Virginia Fringed Mountain Snail

Polygyriscus virginianus

Description

The tiny shell of the Virginia fringed mountain snail, Polygyriscus virginianus, measures only 0.18 in (0.45 cm) in diameter. The shell has four to five whorls, increasing in thickness toward the rim. The shell is pale greenish brown with a white aperture. Eight to ten spiral, comb-like fringes occur inside the low spiral grooves of the shell surface. The living animal inside the shell is white with unpigmented eyestalks and is probably blind. The fringed mountain snail is the only species in it genus. It was originally described in 1947 from weathered shells found in the soil and was not known as a living species until 1971, when Leslie Hubricht found 14 living adults and seven immature specimens. This snail has been studied very little because of its rarity, limited distribution, and secretive habits. It is considered one of the rarest land snails in North America.

Behavior

Little is known about the biology of this snail. It is a burrower and almost never comes to the surface except during extremely wet weather. Its reproduction may be similar to that of Helicodiscus parallelus, which lays two eggs per season.

Its food sources are also unknown, but other species in this family possess radula with numerous small teeth specialized for scraping fungi, algae, and plant cells off surfaces where they graze. Rootlets of herbaceous and woody plants, as well as microscopic plants, are available in the soil layers where this species lives.

Habitat

This species has a very restricted habitat. It occurs along a steep river bank beneath the surface of permanently damp clay soils, loosened with limestone chips. The surface of the ground is relatively free of leaf litter. The site is dominated by pine and oak scrub and honeysuckle.

Distribution

The Virginia fringed mountain snail is presumed to be endemic to Pulaski County, Virginia. It has been found only at a single site on the north bank of the New River opposite the town of Radford in Pulaski County. Only about 30 of these snails have ever been found alive. The entire known range consists of a strip of bluff, embankment, and talus slope, 1.5 mi (2.5 km) long, along the river. The size of the population remains unknown because excavating to census the buried snails would severely disturb the habitat. It is considered very rare.

Threats

Any organism as rare as the Virginia fringed mountain snail can be seriously endangered by events and circumstances that would have little impact on a more plentiful species. Possible threats include the application of herbicides along nearby roadsides, road construction and maintenance, and reactivation of an old quarry adjacent to the habitat. None of these activities is currently anticipated.

Conservation and Recovery

The habitat appears stable; if left strictly alone, the snail will probably continue to survive in small numbers as it has for centuries. The U.S. Fish and Wildlife Service (FWS) Recovery Plan stresses the need for additional research to aid the recovery effort. Suitable habitat within a ten-mile radius may harbor additional populations, and the FWS has negotiated conservation agreements with private landowners to protect the river bank. Eventually, the land could be acquired and managed as a snail preserve.

Contact

U.S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
300 Westgate Center Dr.
Hadley, Massachusetts 01035-9589
Telephone: (413) 253-8200
Fax: (413) 253-8308
http://northeast.fws.gov/

References

Grimm, F. W. 1981. "Distribution, Habitat Requirements and Recovery Needs of the Endangered Land Snail, Polygyriscus virginianus. " Contract Report. U.S. Fish and Wildlife Service, Newton Corner, Massachusettes.

Hubricht, L. 1972. "Endangered Land Snails of the Eastern United States." Sterkiana 45: 33.

Solem, A. 1975. "Polygyriscus virginianus: A Helicodiscid Land Snail." Nautilus 89 (3): 80-86.

U.S. Fish and Wildlife Service. 1983. "Virginia Fringed Mountain Snail Recovery Plan." U.S. Fish and Wildlife Service, Atlanta.