Cave Crayfish

Cambarus zophonastes

Description

The cave crayfish, Cambarus zophonastes, is a cave-adapted species that lacks pigment in the body and eyes. Its beaklike snout bears several spines. The overall body length reaches about 2.5 in (6.4 cm) at maturity. The carapace is translucent.

Behavior

This slow-moving crayfish, which appears lethargic because of its low metabolic rate, is an opportunistic omnivore, feeding on whatever organic matter washes into the cave system. It feeds on organic detritus, aquatic insects, and small crustaceans such as isopods, copepods, and amphipods. The crayfish reproduces very slowly; females deposit eggs perhaps only once in five years. In general, very little is known about the ecology and natural history of cave crayfish, and only limited observations have been made of this species.

Habitat

The cave crayfish is adapted to a constant, cool temperature and total absence of light. For food, deep cave organisms depend for the most part on organic matter imported in the groundwater. One of the primary sources of organic matter in caves is bat guano deposited by colonies of gray bats (My-otis grisescens ), a federally Endangered mammal. When bat populations decline, the entire cave ecosystem suffers from the loss of guano as an energy source.

The cave crayfish is found in an Ozark Mountain cave that has been carved out of the Plattin Limestone formation. The cave is a "solution channel" or "tunnel" cave, most of which is wet and muddy year-round. Many of its passages are flooded during storms and wet seasons. The cave stream flows through 1,400 ft (426.7 m) of passage and emerges at three springs some 150 ft (45.7 m) from the cave entrance.

Distribution

The historic range of this species has not been clarified, but it could not have enjoyed a widespread distribution. More than 170 caves in north-central Arkansas and more than 430 caves in Missouri have been surveyed for this crayfish without success. The species may have never existed beyond the present distribution in Stone County, Arkansas.

The only known population of the cave crayfish is found in Hell Creek Cave in Stone County, Arkansas. Scuba divers located only 15 individuals in deep cave pools in 1983. In 1984 the total population was estimated at less than 50.

Threats

Probably the most significant cause of crayfish decline has been the decline of the (endangered) gray bat population. In the past a colony of over 16,000 gray bats used Hell Creek Cave, but few bats have been seen there in recent years. Though access to the cave is limited, it is feared that the presence of adventurous spelunkers may further reduce the bat species. Cavers also may have a direct, negative impact on the crayfish by forcing the often sedentary crayfish to become active, thus increasing their metabolic rate in a system where energy conservation is highly important.

The existing population is also threatened by water quality degradation from nearby highway traffic and its attendant hazards (such as a 4,000 gal, or 15,141.7 l, gasoline spill in March, 1985), siltation from industrial operations (concrete company and petroleum product storage) and real estate development (residential and commercial), sewage or effluents from septic systems, and transmission line right-of-way maintenance with herbicides. The species apparently has low reproductive rates, characteristic of obligate cave dwellers, and is also susceptible to collecting, a potential threat that looms in the future.

Conservation and Recovery

The Arkansas Natural Heritage Commission owns a 160-acre (65-hectare) tract that includes the entrance of Hell Creek Cave. The agency regulates access to the cave to prevent human disturbance, but much of the watershed surrounding the cave is privately owned. Protection of the habitat can only be assured by controlling the introduction of foreign substances into the groundwater. Monitoring of water quality and population levels will be conducted periodically. The recovery of the cave's gray bat population would aid in the recovery efforts for the cave crayfish as well.

Contact

Regional Office of Endangered Species
U.S. Fish and Wildlife Service
1875 Century Blvd., Suite 200
Atlanta, Georgia 30345
http://southeast.fws.gov/

References

Aley, T., and C. Aley. 1985. "Water Quality Protection Studies at Hell Creek Cave, Arkansas." Report. Arkansas Natural Heritage Commission and the Arkansas Nature Conservancy, Little Rock.

Harvey, M. J., et al. 1981. "Endangered Bats of Arkansas: Distribution, Status, Ecology, and Management." Report. Arkansas Game and Fish Commission, U.S. Forest Service, and National Park Service, Little Rock.

Smith, K. L. 1984. "The Status of Cambarus zophonastes, an Endemic Cave Crayfish from Arkansas." Report. U.S. Fish and Wildlife Service, Atlanta.

U.S. Fish and Wildlife Service. 1988. "A Recovery Plan for the Cave Crayfish, Cambarus zophonastes." U.S. Fish and Wildlife Service, Atlanta.