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 Federally Threatened and Endangered Invertebrates of the Ozarks Aquifer

Benton County Cave Crayfish
Cambarus aculabrum

Image of Benton County Cave Crayfish, courtesy of Mike Slay, The Nature Conservancy
[Photo: copyright Mike Slay, The Nature Conservancy]

Description: The Benton County cave crayfish (cave crayfish) is a small, troglobitic (obligate cave-dwelling) crayfish in the genus Cambarus. The cave crayfish is one of five species of troglobitic crayfish in the Ozark region. The cave crayfish is about 1.8 inches (4.8 cm) long, with white, unpigmented skin and reduced (vestigial) eyes.

Life History: Very little is known about the life history of the Benton County cave crayfish. Consistent with other troglobitic species, the cave crayfish has increased longevity (can live up to 75 years), low egg production, delayed reproductive maturity, and a low metabolic rate. This species feeds on organic matter that is eft by bats or washed into the caves from the surface. The cave crayfish is preyed upon by sculpin fish and other crayfish.

Habitat: The cave crayfish is often found along stream edges or pools of underground streams, but has been observed in all stream and pool habitats (generally less than 20 inches [50 cm] deep) of its two primary locations (Bear Hollow Cave and Logan Cave). The only area the cave crayfish is not found is near cave openings, where it is vulnerable to predation by surface species. The cave crayfish can be found on variable substrates including silt, gravel, and bedrock and requires clear, clean water with high dissolved oxygen content for respiration. Water temperatures of these underground caves are stable and hover around 57 degrees F (14 degrees C) for most of the year. Nutrient levels are generally low, and the cave crayfish relies on transport of organic matter from the surface or bat guano for food.

Distribution: As of 2006, Cambarus aculabrum has been confirmed at four sites in Benton County, Arkansas. These sites are Bear Hollow Cave, Logan Cave, Old Pendergrass Cave and in Brush Creek.

Critical habitat for this species has not been determined. The map below depicts the counties where this species has been reported (USFWS).


Species Distribution of the Benton County Cave Crayfish (Cambarus aculabrum) [Figure: Houston Advanced Research Center using US Fish and Wildlife data]

Species Distribution of the Benton County Cave Crayfish (Cambarus aculabrum) [Figure: Houston Advanced Research Center using US Fish and Wildlife data]

Status: The Benton County cave crayfish is a federally listed (1993) endangered species. There is a recovery plan in place for this species. The current known population of the cave crayfish is estimated at less than 200 individuals, occupying less than four square kilometers of underground streams and pools at four sites. Due to the rapid recharge rates of the karst systems the cave crayfish inhabits, this species is vulnerable to changes in surface and groundwater quality and quantity. Degradation of surface and groundwater resources in the recharge zone constitute a major threat to this species and include contamination by sewage from septic tanks, organic chemicals and pesticides, toxic metals, nutrient loading from animal waste and fertilizer, and residential and commercial construction. Physical disturbance from vandalism at these caves have also been an issue, despite gates erected at cave openings.

Resources:

Graening et al (2006), Cambarus aculabrum

IUCN Redlist, Cambarus aculabrum profile

USFWS, Cave Crayfish Recovery Plan

Hell Creek Cave Crayfish
Cambarus zophonastes

Image of Hell Creek Cave Crayfish, copyright Dante Fenolio
[Photo: copyright Dante Fenolio]

Description: The Hell Creek cave crayfish (or cave crayfish) is a small, troglibitic (obligate cave-dwelling) crayfish in the genus Cambarus. The cave crayfish is one of five species of troglibitic crayfish in the Ozark region. The cave crayfish is about 2.5 inches (6.4 cm) long, with white, unpigmented skin, and reduced (vestigial) eyes. The Hell Creek cave crayfish can be distinguished from close relative by the spines on its rostrum (horn-like protrusion between the eyes).

Life History: The life history of the Hell Creek Cave crayfish is not well documented. Consistent with other related troglobitic species, the cave crayfish likely has increased longevity, low egg production, delayed reproductive maturity, and a low metabolic rate. Reproduction is likely triggered by spring flooding events. Nutrient levels in cave habitats are generally low. Therefore, the cave crayfish relies on transport of organic matter from the surface (during flooding events) or bat guano for food.

Habitat: The Hell Creek Cave crayfish lives in the clean, clear waters of subterranean streams of Hell Creek Cave and Nesbitt Spring Cave in waters 3.3-6.6 feet (1-2 m) wide and 3.3-26.2 feet (1-8 m) deep. The cave crayfish inhabits a total of less than 0.5 square kilometers in these two locations. The conditions in Hell Creek consist of a mean pH of 6.5 and water temperature of 58 degrees F (14.5 degrees C). Graening et al. (2006) measured water quality parameters in Hell Creek as follows: total organic carbon content = 0.5mg/L, total phosphorus = 0.08 mg/L, and E.coli = 50 cfu/100 mL.

