Lee County Cave Isopod

Lirceus usdagalun

Description

The Lirceus usdagalun (Lee County cave isopod) is an eyeless, unpigmented crustacean-like species measuring 0.2-0.3 in (5-7 mm) in length. The body is about 64% longer than wide, and the head is about one-third as long as wide, with deep incisions on its lateral margins.

Behavior

Unlike most other members of its genus, the Lee County cave isopod has adapted to a totally subterranean aquatic existence.

This isopod is undoubtedly a food item in the diet of certain natural predators, including cave salamanders and possibly cave crayfish.

Specific food items eaten by this isopod are unknown. However, it is believed that this species feeds on decaying organic matter consisting of deciduous leaf litter, twigs, and other wood particles. Parts from dead insects, presumably from decomposition of epigean insects that wash into the aquifer, are also eaten. It is also likely that this species feeds on bacteria, fungi, and other microorganisms associated with the organic matter.

Habitat

The area the Lee County cave isopod inhabits is riddled with caves, sinks and ravines in a water-soluble limestone substrate (karst). Such areas are particularly susceptible to contamination of groundwater from surface contaminants leaching through the porous substrate.

Distribution

This isopod was known historically from two cave systems, located approximately 6 mi (9 km) apart, in Lee County, Virginia.

The Lee County cave isopod is known to occur in only one cave in Lee County, Virginia. Since the discovery of L. usdagalun in 1971, biologists have conducted intensive searches of caves in Lee and surrounding counties with the specific goal of finding any additional populations of this species. Although these searches have revealed no additional populations of L. usdagalun, other isopod species of the genus Lirceus have been located in some other caves. When other species fill L. usdagalun's ecological niche in a closed cave ecosystem, there is virtually no chance of finding L. usdagalun.

Threats

This isopod was extirpated by groundwater pollution from one of the two cave systems it originally occupied. This pollution resulted when large quantities of sawdust, the by-product of a sawmill operation, were piled on the ground surface over the cave. Rainwater leached tannins and other toxins from the sawdust and transferred these through the porous substrate into the underlying groundwater, stripping oxygen from the water. Prior to its extirpation, a study comparing the populations in the two caves discovered that the populations differed in many ways. The unique characteristics of the extirpated population have been lost to the species forever.

The Lee County cave isopod could be adversely affected by an increase in human foot traffic through the cave, which could increase siltation in the streams it occupies. Presently, the location of the cave is not widely known, which led U.S Fish and Wildlife Service (FWS) to determine not to designate critical habitat.

Conservation and Recovery

The FWS published a Recovery Plan for the Lee County cave isopod in 1997. The only known critical habitats are privately owned and threatened by various human activities, especially those causing changes in hydrology or water pollution. These habitats must be protected by acquiring the land and designating ecological reserves, or by negotiating conservation easements with the owners. Nearby land-use must be managed to avoid threats to the underground habitat of the endangered crustacean. The populations of the Lee County cave isopod should be monitored, and research undertaken into its biology, habitat needs, and the development of beneficial management practices.

Contacts

U. S. Fish and Wildlife Service
Chesapeake Bay Ecological Services Office
177 Admiral Cochrane Drive
Annapolis, Maryland 21401-7307
Telephone: (410) 573-4500

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

References

Holsinger, J. R. 1979. Freshwater and terrestrial arthropods freshwater and terrestrial isopod crustaceans (order Isopoda). Proc. of symp. on endangered and threatened plants and animals in Virginia. Virginia Polytechnic Institute & State University, Blacksburg.

U.S. Fish and Wildlife Service. 1997. "Lee County Cave Isopod (Lirceus usdagalun ) Recovery Plan." U. S. Fish and Wildlife Service, Hadley, Massachusetts.