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The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

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Common name: gap ringed crayfish

Synonyms and Other Names: Orconectes neglectus chaenodactylus (Williams, 1952). Faxonius neglectus chaenodactylus underwent a reclassification in August 2017, changing the genus of non-cave dwelling Orconectes to Faxonius (Crandall and De Grave 2017).

Taxonomy: available through www.itis.gov

Identification: Ringed Crayfish range in color from olive-green to reddish-tan. The tips of their claws (chelae) are bright orange and are preceded by prominent black or brown annular bands. Chelae are broad and robust, especially in males, with a wide gap between each finger when they are closed (Pflieger 1996). Its rostrum contains a trough-like central depression, which usually has a low ridge positioned along its midline. Male gonopods terminate in two elongate, slightly curved, processes with tips that are separated by a narrow space (Pflieger 1996; Wagner et al. 2010). Two subspecies of Faxonius neglectus are recognized; Faxonius neglectus neglectus (the Ringed Crayfish) and Faxonius neglectus chaenodactylus (the Gap Ringed Crayfish) (Williams 1952; Hobbs 1989; Taylor et al. 2007). Detailed illustrations of morphological features characteristic to each subspecies are given in Williams (1954a) and Pflieger (1996).

The nominate subspecies, F. n. neglectus, is typically light green, tan, or yellow in coloration, with conspicuous reddish markings on its ridges and tubercles (Williams 1954a). Black annular rings posterior to tips of chelae are almost always present in F. n. neglectus (Williams 1954a; Pflieger 1996). Two dark saddle-marks are found on its dorsal surface, one just forward of the cervical groove and the other at the posterior margin of the carapace. A thin, nearly black stripe lays lengthwise along each lateral margin of the abdomen, and the posterior margin of each abdominal segment is trimmed in bright red (Pflieger 1996). The chelae of F. n. neglectus are heavy, and when closed, its finger gape is less than 25 percent of the width of its palm. Its rostrum is prominent, has poorly defined lateral spines, and nearly parallel sides (Williams 1954a).

The subspecies F. n. chaenodactylus is typically dark green, yellowish-green, or flesh-pink in color (Williams 1954a). A broad brownish stripe runs along each lateral margin of the abdomen and converges posteriorly to form a characteristic V-shaped pattern. Chelae have broad, brown rings near their tips, followed by pale yellow color towards their bases (Pflieger 1996). The chelae of F. n. chaenodactylus have more slender claws, with a finger gape that is wider than 25 percent of the width of palm. Additionally, the rostrum of F. n. chaenodactylus is smaller and shorter than that of F. n. neglectus (Williams 1952; Wagner et al. 2010).

Size: Adult Ringed Crayfish (Faxonius neglectus) are moderately-sized, ranging from approximately 3 centimeters (1.2 inches) to 9.7 centimeters (3.8 inches) in total length (Pflieger 1996).

Native Range: The Gap Ringed Crayfish (F. n. chaenodactylus) is endemic to the North Fork White River basin and portions of the Middle White River basin in southern Missouri and northern Arkansas (Wagner et al. 2010).

Alaska	Hawaii	Puerto Rico & Virgin Islands	Guam Saipan

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Ecology: Ringed Crayfish generally inhabit waterways that are clear, permanent flowing river  systems ranging in size from small creeks to large rivers. It’s most frequently associated with firm, rocky substrates in shallow riffles and pools that are free of silt, where it lives in shallow crevasses under rocks and boulders (Williams 1954a; Pflieger 1996). Surveys conducted by Gore and Bryant (1990) found that habitats occupied by F. neglectus in Oklahoma tributaries varied among age groups. Young-of-the-year (YOY) crayfish were more abundant in higher velocity, cobbled-gravel areas; while adults occurred more frequently in lower current stretches with sand substrate and beds of macrophytes (Gore and Bryant 1990). The more recent collections of Schainost (2011) also reflected these findings. Primary habitats of F. neglectus in some regions of Nebraska were observed as beds of aquatic macrophytes and shoreline vegetation, while secondary habitats were documented as rocky riffles (Schainost 2011). Wagner et al. (2008) found that within Arkansas, the subspecies F. n. chaenodactylus also occupied clear streams with aquatic vegetation, and more moderate current velocities. 

