''Cambarus aculabrum'' is a rare species of cave-dwelling

crayfish Crayfish are freshwater crustaceans belonging to the clade Astacidea, which also contains lobsters. In some locations, they are also known as crawfish, craydids, crawdaddies, crawdads, freshwater lobsters, mountain lobsters, rock lobsters, mu ...

known by the common name Benton county cave crayfish.''Cambarus aculabrum''.
National Biological Information Infrastructure. It is native to

Arkansas Arkansas ( ) is a landlocked state in the South Central United States. It is bordered by Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, and Texas and Oklahoma to the west. Its name is from the Osage ...

in the United States, where it is known from only four locations. It is a federally listed

endangered species An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inv ...

of the United States.USFWS
Endangered status determined for the cave crayfish ''Cambarus aculabrum''.
''Federal Register'' April 27, 1993.

Taxonomy and naming

This crayfish was first described to science as a new species in 1987. There has been little formal study of this species due to its rarity. It has been postulated that the four subterranean crayfish species inhabiting the

Ozarks The Ozarks, also known as the Ozark Mountains, Ozark Highlands or Ozark Plateau, is a physiographic region in the U.S. states of Missouri, Arkansas, Oklahoma and the extreme southeastern corner of Kansas. The Ozarks cover a significant port ...

, including ''Cambarus aculabrum'', derive from a common

epigean Epigeal, epigean, epigeic and epigeous are biological terms describing an organism's activity above the soil surface. In botany, a seed is described as showing epigeal germination when the cotyledons of the germinating seed expand, throw off the ...

ancestor species that gained access to a historic cave channel in the Ozark Plateau.

Description

It is about 48 millimeters (1.8 inches) long. As a

stygobite Stygofauna are any fauna that live in groundwater systems or aquifers, such as caves, fissures and vugs. Stygofauna and troglofauna are the two types of subterranean fauna (based on life-history). Both are associated with subterranean environme ...

it is adapted to groundwater environments; it lacks pigment, making it white in color, and has only rudimentary eyes. The body and claws bear numerous stiff hairs, while the

rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ships * Ros ...

is crested with small spines.

Distribution and habitat

The crayfish has been found living in three

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

solutional

cave A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word ''cave'' can refer to smaller openings such as sea ...

s in the

karst Karst is a topography formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant ro ...

landscape of northern Arkansas; Bear Hollow Cave, Logan Cave and Old Pendergrass Cave in Benton County. Additionally, one specimen was found in a pool in Brush Creek in Washington County, having been flushed from the

hyporheic zone The hyporheic zone is the region of sediment and porous space beneath and alongside a stream bed, where there is mixing of shallow groundwater and surface water. The flow dynamics and behavior in this zone (termed hyporheic flow or underflow) is re ...

by flooding. It is not considered an Arkansas

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

species because 58% of one of the Bear Hollow cave recharge zones lies within the neighboring state of

Missouri Missouri is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. Ranking List of U.S. states and territories by area, 21st in land area, it is bordered by eight states (tied for the most with Tennessee ...

, although it has not yet been found in that state. It can be found in all pool and stream habitats within the caves, but is commonly found along the edge of the water. Cave entrances are avoided due to the risk of predation by surface species. Clean, clear and well oxygenated water is required. Water temperatures in the cave generally remain stable at around 57 degrees F. Because of the rapid recharge rates of the cave systems, stream velocity and volume can increase dramatically. During these floods events crayfish can be washed out of the cave systems, exposing them to predation. Several individuals have been found in surface waters downstream of the caves. Because the species is adapted to subterranean environments, it is assumed that it cannot survive outside of the caves. Additional populations of stygobitic crayfish have been identified near the four known locations. Stygobitic crayfish have been observed in Rootville Cave and in a cistern on Spanker Creek in Benton County. They were identified as belonging to the genus ''Cambarus'', but a species determination was not made. The crayfish in the Spanker Creek cistern were killed by the landowner in order to avoid regulation under the

Endangered Species Act of 1973 The Endangered Species Act of 1973 (ESA or "The Act"; 16 U.S.C. § 1531 et seq.) is the primary law in the United States for protecting imperiled species. Designed to protect critically imperiled species from extinction as a "consequence of ec ...

before they could be identified.