Distribution: As of 2006, Cambarus zophonastes has been confirmed at two sites in Stone County, Arkansas. These sites are Hell Creek Cave and Nesbitt Spring Cave.

Critical habitat for this species has not been determined. The map below depicts the counties where this species has been reported (USFWS).

Species Distribution of the Hell Creek Cave crayfish (Cambarus zophonastes) [Figure: Houston Advanced Research Center using US Fish and Wildlife data]

Species Distribution of the Hell Creek Cave crayfish (Cambarus zophonastes) [Figure: Houston Advanced Research Center using US Fish and Wildlife data] . Click on map for larger image.

Status: The Hell Creek Cave crayfish is a federally listed endangered species (1987). There is a recovery plan in place for this species. The current known population (2006) of the Hell Creek cave crayfish is 23 individuals, occupying less than 0.5 square kilometers of underground streams and pools at two sites. Contamination of surface and groundwater resources in the recharge zone of these caves can impact this species and its habitat. Threats to the water quality within these cave sites are contamination by sewage from septic tanks, hazardous materials from roads and illegal dumping, and turbidity from residential construction. Physical disturbance from vandalism at these caves has also been an issue, despite gates erected at cave openings. The Hell Creek Cave once housed a gray bat population, which is no longer found at the site. The gray bat colony provided nutrient input to Hell Creek Cave; the effects of the bat colony loss on the Hell Creek Cave crayfish population are unknown.

Resources:

Graening et al (2006), Cambarus zophonastes

IUCN Red List, Cambarus zophonastes profile

USFWS, Hell Creek Cave Crayfish Recovery Plan

Illinois Cave Amphipod
Gammarus acherondytes

Image of Illinois Cave Amphipod, courtesy of US Fish and Wildlife
[Photo: US Fish and Wildlife]

Description: The Illinois cave amphipod is a small, freshwater crustacean in the family Gammaridae. The Illinois cave amphipod is sexually dimorphic (differences in form between males and females of the same species) with males reaching 0.8 inches (2.0 cm) long and females reaching 0.5-0.63 inches (1.2-1.6 cm) long. This species is bluish-gray in color and has very small, kidney-shaped eyes. The Illinois cave amphipod has long, slender antennae that extend up to half the length of its body.

Life History: Little is known of the life history and ecology of the Illinois cave amphipod. However, in general, amphipods of the genus Gammarus have reduced metabolic rates, unpigmented skin, and reduced (vestigial) eyes. Additionally, species of this genus exhibit internal fertilization (mating may occur for up to 2 weeks), after which eggs are released into the females' brood pouch. Gammarid amphipods carry around 17-21 eggs in the brood pouch, until they are released one month later. Illinois cave amphipods most likely reproduce in gravel riffles, which is their primary habitat. The lifespan of the Illinois cave amphipod is unknown, but related species have a lifespan of approximately one year. Gammarids feed on detritus (decaying organic matter) by shredding and scraping bacterial films from rock surfaces.

Habitat: The Illinois cave amphipod lives in the gravel riffles or pools of dark, underground cave streams in the Salem Plateau karst region of the Ozark aquifer. This species prefers gravel or cobble substrate at depths of 0-4 inches (0-10 cm), although at times they can be found on bedrock or mud at depths up to 16 inches (40 cm).

Distribution: Gammarus acherondytes was historically found at six cave sites in St. Clair and Monroe counties, Illinois. It is currently known from four cave sites and four groundwater systems in Monroe County: Illinois Caverns, Frog Cave, Fogelpole Cave, Krueger-Dry Run Caves and Annbriar Spring, Luhr Spring, Reverse Stream, and Dual Spring groundwater systems.

Critical habitat for this species has not been determined. The map below depicts the counties where this species has been reported (USFWS).


Species Distribution of the Illinois cave amphipod (Gammarus acherondytes) [Figure: Houston Advanced Research Center using US Fish and Wildlife data]

Species Distribution of the Illinois cave amphipod (Gammarus acherondytes) [Figure: Houston Advanced Research Center using US Fish and Wildlife data]. Click on map for larger image.


