Cave Crayfish

Cambarus aculabrum

Description

The cave crayfish is a small, white obligate cave-dwelling crayfish. The body length of this species has been measured to reach up to 1.8 in (4.6 cm). This species has no pigment and has reduced eyes. It also has an acute or subacute apex of the antermomedian lobe of the epistome.

First form males are distinguished by a fully formed and hardened first pleopod (reproductive appendages). These males can be further distinguished from closely related Cambarus setosus and C. tartarus by the absence of a transverse groove separating the proximolateral lobe from the shaft on the first pleopod. It differs from C. zophonastes in that it possesses a longer central projection of the first pleopod that also has a shallow subapical notch.

Behavior

The reproductive habits of this species, as well as other sociobiological information, is not known at this time. This species, however, displays similar reproductive characteristics of other decopods. The males probably begin molting into the reproductive state in late summer with copulation occurring in late summer and fall. Egg laying likely occurs in late winter and early spring. Most males molt back to the nonreproductive form during April.

Habitat

Bear Hollow Cave contains a small stream approximately 660 ft (201.2 m) long and an undescribed pool that are habitat for C. aculabrum. The cave stream flow and depth varies. At times, parts of the stream may dry up leaving tiny pools of water or parts of the stream may completely disappear underground leaving no trace. After some rainfall events the cave may nearly fill up with water, as evidenced by trash found lodged up near the cave ceiling.

Water quality and clarity of Logan Cave Stream is generally high and many water parameters remain relatively constant for much of the year. Most changes in water properties occur when the cave's stream flow increases after a storm.

The cave crayfish is most commonly found along the walls of the pool, or along stream edges.

Distribution

The type locality of this species is Logan Cave as well as its associated stream and lake. The cave cray-fish is also known from Bear Hollow Cave and its associated stream about 23 mi (37 km) from Logan Cave. Both of these areas are located in Benton County, Arkansas.

The numbers of crayfish observed in Logan and Bear Hollow Caves has varied dramatically between cave visits. The greatest number of crayfish observed in a single visit is nine in Bear Hollow Cave and 21 in Logan Cave. In 14 visits to Logan Cave, crayfish were observed on only three occasions. In a 1990 survey, three C. aculabrum were observed in Logan Cave, one of which was dead, and only a single crayfish in Bear Hollow Cave. Six crayfish were observed in Logan Cave during another cave visit in 1995 while four were observed in Bear Hollow Cave. From October 1994 through September 1995, between seven and 21 cave crayfish were observed in Logan Cave.

In an observation of other cave crayfish and troglobitic species, small population sizes have been a result of reduced food sources. As an adaptation to this it has also been observed that these species display a lower metabolic rate, increased longevity, delayed maturity and reproduction and decreased fecundity. The otherwise adaptive characteristic could make the cave crayfish highly vulnerable to environmental pollution and limit this species' ability to recover.

Threats

Cave crayfish are highly specialized for living in stable cave environments with low light and low temperatures and are unable to cope with changes in their habitats that may be induced by human activities. Water quality degradation represents a major threat to C. aculabrum. This species is also vulnerable due to its limited distribution, with only two known populations containing a small number of individuals; its limited reproductive potential; and the potential for take by humans.

Conservation and Recovery

In 1989 the U.S. Fish and Wildlife Service (FWS) purchased 123.9 acres (50.1 hectares) at Logan Cave (the cave crayfish's original locality). This attempt will facilitate preservation activities initiated by the FWS. The rest of the area, however, is privately owned.

A collecting permit is required for collecting for any species, except for fish bait under state regulations. Troglobites are protected from possession and sale by Arkansas state law.

Potential conservation measures and federal involvement are expected to include: (1) Environmental Protection Agency: Clean Water Act's provisions for pesticide registration and waste management actions. (2) Corps of Engineers: Inclusion of the cave crayfish in project planning and operation and during permit review. (3) Federal Highway Administration : Consideration of the cave crayfish in bridge and road construction in known areas of occupancy. (4) Farmers Home Administration: Consideration of impacts of the cave crayfish in loan processes. (5) Soil Conservation Service: Inclusion of the cave cray-fish in farmer's assistance programs.

Contact

U.S. Fish and Wildlife Service
Regional Office
1875 Century Blvd., Suite 200
Atlanta, Georgia 30345
Phone: 404-679-4000
http://southeast.fws.gov/

References

U.S. Fish and Wildlife Service. 27 April 1993. "Endangered and Threatened Wildlife and Plants; Determination of Endangered Status Determined for the Cave Crayfish (Cambarus Aculabrum )." Federal Register 58(79): 25742-25746.

U. S. Fish and Wildlife Service. 30 October 1996. "Recovery Plan for the Cave Crafish (Cambarus aculabrum )." U.S. Fish and Wildlife Service, Atlanta, 37pp.