Diet and feeding

Nutrient levels in the cave water are low, and because of this crayfish feeds on detritus washed into the cave from the surface, and on algae, fungus, and other organisms associated with deposits of

bat guano Guano (Spanish from qu, wanu) is the accumulated excrement of seabirds or bats. As a manure, guano is a highly effective fertilizer due to the high content of nitrogen, phosphate, and potassium, all key nutrients essential for plant growth. ...

Natural history

Like other stygobitic crayfish species, the Benton county cave crayfish has an increased lifespan (up to 75 years) and low reproductive and metabolic rates. Little else is known about its ecology. It has been eaten by the

banded sculpin The banded sculpin (''Cottus carolinae'') is a freshwater fish dwelling mostly in small to moderate sized streams in areas of swift current. Young and juvenile ''C. carolinae'' can mainly be found in pools, riffles, and other shallow habitats whi ...

(''Cottus carolinae'') on at least one occasion.

Conservation Status

As of 2006, the estimated total population of Benton county cave crayfish was less than 200 individuals. Due to its rarity and extremely restricted range, it was listed as endangered by the

United States Fish and Wildlife Service The United States Fish and Wildlife Service (USFWS or FWS) is an agency within the United States Department of the Interior dedicated to the management of fish, wildlife, and natural habitats. The mission of the agency is "working with othe ...

(USFWS) in 1993 and by the

IUCN The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

in 2004. A recovery plan was created by the USFWS in 1996. A number of threats to the survival of this species have been identified. Habitat degradation due to groundwater pollution from residential septic systems and

concentrated animal feeding operation In animal husbandry, a concentrated animal feeding operation (CAFO), as defined by the United States Department of Agriculture (USDA), is an intensive animal feeding operation (AFO) in which over 1,000 animal units are confined for over 45 days a ...

s has been identified as the main threat. Additional threats include trampling by trespassers and explorers in the caves, low reproductive rate, specimen collection, predation, and flooding. A number of measures have been taken to reduce threats to this species. Gates have been erected at the entrance of Bear Hollow and Logan caves to prevent trampling, but due to vandalism this threat remains. A fixed rope line was installed on the wall of Bear Hollow Cave to prevent trampling during official population counts. Additionally, scientific collection of specimens has ceased, with none taking place since the 1980s. Severe penalties under the ESA discourage amateur collection. The primary conservation measure taken to protect this species has been land acquisition and protection. The 46.9 hectare

Logan Cave National Wildlife Refuge Logan Cave National Wildlife Refuge in Benton County, Arkansas became the 455th National Wildlife Refuge on March 14, 1989, under the Endangered Species Act of 1973. This Ozark Mountain refuge, which includes a limestone-solution cave, is locat ...

was created by the USFWS around the entrances to Logan Cave. The Bear Hollow Natural Area and Camden Hollow Natural Area containing the entrances to Bear Hollow Cave and Old Pendergrass cave, respectively, were established by

The Nature Conservancy The Nature Conservancy (TNC) is a global environmental organization headquartered in Arlington, Virginia. it works via affiliates or branches in 79 countries and territories, as well as across every state in the US. Founded in 1951, The Natu ...

. The Nature Conservancy has also established efforts to upgrade septic systems and reforest areas within the cave recharge zones.

References

{{Taxonbar, from=Q3934315 Cambaridae Cave crayfish Crustaceans of the United States Endemic fauna of the United States Freshwater crustaceans of North America Fauna of the Plains-Midwest (United States) Natural history of Arkansas Natural history of Missouri Critically endangered fauna of the United States Taxonomy articles created by Polbot Crustaceans described in 1987 Taxa named by Horton H. Hobbs Jr.