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Species Description

Chickamauga Crayfish

Cambarus (Puncticambarus) extraneus


Classification

Phylum: Arthropoda
Subphylum: Crustacea
Class: Malacostraca
Order: Decapoda
Family: Cambaridae

Description

The Chickamauga Crayfish coloration is usually tan with brown markings or olive with black, saddle-like markings. It has dark olive chelae with numerous cream to orange-colored tubercles (bumps). Its rostrum is adorned with either spines or tubercles. The eyes are rather large and well-developed. The carapace length is usually between 20 and 48 mm (0.75-1.9 in). The broad areola is 2.5 to 4 times as long as it is wide and is decorated with 8-10 pits or spots.

Life Cycle

There have been relatively few life history studies conducted on crayfish. The available life history data for Cambarus extraneus is limited to the form or condition of specimens collected during certain times of the year. First-form (sexually mature) males have been collected during April, May and October. Egg-bearing females have not been collected. Copulation was observed during April. The life cycle of this species is presumed to be fairly similar to the generalized crayfish life history described below. Copulation usually occurs between autumn and spring. Cambarus extraneus copulation has been observed taking place during April. Copulation involves a sexually mature male crayfish grabbing a female and depositing sperm packages (spermatophores) into the seminal receptacle on the abdomen of a receptive female crayfish. Usually during the spring, females secrete a sticky substance on the underside of their abdomen and pleopods in order to attach their eggs. The eggs and sperm (from the seminal receptacle) are then released upon the sticky surface and fertilization occurs. A female carrying eggs on her abdomen and legs is said to be "in berry." Embryos develop and hatch on the underside of females in 2-20 weeks, likely depending upon species and temperature. The immature hatchlings molt (shed their exoskeleton to allow growth) and remain attached to their mother. These first-stage immature crayfish look fairly similar to typical crayfish, but have disproportionately large heads and eyes. Another molting takes place in about 1-2 weeks. These second-stage immature crayfish look even more like adult crayfish. Second-stage or third-stage immature crayfish leave their mother's surface and become independent. These young crayfish continue molting and growing and are usually sexually mature by their second or third autumn. Sexually mature males and females are believed to mate between autumn and summer and many usually die within 3 years of hatching.

Natural History

Adult Cambarus extraneus crayfish often hide under rocks or leaf litter in shallow streams during the day. From dusk until dawn, or on very cloudy days, crayfish come out of hiding and search for food in streams. Crayfish are usually omnivorous scavengers, feeding upon whatever is available. Crayfish eat aquatic vegetation, small fish, aquatic insects and snails. They use their chelae (claws) on their first 3 legs to grab, crush and tear their food. This food is further cut by a number of specialized mouthparts. The main predators of crayfish are fish, frogs, turtles, wading birds, raccoons, otters and humans. Crayfish usually walk slowly across the bottom of their stream habitat using their last 4 walking legs (periopods). When frightened or in danger, however, they quickly escape by "darting" backwards. Crayfish sometimes have extensive scaring on their chelae or are missing appendages. This occurs while escaping predators or fighting with other crayfish. Male crayfish are particularly aggressive with one another and their claw-to-claw combat can be quite intense.

Range

This species is only found in the South Chickamauga Creek Basin in Catoosa, Walker and Whitfield Counties in Georgia and Hamilton County in Tennessee . It prefers shallow, moderately flowing streams and is usually found beneath rocks or leaf litter.

Conservation Status

Cambarus extraneus is listed as Rare within Georgia . It has a small range that is restricted to one small creek basin and is susceptible to changes within its aquatic habitat. Impoundment construction, pollution and other factors that would degrade water quality pose threats to this rare crayfish.

Similar Species

Cambarus girardianus is often found in association with the Chickamauga crayfish. Distinguishing between the two species can be difficult for many individuals that are not trained to identify and differentiate subtle anatomical differences between crayfish species. Identification of the rare Chickamauga crayfish should probably be verified by a trained individual.