The Crayfish Fanclub Newsletter - March 1997
The Crayfish Fan Club Newsletter.Welcome to the Crayfish Fan Club Newsletter.
I would like to take this opportunity to greet new members and to thank everyone for their contribution to the Crayfish Fanclub which you can send via email. Contribution ensures the continuation of the Crayfish Fan Club and the Crayfish Corner website. Please send your crayfish articles, pics, jokes, songs, stories and comments to me at the address below. The information below is exclusive to Crayfish Fan Club members but will be posted on the Crayfish Corner in a few weeks after you receive this.
Crayfish News / GossipHello to all our new members. The fanclub now has more than 20 members. Thanks to you all for your interest. The Crayfish Corner has not been updated much - the new look is still in development
Crayfish InfoThe first article this month is an article from Cave Crayfish in the Logan Cave National Wildlife Refuge:
There are five species of obligate cave-dwelling (troglobitic) crayfish reported for the Ozark region. Only two troglobitic crayfish are known from Arkansas, the endangered Cambarus zophonastes and the endangered Cambarus aculabrum. C. aculabrum was described from two cave streams in Benton County, Arkansas by H.H. Hobbs, Jr. and A.V. Brown (1987). It is a small, white (unpigmented) crayfish with reduced eyes. There is no common name for C. aculabrum.
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. First form males (reproductively active) have been collected during the months of January, February, October and December. Females carrying eggs and young Cambarus aculabrum have not been observed.
On July 15, 1988, the U.S. Fish and Wildlife Service (Service) was petitioned by Dr. Arthur Brown, University of Arkansas, to list Cambarus aculabrum as an endangered species. A finding of insufficient information to indicate the petitioned action was warranted was published by the Service in the Federal Register (53 FR 52745) on December 28, 1988. The finding noted that at the time of the petition there were 29 caves within the Springfield Plateau that were known to harbor cave crayfish, and in only seven of these had the species of crayfish been determined. Recent cave crayfish surveys (Smith 1984, Figg and Lister 1990) and an electrophoretic investigation (Koppelman 1990) have resulted in the identification of these cave crayfish populations, and confirmed the restricted distribution of C. aculabrum. The final rule to list the cave crayfish, C. aculabrum, as an endangered species was effective on May 27, 1993 (U.S. Fish and Wildlife Service 1993).
B. Description and Taxonomic Status
Cambarus aculabrum is a small, white, troglobitic crayfish with an overall body length reaching about 48 millimeters (1.8inches). This species is distinguished from related surface (epigean) species by a total lack of pigment, and by reduced eyes. It is distinguished from its closest troglobitic relatives by an acute or subacute apex of the anteromedian lobe of the epistome. First form males (those with fully formed and hardened first pleopods, or reproductive appendages) are further separated from the closely related troglobitic species, C. 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 first form males of another closely related cave species, C. zophanastes, by a longer central projection of the first pleopod which also has a shallow subapical notch (Hobbs and Brown 1987). Recent studies indicate that C. aculabrum is genetically distinct from the other cave crayfish species (Koppelman 1990).
Cambarus aculabrum is presently known from only two cave streams in Benton County, Arkansas (Figure 1). The type locality, Logan Cave, is an Ozarkian solution channel located in the Mississippian cherty-limestone Boone Formation of the Springfield Plateau (Hobbs and Brown 1987). A stream flows through the entire length of the cave, approximately 2000 meters (m) [6,000 feet(ft)]. Logan Cave also contains a lake approximately 200 m (600ft) long, 2-6 m (6-18ft) wide, and 2-3 m (6-9ft) deep that was formed by the collapse of the cave roof. Water exits the cave approximately 300 m (900ft) from the lake. The U.S. Fish and Wildlife Service purchased 123.9 acres at Logan Cave, including the property that contains the cave's entrances, in 1989. The cave's recharge area covers 30.15 square kilometers (11.64 square miles), most of which is privately owned (Aley and Aley 1987).
Cambarus aculabrum is usually observed along the walls of the pool, or along the stream edges. Population numbers appear to be very small in Logan Cave. As many as six crayfish have been seen during one survey, but often none are evident (Hobbs and Brown 1987). In 14 visits to the cave, Brown observed crayfish on only three occasions (A. Brown in. litt., 1987). Brown has also found three dead cave crayfish (A. Brown, Univ. Ark., pers. comm.). During a 1990 search of the cave lake and stream by Service biologists, only three Cambarus aculabrum were seen, one of which was dead. Six crayfish were observed during a cave visit by Service biologists in 1995. A graduate student working on a study of the threatened Ozark cavefish (Amblyopsis rosae) in Logan cave has observed a total of ? crayfish from 199? to 1995 (Z. Brown, Univ. Ark., pers. comm.).
