will typically react by contracting into its shell, pulling the head of the gray-foot lancetooth snail with it. The snail then feeds on its prey, which may take several hours. This predatory snail may also transport its prey to another place to eat it, by first extending its head towards and contacting its prey, then contracting its own head, dragging it along. Gray-foot lancetooth snails may transport their prey to keep it from conspecifics, or in order to hide from potential predators. (Atkinson and Balaban, 1997; Atkinson, 1998; Hotopp, 2006; Hubricht, 1985; Painter, 2013; Shearer and Atkinson, 2001)

  • Animal Foods
  • mollusks
  • terrestrial worms
  • Plant Foods
  • leaves

Predation

In general, land snails are preyed on by lampyrid beetle larvae and other insects, birds, reptiles, rodents, and other small mammals, particularly voles and shrews. (Burch and Pearce, 1990; Painter, 2013)

Ecosystem Roles

Gray-foot lancetooths serve as predators of other snails, as well as prey to a number of other invertebrate and vertebrate predators. They may also act as intermediate hosts for brain worms (Parelaphostrongylus tenuis), which cause cerebrospinal nematodiasis in various ungulates. (Burch and Pearce, 1990; MDNR wildlife diseases laboratory, 2013)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

As carnivores, gray-foot lancetooth snails eat other snails, some of which are agricultural pests. ("Haplotrema concavum Say, 1821", 2013)

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

Although they may serve as intermediate hosts to parasites which later live in small mammals, these snails do not pose any significant threat to humans. (MDNR wildlife diseases laboratory, 2013)

Conservation Status

The conservation status of gray-foot lancetooth snails has not yet been evaluated. (IUCN, 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

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.

carnivore

an animal that mainly eats meat

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal

chemical

uses smells or other chemicals to communicate

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.

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.

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).

molluscivore

eats mollusks, members of Phylum Mollusca

motile

having the capacity to move from one place to another.

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.

seasonal breeding

breeding is confined to a particular season

sexual

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

solitary

lives alone

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.

visual

uses sight to communicate

References

2013. "Haplotrema concavum Say, 1821" (On-line). Global Biodiversity Information Facility. Accessed December 05, 2013 at http://data.gbif.org/species/2295986/.

2003. "Haplotrema concavum" (On-line). Encyclopedia of Life. Accessed May 22, 2013 at http://eol.org/pages/455034/maps.

Illinois Department of Natural Resources. Illinois Snails and Slugs. 1. Springfield, IL: Illinois Department of Natural Resources. 2009. Accessed December 09, 2013 at http://www.dnr.state.il.us/publications/pdf/00000656.pdf.

2013. "Virginia land snails: Haplotrema concavum" (On-line). Carnegie Museum of Natural History. Accessed December 09, 2013 at http://www.carnegiemnh.org/science/default.aspx?id=21573.

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

Atkinson, J. 1998. Food Manipulation and Transport by a Carnivorous Land Snail, Haplotrema concavum. Invertebrate Biology, 117/2: 109-113. Accessed August 21, 2013 at http://www.jstor.org/stable/3226962.

Atkinson, J., M. Balaban. 1997. Size-related change in feeding preference in the carnivorous land snail Haplotrema concavum (Pulmonata: Stylommatophora). Invertebrate Biology, 116/2: 82-85. Accessed August 21, 2013 at http://www.jstor.org/stable/3226972.

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

Burch, J., Y. Jung. 1988. Land snails of the University of Michigan biological station area. Walkerana, 3/9: 1-177.

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

Hotopp, K. 2006. "Haplotrema concavum (Say, 1821)" (On-line). Pennsylvania land snails. Accessed June 14, 2013 at http://www.carnegiemnh.org/science/default.aspx?id=16827.

Hubricht, L. 1985. The distributions of the native land mollusks of the Eastern United States. Fieldiana, Zoology New Series, 24: 1-191. Accessed August 21, 2013 at http://www.archive.org/stream/distributionsofn24hubr/distributionsofn24hubr_djvu.txt.

IUCN, 2013. "The IUCN Red List of Threatened Species. Version 2013.2" (On-line). Accessed December 13, 2013 at http://www.iucnredlist.org/search.

MDNR wildlife diseases laboratory, 2013. "Brainworm (meningeal worm)" (On-line). Michigan Department of Natural Resources. Accessed May 23, 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 05, 2013 at http://www.fcps.edu/islandcreekes/ecology/disc_cannibal_snail.htm.

Pearce, T. 1989. Loping locomotion in terrestrial gastropods. Walkerana, 3/10: 229-237. Accessed August 21, 2013 at http://www.carnegiemnh.org/uploadedFiles/CMNH_Site/Mollusks/Downloads/Pearce1989.pdf.

Pearce, T. 1990. Spool and line technique tracing field movements of terrestrial snails. Walkerana, 4/12: 307-316. Accessed August 21, 2013 at http://www.carnegiemnh.org/uploadedFiles/CMNH_Site/Mollusks/Downloads/Pearce-1990-Spooling.pdf.

Pearce, T., A. Gaertner. 1996. Optimal foraging and mucus-trail following in the carnivorous land snail Haplotrema concavum (Gastropoda: Pulmonata). Malacological Review, 29: 85-99. Accessed August 21, 2013 at http://www.carnegiemnh.org/uploadedFiles/CMNH_Site/Mollusks/Downloads/Pearce-Gaertner-1996.pdf.

Pilsbry, H. 1946. Land mollusca of North America (North of Mexico), volume 2, part 1. Monographs of the Academy of Natural Sciences of Philadelphias, 3: 1-520.

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 August 21, 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.

Webb, G. 1943. The mating of the landsnail Haplotrema concavum (Say). American Midland Naturalist, 30/2: 341-345. Accessed August 21, 2013 at http://www.jstor.org/stable/2421286.

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