The Benton County cave crayfish is a small white crayfish with reduced eyes. The species is known to occur in three cave systems in Benton County, Arkansas and one upwelling from a stream bottom in Washington County, Arkansas. Almost nothing is known about the life history of this species, and only limited observations have been made. G.O. Graening and U.S. Fish and Wildlife Service biologists hypothesize that these crayfish rely on outside sources of organic matter for food such as leaf litter, dead animals or bat guano. Survey results suggest that their population is stable. However, the small portion of accessible underground habitat and variable survey results suggest that these population surveys provide minimal inference on total population numbers. U.S. Fish and Wildlife Service biologists note that primary threats within the delineated recharge areas are degraded groundwater quality from urban development, farming practices and land conversion, as well as decreased groundwater availability from impermeable surfaces and groundwater extraction. Threats have increased since the species was listed as endangered.
Cambarus aculabrum is a small, white, troglobitic crayfish with an overall body length reaching about 48 millimeters (1 .8 inches). 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 epistorne. 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. zophonastes, 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, Koppelnian and Figg 1995).
The Benton County cave crayfish occurs in three cave systems in Benton County, Arkansas and one system in Washington County, Arkansas. It is found along the walls of pools or stream edges in chert-limestone cave stream systems. Hobbs and Brown noted in 1987, the largest known population is in a dendritic stream channel cave located in the Mississippian cherty-limestone, Boone Formation of the Springfield Plateau. The cave stream is approximately one kilometer in length, with a recharge area of 30.1 square kilometers.
G.O. Graening provided the first analysis of trophicof Ozark cave streams in 2002, including two caves inhabited by Benton County cave crayfish. Graening and Brown later hypothesized that three trophic levels are normal for cave stream food webs:
- A food base of benthic detritus
- A guild of invertebrate consumers such as isopods, crayfish and amphipods
- Predators, in form of fish
This hypothesis suggests that fine benthic organic matter in sediments sustain crustacean detritivores such as the Benton County cave crayfish. However, crayfish diet studies have not been conducted.
The Benton County cave crayfish reaches about 48 millimeters (1.8 inches) in length. It is distinguished from its closest troglobitic relatives by an acute or subacute apex of the anteromedian lobe of the epistorne. First form males - those with fully formed and hardened first pleopods, or reproductive appendages - are further separated from closely-related troglobitic species, the bristly cave crayfish and Oklahoma cave crayfish, by the absence of a transverse groove which separates the proximolateral lobe from the shaft on the first pleopod. It differs from first form males of another closely related cave species, the Hell Creek cave crayfish, by a longer central projection of the first pleopod which also has a shallow subapical notch as reported by H.H. Hobbs and A.V. Brown in 1987.
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