Haplotrema concavum

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.

• Biogeographic Regions
• nearctic nearctic
  • native native

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.

• Habitat Regions
• temperate temperate
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest

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.

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.

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

• Sexual Dimorphism
• sexes alike

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.

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.

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

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.

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

Land snails leave eggs after they are deposited; no parental care is exhibited.

• 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.

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.

• Key Behaviors
• terricolous
• nocturnal nocturnal
• motile motile
• aestivation
• solitary solitary

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.

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.

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

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

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.

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.

• Primary Diet
• carnivore carnivore
  • molluscivore molluscivore

• 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.

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.

Economic Importance for Humans: Positive

As carnivores, gray-foot lancetooth snails eat other snails, some of which are agricultural pests.

• 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.

• Negative Impacts
• causes or carries domestic animal disease causes or carries domestic animal disease

Conservation Status

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

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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