Common Name: KNOTTY BURROWING CRAYFISH
Scientific Name: Cambarus (Jugicambarus) nodosus
Bouchard and Hobbs
Rarity Ranks: G4/S2
State Legal Status: None
Federal Legal Status: None
Description: The overall color of the Knotty Burrowing Crayfish is light brown or olive to darker greenish-brown. The abdomen appears darker than the carapace. The claws are greenish-brown and are covered with orangish to reddish tubercles. The fingers of the claws are orangish and are brightest towards the tips. There are two rows of tubercles along the mesial margin of the palm; the row right along the edge is well-developed. The areola is fairly wide and the rostrum is short, appears blunt, and does not have marginal spines or tubercles. The largest specimen reported for Georgia has a total body length of about 64 mm (2.5 in).
Similar Species: Since no other primary burrowers occur with the Knotty Burrowing Crayfish, it is unlikely to be confused with any other species (Cambarus bartonii is occasionally found in stream bank burrows, see differences below). Very rarely, however, one will be found in a stream. In a stream setting, the species is most likely to be confused with Cambarus (Cambarus) bartonii, C. (Puncticambarus) hiwasseensis, and C. (P.) parrishi. All three of these species are brownish with darker mottling which differs from the solid coloration of Knotty Burrowing Crayfish. In addition, the Knotty Burrowing Crayfish has two rows of tubercles along the mesial margin of the palm which separates it from C. bartonii which only has one row. Lastly, C. nodosus has a blunt, almost square shaped rostrum versus the longer tapered rostrums of C. hiwasseensis and C. parrishi.
Habitat: The Knotty Burrowing Crayfish is almost always found in burrow systems in seepage areas around streams. Hobbs (1981) also reported them from wet ditches. There, burrows are typically complex with many tunnels, particularly where the water table is shallow.
Diet: No studies of the Knotty Burrowing Crayfish are known. Crayfishes are considered opportunistic omnivores and likely feed on live and decaying vegetation, aquatic insect larvae, small fishes, and dead animal matter.
Life History: Males in reproductive condition have been collected in Georgia in April, June, and November. Seven females carrying eggs and/or young were found in June. Number of eggs ranged from 1-28. Number of young on one female was 22 and number of eggs/young on another female was 14/11. The total length of the smallest breeding male from Georgia is about 53 mm (2.1 in) and the smallest female with eggs is about 53 mm (2.1 in) in length (Hobbs 1981).
Survey Recommendations: This Knotty Burrowing Crayfish is typically found in burrows in seepage headwater areas of streams. This species is difficult to collect because the water table is usually near the surface of the ground which typically results in the crayfish excavating an extremely complex burrow system. Several tunnels may have to be followed to find the animal. Despite many tries, I have only collected this species about five times.
Range: The Knotty Burrowing Crayfish is known from the headwaters of the Chattahoochee, Savannah, Hiwassee, and Nottely river systems in Georgia, North Carolina, South Carolina, and Tennessee (Eversole and Jones 2004; Hobbs 1981; Simmons and Fraley 2010). A population was recently discovered in the headwaters of the Little Tennessee River system in Georgia (Skelton, unpubl. data).
Threats: Small distribution is considered a threat since the loss of a single population would noticeably reduce its presence in the state. Fortunately, at least some populations occur on US Forest Service land, and therefore receive some protection.
Conservation and Management Recommendations: Conserving populations of the Knotty Burrowing Crayfish will require general watershed level protection measures, including the protection of riparian zones, control of sediment and nutrient runoff from farms and construction sites, and limiting the amount of impervious cover (e.g., pavement) within occupied watersheds. Areas with burrows should be protected from land disturbing activities and activities that could alter groundwater resources. Environmental education programs should include information about burrowing crayfishes and encourage protection of burrows. This species is probably more abundant in Georgia than the map below indicates. As mentioned above, it is difficult to collect. Intensive targeted surveys will likely yield additional populations.
Eversole, A. G. and D. R. Jones. 2004. Key to the Crayfish of South Carolina. US Forest Service Publication. 79 p.
Hobbs, H. H., Jr. 1981. The crayfishes of Georgia. Smithsonian Contributions to Zoology 318:1-549.
Simmons, J. W. and S. J. Fraley. 2010. Distribution, status, and life-history observations of crayfishes in western North Carolina. Southeastern Naturalist 9 (Special Issue 3):79–126.
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.
Date Compiled or Updated: October 2012