The life history of F. neglectus is like that of other species in the genus Faxonius (Price and Payne 1978; Larson and Magoulick 2008). A study on F. n. chaenodactylus in North Sylamore Creek, Arkansas, found that adults breed once each year, and their breeding season ranges roughly from October to April. Females bear eggs from mid-April to mid-June, and the juveniles hatch late in the spring (Price and Payne 1978). Faxonius neglectus reach reproductive maturity at a relatively small size. The average minimum size at sexual maturity in F. n. neglectus is approximately 13.5 millimeters (mm) cephalothorax length (CL). It is estimated that 50% of juveniles will reach maturity by the end of their first summer of growth (Price and Payne 1978; Larson and Magoulick 2008). The recruitment of YOY crayfish in the fall changes their population structure from consisting of primarily adult-sized individuals (in the spring) to a fall population that is dominated by subadult-sized individuals (Price and Payne 1978; Larson and Magoulick 2008). While the average lifespan of F. neglectus is approximately 2.5 years (Price and Payne 1978; Pflieger 1996), Pflieger (1996) observed a few individuals that lived up to five years in age.

Means of Introduction: Nonnative populations of Faxonius neglectus are suspected to have been introduced through means of bait bucket releases, pet releases, and incidentally with the stocking of fishes (Bouchard 1977; Daniels et al. 2001; Taylor et al. 2004).

Status: In 1998, the first record of F. n. chaenodactylus was collected from the western portion of the Spring River in Missouri (Flinders and Magoulick 2005). At the time of collection, it was the dominant species in the river runs from which it was collected (Flinders and Magoulick 2005). It now occurs in high numbers in the West Fork of the Spring River drainage, and established populations extend well into the South Fork (Flinders and Magoulick 2005; Flinders and Magoulick 2007).

Impact of Introduction: In his initial report, Bouchard (1977) hypothesized that Faxonius neglectus would displace the native Signal Crayfish (Pacifastacus leniusculus) within the Rogue River basin. Despite this, site occupancy studies later conducted by Pearl et al. (2013) did not find a negative relationship between the presence of P. leniusculus and F. neglectus. The discovery of the introduced Gap Ringed Crayfish (F. n. chaenodactylus) in the Spring River drainage of southern Missouri and northern Arkansas raised concern for the imperiled Coldwater Crayfish (F. eupunctus) and other native species that inhabit the drainage (Flinders and Magoulick 2005). Further sampling of the region revealed that F. n. chaenodactylus was negatively associated with F. eupunctus and the Hubbs’ Crayfish (Cambarus hubbsi) within the drainage (Flinders and Magoulick 2007). Faxonius eupunctus and Cambarus hubbsi no longer occurred throughout much of their former range in the Spring River where F. neglectus is now abundant. A narrow zone of overlap was found between F. n. chaenodactylus and F. eupunctus; however, densities of F. eupunctus were extremely low in these areas (Flinders and Magoulick 2007). In Tumbling Creek Cave, MO, the invasion of Ringed Crayfish poses a threat to native species such as the federally endangered Tumbling Creek Cavesnail (Antrobia culveri), as it may potentially be preyed upon by crayfish (Mouser et al. 2019).

References: (click for full references)

Bouchard, R.W. 1977. Distribution, systematic status and ecological notes on five poorly known species of crayfish in western North America (Decapoda: Astacidae and Cambaridae). Freshwater Crayfish 3:409-423.

Daniels, R.A., D.C. Murphy, and M.W. Klemens. 2001. Orconectes neglectus is established in the northeast. Northeastern Naturalist 8(1):93-100.

Flinders, C. A., and D. D. Magoulick. 2005. Distribution, habitat use and life history of Stream-Dwelling Crayfish in the Spring River drainage of Arkansas and Missouri with a focus on the imperiled Mammoth Spring crayfish (Orconectes marchandi). The American Midland Naturalist 154(2):358-374.

Gore, J.A., and R.M. Bryant Jr. 1990. Temporal shifts in physical habitat of the crayfish, Orconectes neglectus (Faxon). Hydrobiologia 199:131-142. https://link.springer.com/article/10.1007/BF00005605

Hobbs, H.H., Jr. 1989. An illustrated checklist of the American crayfishes (Decapoda: Astacidae, Cambaridae, and Parastacidae). Smithsonian Contributions to Zoology 480:1-236.