Cambarus aculabrum is also known from Bear Hollow Cave, located approximately 38 kilometers (23miles) from Logan Cave. Bear Hollow Cave is also a solution tunnel in the Boone Formation and contains a small stream approximately 200 m (600ft) long and 0.2 m (8inches) deep at low flow (Hobbs and Brown 1987). The cave may completely fill up with water after some rainfalls. Although there is less available habitat in Bear Hollow Cave than in Logan Cave, as many as nine crayfish have been seen during a single visit (Hobbs and Brown 1987). As in Logan Cave, however, numbers of crayfish observed may vary dramatically between visits. In the Service's 1990 survey, only a single crayfish was found in the Bear Hollow Cave stream while four were observed in a 1995 cave visit. The extent of the Bear Hollow Cave recharge area is unknown. The cave's entrance and surrounding property are privately owned.
Cave organisms, including Cambarus aculabrum, are specially adapted to survive in cave ecosystems. Many cave dwelling species (troglobites) have reduced metabolic rate, delayed reproduction, reduced number of eggs produced, increased longevity, reduced or nonexistent eyes and loss of pigmentation (Culver 1982; Brown et al. 1994). Like all other troglobites, cave crayfish rely on outside sources of organic matter for food. Organic matter, such as leaf litter, is carried in as detritus by cave streams or carried in by animals, such as bats, which provide organic matter through their feces (guano) or their bodily remains. Being aquatic organisms, crayfish require dissolved oxygen in the water for respiration.
Besides the endangered cave crayfish, Logan cave supports another threatened troglobite, the Ozark cavefish (Amblyopsis rosae). Non-obligate, cave inhabitants (troglophiles) include banded sculpins (Cottus carolinae), two species of crayfish (Orconectes neglectus and O. punctimanus), and at least three salamanders (Brown et al. 1994). Other important species using Logan cave seasonally or occasionally include threatened Indiana bats (Myotis sodalis), eastern pipistrelle bats (Pipistellus subflavus) and a maternity colony of endangered gray bats (M. grisescens).
Bear Hollow Cave has not been studied to the same extent as Logan Cave because it is located on private property. Besides Cambarus aculabrum, the grotto salamander (Typhlotriton spelaeus) and the eastern pipistrelle bat have been seen inside the cave. A fish scale of the Ozark cavefish (Amblyopsis rosae) was found in Bear Hollow Cave although no cavefish have been seen (Willis and Brown 1985). The cave could support the threatened Ozark cavefish and other aquatic organisms since there are available microfauna (aquatic food base) (A. Brown, Univ. Ark., pers. commun.).
E. Reasons for Listing
This species is known from only two cave sites in northeast Arkansas and is vulnerable to disturbance. Factors most likely to limit or cause the decline of Cambarus aculabrum include the following: (1) destruction of habitat including water quality degradation; (2) disturbance by amateur spelunkers or trespassers; (3) collecting; (4) low reproduction potential; (5) competition and predation by troglophilic species.
Cambarus aculabrum is an aquatic organism which has adapted to living in cave streams containing relatively clean water. Any factor which impacts surface water and groundwater quality in the vicinity of the caves' recharge area can ultimately impact the survival of C. aculabrum and other cave creatures. Crayfish must have dissolved oxygen in the water for respiration. Severe water contamination by sewage, animal waste, gasoline, or a number of other materials, may result in seriously depleted oxygen concentrations and suffocation of cave crayfish. Contamination by toxic compounds, including heavy metals, many organic chemicals, and pesticides can be lethal to aquatic cave fauna, including crayfish. Sedimentation can clog gills, damage or destroy breeding habitat, and harm invertebrates upon which crayfish feed. Additional threats to water quality include alteration of drainage or hydrologic patterns; lower ground water levels; and physical destruction of the cave.
Water quality of Logan Cave is primarily threatened by hog and poultry operations adjacent to or within the groundwater recharge area (Aley and Aley 1987). The Aley and Aley study (1987) also identified residential development as a potential source of water contamination in the Logan Cave aquifer. Residential development is the primary threat to the Bear Hollow Cave crayfish population. Residential development may degrade water quality in caves by leakage from sewage disposal systems and solid waste landfills; sedimentation; increased storm runoff; and increased use of lawn fertilizers, herbicides, and pesticides. Residential growth also attracts secondary developments such as roads and gasoline stations which contribute to water quality degradation, e.g., sedimentation, gasoline and oil spills (Aley and Aley 1987).
