{{Short description|Species of crayfish}} {{Speciesbox
| genus = Cambarus | species = aculabrum | authority = Hobbs & Brown, 1987 | status = CR | status_system = IUCN3.1 | status_ref = <ref name="iucn status 15 November 2021">{{cite iucn |author=Cordeiro, J. |author2=Jones, T. |author3=DiStefano, R. |author4=Thoma, R.F. |date=2010 |title=''Cambarus aculabrum'' |volume=2010 |article-number=e.T3688A10018152 |doi=10.2305/IUCN.UK.2010-3.RLTS.T3688A10018152.en |access-date=15 November 2021}}</ref> |status2=LE |status2_system=ESA |status2_ref=<ref name=ecos>{{cite web|url=https://ecos.fws.gov/ecp/species/5011|title=Benton County cave crayfish (''Cambarus aculabrum'')|website=Environmental Conservation Online System|publisher=U.S. Fish & Wildlife Service|access-date=2 September 2023}}</ref><ref name=fws>{{cite journal|author1=Paul D. Hartfield|author2=USFWS|title=Endangered status determined for the cave crayfish ''Cambarus aculabrum''|journal=Federal Register|date=27 April 1993|volume=58|issue=79|pages=25742–25746}} {{Federal Register|58|25742}}</ref> }} '''''Cambarus aculabrum''''' is a rare species of cave-dwelling [[crayfish]] known by the common name '''Benton county cave crayfish'''.<ref name=nbii>[http://www.nbii.gov/portal/server.pt/community/threatened_and_endangered_species/2036/benton_cave_cave_crayfish/7536 ''Cambarus aculabrum''.] {{Webarchive|url=https://web.archive.org/web/20110928224451/http://www.nbii.gov/portal/server.pt/community/threatened_and_endangered_species/2036/benton_cave_cave_crayfish/7536# |date=2011-09-28 }} National Biological Information Infrastructure.</ref><ref name=grae>{{cite journal |author1=G. O. Graening |author2=Michael E. Slay |author3=Arthur V. Brown |author4=Jeffrey B. Koppelman |year=2006 |title=Status and distribution of the endangered Benton cave crayfish, ''Cambarus aculabrum'' (Decapoda: Cambaridae) |journal=[[The Southwestern Naturalist]] |volume=51 |issue=3 |pages=376–439 |url=http://www.csus.edu/indiv/g/graeningg/Pubs/swna-51-03-376.pdf |jstor=20424733 |doi=10.1894/0038-4909(2006)51[376:SADOTE]2.0.CO;2|s2cid=86756024 }}</ref> It is native to [[Arkansas]] in the United States, where it is known from only four locations.<ref name=grae/> It is a federally listed [[endangered species]] of the United States.<ref name=ecos/><ref name=fws/>
==Taxonomy and naming== This crayfish was first described to science as a new species in 1987.<ref name=fws/> There has been little formal study of this species due to its rarity.<ref name=grae/>
It has been postulated that the four subterranean crayfish species inhabiting the [[Ozarks]], including ''Cambarus aculabrum'', derive from a common [[epigean]] ancestor species that gained access to a historic cave channel in the Ozark Plateau.<ref name=hobbs/>
==Description== It is about 48 millimeters (1.8 inches) long. As a [[Stygofauna|stygobite]] it is adapted to groundwater environments;<ref name=grae/> it lacks pigment, making it white in color, and has only rudimentary eyes.<ref name=nbii/> The body and claws bear numerous stiff hairs, while the [[Rostrum (anatomy)|rostrum]] is crested with small spines.<ref name="hobbs">{{cite journal |last1=Hobbs |first1=Horton H. |last2=Brown |first2=Arthur V. |title=A New Troglobitic Crayfish From Northwestern Arkansas (Decapoda: Cambaridae) |journal=Proceedings of the Biological Society of Washington |date=1987 |volume=100 |issue=4 |pages=1040–1048 |url=https://ia800205.us.archive.org/32/items/biostor-74843/biostor-74843.pdf |access-date=26 March 2022}}</ref>
==Distribution and habitat== The crayfish has been found living in three [[limestone]] [[Solutional cave|solutional]]<ref name = hobbs/> [[cave]]s in the [[karst]] landscape of northern Arkansas; Bear Hollow Cave, Logan Cave and Old Pendergrass Cave in [[Benton County, Arkansas|Benton County]]. Additionally, one specimen was found in a pool in Brush Creek in [[Washington County, Arkansas|Washington County]], having been flushed from the [[hyporheic zone]] by flooding. It is not considered an Arkansas [[Endemism|endemic]] species because 58% of one of the Bear Hollow cave recharge zones lies within the neighboring state of [[Missouri]], although it has not yet been found in that state.<ref name=grae/>
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 °F.<ref name=nbii/> 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.<ref name=grae/>
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]] before they could be identified.<ref name=grae/>
==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 [[Guano|bat guano]].<ref name=fws/><ref name=nbii/>
==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.<ref name=nbii/> Little else is known about its ecology.<ref name=grae/>
It has been eaten by the [[Cottus carolinae|banded sculpin]] (''Cottus carolinae'') on at least one occasion.<ref name=grae/>
==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]] (USFWS) in 1993 and by the [[International Union for Conservation of Nature|IUCN]] in 2004. A recovery plan was created by the USFWS in 1996.<ref name=grae/>
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]]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.<ref name=grae/>
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]] 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 has also established efforts to upgrade septic systems and reforest areas within the cave recharge zones.<ref name=grae/>
==References== {{Reflist}}
{{Taxonbar|from=Q3934315}}
[[Category:Cambarus]] [[Category:Cave crayfish]] [[Category:Endemic crustaceans of the United States]] [[Category:Freshwater crustaceans of North America]] [[Category:Fauna of the Plains-Midwest (United States)]] [[Category:Natural history of Arkansas]] [[Category:Natural history of Missouri]] [[Category:Critically endangered fauna of the United States]] [[Category:Taxonomy articles created by Polbot]] [[Category:Crustaceans described in 1987]] [[Category:Taxa named by Horton H. Hobbs Jr.]]