Imhoff, E.M., M.J. Morre, and R.J. DiStefano. 2012. Introduced alien Ringed Crayfish (Orconectes neglectus neglectus [Faxon, 1885]) threaten imperiled Coldwater Crayfish (Orconectes eupunctus Williams, 1952) in the Eleven Point River drainage, Missouri, USA. Aquatic Invasions 7(1):129-134. http://www.aquaticinvasions.net/2012/AI_2012_1_Imhoff_etal.pdf.

Larson, E.R., and D.D. Magoulick. 2008. Comparative life history of native (Orconectes eupunctus) and introduced (Orconectes neglectus) crayfishes in the Spring River drainage of Arkansas and Missouri. American Midland Naturalist 160(2):323-341.

Magoulick, D.D., and R.J. DiStefano. 2007. Invasive crayfish Orconectes neglectus threatens native crayfishes in the Spring River drainage of Arkansas and Missouri. Southeastern Naturalist 6(1):141-150.

Mouser, J., D.C. Ashley, T. Aley, and S.K. Brewer. 2019. Subterranean invasion by Gapped Ringed Crayfish: Effectiveness of a removal effort and barrier installation. Diversity 11(1):3.

Pearl, C.A., M.J. Adams, and B. McCreary. 2013. Habitat and co-occurrence of native and invasive crayfish. Aquatic Invasions 8(2):171-184.

Pflieger, W.L. 1996. The Crayfishes of Missouri. Missouri Department of Conservation, Jefferson City, MO.

Price, J.O., and J.F. Payne. 1978. Multiple summer molts in adult Orconectes neglectus chaenodactylus William. Freshwater Crayfish 4:93-104.

Reimer, R.D. 1969. A report on the crawfishes (Decapoda: Astacidae) of Oklahoma. Proceedings of the Oklahoma Academy of Science 48:49-65.

Schainost, S.C. 2011. The Ringed Crayfish, Orconectes neglectus neglectus, in Nebraska with a revision of its distributional range. Transactions of the Nebraska Academy of Sciences 32:59-68. http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1003&context=tnas

Taylor, C.A., S.N. Jones, and E.A. Bergey. 2004. Crayfishes of Oklahoma revisited: new state records and checklist of species. The Southwestern Naturalist 49(2):250-255.

Taylor, C.A., G.A. Schuster, J.E. Cooper, R.J. DiStefano, A.G. Eversole, P. Hamr, H.H. Hobbs III, H.W. Robison, C.E. Skelton, and R.F. Thoma. 2007. A reassessment of the conservation status of crayfishes of the United States and Canada after 10+ years of increased awareness. Fisheries 32(8):372-389. http://dx.doi.org/10.1577/1548-8446(2007)32[372:AROTCS]2.0.CO;2

Wagner, B.K., C.A. Taylor, and M.D. Kottmyer. 2008. Stream crayfish of the northeast Arkansas Ozarks. The Arkansas Game and Fish Commission, SWG Project T20-8 final report.

Wagner, B.K., C.A. Taylor, and M.D. Kottmyer. 2010. Status and distribution of the Gapped Ringed Crayfish, Orconectes neglectus neglectus, in Arkansas. Journal of the Arkansas Academy of Science 64:115-122. http://libinfo.uark.edu/aas/issues/2010v64/v64a22.pdf

Williams, A.B. 1952. Six New Crayfishes of the Genus Orconectes (Decapoda: Astacidae) from Arkansas, Missouri and Oklahoma. Transactions of the Kansas Academy of Science (1903-) 55(3):330-351. https://www.jstor.org/stable/3626240.

Williams, A.B. 1954a. Speciation and distribution of the crayfishes of the Ozark Plateaus and Ouachita Provinces. https://archive.org/stream/cbarchive_41917_speciationanddistributionofthe1902/speciationanddistributionofthe1902#page/n15/mode/2up/search/harrisoni. Accessed on 06/16/2017.

Williams A.B. 1954b. An Explanation for the Distribution of a North American Crayfish. Ecology 35(4):573-575. https://www.jstor.org/stable/1931047.

Author: Procopio, J.

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.