Both cave sites have been vandalized and disturbed frequently in the past. The entrances to Logan Cave have been purchased by the Service and access is restricted. Despite protection afforded the cave, refuge staff estimated 10 cases of trespass for the period from April-July 1995. At least two researchers also visit the cave per month also (C. Mitchell 1995, in litt.). Logan cave is monitored by a light sensitive device located inside which records the time and date when activated but it is not regularly checked nor maintained. Bear Hollow Cave is privately owned and the owners in cooperation with Arkansas Game and Fish Commission had the cave entrance gated in 19??, but, vandals destroyed the gate door and subsequently entered the cave. It is unknown when the gate vandalism occurred since there is currently no one scheduled nor responsible for monitoring cave trespass. Arkansas Game and Fish Commission along with the land owners plan to replace the gate at a later unspecified date.
Disturbance by amateur cavers and trespassers impacts the physical condition of individual cave crayfish. Obligate cave dwellers have a low metabolic level and have limited opportunities to feed (Culver 1982). Any physical activity resulting from disturbance uses up energy that would be used in feeding or possibly reproduction. Physical disturbance is a direct threat in Bear Hollow Cave because it agitates stream bottom sediments causing turbidity and reduced visibility which greatly increases the likelihood that a cave crayfish may be stepped on, causing injuries or death. Disturbances at Logan Cave can interrupt breeding or feeding activity of the endangered cave crayfish, the endangered gray bat, the threatened Ozark cave fish, and the threatened Indiana bat along with other cave creatures. It is especially important to protect the maternal colony of gray bats at Logan Cave because both the cave crayfish and Ozark cavefish rely indirectly or directly on the bat guano (organic input) for food.
Most troglobitic species, including Cambarus aculabrum, have a low reproductive rate and a relatively long maturity period. Removal of any cave crayfish by collectors will affect the ability of the species to reproduce. Loss of mature individuals capable of reproducing obviously causes a decline in population levels. All troglobitic species are protected by Arkansas Game and Fish Commission Regulation #1817 entitled, "Wildlife Pet Restrictions" and cannot be possessed as pets and their sale is prohibited (Wilson 1990, in litt.)
Troglophilic predation and competition may impact cave crayfish population levels. In general food resources are poor in cave environments (Culver 1982 and Brown et al. 1994). As part of an organic carbon resources study in Logan Cave, Brown et al. (1994) examined the gut contents of three troglophilic sculpin and found the remains of Cambarus aculabrum inside one sculpin. Brown et. al. (1994) also analyzed gut contents of 15 troglophilic crayfish species (Orconectes neglectus and O. punctimanus) and found that they had eaten other crayfish but it could not be determined what species of crayfish were eaten. There is the possibility that C. aculabrum is preyed upon by troglophilic crayfish, especially near the cave entrance where troglophiles are more abundant. The troglophilic sculpin and crayfish were more abundant at the cave entrance and also utilized the increased food resources near the cave entrance (Brown et al. 1994). Further research is needed to determine whether the increases in food resources near cave entrances is human induced (anthropogenic enrichment) and whether the abundance of troglophiles is related to the increased food resources.
F. Literature Cited
Aley, T. and C. Aley. 1987. Water quality protection studies, Logan Cave, Arkansas. Ozark Underground Laboratory. Report to Arkansas Game and Fish Commission. pp. 1-2, 11-15.
Brown, A.V., W.K. Pierson, K.B. Brown. 1994. Organic carbon resources and the payoff-risk relationship in cave ecosystems. Second International Conf. on Ground Water., U.S. Env. Protect. Ag. pp. 67-76.
Culver, D.C. 1982. Cave Life (Evolution and Ecology). Harvard Univ. Press. pp. 35, 51-54.
Figg, D.E. and K.B. Lister. 1990. Status survey of the troglobitic crayfish Cambarus setosus in Missouri. Missouri Department of Conservation. 7 pp.
Hobbs, H.H., Jr. and A.V. Brown. 1987. A new troglobitic crayfish from Northwestern Arkansas (Decapoda: Cambaridae). Proc. Biol. Soc. Wash. 100(4), pp. 1041-1048.
Koppelman, J.B. 1990. A biochemical genetic analysis of troglobitic crayfish (Cambarus spp.) in Missouri, Oklahoma and Arkansas. Report to Missouri Department of Conservation, Oklahoma Natural Heritage Inventory, and Arkansas Game and Fish Commission. 12 pp.
Smith, K.L. 1984. The status of Cambarus zophonastes Hobbs and Bedinger, an endemic cave crayfish from Arkansas. Arkansas Natural Heritage Commission, Little Rock, Arkansas. 15 pp.
U.S. Fish and Wildlife Service. 1993. Endangered and threatened wildlife and plants; determination of Cambarus aculabrum (cave crayfish) to be an endangered species. Federal Register 58(79):25742-25746.
Willis, L.D. and A.V. Brown. 1985. Distribution and habitat requirements, of the Ozark Cavefish, Amblyopsis rosae. Am. Midl. Nat. 114: 311-317.