Status: The Illinois cave amphipod is a federally listed (1998) endangered species. There is a recovery plan in place for this species. The Illinois cave amphipod lives in shallow karst groundwater of the Springfield Plateau. Due to the shallow nature of this karst area, it is highly sensitive to contamination. Gammarid species require high oxygen content, cool water temperatures and clean water to survive. Threats to water quality include agricultural pesticides and fertilizers, residential sewage waste, runoff from roads, illegal dumping, and potential salinization from oil extraction processes. Panno et al. (2001) found nitrate concentrations in Springfield Plateau springs ranging from 2.3-7.5 mg/L (natural levels are 1.4 mg/L), with most of the non-natural contribution coming from row crop fertilizers. Compounds such as DDE (breakdown product of the pesticide, DDT), and dieldrin (breakdown product of the pesticide, aldrin) were found at high levels (.031 ppm and .016 ppm, respectively) in the caves and springs in the area inhabited by the Illinois cave amphipod. High levels of fecal bacteria were found in springs and caves in the area. There are also threats from flow disruption due to quarry mining and road construction in the area. Flow disruption can cause fluctuations in temperature. Commercial caving and vandalism represent a threat due to physical disturbance to habitat.

Resources:

USFWS, Illinois Cave Amphipod Factsheet

USFWS, Illinois Cave Amphipod Recovery Plan

Tumbling Creek Cavesnail
Antrobia culveri

Image of Tumbling Creek Cavesnail, courtesy of David Ashley, US Fish and Wildlife
[Photo: David Ashley, US Fish and Wildlife]

Description: The Tumbling Creek cavesnail is a small, aquatic snail in the Hydrobiidae family. Individuals are 0.1 inches (2.3 mm) tall with a diameter of 0.08 inches (2.0 mm) The body of the Tumbling Creek cavesnail is white, with a pale yellow conical shell that has 3 to 3 1/2 whorls. Like many other troglobitic (obligate cave-dwelling) species, the Tumbling Creek cavesnail is blind.

Life History: Little is known about the life history or ecology of the Tumbling Creek cavesnail. Biologists believe that this species feeds on the microscropic biofilm that grows on the underside of rocks and on bedrock. This means that the Tumbling Creek cavesnail indirectly relies on nutrients in bat guano for its food. The reproductive behavior of the cavesnail is not well documented, but they most likely deposit their egg masses on rock and gravel that is free of sedimentation. The lifespan is thought to be one to five years, similar to related species.

Habitat: The Tumbling Creek cavesnail inhabits the gravel substrate of Tumbling Creek and is often observed underneath rocks within the stream. It has also been seen on bare bedrock with fine sand deposits. The cavesnail is predominantly found at sites that are unsilted. Stable stream banks and riffle-run- pool habitats are also requirements for good cavesnail habitat. Additionally, the stream flow required to maintain good habitat for this species is 0.07-150 cubic feet per second. Water temperatures in the range of 55-62 degrees F (12.8-16.7 deg C), dissolved oxygen levels greater than 4.5 mg/L and turbidity less than 200 ntu (Nephelometric Turbidity Units) are also required for optimal cavesnail habitat.

Distribution: Antrobia culveri is only known from aquatic habitats in Tumbling Creek cave in southwest Missouri in Taney County.

Critical habitat for this species has not been determined. Critical habitat has been proposed and the US Fish and Wildlife Service (USFWS) will make a final ruling concerning the Tumbling Creek cavesnail's critical habitat in July 2011. The map below depicts the county where this species has been reported (USFWS).


Species Distribution of the Tumbling Creek cavesnail (Antrobia culveri) [Figure: Houston Advanced Research Center using US Fish and Wildlife data]

Species Distribution of the Tumbling Creek cavesnail (Antrobia culveri) [Figure: Houston Advanced Research Center using US Fish and Wildlife data]

Status: The Tumbling Creek cavesnail is a federal (2002) and state (2001) listed endangered species. This species was listed due to a dramatic decline in population between 1974 and the time of listing in 2002. In 1974, the Tumbling Creek cavesnail population was estimated at over 15,000 individuals and by 2002 only 40 individuals could be located. Between 1996 and 2003, the USFWS observed a declining trend in the population, often only counting a few individuals per survey. The declining trends in the Tumbling Creek cavesnail population are due to sedimentation (from overgrazing in the recharge area), nutrient enrichment from poultry and swine waste and septic tanks, and toxic materials from roadway spills and sinkhole dumping. Physical disturbance from commercial caving and vandalism represent an important threat to this species because these disturbances not only disturb Tumbling Creek cavesnail habitat, but they may cause a decline in bat populations, limiting the nutrient inputs to the cave ecosystem.

Resources:

USFWS, Tumbling Creek Cavesnail Factsheet

USFWS, Tumbling Creek Cavesnail Proposed Critical Habitat

USFWS, Tumbling Creek Cavesnail Recovery Plan


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